Mod13 Fluoro 20130829 v2-Printable

7/21/2019 Mod13 Fluoro 20130829 v2-Printable

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FLUOROSCOPY & INTERVENTIONAL IMAGINGBUSHBERG CHAPTER 9

RSNA & AAPM PHYSICS CURRICULUM: MODULE 13

Rene (Dickinson) Butler, MS, DABRMedical Physicist

University of Washington Medical Center

Department of Radiology

Diagnostic Physics Section

[email protected]


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General Fluoroscopy:Modes of Operation & System Components

UW and Rene Butler, MS, DABR


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Fluoroscopy vs Projection RadiographyPARAMETER G.I. FLUOROSCOPY RADIOGRAPHY

kVps 60 - 120 50 - 130

mA values 0 - 5 (continuous) 200 - 8000 - 100 (pulsed)

X-ray Tube Focal Spot Size 0.3 - 0.6 mm 1.0 - 1.2 mm

Exposure Duration 0.5 - 15 minutes 0.01 - 0.3 seconds

Image Receptor Input Radiation Dose per image 0.01 - 0.15 mGy / image 4 - 10 mGy/image

Patient skin Dose Rates 10 - 60 mGy / min 0.2 - 10 mGy / image

Source-to- Skin Distance (SSD) 30 - 50 cm 60 - 145 cm

Source-to-Image Receptor Distance (SID) 80 - 120 cm 100 or 182 cm

Typical Spatial Resolution1 - 2.0 LP/mm (Image Int.)

3 - 10 LP/mm2.5 - 3.0 LP/mm(Flat Panel)

Image Quantum Mottle High Low

Staff Exposure to Scattered Radiation Yes No

c.f. AAPM/RSNA Web Module: Fluoroscopy systems. Section IV. Table1. UW and Rene Butler, MS, DABR


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Low(er) Exposure Rates general fluoroscopy

Continuous typically display is 30 fps or greater

Maximum dose rate = 10 R per min [87.3 mGy/min] (10 CFR Part 20) Pulsed fluoroscopy

Maximum dose rate = 10 R per min [87.3 mGy/min] (10 CFR Part 20)

High(er) Exposure Rates leads to rapid dose accumulation

High dose rate Specially activiated fluoroscopy (enable buttons orseparate pedal) Maximum dose rate = 20 R/min [175 mGy/min] with audible signal (10 CFR Part 20)

Not found on modern fluoroscopy suite systems, common on c-arms Road Mapping & Digital Subtraction Angiography (DSA): real-time

subtraction of pre- and post-contrast injection images to improve theperception of low-contrast vessels

3D rotational angiography or CT acquisitions

FluoroscopyModes of Operation



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Typical entrance exposure rates to the patient:

For thin patients/body parts: dose rate is roughly 1-2 R per min [8.7 to

17 mGy per min] for thin body partsSkin injury threshold in normal mode can be reached in

approximately 118 to 230 min

For average patient sizes: dose rate is roughly 3-5 R per min [26 to

44 mGy/minSkin injury threshold in normal mode can be reached in


For heavy patient sizes: dose rate is roughly 8-10 R per min [70 to

87.3 mGy/minSkin injury threshold in normal mode can be reached in





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If temporal resolution is not needed (e.g. guiding a catheter from the

femoral artery to aortic arch), use pulsed fluoro to reduce patient (and

personnel!) dose Also reduces motion

30 fps

15 fps

display

display

c.f. AAPM/RSNA Physics Tutorials for Residents: MS Van Lysel. Fluoroscopy: OpticalCoupling and the Video System. Radiographics. Nov 2000; 20: 1769-1786.




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Continuous vs. pulsed

Continuous 30 fps w/ 33 msec per frame @ 2 mA (0.066 mAs)

Pulsed 30 fps w/ 10 msec per frame @ 6.6 mA (0.066 mAs)** Same exposure to patient, but less motion artifact **

Pulsed 15 fps w 33 msec per frame @ 2 mA (0.033 mAs)

1 second exposureContinuous Fluoro30 fps, 33 msec

per frame

Pulsed Fluoro15 fps, 33 msec

per frame

Pulsed Fluoro

30 fps, 10 msecper frame

2 mA

6.6 mA

2 mA




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8.76 mGy per R

14.7 R per min = 128.8 mGy per min






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Digital Subtraction Angiography

(DSA): real-time subtraction of

pre- and post-contrast injectionimages to improve the

perception of low-contrast

vessels

Removal of background anatomy

and tissue

Increased image noise

Clinically used for diagnostic and

therapeutic applications of vessel

visualization throughout the entirebody

c.f. AAPM/RSNA Physics Tutorial for Residents: Digital Fluoroscopy. Radiographics. Vol 21. March 2001.

DSA cerebral arteriogram. a. Unsubtracted digital fluoro.b-d. Subtracted DSA images obtained at 3 progressivetime points during contrast injection.

FluoroscopyImaging Techniques



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Road mapping

A DSA sequence is performed and the frame w/ maximum vessel

opacification is identified The road map mask is subtracted from subsequent live fluoro images to

produce real-time subtracted fluoro images

e.g.: a wire is steered by using the road map for cues on maneuvering through

vasculature

3D rotational angiography

Philips Xper CT

c.f. AAPM/RSNA Physics Tutorial for Residents: Digital Fluoroscopy. Radiographics. Vol 21. March 2001.

FluoroscopyImaging Techniques



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What type of configuration is preferred for a urology suite?

Why?

Kidneys & bladder are closer to the image receptor, therefore, reducing

focal spot blur.

What is the negative of this room set-up?

Because the tube is above the patient, the scatter radiation is projected

back into the procedure room; whereas for GI fluoroscopy rooms, the

entrance point is below the table and lead shield curtains attenuate the

scatter radiation.


Web ModulesClinical Applications


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Under table tube

Gastrointestinal room

Remote rooms

C-arm (mobile)

Operating rooms or floor clinics

Orthopedic joint replacement, endoscopy, colonoscopy Positioning flexibility

Angiography, IR rooms

Over table tube

Urology

c.f. AAPM/RSNA Web Module: Fluoroscopy systems. Section III.A-E. UW and Rene Butler, MS, DABR

Web ModulesClinical Applications


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Fluoroscopy System ComponentsImage Intensifier (II) vs Flat-Panel Detectors (FPD)

Flat-panel

detector

c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2nd ed., p. 232. UW and Rene Butler, MS, DABR


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Image intensifier system components:

II vacuum bottle (housing); input screen (x-ray

to e-); electronic lenses; output phosphor (e-s to

visible light) Lenses and aperature

Optical coupling w/ accessory port

Viewing electronic output image video or more

commonly charged-coupled device (CCD)

detectors

c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2nd ed., p. 232, 239.

Fluoroscopy System ComponentsImage Intensifier (II) vs Flat-Panel Detectors (FPD)



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Review QuestionsFor the image intensifier shown, match the following: (answers may

be used more than once)

A. Light photons.

B. X-ray photons.

C. Microwaves.

D. Electrons.

E. Infrared photons.

I represents

II represents

III represents

IV represents

V represents

B.

B.

A.

D.

A.



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In vacuum electrons (e-s) are influence by environment

Input screen converts x-rays to e-s

1 mm aluminum window creates vacuum

Support layer

Input phosphor Cesium Iodine (CsI) crystal; Converts x-rays to light

Photocathode Layer of antimony and alkali metal; emits electrons when struck

by light; 10-20% conversion efficiency

Electronic lenses 25 kV 35 kV electric field between input and output

(electronic gain)


Fluoroscopy System ComponentsImage Intensifier (II)


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Output phosphor converts e-s to visible light

Zinc cadmium sulfide (ZnCdS)

Anode thin coating of aluminum on the vacuum side of output phosphor

Each e- interacts in the phosphor creating ~1000 light photons

Some fraction of the output light emitted by ZnCdS phosphor is reflected at the

glass window; known as veiling glare, which reduces image contrast


Fluoroscopy System ComponentsImage Intensifier (II)


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Solid-state devices

Thin, carbon fiber protects CsI phosphor and photodiode array

INDIRECT digital detector Input phosphor CsI converts x-rays to light photons

X-rays interact in CsI and create ionizations; some deposited energy is

emitted as light

Photodiode array An array of detector elements each

element is 200 microns (0.2 mm)

Absorbs light and converts energy into free

electron charge that is stored in each cellof the array

Charge stored is proportional to the incident

light, which is proportional to the # incident

(absorbed) x-rayc.f. Granfors & Albagli. Scintillator-based flat-panel x-ray imaging detectors. Journal of the Society for Information Display. June 2009.


Fluoroscopy System ComponentsFlat-Panel Detectors (FPD)


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Patient & Personnel Safety in Fluoroscopy



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Identify the technique factors and appropriate system

features to use to optimize image quality while minimizing

patient dose.

1. FPD (or II) close to patient

2. Grid in

3. Collimate!

4. Increase SSD (source-to-skin distance) to

decrease ESD (entrance skin dose)

*Note: geometry limitations withshorter personnel

AAPM/RSNA Resident Physics Curriculum: Module 13: Fluoroscopy & Interventional Imaging

Clinical Application



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Describe the geometric factors that affect operator dose

during an IR procedure.

1. Lead apron

2. Thyroid shield

3. Protective eyewear4. Radiation badge

5. Adjust dose settings when possible (pulse) to

reduce scatter

6. Distance, when possible7. Shielding, when possible





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Describe the geometric factors that affect operator dose during an IR procedure

scatter geometry for the frontal and lateral tubes in a NIR suite.

c.f. ZH Anastasian et.al. Radiation Exposure of the Anesthesiologist in theNeurointerventional Suite.Anesthesiology 2011; 114: 512-20.

General set-up for angio/IR suites:

Frontal tube: positioned w/ tubebelow patient

Scatter to personnel minimizedby lead drapes

Lateral tube: positioned so radiologistis on the same side as the FPD or II

Scatter is projected from theskin back toward the x-ray tube Higher scatter for personnel on

tube side of lateral tube. Usemoveable shields!





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General set-up for angio/IR suites:

Frontal tube: positioned w/ tubebelow patient

Scatter to personnel minimizedby lead drapes

Lateral tube: positioned so radiologistis on the same side as the FPD or II

Scatter is projected from theskin back toward the x-ray tube

Higher scatter for personnl ontube side of lateral tube. Usemoveable shields!



c.f. ZH Anastasian et.al. Radiation Exposure of the Anesthesiologist in theNeurointerventional Suite.Anesthesiology 2011; 114: 512-20. UW and Rene Butler, MS, DABR

Describe the geometric factors that affect operator dose during an IR procedure

scatter geometry for the frontal and lateral tubes in a NIR suite.


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c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2nd ed., p791.

Bushberg Table 23-18. Nuclear Regulatory Commission (NRC) Regulatory Requirements:

Maximum Permissible Dose Equivalent Limitsa

Maximum Possible Annual Dose Limit

Limits mSv rem

Occupational Limits

Total effective dose equivalent (ED) 50 5

Total dose equivalent to any individual organ

(except lens of eye)500 50

Dose equivalent to the lens of the eye 150 15

Dose equivalent to the skin or any extremity 500 50

Minor (< 18 years old) 10% of adult limit 10% of adult limit

Dose to an embryo/fetusb 5 in 9 months 0.5 in 9 months

Non-occupational (Public) Limits

Individual members of the public 1.0 per yr 0.1 per yr

Unrestricted area 0.02 in any 1 hr c 0.002 in any 1 hrc

a These limits are exclusive of natural background and any dose the individual has received for medical purposes; inclusive of internal committed doseequivalent & external effective dose equivalent (i.e., total effective dose equivalent).bApplies only to conceptus of a worker who declares her pregnancy. If the limit exceeds 4.5 mSv (450 mrem) at declaration, conceptus dose forremainder of gestation is not to exceed 0.5 mSv (50 mrem).c This means the dose to an area (irrespective of occupancy) shall not exceed 0.02 mSv (2 mrem) in any 1 hour. This is not a restriction ofinstantaneous dose rate to 0.02 mSv per hour (2 mrem per hour).

Radiation Protection and Fluoroscopy/IR



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Radiation Protection and Fluoroscopy/IR Badging OUTSIDE the lead near the neck/collar Generally, no double badging (except pregnant personnel)

Monitors total exposure, eye dose, extremity

Total annual limit for occupation radiation worker is 50 mSv/year

Total eye lens dose limit is 150 mSv (or 20 mSv; ICRP) per year

Lead aprons Lead equivalent = 0.25 mm: absorbs > 90% of scatter

Lead equivalent = 0.35 - 0.50 mm: absorbs 95 - 99% of scatter (but

heavier, so is it feasible to wear??) Use a lead thyroid shield at all times

Protective gloves of 0.5 mm lead of greater should be worn ifhands are going to be near but outside the primary beam Toprotect hands during fluoroscopy, it is recommended:

Keep hands out of and away from the x-ray field when the beam is onunless physician control of invasive devices is required for patient careduring fluoroscopy

Work on the exit-beam side of the patient whenever possible

Monitor hand dose



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Radiation Protection and Fluoroscopy/IR Leaded glasses:

Recommended that all full-time radiology interventionists andanesthesiologists should wear leaded eye protection

Measured lens entrance dose is ~2.5 +/- 2.0 Sv (radiologist);therefore ~30,000 procedures to reach current 150 mSv/year limit(based on current NRC Dose Limits)

NEW!! The ICRP recently released a statement stating lower dosethresholds for cataracts were appropriate.

The previous ICRP threshold (and current NCRP or US threshold) of 4Gy (acute exposure) and 8 Gy (chronic exposure)

Reduced to 0.5 Gy for acute and chronic exposures, based on recentstudies of patients and occupational workers.

Note, even though the USA has yet to adopt this ICRP threshold, it isanticipated change.

Because of this lower cataract threshold, the ICRP slashed theoccupational dose limit for the lens of the eye to 20 mSv in a year,averaged over a defined period of five years.

The cumulative lens dose should not exceed 50 mSv in any single

year.


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Fluoroscopy the Ten Commandments1. As patient size increases As image quality decreases, patient dose increases, personnel

dose increases

2. Exposure time Total fluoro time directly affects patient dose, but also distributing

dose over the skin (can you rotate/move tube to a different

position??)

3. Use appropriate dose and dose-rate settings Pulsed vs continuous

Standard FOV vs mag modes



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Fluoroscopy the Ten Commandments4. X-ray tube position Raise/lower patient away from x-ray tube to decrease ESD

Lateral and oblique tube positions general have higher ESDs

c.f. LK Wagner & BR Archer. Minimizing Risks from Fluoroscopic XRays: Bioeffects, Instrumentation, and Examination. 2004: 4th Edition. UW and Rene Butler, MS, DABR


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c.f. LK Wagner & BR Archer. Minimizing Risks from Fluoroscopic X Rays:Bioeffects, Instrumentation, and Examination. 2004: 4th Edition.

Fluoroscopy the Ten Commandments5. Proximity of II or FPD to Patient improves image quality anddecreases radiation dose


SID = 110 cm, varied SOD


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Fluoroscopy the Ten Commandments6. Inverse Square Law

Reduce the dose through the use of distance if and when you can.

Given: Exposure rate at 2 ft is 90 mR/hr


9 ft24 ft21 ft2

2 ft

4 ft

6 ft

Exposure Rate at 4 ft = (90 mR/hr)(2ft/4ft) = 22.5 mR/hr2

Exposure Rate at 6 ft = (90 mR/hr)(2ft/6ft) = 10 mR/hr2

1 ft

1 ft

2 ft

2 ft

3 ft

3 ft

2

2

1

12

D

DEE


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Fluoroscopy the Ten Commandments Magnification

Electronic mag generally higher doses when using mag modes (though

may not always be

Geometric mag increase distance between patient and II; typically

increases dose by the square of the magnification

Grid remove grid for thin patients or if the image contrast is not

affected by the scatter

Collimation!!

Personnel Safety use time, distance and shielding to your

advantage whenever possible; always wear lead aprons, use badges

to monitor individual dose



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Skin Injury Case Reports & Radiation Dose



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Skin Injuries Case Reports

This is a 49-yr old woman with 8-yr history of refractory supraventricular tachycardia. The patient was exposed to about

20 min of fluoroscopy with her elbow about 20-25 cm from the x-ray source. The circular port of the x-ray systemdefined the sharply demarcated border of the injury.

Fig.8b show sharply demarcated erythema above right elbow at 3 weeks after RF cardiac cath ablation.

Fig. 8c shows tissue necrosis 5 months after procedure.

Fig. 8d shows injury with humerus visible about 6.5 months after procedure.

Fig. 8e shows the surgical flap about 10 months after fluoroscopy procedure.

Fig 8bFig 8c

Fig 8dFig 8e



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ref: ICRP Publication 85, Case 1 (photographs courtesy of T. Shope).

(a) The patients back 68 weeks after multiple coronary angiography and angioplasty procedures.

(b) The injury approximately 1621 weeks after the procedures. A small, ulcerated area is present.

(c) The injury approximately 1821 months after the procedures. Tissue necrosis is evident.

(d) Close-up photograph of the lesion shown in (c).



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Radiation injury in a 60-year-old woman subsequent to

successful neurointerventional procedure for the treatment

of acute stroke. Estimated fluoroscopy time was more than

70 minutes; 43 imaging series were performed during

course of the procedure. The head was not shaved. Note

focal epilation on scalp and skin injury on neck but not on

scalp. No dose estimates were available for this case.

ref: Balter et al. Radiology. Feb 2010. Vol 254:2



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UW and Rene Dickinson, MS


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FDA Advisory In the late 1980-early 1990s, the US FDA documented

reports of at least 40 cases of radiation-induced burns to

patients from fluoroscopically guided procedures.

Fluoroscopic radiation is a carcinogen. While the risk of

cancer from fluoroscopy is usually very small, it is

essential that the radiation be properly controlled tominimize this risk to patients, to operators and to

personnel.

On September 9th, 1994, the FDA issued an advisory for

facilities that use fluoroscopy for invasive procedures.



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FDA AdvisoryRecommendations

Appropriate credentials and training for physicians

performing fluoroscopy Operators be trained and understand system operation,

and implications of radiation exposure for each mode of

operation

Physicians be educated in assessing risks and benefits

on a case-by-case basis for patients

Patients be counseled regarding the symptoms and

risks of large radiation exposures Physicians justify and limit use of high dose rate modes

of operation



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Washington State Law

WAC 246-225-020

Operators shall be adequately instructed in safe operatingprocedures and shall be able to demonstrate competence

A medical x-ray machine operator shall be licensed,certified or registered by the department as either: a licensed health care practitioner

a certified diagnostic or therapeutic RT

a registered x-ray technician

Nurses or PAs need training if asked to operate x-rayequipment

Physician is ultimately responsible for assuring that the x-rays are safely and properly applied and that appropriateradiation protection measures are followed



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Image Quality (Dose) in Fluoroscopy



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Review QuestionsA 9-in. multi-mode image intensifier (II) is switched to the 6-in.

mode. As a result, the image will be ________ , and the

automatic brightness control system (ABC) will _________ the

exposure to the II and the patient.

A. magnified, decrease

B. magnified, increase

C. minified, increase

D. magnified, not change

E. minified, decrease



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Small FS general fluoroscopy (minimize blurring)

Large FS digital spots only (tube loading)

In general, the spatial resolution of the I.I. alone is 3.5-6.0

LP/mm

Smaller structures are minified less (spread over a larger portion ofthe output phosphor), this enlargement of the displayed image

improves the limiting resolution of the imaging system

The typical spatial resolution of most current FPD image

receptors is about 2.5 3.0 LP/mm for all FOVs.


Web ModulesClinical Applications Spatial Resolution


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With regard to a flat panel, what is binning?

What is the advantage?

What is the disadvantage?

Example:

8 x 8 matrix; 10 photons per pixel

4 x 4 matrix; 160 photons per pixel

10 10 10 10 10 10 10 10

10 10 10 10 10 10 10 10

10 10 10 10 10 10 10 10

10 10 10 10 10 10 10 10

10 10 10 10 10 10 10 10

10 10 10 10 10 10 10 10

10 10 10 10 10 10 10 10

10 10 10 10 10 10 10 10

160 160

160 160

Less Quantum Mottle, the patient radiation dose can be

significantly reduced while maintaining the same image noise.

However, binning does reduce the spatial resolution of the image.

Binning is especially useful for a large FOV where there would be

too many pixels in the image

= sqrt(10) = 3.2SNR = N/ = sqrt(N) = 3.2

= sqrt(160) = 12.6

SNR = 12.6


Web ModulesClinical Applications Spatial Resolution (and noise)


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What percent of dose is a single fluoroscopy image relative

to a general radiography image?

About 1% (typically 450 to 1800 images per minute of fluoroscopy)

0.01-0.15 mGy per image (fluoro)4-10 mGy per image (radiography)


Web ModulesClinical Applications Radiation Dose


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Spatial resolution

System detector limitations FOV, matrix, DELs, video capabilities,

binning

e.g.: FPD detector element sizes

GI studies @ 2.5-3 lp per mm

Using mag, the resolution improves to @ 3.5-6 lp per mm

Television systems limit resolution to about 1-2 lp per mm for GI systems and 2-4 lp per

mm for angio systems

Focal spot size and geometry keep patient adjacent to detector!! This

reduces focal spot blur

Motion, temporal factors affecting image blur

In general, pulsed fluoro reduces motion blur improve resolution


FluoroscopyFactors Affecting Image Quality


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Contrast

Scattered x-rays (grid), veiling glare (II only)

kVp and filtration if the average (effective) energy of the x-rays is

increased, then contrast decreases

Collimation decreases scatter contribution

Radiation dose and noise increasing the mA, decreases the noise and

therefore improved contrast

Image processing smoothing algorithms and frame averaging reducesimage noise, which improves contrast; edge enhancement algorithms

increase image noise, therefore contrast degrades

Contrast media (iodine, barium, or air) enhances contrast of anatomical

structures


FluoroscopyFactors Affecting Image Quality


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Image Quality: II vs FPDIMAGE QUALITY II Systems FPD Systems

If FOV is reduced (mag mode) improved spatial resolutionImproves or stays the same (no

geometric minification for FPD)

Binning n/areduces spatial resolution,improved SNR by decreasing

mottle

Focal spot size use small FS to decrease focal spot blur, except for digital spots

Limiting resolutionII resolution (3.5-6 LP/mm), butsystem resolution is limited by

television system (1-4 LP/mm)

limited by DEL (2.5-3 LP/mm)

Dynamic range limited generally, no limitation

Contrastincreasing the kVp and/or filtration increases the average energyof the x-rays and the number of Compton scatter events, therefore

image contrast is degraded

Collimationlimits number of scattered photons and extraneous irradiation of

tissue

c.f. AAPM/RSNA Web Module: Fluoroscopy systems. Section VIII: A-F. UW and Rene Butler, MS, DABR


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Goal is to keep the # photons constant maintains SNR regardless of

patient thickness (or attenuation)

c.f. AAPM/RSNA Web Module: Fluoroscopy systems. Section X.A-7.

Programming the generator:

If generator responds byincrease kV for thicker (moreattenuating) regions, thencontrast is compromised butdose is lower

For procedures where contrastis critical (e.g. angiography) thegenerator programmed toincrease mA first. Preserves

contrast, but at the cost ofincreased dose to patient


FluoroscopyFactors affecting Radiation Dose (and Image Quality)


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ABC = automatic brightness control

higher kVps on the x-ray tube

more x-ray tube current (higher mA) opening the aperture to increase the brightness

longer x-ray pulse width

less x-ray beam filtration

or some combination of these

factors



c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2nd ed., p. 247.


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ABC systems X-ray beam kVp and filtration

Aperture smaller aperture blocks more light from output phosphor,

and decreases dose rate (the aperture is used to balance an acceptable

amount of noise w/ an acceptable level of patient dose rate) Pulse vs continuous fluoro

Conversion gain as an II ages, the amount of light produced in the

input phosphor decreases and the conversion gain decreases this

results in GREATER RADIATION DOSE because the II is less efficient

Geometry

Decreased SID dose

Image receptor close to patient

FOV selection

II system: smaller (mag) FOVs increase the

dose

FPD: may not increase x-ray output

c.f. AAPM/RSNA Web Module: Fluoroscopy systems. Section IX.B. UW and Rene Butler, MS, DABR



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Radiation Dose: II vs FPD

Radiation Dose II Systems FPD Systems

If FOV is reduced (mag mode) increases the radiation dose not necessary to increasethe dose

Increasing the SID increases the radiation dose

Adding filtration (e.g. Cu)preferentially removes low energy x-rays, therefore decreasing

the dose

Smaller aperature (large F)

increases the radiation dose(aperature balances acceptable

amount of image noise with an

acceptable level of patient dose)

n/a

Increasing kVp reduction in radiation dose (more x-rays penetrate the patient)

Reducing the pulse rate reduction in radiation dose

Decreasing conversion gainincreases the radiation dose (in

aging IIs)n/a

c.f. AAPM/RSNA Web Module: Fluoroscopy systems. Section IX: A-J. UW and Rene Butler, MS, DABR

R i Q ti


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Review QuestionsAn interventional radiologist performed 5000 fluoroscopically

guided procedures last year. His annual occupational exposure

was reported as background. What is the most likely

explanation?

A. All procedures were performed remotely from the x-ray control

room.

B. His badge was worn under a 0.5mm lead apron.

C. The radiologist never wore his radiation badge while working.

D. The departments control badges were stored in the

interventional control room.

E. There was a persistent failure at the radiation badge company.


R i Q ti


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Review QuestionsWhich one of the following scenarios will result in the highest skin

dose to the patient?

A.B.

C.

D.

Short SSD plus large SID results in higher patient dose. Use of the

grid also requires higher patient dose.



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Questions?


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