Technology fundamentals

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Building the body area network

Industry alliance tackles technical, policy challenges

European project helps manage broken heartsat home

Medical imaging makeover

Data acquisition systems allow stop-action cardiacimaging in one scan

Managing digital imaging’s mountains of data

Mixed-signal, embedded open doorsfor digital imaging

Automated blood test is a breeze

Camera in a pill surveys GI tract

Body fat meter is thinly priced

Inside the art of pulse oximetryCO

NT

EN

TS

2 E E T i m e s |The diagnosis for medical electronics | D e c e m b e r 7 , 2 0 0 9

Opinion


Once the political posturing,

demagoguery and horse trad-

ing cease, it’s far from clear

whether Americans will actu-

ally achieve health care re-

form. The guess here is that, in

time-honored Washington fashion, all sides

in this noisy, high-stakes debate will claim

political victory while condemning the other

side either for effecting a “government

takeover” of the U.S. health care system

or for blocking “fundamental reform” of a

system that accounts from anywhere be-

tween one-fifth to one-sixth of the U.S.

economy, depending on which Senate floor

speech you choose to believe.

This is indeed a sad state of affairs, but

not wholly unexpected, given the political

and economic stakes for the health care

industrial complex.

Assuming Congress approves health

care legislation this year and President

Technology fundamental to reformBy George Leopold

Barack Obama signs it

into law, a key question

in implementing re-

forms is what role tech-

nology can play in

reducing skyrocketing

medical bills.

Up to now, many diag-

nostic technologies

have greatly improved

U.S. health care while

saving countless lives.

Those technologies re-

main expensive, how-

ever, making it awfully

tempting for a medical

specialist to order

another high-ticket

test—which may or

may not be needed—


Opinion

Music: Cross Douglas Road by Patrick O’Rourke, www.patrickorourke.com

Opinion


as a way to pay off the huge up-

front investment in the latest med-

ical equipment.

If we are to reduce medical costs,

such practices must stop.

Part of the problem with soaring

health care costs is that medical

school graduates confront huge

tuition bills that drive them into

lucrative specialty medicine and

away from general practice.

One of the best stories we’ve

seen during the health care debate

focused on a general practitioner

who was struggling to meet the

needs of her community and keep

her practice afloat amid a ceaseless

tide of health insurance paperwork.

The MD could barely afford to em-

ploy file clerks to handle the flood of

forms. One office worker left to take

a job at Starbucks, where she could

get the medical benefits the doctor

could not afford to provide.

It is physicians like this one who

desperately need technology’s help

to survive and, perhaps one day,

thrive. For technology companies that

have created the senior position of

chief medical officer, a huge opportu-

nity exists to customize existing tech-

nologies to serve these medical

professionals and not just the spe-

cialists whose offices are already

filled with the latest diagnostic tools.

None of us is getting any younger,

and some of us are facing life-and-

death medical decisions about our

aging parents. Technology alone

won’t heal what ails the U.S. health

care system, but it is a critical tool

in the fight to put patients ahead of

profits and politics. p

About the AuthorGeorge Leopold is news director forEE Times.

email: [email protected]

Body area nets


Networked medical devices hold

the promise of more-effective

and lower-cost health care, as

services traditionally delivered

in clinical settings become

accessible in the home. The rationale be-

hind the shift is sound, but the business,

regulatory and technical hurdles are many.

The problem is clear: The United States

last year spent an estimated $2.5 trillion—

18 percent of its GDP—on health care.

Yong-Min Kim, a professor of electrical engi-

neering at the University of Washington,

notes that much of that spending was for

costly hospital care, often delivered long

after the onset of chronic problems that

could have been better managed early on.

A critical component of the solution “is

in embedded or wearable devices linked to

therapy,” said Joseph Smith, vice president

of emerging technologies at Johnson &

By Rick Merritt

Wearable devices and implants couldhelp cure what ails health care

Building the body area network

Johnson Services Inc. (New

Brunswick, N.J.), which oversees

dozens of medical businesses.

“We don’t yet have the treatment

paradigms for continuous care for

chronic diseases, but I think we will

get there,” Smith said in September

at the IEEE Engineering in Medicine

and Biology Society’s annual confer-

ence (EMBC).

“We all have a responsibility to

be involved in health care reform,”

Rebecca Bergman, a vice president

of new therapies at Medtronic (Min-

neapolis), said at EMBC. “Tech is

not at the core of this issue, but we

should make tech part of the solu-

tion and not part of the problem.”

A group from Australia reported

at the conference on a program


Health care, American styleHigh costs are due in part to late-stage treatments, administered with expensive equipment in hospital settings

$2.5 trillion Amount spent domestically each year on health care

18%Portion of U.S. GDP spent on health care

45%U.S. share of world health care spending in dollars

45-50 millionNumber of uninsured Americans

66%Percentage of Americans who are overweight

65 millionNumber of Americans with chronic heart problems

20 million:Number of Americans with diabetes

100,000Number of people who die in the U.S. each year from preventable treatment errors

One hourAmount of time spent on paperwork for each hour of health care delivered in the U.S.

50%Amount of U.S. health care dollars typically spent in the last six months of a patient’s lifeSources:Yong-Min Kim, University of Washington; Joseph Smith, vice president of emerging technologies atJohnson & Johnson Services Inc.; EE Times

Body area nets


that remotely monitored former car-

diac patients participating in an ex-

ercise program. The program,

developed in conjunction with Nokia,

helped reduce the number of pa-

tients readmitted to hospitals from

the typical 28 percent to 8 percent.

Such efforts are fueling interest in

a rising tide of networked medical

devices and services. “I’m in the

thick of it,” said serial entrepreneur

Mir Imran, who in the mid-1980s de-

veloped one of the first implantable

cardiac defibrillators. “I’m thinking

about clinical problems and optimiz-

ing solutions for them, and leverag-

ing electronics heavily—whether for

drug delivery or new kinds of im-

plants, or putting sensors where they

have never been, for example in a

hip or knee replacement.”

In one project, Imran is working

with Texas Instruments to equip

cardiac stents with an RFID tag, a

microelectromechanical system

(MEMS) flow sensor and a tiny radio

to report on the flow of blood

through the passage. The goal is an

early warning system for the nearly

7 percent of stents that become

blocked over time.

Business hurdles

It’s easy to think of ways to extend

today’s wealth of consumer and

computer technologies to medical

applications. What’s harder is mak-

ing such concepts reliable enough

to earn the trust of the doctors who

would use them, the regulators who

RRThe body electric

Julien Penders, a program manager forbody area networktechnologies at IMEC(Leuven, Belgium),offers a primer onBANs and wearabledevices.

Click image to launch video

Body area nets

9 E E T i m e s |The diagnosis for medical electronics | D e c e m b e r 7 ,

would approve them and the insurers

who would pay for them.

Jonathan Collins, principal analyst

at ABI Research, predicts the use of

wearable consumer fitness devices

will grow rapidly over the next few

years as the devices adopt standards

like Bluetooth. By contrast, devices

for professional clinical use in hospi-

tals and homes will take longer to

adopt proprietary technologies

geared for their special needs. But “if

a couple of [medical electronics] ven-

dors solidify around a particular wire-

less spec, it won’t need to be a

[standard on the scale of] Bluetooth,”

Collins noted.

Analyst Stephan Ohr, who co-

authored a recent Gartner report on

telemedicine, noted that “today, a

nurse comes to your home, takes

your blood pressure and transmits

the reading to a remote doctor using

EEG

Hearing

ECG

Blood pressure

Toxins

Implants

WLAN

DNAprotein

Glucose

Positioning

Vision

POTS

Cellular

Network

Source: IMEC

Body Area Network for health & comfort monitoring

RRHeart and home

Philips describes howa variety of home sensors could workwith cell phones andTVs to allow remotemonitoring of patients’cardiac conditions.


Body area nets


an Internet connection, but more-

automated patient monitoring using

wireless is still 10 years out. The

biggest reason is that doctors don’t

trust [the new devices]—they really

don’t know what to do with the

data—and insurance companies

won’t pay for them.”

Indeed, the biggest challenge may

be getting someone to pay for home

care systems and services. By the

end of 2008, as many as 600,000

of the estimated 2.5 million im-

planted devices in use were linked to

home systems that transmitted data

automatically to clinics for remote

monitoring. But none of the compa-

nies providing those remote services

is being adequately compensated

for them, said John LaLonde, vice

president of R&D for Boston Scien-

tific’s pacemaker group, which has

150,000 implant users on its re-

mote monitoring service.

Some companies sell the remote

services bundled into the cost of the

implants, LaLonde said; others

lease the home devices and sell the

services outright, and a few have se-

cured reimbursement from insur-

ance providers. Despite the many

experiments, “the business models

in place today just do not get it

done,” LaLonde said. “I contend we

are in a race to the bottom, in

which investment drives up expec-

tations and more investment with-

out capturing value.”

RRNot just a Band-Aid

Bandages one daycould integrate active componentsthat stimulate

the skin tospeed healing, thenlet you know whenthey are ready to beremoved.Click image to launch video

Body area nets


There are technical issues, too. For

example, making sure that digital

health records can be read by any

system in a way that’s both secure

and bandwidth-stingy is “a monumen-

tal task involving many disciplines,

and it’s going to take 10 years to re-

solve,” said entrepreneur Imran.

As for hardware, today’s monitor-

ing devices often require conductive

gels to make good contact with the

skin, but few users will fuss with the

gels. So researchers are working on

a class of dry sensors that could be

worn in clothing, reliably detecting

microvolt-level biosignals while filter-

ing out the noise that comes from

brushing against skin and cloth.

“That’s the big problem, and so far

researchers are just scratching the

surface of it,” said Lindsay Brown, a

body area networking specialist at

IMEC (Leuven, Belgium).

Engineers at Analog Devices Inc.

are combining capacitive converters

RRDialysis untethered

By 2014, startup Nanodialysis (Eindhoven,Netherlands) hopes to field a wearable system for patientswith kidney failure,eliminating regulartrips to the hospital.

Global shipment forecasts for wireless body sensors:2009 vs. 2014Units (millions)

Segment 2009 2014 CAGR(’09–’14)

Sports and fitness 10.42 180.55 76.91%

In-home health management 0.35 59.41 179.31%

Hospital/clinic-based 0.88 180.48 189.95%monitors

Total 11.65 420.44 104.87%Source: ABI research


Body area nets


and a ring of electrodes in a design

that could enable better sensors as

well as touch-sensitive surfaces. ADI

is also working on ways to inject a

signal into the body to measure im-

pedance, for gauging fat content or

even for modeling the dynamics of

the skin, said Paul Errico, a strategic

marketing manager with ADI’s con-

sumer health segment.

Another issue is which wireless

technologies BANs should ride.

A low-energy Bluetooth variant de-

signed to work on button-cell devices

will be ratified in December. Compa-

nies including CSR, Nordic Semi-

conductor and Texas Instruments

are testing chips for it. An IEEE

802.15.6 standard for BANs, mean-

while, is in an early stage of defini-

tion. The FCC could rule before the

end of the year on a request from GE

Healthcare to allow a Wi-Fi variant for

BANs in the 2,360- to 2,400-MHz

band. ZigBee is yet another player

with its own health care profile.

The Continua Health Alliance, an

ad hoc industry group promoting

home care systems and services,

has blessed both Bluetooth and

ZigBee to date.

Implants are already using the Med-

ical Implant Communications Service

(MICS) band, a 402- to 405-MHz snip-

pet of spectrum approved in the mid-

1990s for communications with

external programmers and gateways.

The FCC approved 1-MHz sidebands

for MICS in March that developers

such as Saurin Shah of Medtronic will

support in next-generation chip sets

for various uses, including one-way

links between external devices.

“The jury is still out on [which

wireless approach will be] the win-

ner,” said Karthik Vasanth, product

line manager for the medical busi-

ness unit at Texas Instruments.

Multiple wireless links will proba-

bly coexist in tomorrow’s BANs,

and all of them will likely have to be

tooled or retooled to meet medical

RRWatch your step

Sensors that clip on to shoes couldmonitor the gait ofpeople who have difficulty walking,helping to preventdebilitating falls.


Body area nets

13 E E T i m e s |The diagnosis for medical electronics

applications’ unique requirements.

At EMBC, a Shenzhen, China, re-

search institute showed a modified

802.15.4 media access controller

using simplified protocols to en-

hance sensor node battery life. And

Qualcomm showed a compressed

sensing algorithm that reduces the

amount of data acquired and sent

on a BAN using any radio. Thus far,

the company has applied it to blood

pressure and heart rate sensors. p

RRNight patrol

A wireless monitorworn at home cancheck for sleep apneawith as much accuracyas the more-complexand more-expensivesystems now used onlyin clinics.Click image to launch video

Now that implants are a well-

established therapy for a

handful of heart conditions,

medical electronics compa-

nies are working on a host of

new devices and uses for

them. Many of the efforts are

focused on the brain.

A growing body of research

suggests that well-targeted

electrical stimulation of

nerves can generate positive

results across a broad range

of conditions, from addiction

to epilepsy, Parkinson’s

disease and depression. “I

think we are on the verge of

this tipping point,” said

Christopher Chavez, who

heads a neuromodulation

company acquired in 2005 by

St. Jude Medical. That group

will see its business in neural

Tapping into the brainNeural stimulators open new directions for implants beyond the heart

RRVideos

Tim Denison, a senior engineeringmanager at Medtronic in Minneapolis,shows a prototype for an implant thatlistens to brain waves and stimulatesneurons to test for a variety of ailments.See the full story at:www.eetimes.com/showArticle.jhtml;?articleID=219500873"

Mir Imran gives a tour of his design for the first implanted cardiac defibril-lator, approved by the FDA in 1985and now used by thousands. Now a serial entrepreneur, Imran is helping to establish a foundry for implants.

Body area nets


implants rise from $24 mil-

lion in 2000 to an estimated

$320 million this year,

Chavez said. Industrywide,

neural implants represent

about a $2 billion business

today, growing at double-digit

rates to about $3.9 billion in

2014, he estimated.

The U.S. Food and Drug

Administration has approved

eight uses for neural stimula-

tors thus far. “We believe

each one is less than 10 per-

cent penetrated in its target

application, and 10 new uses

are still waiting to be ap-

proved,” Chavez said.

The shift comes at a good

time for implant makers,

which are expecting the

declining number of smokers

and rising use of stents to

lessen need for heart im-

plants. By contrast, more than

a third of global health issues

are neurological in nature, a

percentage that is expected to

expand as people live longer.

Pacemaker giant Medtronic

already has devices for ail-

ments like Parkinson’s and

“has a pipeline [of neural im-

plants in development for]

OCD [obsessive-compulsive

disorder, depression, epilepsy,

migraine, fecal incontinence,

some kinds of pain and de-

generative diseases,” said

Richard Kuntz, chief science

officer at Medtronic.

Earlier this year, Medtronic

said it had begun animal tri-

als of a closed-loop system

to listen and respond to brain

waves automatically.

Neural stimulators have

been shown to be effective in

tests, though much of the un-

derlying brain science remains

a mystery. For example, de-

pressed patients who did not

respond to shock therapy can

Neural stimulators are

effective in tests, but

much of the underlying

science is a mystery

Body area nets


be shown smiling in videos when

stimulated by a neural implant.

“It’s a little eerie,” said Kuntz.

“We really don’t know how it works,

because we are talking about

some of the most complicated

physiology of the body.”

Jonathan Sackner-Bernstein, an

associate center director at the

FDA, took a contrarian position in

one of several forums on deep

brain stimulation at an IEEE bio-

engineering conference in Septem-

ber. “You still have to have brain

surgery [to have an implant in-

stalled], and I am not sure many

people would want to have a scar

across their skull,” he said, calling

instead for more radical innova-

tions in genetic therapies.

Indeed, the long-term future be-

longs to biological treatments,

many researchers believe. For ex-

ample, “we need to think different

and make a cell a genetically con-

trolled, programmable pacemaker,

with tissues taught to beat on their

own,” said Joseph Smith, vice pres-

ident of emerging technologies at

Johnson & Johnson Services Inc.

(New Brunswick, N.J.).

But a more immediate task for

companies such as Medtronic lies

in shrinking the size of today’s

10-cc cardiac implants, eliminating

the electronic leads that are the

cause of most failures.

“We believe it is possible to get

this device down to 1 cc in size

without a lead, so the device itself

is in the heart,” said Rebecca

Bergman, a vice president of new

therapies at Medtronic. “We hope

[to have such prototypes] in

animals to define those issues

The futurebelongs to

genetictherapies,

someresearchers

argue

Body area nets


in the near future.”

Others see further directions

for implants.

“The next big revolution will be

implantable, closed-loop drug

delivery systems,” said Mir Imran,

who developed one of the first

implantable cardiac defibrillators.

“There are therapeutic proteins

and peptides available, but they

have to be delivered directly into

the brain because the stomach

chews them up.”

Such devices will eliminate side

effects when drugs are delivered to

the entire body. Closed-loop sys-

tems that can sense the need for a

drug and deliver a proper dosage

will be key to breakthroughs such

as an artificial pancreas for dia-

betes, Imran said.

Imran is working on as many as

five different implant concepts

today. He also acquired Modulus

(San Jose), an implant maker, to

bolster its role as a foundry for

devices that he believes will be

designed by an expanding set of

sometimes small companies and

startups. Today most implants are

made by large, vertically integrated

companies, such as Medtronic and

St. Jude Medical, that control most

aspects of the design.

“If you develop an implant today,

you have to go to a dozen manufac-

turers to put it all together,” Imran

said. “You end up spending three

times as long and 10 times as

much money to get the result you

should.” — Rick Merritt

‘The nextrevolution will beclosed-loop drug deliverysystems’

About the AuthorRick Merritt is editor at large of EE Times.


Telehealth


Information technology is already

used today to exchange health-

related information, but proponents

of the nascent telehealth concept

see an opportunity to do far more.

They envision a world in which elderly

patients and others with chronic health

problems use connected medical devices

to transmit their vital signs seam-

lessly to the health care profes-

sionals monitoring their status.

Such technology, they argue, would

improve the quality of care while

requiring fewer face-to-face doctor

visits, thereby increasing the effi-

ciency of health care delivery and

By Dylan McGrath

Industry alliance tacklestechnical, policy challenges

containing its cost.

Before that vision can be realized

on a grand scale, however, there are

technical, regulatory and cultural

hurdles to clear, including getting

health care professionals to accept

a sea change in how they conduct

business.

According to Rick Cnossen, direc-

tor of personal health enabling for

Intel’s Digital Health Group, an

immediate obstacle to widespread

adoption of telehealth solutions is

the lack of open, standards-based

architectures.

Cnossen, who is also president

and chairman of the Continua

Health Alliance, believes telehealth


Welcome to the foundry

Mir Imran, developer of one of the first implantable defibrillators, opened the doorsof his Silicon Valley company Modulus toshow how implants are made.

Small hybrids

Imran describes the unique (hybrid, denseand flexible) printed-circuit boards used in implants.

Ties that bond

Wire bonding is one of the methods used todeliver dense boards for implants.

Click images to launch video

The making of an implantAlthough the market for internal medical devices is expanding rapidly, the process for making implants

still relies heavily on painstaking manual labor

Telehealth

Telehealth


will not achieve its potential unless

devices are based on nonproprietary

protocols and are interoperable.

“We’ve seen this [interoperability

scenario] play out time and time

again,” said Cnossen. He pointed to

the standardization effort around

the Universal Serial Bus, which dis-

placed a plethora of proprietary in-

terfaces and revolutionized the way

computers communicate with pe-

ripheral devices.

The Continua Health Alliance is

a nonprofit industry coalition dedi-

cated to establishing a system of

interoperable, connected personal

health products. The organization,

established in 2006, now has more

than 200 member companies, span-

ning the gamut from tech heavy-

weights like IBM, Intel and Samsung

Electronics to powerful health insur-

ance firms such as Aetna Inc. and

Kaiser Permanente Inc.

Continua includes technical work-

ing groups that evaluate existing

Some assembly required

Technicians attach a battery and leadwires to each implant by hand.

In the can

The pc board is then folded and insertedinto a titanium container.


Telehealth


standards and work with standards

bodies such as the IEEE and ISO to

bridge gaps on the road to interop-

erable telehealth solutions. Con-

tinua’s policy working groups lobby

governments with an eye toward

influencing legislation.

Taking a page from the playbook

of the Wi-Fi Alliance, Continua has

also established a rigorous test

and certification program to ensure

that products bearing the Continua

logo are fully interoperable.

In February, Continua announced

it had completed the first version

of its design guidelines, developed

for device manufacturers that in-

tend to put their products through

the Continua certification process.

Since then, a total of eight products

have achieved certification.

Cnossen said he expects the

pace of certifications to pick up a

bit “now that we’ve got the ball

rolling.” The alliance is currently

working on version two of its

guidelines.

Continua’s initial thrust has heav-

ily focused on the technical as-

pects of creating interoperability

between devices, Cnossen said,

but lately there has been a shift

toward more focus on the organiza-

tion’s policy activities.

In the United States, that effort

consists primarily of pushing for

more reimbursement for telehealth

services from Medicare and Medic-

aid. Similar lobbying efforts are

under way in other regions, notably

Laser weldingLaser welding

In one of the few automated processes inthe final assembly stage, a laser welderseals the titanium can.

A plastic hatA plastic hat

A plastic header is fitted onto the can,forming a seal that also shields the leadwires that attach to the body.


Telehealth


Europe and Japan, Cnossen said.

Telehealth is taking off, Cnossen

said, but it would grow more quickly

if government programs reimbursed

providers for more services. “Gov-

ernments can be a little slow to

change,” he said. “They like to see a

lot of data.”

But with the debate currently

raging in Washington over U.S.

health care reform, and with a new

political party in power in Japan for

the first time in decades, this is a

time when Continua’s policy efforts

could have an impact, according

to Cnossen.

“In the U.S., we have a great op-

portunity over the next six months

that could be very positive for tele-

health legislation,” he said.

Another hurdle that telehealth

must clear, however, is getting doc-

tors to buy in. With demands on their

time rising for training and other ac-

tivities, physicians are wary of how

much effort might be required to

accumulate and monitor the poten-

tially voluminous data generated by

connected healthcare devices.

Software that manages the flow of

information and provides high-level

analysis is therefore required,

Cnossen said.

Regulatory bodies that approve

medical equipment for disease

monitoring, such as the U.S. Food

and Drug Administration are also

cautious, he said.

Continua has had preliminary dis-

cussions with the FDA about the

technology, Cnossen said. “They

know this is happening. They want

to work with the industry.” p

About the AuthorDylan McGrath is West Coast online

editor at EE Times.


H e a r t C y c l e


Amix of hardware and software builtinto everyday items such as cloth-ing and bedding could let cardiacpatients manage their health athome under the European Union’s

HeartCycle project. The four-year collabora-tive research effort is part of a wider pushto find innovative ways to deliver healthcare more effectively—and at lower cost—as Europe’s population grays.

HeartCycle aims to create a closed-loopfeedback system to help cardiac patientsmonitor their conditions without numerousvisits to their physicians. The systemwould report automatically to clinicians sothat if changes needed to be made in thetreatment protocol or in the patient’slifestyle, that information could be con-veyed over a computer network.

While face-to-face consultations are

European project helps manage broken hearts at homeBy Peter Clarke

H e a r t C y c l e


more personal, the monitoring en-abled by systems such as Heart-Cycle could alert patients and clini-cians quickly to small changes in apatient’s condition that might nototherwise be spotted until they be-came serious problems. Such sys-tems would complement face-to-face visits, though ideally the lat-ter would be required less often—and would less often take placeunder dire circumstances.

The HeartCycle project launchedon March 1, 2008, and has a budgetof 22 million euros (about $33 mil-lion), with the EU providing about 14million euros (about $21 million).The work is led by Philips Research(Aachen, Germany) and involves 17other academic and industry groups,including Clothing Plus Oy (Kankaan-paa, Finland), Koninklijke PhilipsElectronics NV (Amsterdam, Nether-lands) and Medtronics Iberica SA

“At home”/Patientplatform

(e.g. MyHeart)

Telemedicineplatform

(e.g. MOTIVA)

Value is createdby closing the loop!

Medicalprofessionals

“At home”healthcare

Patient

Importantdecision point!

Therapy, feedback

Measurements, detection, prediction

Anal

ysis

, dec

isio

ns

The HeartCycle closed-loop management approach comprises two loops.

H e a r t C y c l e


(Madrid, Spain).Developing “the next generation of

telemonitoring systems requires amultidisciplinary approach” that in-volves more than just bridging exist-ing islands of automation andnetworking, said HeartCycle projectcoordinator Harald Reiter, who isbased at Philips Research. “Defi-nitely, the project is based on inno-vation,” Reiter said. “If you just tryto use the existing technology, it isnot enough.”

To that end, the project targets the“domestication” of a number of sen-sor types and equipment. Some ofthe technology is in use now in hos-pitals but is being customized forhome use; other work involves novelsensors.

One technology is a bio-impe-dence monitor (BIM), used to meas-ure the presence of fluid in thetissues. BIM systems can be used

Bio-impedence monitor.

Matsense sensorfoil for the Smartbedsystem.

H e a r t C y c l e


to predict decompensation, or theinability of the heart to maintain ad-equate circulation.

Frequent home bio-impedencemeasurement can open up the pre-diction window for decompensationfrom only one or two days (via sim-ple blood-pressure measurement) totwo weeks, according to Heartcycledocumentation. “This allows treatingthe patient at home, and the hospi-tal is avoided,” said Reiter.

The challenge is to remake bulkyhospital equipment so that patientscan manage the gear in a home set-ting. Toward that end, electronic tex-tile developer Clothing Plus isworking on a measurement vest thatwould let patients easily positionelectrodes in the correct place fortesting and might have to be wornfor only 10 minutes a day.

Another sensor within the program

is the MatSense foil, a bed-sizedpressure sensor on which the pa-tient sleeps. Composed of an arrayof capacitive sensors, it can provideboth ballistocardiogram and move-ment signals.

Specific algorithms are beingdeveloped to calculate heartbeatintervals, respiration cycle andmovement. The technology can beused to monitor sleep quality,as a change in sleep patterns could

A vest withtextileelectrodes is one element of the in-homebio-impedancemonitor.

The goal is a daily measurement procedurethat takes only 15 minutes. Use of the vest ensures that electrodes are positioned thesame way on the body each time the test is run. The measurement is started via an interfacing PDA and runs automatically.

H e a r t C y c l e


presage the need for an in-personexam or a change in medication.

The flow of data and intelligenceacross networks and around thesystem is a key aspect of the Heart-Cycle project. For example, auto-mated systems are needed tomonitor the data, extract useful in-formation and alert professionals atappropriate times.

“There are not enough nurses tobe looking at the data all the time,”said Reiter. “This is our main focus.

“While the networks for communi-cation will be ZigBee, Bluetooth,USB and so on, the algorithms toalert the nurses [must be devel-oped]; this is our major work.”

Thus far, the EU project has under-taken extensive consultation to develop the usage cases and the requirements for equipment andsoftware. Preparatory work has alsobegun for a program of clinical trials.All of the equipment must be CE certified for medical device use, andthat requires planning.

A longer-term goal is to includedata from implanted devices suchas pacemakers, although that workis still in the conceptual stage,Reiter said.

Clinical trials of HeartCycle tech-nology are due to start in March2011 and could take six months toone year to complete.

Successful completion “wouldmark the end of the project, but before that we will have pretrials totest and justify certain elements,including sensors and electronics,”said Reiter. p

The Smartbed, based on the MatSense foil, captures a person’s vital signs—including heartrate, breathing rate and sleep quality—during thenight in an unobtrusive way, without the need toglue electrodes to the skin.

The Clothing Plus-designed vestshould need to be worn for only a few minutes a day.

About the AuthorPeter Clarke is European news director for EE Times.


D i g i t a l i m a g i n g


Digital medical imaging is an en-abler for the anticipated adop-tion of electronic medicalrecords by health care providersindustrywide, replacing analog

films—which must be carried by hand fromone health care provider to the next—withdigital bits that are acquired, processed,seamlessly streamed to multiple locationsvia wired and wireless transmission, andarchived electronically for readyretrieval.

For it all to work as envisioned,

standards had to be established. The Medical Imaging & Technology Alliance,a division of the National Electrical Manu-facturers Association, is the collectivevoice of medical imaging equipment devel-opers and manufacturers. One of thegroup’s goals is expanded global accept-ance of the Digital Imaging and Communi-cation in Medicine standard. DICOM allowsdigital imaging technologies to interact

Medical imaging makeoverBy Nicolas Mokhoff

Films carried by hand are giving wayto bits seamlessly streamed

D i g i t a l i m a g i n g


seamlessly, so imaging results canbe shared among all the parties re-sponsible for a patient’s care, withan eye toward effecting the bestcourse of treatment.

Radiology began as a medical sub-specialty in the first decade of the1900s, after the discovery of X-rays.For the first 50 years of radiology,the primary examination involvedcreating an image by focusing X-raysthrough the body part of interestand directly onto a single piece of film inside a special cassette. Digital imaging techniques emergedin the 1970s with the first clinicaluse and acceptance of the com-puted tomography (CT) scanner.

In the three contributed articlesthat follow, authors from Analog De-vices, Samplify and Texas Instru-ments touch upon the main issuesthat make digital medical imagessuch powerful diagnostic tools.

Analog Devices’ Scott Pavlik de-tails what he calls the most cutting-edge technology for heart imaging inthe emergency room: CT scannerswith data acquisition systems thatcan enable stop-action imaging of abeating heart in one scan. Theequipment produces a completeimage in just one rotation aroundthe body, completing the scan soquickly that the heart does not moveappreciably during the procedure. Inthis way, the scan does not need tobe synchronized with the period be-tween heartbeats.

Samplify’s Allan Evans and Al Wegener observe that the sharing ofmedical imaging data among healthcare providers requires portabilitynot only of the reconstructed imagesbut also of the raw data used to re-construct the images. The challengein archiving such data in the contextof electronic medical records is its

sheer volume. Samplify’s answer is asolution whose signal compressionratios provide reductions in data ac-quisition rates from 2:1 up to 3:1.Allowing the raw data to be readilyrepurposed avoids the need to repeatcostly medical imaging procedures.

Texas Instruments’ Suribhotla(Raja) Rajasekhar addresses thetrends and challenges affecting the electronics for various imagingmodalities, including digital X-ray,ultrasound, CT scan and MRI. Digitalimaging in the 21st century, Ra-jasekhar notes, promises superiordiagnostic capability, image archiv-ing and on-demand image retrievalanytime, anywhere. p

About the AuthorNicolas Mokhoff is research editor of EE Times.


S i g n a l a c q u i s i t i o n


The most cutting-edge technologyfor heart imaging in the emer-gency room is a computed to-mography (CT) scanner that canprovide a high-quality image of a

patient’s heart with one scan and very littleprep time. Two factors are key to achievingthis: The CT scanner can do the entireimage in one rotational scan around thebody, and the scanner is fast enough sothat the heart does not move appreciably

during the procedure; therefore, the proce-dure does not need to be synchronizedwith the period between heartbeats.

If this can be achieved, the patient doesnot need to go through the extensive prepof having an ECG (electrocardiogram) at-tached and monitored to pinpoint the exacttime between beats when the heart is still.The resultant time savings enables a quickdiagnosis and saves costs.

To get a complete, accurate image in one

Data acquisition systems allow stop-action cardiac imaging in one scanBy Scott Pavlik



Data Acquisition Systems (ADCs)� 1,000 AFE signal chains per slice

Detector array

vs.

vs.

Linear pixeldetector array(1 pixel by Y pixels)

Grid area pixeldetector array(X pixel by Y pixels)

Single slice Multi slice

CrystalScintillatorsconvert X-rays to light,followed by photo diodesthat generate currentproportional to light andX-ray intensity, which ismeasured by Current-to-digitalconverters

diode. The photodiode current (I) isconverted to voltage (V) through alow noise I-V amplifier/integrator.The I-V channels are then multiplexedthrough a 24-bit, 128-channel A/Dconverter, and the digital outputs arefed to the signal processor to pro-vide the decoded CT image.

Analog Devices Inc.’s ADAS112824-bit, 128-channel A/D converterpacks this capability into a 10 x

Those specs lead to a system thatneeds 256,000 channels of fast,accurate data acquisition. Eachchannel includes a crystal scintilla-tor that converts X-ray energy intolight, which is detected by a photo-

revolution, a 256-slice scan must bedone, for a sufficient horizontal reso-lution of about 0.5 mm. To achievesufficient radial resolution, about1,000 scanning channels are used.



10-mm mini-BGA using 4.5mW/channel. The total powerfor the data acquisition sectionis then just over 1 kW for a256-slice system, enabling abetter than 50 percent powerreduction over typical equip-ment of comparable complexity.Overall power is further re-duced by the improved speed.Applications include dynamicimaging, to observe the heartor other organs in motion.

Finding blood flow anomaliesThe blood delivery system hastwo major components: theheart and the vascular systemof arteries, veins and capillaries.Doppler ultrasound imaging systemscan be used to determine blood flowrates as well as identify blockages,restrictions or leaks.

Doppler ultrasound sends a contin-

uous wave (CW) signal, usually asine wave, or pulse into the bloodstream which is reflected back fromthe blood cells. As in all Doppler sys-tems, the change in frequency result-ing from the wave’s interaction with

the moving particles can be usedto calculate the particle, or flow,velocity. With a finely focused ul-trasound beam, the velocity canbe plotted across the width ofthe blood vessel to determineuniformity of blood flow. If the ve-locity plot is the classic parabola,then there is smooth, laminarflow; a distorted pattern wouldreveal obstructions or structuralproblems in the vessel.

The use of a pulse ultrasoundwaveform provides additional in-formation by measuring transittime to provide a map of a givenvessel. While the technique canbe valuable for diagnosing and

locating vascular disease, it will alsobecome increasingly useful for diag-nosing traumatic injury and stroke.The pulse ultrasound image can beused to find stoppage or leakage inthe flow pattern.

UltrasonicTransducer

Frequency and/orphase of reflected

sound changes withspeed/direction

of blood flow

A CW signal or pulse is sent into the bloodstream and reflected back from the cells.



Ultrasound signal acquisition is at-tenuated by the square-of-the-dis-tance law, both in transmission andin reflection, leading to the need tohandle a dynamic signal range ap-proaching 160 dB. One developmentthat provided ultrasound systemswith the accuracy and discriminationneeded to provide clear images wasa combined low-noise amplifier andI&Q demodulator or phase shifterdeveloped by Analog Devices. Theconcepts have been expanded toyield the AD9276/77.

Ultrasound designers can now de-velop smaller systems for use inpoint-of-care applications. p

Doppler ultrasound enables fast point-of-care diagnosis of vascular anomalies that can lead to disease

Stroke•Progressive blockage of brain arteries (ischemic)•Rupture or aneurysm (hemorrhagic)

Carotid artery blockage•Progressive blockage of arteries to brain•Most common cause of paralyzing strokes

Heart disease•No. 1 cause of death in the U.S.

Abdominal aortic aneurysm (AAA)•Tenth leading cause of death in men 50+•700,000 undiagnosed in U.S.

Peripheral artery disease•Poor circulation in the legs•Can cause serious disability•Can lead to amputation•20% of people 70+ have PAD

About the AuthorScott Pavlik is worldwide strategicmarketing manager for AnalogDevices’ Healthcare Group. He holdsa BSEE from Clarkson University.


D a t a C o m p r e s s i o n


At no time has digital imaging beenmore important to medical imag-ing applications than in today’s cli-mate of health care reform.Indeed, the current U.S. economic

stimulus program calls for $19 billion infunding to facilitate health care providers’adoption of electronic medical records.

Such a move will drive up demand not

only for archiving of final images createdby medical imaging technologies, but alsofor storage of the raw data from whichthose images are formed. In an environ-ment where medical records are trans-ferrable from one health care providerto another, portability of the raw data en-ables that data to be repurposed for dif-ferent end uses and thereby avoids the

Managing digital imaging’smountains of dataBy Allan Evans and Al Wegener



ogist may retrospectively recon-struct new volumetric images usingdifferent back-projection algorithms to highlight certain anatomical

data from a single CT scan can bereused to form volumetric imagesthat can support multiple end uses.

For example, when the X-ray datafrom the scan is first captured, gen-erally an image is reconstructed tosupport an initial diagnosis by theattending radiologist. If a secondopinion is required, a second radiol-

need to repeat costly medical imag-ing procedures.

Among the imaging modalities,computed tomography may stand tobenefit the most from raw-dataportability to support multiple enduses. First, CT scans are expensive,running in excess of $1,000 perscan, second only to MRI. Second,

Among the imaging modalities, CT scans could benefit the most

from raw-data portability

Click either image for correct answer



features. If the diagnosis requiressurgical intervention, the surgeonmay utilize the CT data to plan a laparoscopic or endoscopic proce-dure. Finally, the CT data might beused a fourth time, as registrationof the anatomical features to guide the surgeon during the surgi-cal procedure.

CT image data captured in digitalform becomes portable acrosshealth care providers, enabling thepatient to seek the provider who canprovide the greatest probability of asuccessful outcome, without havingto pay each provider to repeat thecostly scans.

As we have just illustrated, porta-

bility of medical imaging data amonghealth care providers requires notjust portability of the reconstructedimages, but also portability of the

CT image data captured in digital form becomes portableacross health care providers

Click either image for correct answer



X-ray or sonogram data used to re-construct the images. The challengefor archiving this data in the contextof electronic medical records is itssheer volume.

A modern CT machine captures X-ray data at a rate of 1 Gbyte/second, resulting in 30 Gbytes for a30-second scan. Ultrasound cangenerate similar volumes of data,with each frame composed of hun-dreds of scan lines that themselvesare composed of thousands of sam-ples. At 30 frames per second, ultra-sound data acquisition can exceed20 Mbytes/s and result in data setson the order of 10 Gbytes for scanslasting a few minutes.

The size of these data sets can bea limitation to their portability if theycannot be easily provided on a stor-age medium to the patient, or if thetime to transmit them from onehealth care provider to another

greatly exceeds the time to repeatthe scan.

Signal compression represents apromising solution to the problem ofportability of medical imaging data.In a paper presented at the SPIEMedical Imaging Conference in Feb-ruary, Samplify Systems, GE Health-care and Stanford Universitydemonstrated the efficacy of signalcompression, in both lossless andnear-lossless modes, to achievecompression ratios that providecompelling reductions in data acqui-sition rates, from 2:1 up to 3:11. Aset of images accompanying this ar-ticle (page 34) presents one of theimage pairs used in the survey thatwas highlighted in the SPIE paper;

the authors challenge the readers topick which image was formed fromraw data and which one from com-pressed data.

Samplify has performed similarstudies with ultrasound OEMs, usingimages formed from pre- and post-beamformed data at compressionratios of up to 3:1. Another image

Signal compression holdspromise for enabling portability

of medical imaging data



set accompanying this article (page35) repeats the image comparison,but with ultrasound images. Again,the authors challenge the readersto find any differences—and thistime we have even made it easierby showing wire phantoms.

By providing a 75 percent reduc-tion in the storage or transmissionrequirements for medical imagingdata, signal compression makes thedata portable by enabling the datasets to be provided to the patient onlow-cost dual-layer DVDs or by reduc-ing the transmission time for send-ing the data sets from one providerto another.

Signal compression provides the

promise of reducing health carecosts by increasing the portabilityof medical imaging data and there-by reducing the need for duplicatescans.

Moreover, signal compression canprovide this benefit while actuallydecreasing the cost of medical imaging equipment, by reducing dataacquisition times.

In CT machines, faster data ac-quisition rates result in lower costsfor mechanical rotary joints or sliprings as well as for the RAID drivesused to buffer the data prior toimage reconstruction.

Similarly, signal compression in ultrasound machines reduces I/Obottlenecks between the analogfront end and the digital signal processing elements.

Signal compression can be em-

bedded in the data acquisition silicon without added cost relative tothat of existing A/D converters builton legacy processes. p

References1Wegener A., Chandra N., Ling Y., Senzig R.,Herfkens R. 2009. Real-time compression of rawcomputed tomography data: Technology, architec-ture and benefits. Proceedings of the SPIE MedicalImaging Conference, Vol. 7258 (March).http://tiny.cc/6Nemt

About the AuthorsAllan Evans is vice president of marketingat Samplify Systems Inc.Al Wegener is Samplify founder and CTO.

email: [email protected]; [email protected]

M i x e d - s i g n a l a p p s


Digital imaging in the 21st cen-tury comes with the promise ofsuperior diagnostic capability,image archiving and on-demandretrieval anytime, anywhere.

Since the advent of digital techniques formedical imaging in the early 1970s, digitalimaging has grown significantly in impor-tance. Recent advances in design capabili-ties for mixed-signal semiconductors offerunprecedented electronics packing densi-

ties in imaging systems, leading to tremen-dous advancements in medical imaging. Atthe same time, embedded processorshave dramatically increased the capabili-ties for medical image processing and real-time image display for faster and moreaccurate diagnosis.

The convergence of these technolo-gies, coupled with emerging standards forelectronic health records, is providing theimpetus for better patient care.

Mixed-signal, embedded open doors for digital imagingBy Suribhotla (Raja) Rajasekhar



Digital X-ray systemsConventional X-ray sys-tems use a film/screensetup to detect the X-rays transmittedthrough the body. Bycontrast, the digital X-ray’s signal chain inthe detector systemcomprises a photode-tector array that con-verts radiation to anelectric charge. Chargeintegrator circuits andanalog-to-digital con-verter circuits then digi-tize the inputs. A blockdiagram of a typical digital X-ray system isshown at left.

Digital X-ray systemperformance is closelyrelated to the noise performance of the

X-ray: Medical/Dental solutionSource: Texas Instruments



integrator and ADC blocks. The level ofelectronic integration required to supporta large number of signal channels in asystem for higher image quality at lowpower consumption sets the bar for inno-vation. The high-performance analog com-ponents that make up the detectorsystem, as well as the embedded proces-sors that perform advanced image pro-cessing, offer advantages overconventional X-ray systems, supporting awide dynamic range that potentially re-sults in better image contrast and lowerlevels of X-ray exposure, while generatingdigital images for electronic storage andtransmission.

Ultrasound systemsThe receive channel signal chain of an ul-trasound system includes a low-noise am-plifier (LNA), variable-gain amplifier,

low-pass filter and high-speed, high-res-olution ADC. These elements are fol-lowed by digital beamforming, imageand Doppler processing, and additionalsignal processing software.

The noise and bandwidth characteris-

Bringing ultrasoundto the patient: Victimsof war (l.) and naturaldisaster (below) canbe quickly assessedon site.Photos courtesy of SonoSite



tics of the signal chain componentsdefine the system’s overall perform-ance ceiling. There is a thrust to inte-grate more high-performancechannels in smaller areas, while dis-sipating lower system power. Typicalhandheld ultrasound systems wouldhave about 16 to 32 channels,whereas high-end systems mighthave well over 128 channels for en-hanced image quality.

To reduce the printed-circuit boardfootprint for the full array of thesechannels, the focus is to integrateas many channels as possible in theanalog front-end IC. Power consump-tion in the overall system is anotherimportant performance metric forhandheld systems.

Another area of innovation is to in-tegrate the receive-side electronicsdirectly into the probe. This couldhelp reduce the distance from thelow-voltage analog signal sources in

This child’s grainy “firstbaby photo” wasrecorded in 2003 . . .

. . . This toddler’s in uterocloseup was captured justthree years later.



the probe to the LNAs and, hence,could reduce signal losses. Integra-tion could further increase the num-ber of probe elements, therebyenhancing 3-D imaging.

Apart from the analog signal chainconsiderations, the high-performanceand low-power embedded processorscan perform beamforming and imageprocessing faster and more efficientlythan was previously attainable in aportable-form-factor device.

MRIA full-body MRI system could have acoil matrix with as many as 76 ele-ments or channels. Additionally, thelow-voltage analog inputs traveldown long coax cables from the ex-tremity coil to the analog signalchain preamp. Two key challengesstand out for the MRI receive signalchain: how to achieve high signal-to-noise-ratio (of about 84 dB or 14

bits minimum) and how to realizevery high total dynamic range (ofabout 150 dB/Hz minimum) for theoverall system. Achieving high SNRdemands a high-performance pre-amp with an ultralow noise figure.The high-dynamic range requirementis realized via such schemes as dy-namic gain adjustment or analoginput compression.

In general, the number of coils em-ployed in an MRI system is expectedto increase, yielding better imagecoverage and faster image scans.That increase may require further op-timization in the signal communica-tions between the coils andpreamps, and with the main systemwhen using high-speed digital or opti-cal links. Additionally, high levels ofintegration could lead to changes insystem partitioning, perhaps by mov-ing the electronics closer to thecoils. As a result, nonmagnetic IC

packaging and compliance with morestringent power dissipation and areaconstraints may be required. A suc-cessful implementation could pro-vide advantages such as reducinginput signal attenuation to providehigher-quality medical images.

Digital imaging is one of the mostactive areas of technological devel-opment in medicine, driven by ad-vancements in analog/mixed-signalcapabilities and embedded process-ing. The available technologiesboost the performance of imagingsystems and ultimately enhance thequality of medical care. p

About the AuthorSuribhotla (Raja) Rajasekhar is a designengineer at Texas Instruments. He holdsan MS from Johns Hopkins University,a BTech from the Indian Institute of Technology in Chennai and an MBA from

the University of Texas at Austin.



Personal blood glucose monitorshave evolved to become afford-able and highly portable electronicdevices. The BGMs in use todayare little electrochemistry labs.

The Ascensia Breeze, made by Bayer AG,is one of several major brands of BGMs.All rely on the same basic techniques formeasurement: A small sample of bloodfrom a skin prick is collected and suppliedinto a chemical reaction by way of a teststrip or sample collector, which interfacesto system electronics for electrochemicalanalysis.

Ascensia brings a level of convenience tomonitoring by use of a disk containing thechemistry needed for measurements. Theindividual test strips of many other metersare replaced in the Breeze by an insertedcartridge disk system that holds 10 sam-ple strips.

Whereas traditional meters require theuser to manually enter the coding datastamped on the sample strip box to adjust

By David Carey

Automated blood test is a BreezeBuilt-in code for sample analysis

takes some of the sting out of a still-invasive process

for variable reactivity, with the As-censia Breeze the coding informa-tion is built in. By eliminating thehuman dimension of data entry cod-ing, the smart disk ensures that


G l u c o s e m e t e r

error-free calibration data is auto-matically known. As with consumerelectronics of all stripes, ease ofuse applies: To perform a test, theuser simply opens the meter, inserts

a 10-test disk and cycles the pullbar at the Breeze’s lower end to ex-pose a test strip. Once a blood sam-ple is applied, a reading is ready tobe taken.

Custom ASIC#36000025HAnalog ASIC/Coulometer

NEC#uPD78F0338GC8-bit microcontroller with memory and peripherals

Catalyst Semi#CAT25C32V1Serial E2PROMmemory—4 kbytes



I didn’t buy a disk, so I can’tspeak to the particulars inside thatconsumable element of the design.But the presence of a polymer-thick-film flex circuit in the Breeze sug-gests an electrical readout ofcalibration information from thedisk, perhaps stored in a small, in-expensive serial memory chip oreven through something as simpleas a laser-trimmed resistor. The con-necting flex circuit—located on theflip door used to house the disk—makes contact by spring-loaded pin

fingers. Signals are then routed tothe door hinge, where a zebra stripconnector routes the connections tothe circuit board assembly in the en-closure portion of the Breeze’sclamshell design. (Back to that pointin a moment.)

A fairly complex mechanical appa-ratus in the main clamshell housingcontains the indexing apparatusboth to present a test strip from thedisk and to index to new test stripsites when the test is complete. Arotating ratchet mechanism spins

the disk a notch afterevery use by translatingthe reciprocating motionused to expose the stripinto a rotary motion simultaneously.

The Breeze’s singlerigid circuit board is home to threechips, all of which are powered by asingle lithium coin cell battery.

Starting with the business end ofthe design, a custom ASIC(3600025H) is responsible for theelectronics side of the electrochem-istry used in the glucose monitor.Given the proprietary nature of thechip, details are sketchy; but to afirst order, the part must be support-ing the coulometry used as the

The presence of apolymer-thick-filmflex circuit suggestselectrical readout ofcalibration data



basic glucose measurement tech-nique. Constant current (ampero-static) or constant voltage (potentio-static) coulometry essentially countsthe number of electrons needed tocomplete the reaction of the teststrip chemistry and the blood sam-ple. Glucose levels are presumed tocorrespond to differing coulometricreadings acquired in the mostly ana-log ASIC, and the disk’s calibrationdata is also connected to the chipby way of the previously mentionedflex circuit connector.

Once the ASIC has completed its

electrochemical test measurementand is calibrated for coded reactivevariations, the output is sent to anNEC µPD78F0338GC microcon-troller. No A/D converter from theASIC is obvious at the die level, so itseems plausible that signal conver-sion takes place in the NEC part’sinternal A/D, where it can be manip-ulated to a displayed glucose levelon the Breeze’s segment LCD.

The LCD is driven directly by themicrocontroller, which also handlesthe button input. Similarly, the NECdevice is used to interface to theproduct’s headphone-style connec-tor, which implements a data port toallow the unit’s 100-reading memoryto be downloaded for analysis on a

host PC. To hold reading data for re-view or download, the unit employs4-kbyte E2PROM from Catalyst.

Consumables are about $6 to $9per disk. The Breeze meter likelyhas manufacturing costs in the $10to $15 range-—a fraction of its $70to $80 price.

Noninvasive BGM solutions are onthe drawing board, but none hasreached commercial consumer costtargets with the accuracy of directmeasurement.

Until that is achieved, the coulom-etry and supporting electronics ofthe invasive BGM have been en-hanced with automated sample pro-cessing to take some of the stingout of a tough task. p

The meter likely costs between$10 and $15 to manufacture—a fraction of its $70 to $80 price


It’s not quite at the level of HarryKleiner’s 1966 movie classic “Fantas-tic Voyage,” but Given Imaging Ltd.’sPillCam is an intriguing step forward.Able to provide physicians with an in-

ternal view of a patient’s digestive path,the PillCam is an ingestible diagnostic toolthat provides images of the small intestinewithout invasive surgery or probes.

The traditional endoscopic process relieson a tethered apparatus. Given Imaging(Yoqneam, Israel) used ultra-efficientCMOS design (to keep power consumptionto a minimum) and dense optoelectronic

packaging to devise an endoscopy ap-proach that goes down a little easier: The patient swallows the camera pill, thecapsule progresses via natural processesthrough the digestive tract, and image datais relayed to an external receiver belt foreventual download and diagnostic reviewby a doctor.

The PillCam is about the size of amegavitamin, at 26.4 mm (almost exactly

By David Carey

Camera in a pill surveys GI tractThe body’s motility provides the

PillCam locomotion; advancedelectronics make the rest possible

1 inch) long and 11.3 mm (0.45inch) wide—not teeny, but ingestibleby most patients. It weighs a mere 4 grams and contains all image-capture, illumination, activation,


C a m e r a i n a p i l l

transmission and control circuitswithin a two-piece biocompatibleplastic capsule. An opaque lowershell surrounds most of the elec-tronics, while a clear dome is fused

to the lower shell to provide a view-through window for the camera lenslocated inside.

The clear dome also allows a set of six miniature white LEDs

#GILO_P (custom)256 x 256-pixel color CMOS

image sensor

Photobit (Now Micron)#399

1.55-V/55-mA-hr silveroxide watch battery

(2) Eveready

#20481 (custom)Transmitter/controller

GIT (foundry unknown) 27-MHz crystalTEW

Plastic lens

Reed switch

Lens/Illumination layer Imager layer Switch layer Transmitter layerSide 1

Transmitter layerSide 2

White LED

Coil antenna



surrounding the lens to illuminatethe gastrointestinal (GI) tract as thepill moves through it.

Playing doctorNow it’s our turn to have a look in-side the pill.

After an incision at the seam ofthe two case halves (I’m alreadyfeeling a little medical here), thecapsule can be popped open andthe stack of electronic componentsremoved. Five distinct strata formthe capsule internals, with variousforms of interconnect between thelayers of circuits.

Starting at the top level-—that is,the level closest to the transparentportion of the capsule-—we find thelens/illumination layer. An annularprinted-circuit board surrounds thesingle plastic molded lens, support-ing the LEDs and their associated

current-limit resistors. Below the lens level is the imager

layer, home to a 256 x 256-pixelCMOS color image sensor. Markingson the chip indicate it is a customdevice from Photobit, a company ac-quired by Micron Technology in 2001and spun out as Aptina in 2008.

Combined with the plasticlens, the camera offers aclaimed 140° viewing angleand 0.1-mm feature resolu-tion within the GI tract beingimaged.

Power managementBehind the imager layer is apair of Eveready No. 399 sil-ver oxide watch batteries,wired in series to create thesole 3-volt supply for the Pill-Cam. The two button cellsprovide 3 V at 55 mA-hr, or

165 mW-hr of total available energy. Since the device runs for up to

eight hours, a time-averaged powerdraw of approximately 20 mW is

The camera offers a 140°viewing angle and 0.1-mmfeature resolution



implied.The switch layer located behind

the batteries provides the means to preserve precious battery energybefore the PillCam is ingested bythe patient. A reed switch mountedon the switch layer circuit board isheld open by a magnet in the Pill-Cam’s shipping holster, interruptingthe battery connection. When thepackage is opened and the capsuleis removed from its holster for swal-

lowing, the reed switch closes, andpower to the PillCam begins to flow.

The final strata of the PillCam—the transmitter layer—is home tothe only other integrated circuit inthe unit: a custom ASIC developedby Given Imaging and of unmarkedfoundry origin. The chip must pro-vide system control along with radiotransmission. A 27-MHz crystal lo-cated on the reverse side of thetransmitter layer is consistent withboth functions.

The 3.2 x 3.5-mm flip-chip appli-cation-specific IC contains a smallblock of logic, a very small memoryarray and a variety of mixed-signalcircuits. Since the output from theimage sensor is presumed to bepreconverted to digital form, theradio and LED drive circuits are thelikely functions included in the ana-log portion of the ASIC.

RF emission guidelines Per FCC filings, the transmitter oper-ates at either 432.13 or 433.94MHz, with minimum-shift-keying mod-ulation. MSK has the general bene-fits of providing constant-envelopemodulation, transmitter simplicityand good spectral efficiency. A sim-ple air coil is the radiating antenna

The PillCam measures aboutan inch long—not teeny, but ingestible by most patients



element, tucked into the roundedcapsule end opposite the camera.Transmit power is held low to man-age power consumption, as the re-ceiver antennas are in proximity tothe waist-worn monitor.

Nevertheless, FCC filings indicatethe PillCam stays within emitted RFguidelines only when the pill is in-side the body. The minute or so thatit takes the pill to go from acti-vated/depackaged form to ingestionis apparently given a waiver as partof the PillCam’s regulatory approval.

Single boardThe image capture, switch andtransmitter layers are all fabricatedon a single rigid-flex printed-circuitboard. Delayering the board amongthe three islands of functionalitycreates flex circuits to interconnectthose regions.

The assembly is folded up around

the batteries, and a pair of gold-plated coil springs distributes powerfrom the imager layer to the lens/il-lumination layer through holes in thelens barrel.

The eight-hour PillCam lifetimeprovides up to 57,000 images at arate of two frames per second, withthe LEDs flashing only during imagecapture. Given the limited availableenergy, the combination of low-power CMOS imagers, spartanlogic, efficient radio design andpulsed white LEDs for illuminationis critical.

Bringing all these pieces togetherto create an ingestible camera-bot isan amazing benchmark in technicalprogress. The body’s motility pro-vides the PillCam locomotion, butadvanced electronics make the restpossible.

It certainly brings new meaning tothe phrase “internal medicine.” p


There always seems to be somemedical widget at my local Wal-green’s that gets the wheels of cu-riosity turning. This time it wasOmron’s $50 (or less) HBF-306 per-

sonal body fat meter. It’s not ordinarily thekind of device people pick up for fun; butalong with my technical curiosity about howit worked, I thought it might help me checkmy progress in keeping off the pounds. Asit turns out, the device functions on a sur-prisingly simple premise with correspond-ingly spartan—and mostly analog—electronics used for implementation.

The HBF-306 resembles a handheldgame controller, with two handles grippedby the subject during the measurementprocess and a center “pod” containingmeasurement electronics. The handlescontain two electrodes each, formed by pre-sprung metal encircling the plastic enclo-sures. Test subjects wrap their handsaround the grips, making contact with theelectrodes. AAA batteries power the device,

By David Carey

The HBF-306 functions on a simplepremise, with spartan electronics

that go heavy on the analog

Body fat meter is thinly priced

further evidence of the elegantlysimple electronics within.

With a retail price as low as $30,there’s little budget for fancy med-ical-grade monitoring. Traditionally,accurate body composition measure-ment relies on dual X-ray absorp-tiometry or hydrostatic weighing,which records the apparent weightof a subject underwater with thelungs emptied of air. Measurementsof body folds and other physicalcharacteristics are also common.The Omron unit clearly lacks X-rays,a test pool or a set of calipers, sosomething else is going on.

With a bit of poking around onOmron’s Web site and through thepatent literature, it becomes clearthat the HBF-306 relies on bioelec-trical impedance analysis. BIA meas-ures the subject’s body impedance,recorded under carefully controlledmeasurement conditions, and com-

bines the results with user input andcorrelated lab-gathered data to esti-mate body fat percentages.

The human body’s conduction hasboth a resistive and reactive compo-nent, with the resistance beingdriven by water-bearing tissue andthe capacitive reactance stemmingfrom the insulating membranesaround each cell. Lean tissues arecharacterized by a relatively low re-sistance, with fat and bone beingpoor conductors, given their low re-tention of fluids and electrolytes.Determining a precise RC model tomimic the human body has been asubject of debate, but to a firstorder, the impedance can seeminglybe modeled as a parallel RC circuit.

Measurements begin by having thesubject enter sex, height, weight andage. The device adjusts for variablesthat affect impedance and its ulti-mate correlation to body fat percent-

age. From what I could determine,Omron accumulated a database offat percentages with a large and pre-sumably varied group of test sub-jects using the traditionally accuratemeans mentioned previously. Byknowing lab-grade numbers for eachperson and measuring the imped-ance corresponding to each case,Omron developers created the data-base. The assumption is that anygiven result with the HBF-306 can beassigned a percentage of body fatcorresponding to more rigorously ac-quired lab data (once corrected ac-cording to the user-specific inputs).

The method isn’t perfect and issubject to other variables. The handcontact during measurement mustbe steady, and Omron’s patents indi-cate a narrow range of time-lapsedreadings within which impedancemust be seen, or the test will abort.The instructions also indicate that


B o d y f a t m e t e r



the user must have both arms ex-tended to 90° angles in a standingposition and with feet spreadslightly apart. These requirementsall speak to the need for a pre-dictable body geometry that doesn’t

cause electrical shunts, which mightpoison the measurement and corre-lation. Finally, because the body’simpedance varies over the course ofthe day with fluid intake and activity,Omron outlines specific times and

circumstances under which reliablereadings may be achieved. Adjust-ments for musculature and nominalsubject conditioning (“athletemode”) are also possible.

The Omron device essentially

#TS924Quad op amp

ST

#M38223M4H8-bit microcomputer with

2-kbyte mask ROM

Renesas #SN74LV4066A Quad bidirectional

analog switch

Texas Instruments

#SN74LV4052A Dual four-channel analog

multiplexer/demultiplexer

Texas Instruments

#S-93C46 Serial E2PROM memory—128 bytes

Seiko Instruments



comprises a simple impedancemeter and a little database. Be-cause complex impedance is to bemeasured, an ac signal must beused; here, Omron implements aconstant-current 500-µA, 50-kHz sig-nal applied across two of the fourelectrodes—one for the left hand,the other for the right. The two re-maining electrodes serve as thepickups to sense the impedance bymeasurement of the voltage riseand phase shift caused by the equiv-alent RC circuit of the body.

Electronics for the analog-meterfront end are limited to an STMicro-electronics TS924 quad op amp,likely used partly for the oscillator,partly for the detected voltage ampli-fier to determine resistive valuesand partly for implementation of ademodulator, which serves for phasedetection. Two Texas InstrumentsSN74LV4052 four-channel analog

mux/demux chips and a single TISN74LV4066 quad bidirectional ana-log switch create what might be ananalog signal fabric, suggestive of areversing circuit to make measure-ments in two directions. That bit is alittle unclear.

The biggest IC is a RenesasM38223M4H 8-bit microcontrollerwith 16-kbyte ROM and 512-byteRAM-—nothing new, given a die-level1986 copyright date. The microcon-troller has A/D circuit peripherals fordigitizing demodulator and amplifieroutputs, along with the digital smartsto do measurement lookup and cor-relation of body fat percentage.

The user interface of front-panelswitches and the direct-drive mono-chrome LCD are also in the line ofduty for the Renesas part. A 1-kbitSeiko Instruments serial E2PROMsupplements the controller’s on-chipmemory, perhaps storing code, corre-

lation data or measurement results.A CEM circuit board provides a

low-cost substrate on which tomount the ICs and 80-odd discreteand passive components. The boarduses cost-saving, silver-paste-filledvia holes with a sealing overprint.

All told, a few bucks for chips andsupport components and less than$10 for display and casing add up toa roughly $15 parts cost that, com-bined with clever software, offers aninexpensive way for folks to estimatetheir body composition. (I did OK onmy own test, but I didn’t knock it outof the park. See you at the gym.) p

About the AuthorDavid Carey is president of Portelli-gent (Austin, Texas), which producesteardown reports and related industryresearch on wireless, mobile and per-sonal electronics.



Portable instruments have assumeda high-profile role in personalhealth monitoring. Here we exam-ine the Omron Intelli-Sense HEM-711AC blood pressure monitor,

which accomplishes some sophisticatedmetrology for a surprisingly low price, in apackage that’s usable at home or on thego. With a retail price of around $60, theproduct clearly relies on low-cost design,but the need for accuracy also requiredsome clever engineering.

Omron Healthcare Inc., a division of thediversified Kyoto, Japan-based Omron, is

likely the top maker of blood pressuremonitors for personal use, and the group’sfocus is firmly rooted in health-monitoringproducts for both consumers and medicalprofessionals.

The HEM-711AC comes with the familiararm cuff and a base unit roughly the sizeof a small paperback. While not tinyenough to fit in a pocket, the device is cer-tainly portable, and a push of a button is

By David Carey

With clever engineering, Omron’sportable monitor turns capacitance

changes into useful data on the cheap

Track your blood pressure for $60

all it takes to make the system inflate the arm cuff to the appropri-ate pressure. Electronics then auto-matically take measurements forsystolic and diastolic pressure,along with heart rate, and displaythe data on a 2.5-inch liquid-crystal display. The unit is powered by fourAA alkaline cells or a supplied acadapter.

The HEM-711AC—along with mostother personal blood pressure mon-itors sold—uses the “oscillometric”technique for measurement. Oscil-lometric monitoring relies on thetracking of pressure oscillation pat-terns in the cuff during its stepwisedeflation. Proprietary algorithmsthen translate observed fluctua-tions into systolic and diastolicpressure values.

While there has been much debate about the technique’s useful-ness to doctors, the consensus


B l o o d p r e s s u r e m e t e r

In BriefThe Omron HEM-711AC blood pressure monitor tracks animportant health issue with reasonable accuracy and af-fordability. Rather than lean on leading-edge technology,the product uses simple transducers and clever circuit de-sign to deliver an end system for about $60 retail. TheHEM-711AC's cost is driven as much by pneumatics andmechanics as by its electronics, which amount to littlemore than a capacitive sensor, quad-logic gate and MPU.The design shows that clever engineering can hold its ownagainst brute-force technology alternatives. For those whoappreciate simple elegance, it's worth a look.

seems to be that it is good enoughfor general trend monitoring.

Internally, the HEM-711AC con-tains a motor-pump combination, anelectronically operated air pressurerelease solenoid valve, the 2.5-inchLCD, a single circuit board and airtubing to connect the pressurizedcomponents.

The rubber tube from the cuff en-ters the base unit and is pluggedinto a pressure sensor mounted di-rectly on the circuit board. The samerubber hose is connected to thepump and release valve, which han-dle the pneumatics.

The pressure sensor in this caseis a mechanical diaphragm that is



depressed in proportion to appliedpressure. The deflected “drumhead”of the diaphragm forms one of twoplates of what is effectively an air-di-electric capacitor, with a fixed platein the pressure sensor parallel tothe movable plate. Pressurechanges in the system correspondto shifts in the variable capacitor.

The clever part is turning capaci-tance changes into useful data onthe cheap. The precise details of im-plementation get a little fuzzy at thispoint, but trace-out of the circuitsuggests that the variable capacitor(pressure sensor) is used to modifythe frequency of a ring oscillatorformed from the four gates in theToshiba 74VHC02 quad NOR gate.Wiggles in pressure correspond towiggles in the ring-oscillator fre-quency. The output is connected tothe monitor’s electronic workhorse:the CK29U-3B53 a proprietary 8-bit

microcontroller from Toshiba. Exactly what happens next in the

microcontroller is also a little un-clear, but some form of frequencycounter or frequency-to-voltage con-version is presumed. The output of

either is used to drive the internalalgorithms, which determine a corre-sponding systolic or diastolic pres-sure value for display on the LCD.The Toshiba microcontroller drivesthe LCD directly. It also controls the

Capacitive pressuresensor



user buttons, pump motor and airpressure release solenoid. A SeikoInstruments E2PROM, the S-29221, holds the limited amountof boot code needed.

Detailed analysis of the productpegs the manufacturing cost-of-goods-sold at below $20, with aroughly even split between electron-ics and system mechanicals.

The simple elegance of the trans-ducer/ring oscillator solution at theheart of the HEM-711AC is critical tothe low observed COGS. By the addi-tion of simple, inexpensive electron-ics around the sensing method, animportant health-monitoring tool canbe delivered to a mass consumerbase at a nice profit. p

Toshiba#TC74VHC02FQuad 2-inputNOR gate

Toshiba#CK29U-3B538-bit microcontroller + ROM

Seiko Instruments#S-292212-kbit E2PROM

Ricoh#RH5RL38A3.8-V voltageregulator(SOT-89 package)

60 E E T i m e s |The future of medical electronics | D e c e m b e r 7 , 2 0 0 9

Few disciplines can turn the coldscience of metrology into pure artas quickly as medical diagnosticscan. Its practitioners transcendthe confines of biology, chemistry

and physics, borrowing from each disci-pline—and stretching the limits of technol-ogy—first to divine what to measure, thento make the measurements and extractthe desired information from the data.

Transformation of the raw values into valu-able metrics requires the development andimplementation of special signal-processingalgorithms. By melding what is already

By Patrick MannionInside the art of pulse oximetry

Masimo’s Radical-7 takes blood analysis out of the lab

and into the field

known with carefully thought-out as-sumptions that are based on yearsof research and experiential data,such algorithms often form the intel-lectual property heart of advanced di-agnostic equipment.

Certainly, that holds true forMasimo’s Radical-7 Signal Extrac-tion Pulse-CO Oximeter. At the cross-roads of science and art , the Radical-7 combinespatented signal-extraction algo-rithms and advanced spectrographicand signal-acquisition technology inan efficient and intuitive design thattakes blood analysis out of the laband into the field, accelerating thetime to diagnosis (and thus to treat-ment).

The Radical-7 weighs in at around$6,000 in its baseline configuration,rising to approximately $15,000 forall the bells and whistles, but thosewhose lives it has helped save


P u l s e o x i m e t r y

through its in vivo, noninvasivemethodology would consider that asteal. The system can extract an ac-curate signal even when the subjectis moving, and it is undaunted byvariations in bone density and skinpigmentation.

“It’s a no-brainer to take a vial of blood, put it in a test tube or cuvette, put that in a spectropho-tometer and get [the desired] infor-mation,” said Anand Sampath,Masimo’s executive vice presidentof engineering. “Physicists andchemists know how to do this onthe bench.” It’s another matter,Sampath said, “to do it in vivo,where the blood is actually pulsatingand you have all kinds of artifactsand tissues.”

But there are times when in vivotesting is the best, and perhaps theonly, option. In an office tower fire,for example, portable equipment for

noninvasive analysis would allowlarge numbers of people to betested on site for carbon monoxide(CO) poisoning.

“There’s no way to do it without adevice like ours,” said Sampath.“You’d literally have to take them toa hospital and draw blood, and itwould take hours [to get results].Meanwhile the damage is done.”

Now, he said, “it’s something aguy in an ambulance can do.”

Sampath pointed to the ability ofMasimo’s systems to monitor a mov-ing subject, compensating for the ar-tifacts that such movementintroduces. Invented by Masimo in1996 (and covered in U.S. PatentNos. 6,263,222, 6,770,028,6,658,276, 6,157,850, 6,002,9525,769,785 and 5,758,644, amongothers), this capability appliesacross all situations but is particu-larly helpful in the case of prema-


ture babies, whose blood oxygen lev-els need constant monitoring butwho are unlikely to remain still forthe procedure. Until the advent of effective in vivo testing, such infantswere sometimes given too much oxygen, causing retinopathy of pre-maturity (ROP); severe cases oftenresulted in blindness, according toSampath.

The company’s previous-genera-tion Radical pulse oximeter, basedon Masimo SET (signal extractiontechnology) two-LED technology,could extract basic information such as arterial oxygen saturation,pulse rate and perfusion (pulsestrength). The Radical-7 uses thecompany’s Rainbow SET seven-LEDtechnology to enable the extractionof more advanced parameters,such as carboxyhemoglobin (to testfor carbon monoxide poisoning),methemoglobin (to check for overdoses of painkillers such as




benzocaine and for poisoning fromchemicals such as nitrates) andtotal hemoglobin, as well as oxygencontent and arterial oxygen satura-tion. It also charts the pleth wave-form (heartbeat) and provides apleth variability index.

The basic measurements and rawdata are generated using well-trod-den spectrographic principles of ab-sorption at different wavelengths, inthis case using LEDs as the lightsource. “We won’t discuss the spe-cific wavelengths,” said Sampath,“but the two-LED [Masimo SET] sys-tem has a visible LED and a near-IR[infrared] LED, whereas the Rainbow[SET] has several visible LEDs andseveral near-IR LEDs.”

While the use of LEDs in such ap-plications is not new, Masimo hasadvanced the technology with itsown design.

The real innovation, however, isthe company’s signal extractiontechnology.

At the time of its introduction, SETwas a new and fundamentally dis-tinct method of acquiring, process-ing and reporting arterial oxygensaturation and pulse rate data. Ituses adaptive filters (widely de-ployed in communications systems)to accurately establish a “noise ref-erence” in the detected physiologi-cal signal sent back from thesensor. The reference allows the di-rect calculation of arterial oxygen

saturation and pulse rate. Becauseit is not bound by a conventional“red over infrared” ratio approach,the Masimo SET system greatly miti-gates the problems of motion arti-facts, low peripheral perfusion andmost low signal-to-noise situations,allowing it to be used in low-signal,high-motion applications.

How does one derive such a refer-ence where none is present? “Thisis the fundamental problem wesolve with an algorithm called theDiscrete Saturation Transform en-gine, or DST engine,” said Sampath.

All algorithms are based on as-sumptions. The higher the numberof assumptions, the weaker the al-gorithm. The DST engine makes only



one assumption, that arterial bloodhas higher oxygenation than venousblood does.

Working from that single assump-tion, the DST engine allows theMasimo system to separate and con-sequently calculate the optical den-sity ratios that correspond to thearterial oxygen saturation and esti-mated venous oxygen saturation.Those optical densities are notknown beforehand but are required toobtain the appropriate reference sig-nals for adaptive noise cancellation.

The signal processing at the heartof Masimo SET proved so powerfulunder patient motion conditions thatit became central to a patent-in-fringement dispute between Masimoand longtime competitor Nellcor. The

issue was finally put to rest in Janu-ary 2006 when, after Masimo wonthe patent suit in both district andappellate courts, the companies ar-rived at a settlement agreement.

Winning patent battles is onething, but the proof of a good algo-rithm is in its efficacy—in this case,how accurate it is relative to estab-lished techniques.

According to Sampath, in carboxy-hemoglobin measurements, theMasimo system achieves accuracyof +/–3 percent, vs. +/–2 percentin the lab. For methemoglobin meas-urements, the window narrows to+/–1 percent, “the same as with in-vasive techniques,” he said.

For hemoglobin measurement ac-curacy, the figure for the Radical-7 is1 gram per deciliter (g/dL), vs. 0.5g/dL in the lab.

“All of these are for 1 standard de-viation, or 67 percent of the popula-

tion,” Sampath said.Given the parameters of the de-

sign, with so much dependent uponaccurate sensing of low-level signalsand their back-end processing, thedesigners of the Radical-7 had theirwork cut out for them. They had tomake wise design and componentchoices with respect to signal acqui-sition, conditioning, amplification,conversion and, ultimately, a signal-processing platform.

From theory to designRemoving the top cover with its at-tached display and keypad exposesthree boards, with the smallest, theMX-1, on top. As always, size can be deceiving: It turns out the MX-1contains almost all of the system’ssecret sauce—everything from ana-log inputs from the sensors to themain signal processing.

“These are very small physiological

The MX-1 contains almost all ofthe secret sauce, from analog inputs to signal processing



signals—very sensitive to noise andartifacts—so all the electronics,from the sensor all the way throughto the signal processing, is all fun-damentally new and proprietary,”said Sampath.

The signals being captured are10x to 100x smaller than those en-countered at the input of an RFradio system, Sampath said, empha-sizing the importance of board lay-out and good design practices inmaintaining signal integrity by ensur-ing proper signal handling.

But there’s more to it than that,he added, noting that many compa-nies deal with signals in this range.For Masimo, it has more to do with having the technology necessary to accommodate patients with varyingdegrees of skin pigmentation, bonedensity, tissue scattering and so on.“Because of our signal integrity, weare able to work with the most peo-

ple on the planet, literally, simply be-cause of the amount of attentionwe’ve given to this topic,” he said.

At the heart of the MX-1 is thesignal-processing IC: the AD90801custom ROM product from AnalogDevices Inc. Sampath acknowl-edged the device was based on aSharc-family processor from ADI but would not specify which one. An online search of SEC and otherdata, however, points to a digitalsignal processor from the ADSP-2136x line.

Masimo’s designers chose thatDSP because for their application,“the most important function wasperformance, especially floating-point performance for the precisionthat we needed,” said Sampath. Atthe time of the initial design, circa2004-2005, the part in questionwas the best choice for the tasks athand, he said.

The AD90801 is fed by anAKM5355VT low-voltage, 16-bit analog-to-digital converter and issupported by Silicon Storage Tech-nology’s SST34HF1621C Combo-Memory, which integrates 16 Mbitsof flash with 2 Mbits of SRAM.

The AKM5355VT is a delta-sigmaconverter originally intended for



audio applications, so it comes withan input gain amplifier, making itideal for the MX-1’s low-input signallevels. The analog signal input ofthe AK5355 is single-ended, elimi-nating the need for external filters.That not only saves space and costbut also improves overall signal in-tegrity by narrowing the opportuni-ties for signal loss and interference.The part is housed in a space-saving16-pin TSSOP.

Further down the signal chain, atthe connector where the signalsfrom the sensor first enter theboard, is another critical IC: ADI’sAD820, a precision, low-power FETinput op amp that amplifies the low-level signals from the sensor. Thepart can operate from a single sup-ply of 5 V to 36 V, or from dual sup-plies of +/–2.5 V to +/–18 V. Itfeatures true single-supply capabil-ity, with an input voltage range ex-

tending below the negative rail. Thatrange lets the device accommodateinput signals below ground in the sin-gle-supply mode, another prerequisitefor meeting the MX-1’s needs.

On the digital-to-analog conver-sion side, the main IC is ADI’sDAC8043AF, a high-accuracy 12-bitmultiplying DAC featuring serialinput, double buffering and 5-V operation at less than 10 µA with a 1-microsecond settling time.

Control, housekeeping and otherprocessing functions are performedby Texas Instruments’ ultralow-powerMSP430F169 16-bit microcontroller.

The back of the MX-1 is mainly de-voted to driving the LEDs, in thiscase using a bank of eightAD5449YRU 12-bit, dual-channel

current-output DACs from ADI. Also on the back are three

SN74LVC573A octal transparent D-type latches from TI that featurethree-state outputs designed specifi-cally for driving highly capacitive orrelatively low-impedance loads.

The output of the DSP is fed via a10-pin connector on the back of theMX-1 to the main instrument board,which performs the core operationalfunctions of a patient monitor, suchas computation and display ofmeasurement results, as well asuser-interface and other controlfunctions. Another Sharc showsup here: the ADSP-21062L, a high-performance signal processor origi-nally intended for communications,graphics and imaging applications.

Having a high-end DSP on a boardthat’s essentially geared for low-endcontrol and minor processing func-tions seems like overkill. Sampath

‘Because of our signal integrity,we are able to work with the mostpeople on the planet, literally’



acknowledged that the choice heredidn’t have to be a Sharc and couldhave been any embedded-typeprocessor, but he added that sinceMasimo was already using the ADItools, “using it [the 21062L] on themain board was more an artifact ofconvenience.”

Newer Masimo systems do, infact, use a generic IC with an ARMcore, but Sampath would not identifythe device or its maker.

The DSP is supported by 16 Mbitsof single-die MirrorBit flash fromSpansion (S29AL016D90TF102)and 4 Mbits of low-power SRAMfrom Alliance (AS6C4008).

Next to those devices sits theSC28L92A1B, a 3.3/5.0-V dual uni-versal asynchronous receiver/trans-

mitter (DUART) from NXP.Other logic on the top side of the

board includes an Epson RTC724234-bit real-time clock module withbuilt-in crystal, an NXP 7555CD gen-eral-purpose CMOS timer, a FairchildSemiconductor LCX245 low-voltagebidirectional transceiver and a TIHC163 4-bit synchronous binarycounter. The HC163 features an in-ternal carry look-ahead for high-speed counting.

The back of the control board in-cludes four TI HC595 8-bit shift reg-isters with three-state outputregisters; two HC165 8-bit parallel-load shift registers; one HC138three-line to eight-line decoder/mul-tiplexer; one TI HC163 4-bit binarycounter; and, from Fairchild, an

HC32 quad two-input OR gate andan HC541 octal line driver. NXP con-tributes its HEF4013BT dual D-typeflip-flop.

The third board on the Radical-7’shandset is the main display board,driven by an EpsonS1D13A04F00A1 LCD controller.

Intelligent docking stationThe clean design of the docking sta-tion that charges the Radical-7handset seems straightforward atfirst blush, but Sampath pointed totwo key features.

The first is the “flipping” screen,which switches to horizontal modewhen the handset is attached to thedocking station. This was initially ac-complished using a gravity-detect



switch, but newer versions incorpo-rate an accelerometer.

The second feature lets the Radi-cal-7 connect to third-party monitorsand regenerate the physiological sig-nal. “Existing operating rooms al-ready have patient-monitor devices;all they need is our technology,” saidSampath. Using a feature calledSatShare, the station can displaythe captured measurements onthird-party monitors, which in turncan be integrated into a hospital’sinformation management system.This also allows patients’ physiologi-cal measurements to go directly intotheir electronic medical records.

To do this, the docking stationrelies on yet another Sharc pro-cessor. This time it’s the lower-costADSP-21065L, a general-purpose,programmable 32-bit DSP with fixed-or floating-point capability. The21065L is supported by 8 Mbits

of boot-sector flash from AMIC Tech-nology (A29L008AUV) and 2 Mbitsof SRAM from Alliance Memory(AS6C2008).

FDA approvalsAs a medical system, the Radical-7had to square with IEC as well asFDA regulations. “When we intro-duced this in 2005, we had to passall the leakage current, EMC and iso-lation standards as part of IEC [certi-fication],” said Sampath. Masimoaccomplished that by “sticking tofundamentals” with respect to lay-out, ensuring that clocks had ade-quate ground plane protection andthat trace paths for high-power sig-nals were appropriately managed.

Despite Masimo’s system-designprowess, it’s worth noting that thecompany commonly licenses its MX-1 technology to other medicalsystem manufacturers. p

About the AuthorPatrick Mannion is editorial directorof TechOnline.


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