AOT L C-Arm Introduction
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Transcript of AOT L C-Arm Introduction
7/23/2019 AOT L C-Arm Introduction
http://slidepdf.com/reader/full/aot-l-c-arm-introduction 1/26
Introduction to C-arm technology
7/23/2019 AOT L C-Arm Introduction
http://slidepdf.com/reader/full/aot-l-c-arm-introduction 2/26
Learning outcomes
• Identify all C-arm components and related equipment
• Describe configuration and constraints of C-arm
•Describe capabilities and clinical application of C-armfor pre-, intra-, and postoperative imaging
• Explain optimal positioning of patient, healthcare staff, and
equipment, while minimizing radiation exposure
7/23/2019 AOT L C-Arm Introduction
http://slidepdf.com/reader/full/aot-l-c-arm-introduction 3/26
Outline
• hat is a C-arm!
• Image acquisition" collimation
• Image intensifier
• C-arm movement
• #se of C-arm" pre-, intra-, and postoperatively
• C-arm attitude"
• $rotective clothing
• %echnical contributions to radiation dose reduction
• &ow much radiation is safe!
7/23/2019 AOT L C-Arm Introduction
http://slidepdf.com/reader/full/aot-l-c-arm-introduction 4/26
• 'emi-circular ‘C’-shaped arm
• (-ray source fixed to one end
• Image intensifier fixed to other
end
•
Display screen shows liveimage feed
What is a C-arm?
Image courtesy of 'iemens
• Image intensifier requires
reduced amount of radiation to
produce image
7/23/2019 AOT L C-Arm Introduction
http://slidepdf.com/reader/full/aot-l-c-arm-introduction 5/26
Image acquisition: collimation
• (-rays pass out of vacuum tube through a window sealed onto
vacuum envelope of x-ray tube
• 'ize of window can be controlled )collimation*
• %he smaller the window, the sharper the x-ray and the smaller the
dose of radiation
7/23/2019 AOT L C-Arm Introduction
http://slidepdf.com/reader/full/aot-l-c-arm-introduction 6/26
Image intensifier
• (-rays absorbed by image
intensifier, and thereby fluoresce
• Image intensifier allows low-
intensity x-rays to be amplified
• +agnifies intensity produced in
output image
•esult" less radiation emitted
7/23/2019 AOT L C-Arm Introduction
http://slidepdf.com/reader/full/aot-l-c-arm-introduction 7/26
C-arm movement
• +obile C-arms limited in
degree of movement
&orizontal
'wivel
otation
ertical
7/23/2019 AOT L C-Arm Introduction
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• .rbital rotation around /$ and lateral views 01234
• C-arm cannot rotate more than the horizontal position
• (-ray source on far side of body part being imaged
C-arm orbital rotation
.rbital rotation Image intensifier (-ray tube
7/23/2019 AOT L C-Arm Introduction
http://slidepdf.com/reader/full/aot-l-c-arm-introduction 9/26
Image acquisition using the C-arm
• &igh-quality images
• 5eam of x-ray travels perpendicular to limb6bone
• Image intensifier as close to patient as possible
7/23/2019 AOT L C-Arm Introduction
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Surgical application of C-arm
• 5efore surgical incision• Eg, confirm and grade degree of ligament damage
• Intraoperatively
• Eg, guide reduction and fixation
• $ostoperatively• Eg, chec7 fixation
7/23/2019 AOT L C-Arm Introduction
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Surgical C-arm application: or!flo e"ample
7/23/2019 AOT L C-Arm Introduction
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#reoperative application: traction films
5one overlap prevents planning %raction films
facilitate planning
7/23/2019 AOT L C-Arm Introduction
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'tress view of complete rupture of ulnar collateral ligament of
metacarpophalangeal 8oint of thumb )s7i thumb*
#reoperative application: screening for ligament
instability in s!i thumb
7/23/2019 AOT L C-Arm Introduction
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Intraoperative application: dynamic hip scre
$%&S'
7/23/2019 AOT L C-Arm Introduction
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Intraoperative application: distal radial pinning
Do not place wrist
directly on x-ray source
during surgery
Intraarticular distal radius fracture
treated with multiple 9-wires
7/23/2019 AOT L C-Arm Introduction
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#ostoperative application: assessment of
reduction(fi"ation
/ssessment of 'chatz7er II
tibial plateau fracture fixation
/ssessment of femoral nailing
)showing malrotation*
7/23/2019 AOT L C-Arm Introduction
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:eaded apron
/$" 1;-fold decrease in scattered radiation
:ateral" <-fold decrease in scattered radiation
%hyroid collar
3=>-fold decrease in scattered radiation
Eye protection
?=1> mm lead-equivalent goggles provide @?Aattenuation of radiographic beam
Bloves
;?;<A protection at >3> 9
)adiation: protective clothing
7/23/2019 AOT L C-Arm Introduction
http://slidepdf.com/reader/full/aot-l-c-arm-introduction 18/26
• $osition x-ray tube under and close to
patient
• +ar7 C-arm on floor and beam position
on patient
• #se integrated lasers on x-ray tube and
image intensifier for positioning
• #se pulse acquisition, avoid screening
• Collimate when possible
• irtual patient anatomy selection"
correct dose for specified body area• 'elect dose rate in line with patient size
• +aintain distance from patient
C-arm *attitude* and technical contributions to
radiation dose reduction
7/23/2019 AOT L C-Arm Introduction
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)educing e"posure to radiation
• +inimize duration of exposure
• 9eep beam time to minimum
• %rial screen after positioning patient
• ely on stored images when possible
7/23/2019 AOT L C-Arm Introduction
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• $lace x-ray tube and
image intensifier to
minimize scatter
• $atient as close to
image intensifier and
as far from x-ray tube
as possible
+asic C-arm positioning
7/23/2019 AOT L C-Arm Introduction
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,-ray tube position
'taff exposed to
increased radiation
'taff exposed to reduced radiation
7/23/2019 AOT L C-Arm Introduction
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bsorption and scatter
• or every 1??? photons
reaching patient
• 03? reach image detector
• 01??–3?? scattered
•
remainder are absorbed bypatient )radiation dose*
• 'cattered dose is higher at
x-ray tube sideimage intensifier x-ray tube
7/23/2019 AOT L C-Arm Introduction
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Dose 1>?
Dose 3??
Intensifier diameter elative patient entrance
dose m'v6h
13F )23 cm*
GH )33 cm*
;H )1; cm*
<=>H )11 cm*
Dose 1??
Dose 2??
%he smaller the image intensifier diameter,
the greater the patient entrance dose
.actors affecting patient doses
7/23/2019 AOT L C-Arm Introduction
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• or staff, the further
from the patient the
lower the dose of
scattered radiation
/"ample of dose-rate around the C-arm
7/23/2019 AOT L C-Arm Introduction
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adiation dosimeter
)monitor*
• 3? m'v per year, average over
defined periods of > years
• &ow do you 7now how much
radiation you have received!
&o much radiation is safe?
7/23/2019 AOT L C-Arm Introduction
http://slidepdf.com/reader/full/aot-l-c-arm-introduction 26/26
Summary
• +ain components of C-arm" x-ray source, image intensifier, image
display screen
• C-arm used to improve outcomes during pre-, intra, and postoperative
procedures
• %o reduce radiation exposure"
• $osition image intensifier close to patient
• 'urgeon and staff wear protective clothing and stand at safe
distance from C-arm• $ulse acquisition used as often as possible )avoid screening
unless necessary*