Shoulder Imaging Optimizing Bone CT: General Bones S C H There are always 3 things technologists Radiographs can do to optimize Bone CT AP &
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Transcript Shoulder Imaging Optimizing Bone CT: General Bones S C H There are always 3 things technologists Radiographs can do to optimize Bone CT AP &
Shoulder Imaging
Optimizing Bone CT: General
Bones S C H There are always 3 things technologists
Radiographs
can do to optimize Bone CT
AP & Obl
Ax & WP 1) Optimize Patient Positioning
Try to center the bone
Y & ACJ
Get other bones/metal out of scanning FOV
AC Injury
GH Dislocate 2) Optimize Scanning Technique
Thin slices, 50% overlap
Anterior
Use small focal spot, small display FOV
Posterior
CT
3) Optimize Reformats
Final Case
2D: Angle slices relative to ANATOMY
Conclusion
3D: Rotate & Segment
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© 2014 Ken L Schreibman, PhD/MD
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Shoulder Imaging
Optimizing Bone CT: Shoulder
Bones S C H 1) Optimize Patient Positioning
Radiographs Try to center the bone This depends on body habitus
AP & Obl Get other bones out of scanning FOV This does not
Ax & WP
Y & ACJ
Shrug
AC Injury
DOWN
GH Dislocate
contraAnterior
lateral
Posterior
Gets contralateral shoulder
Shrug UP
CT
out of scan FOV, minimizing
ipsilateral
Final Case
streak artifacts from that side
Scooch patient over CT: AP Scout
Conclusion
S,A 66yoM
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© 2014 Ken L Schreibman, PhD/MD
“Schreibman Shrug”
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Shoulder Imaging
Optimizing Bone CT: Shoulder
Bones S C H 1) Optimize Patient Positioning
Radiographs Try to center the bone This depends on body habitus
AP & Obl Get other bones out of scanning FOV This does not
Ax & WP GET METAL OUT OF SCANNING FOV!
Y & ACJ
AC Injury
GH Dislocate
Anterior
Posterior
CT
Gets metal contralateral ABER keeps metal contralateral
Final Case
shoulder out of scan FOV shoulder within the scan FOV
Conclusion CT: AP Scout
CT: AP Scout
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© 2014 Ken L Schreibman, PhD/MD
“Schreibman Shrug”
C,B 83yoF
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Shoulder Imaging
Optimizing Bone CT: General
Bones S C H 2) Optimize Scanning Technique
Radiographs
(This is what my physicist tells me..)
AP & Obl a) Use Small Focal Spot
Ax & WP
Cannot manually select small focal spot
Y & ACJ
Small focal spot comes on automatically if
AC Injury
GH Dislocate the mA<particular value, based upon the kV
Ask your Application person for your CT scanner
Anterior
Posterior Can use Automatic Exposure Control (AEC)
CT
Set the Max mA value to be less than the
Final Case
maximum allowed mA for the small focal spot
Conclusion
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Shoulder Imaging
GE CT Scanner mA Limits
Bones S C H
Radiographs
AP & Obl
Ax & WP
Y & ACJ
AC Injury
GH Dislocate
Anterior
Posterior
CT
Final Case
Conclusion
Scanner Name
Discovery CT750HD
Scan FOV
Normal mode:
Large Focal Spot
Hi Res mode:
Large Focal Spot
Normal mode:
Small Focal Spot
Hi Res mode:
Small Focal Spot
LightSpeed VCT 64,
LightSpeed 16 Pro, &
Optima CT 580
Large Focal Spot
Revolution Evo
&
Optima CT660
Large Focal Spot
LightSpeed 16, &
LightSpeed 8
Large Focal Spot
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© 2014 Ken L Schreibman, PhD/MD
Small Focal Spot
Small Focal Spot
Small Focal Spot
140 kV
120 kV
100 kV
80 kV
715
835
800
700
540
625
750
700
10 - 490 10 - 570 10 - 680 10 - 620
10 - 360 10 - 420 10 - 500 10 - 620
715
800
770
675
10 - 335 10 - 335 10 - 310 10 - 300
515
560
480
400
What kV to
use?
Adults:
At least 120
Large
Adults:
Use 140
Small child:
Use 100
10 - 170 10 - 200 10 - 240 10 - 300
380
440
420
400
10 - 170 10 - 200 10 - 240 10 - 300
Courtesy of Frank Ranallo, PhD, DABR
Physicist- UW Radiology Department
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Shoulder Imaging
Optimizing Bone CT: General
Bones S C H 2) Optimize Scanning Technique
Radiographs
(This is what my physicist tells me..)
AP & Obl b) Thin slices with 50% overlap
Ax & WP
Shoulder: Thin but not too thin (1-1.5mm)
Y & ACJ
<1mm slices may be too noisy (We use 1.25mm)
AC Injury
GH Dislocate 50% overlap yields better reformats
Adds information to the stack of axial images
Anterior
Posterior Pitch close to 0.5
CT
Reduces helical artifacts
Uses less mA, hence use small focal spot
Final Case
Conclusion
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© 2014 Ken L Schreibman, PhD/MD
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Shoulder Imaging
Optimizing Bone CT: General
Bones S C H 2) Optimize Scanning Technique
Radiographs
(This is what my physicist tells me..)
AP & Obl c) Use smallest possible display FOV to
Ax & WP
maximize resolution
Y & ACJ
Display FOV always = 512 pixels
AC Injury
GH Dislocate Display FOV smaller pixel size
Anterior
Smaller pixel size higher resolution
Posterior Just a little math…
CT
50cm display FOV / 512 pixels pixel size ≈ 1 mm
Final Case
Conclusion 25cm display FOV / 512 pixels pixel size ≈ ½mm
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© 2014 Ken L Schreibman, PhD/MD
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Shoulder Imaging
Optimizing Bone CT: Shoulder
Bones S C H 2) Optimize Scanning Technique
Radiographs
(This is what my physicist tells me..)
AP & Obl d) Use “Ultra High Resolution” (UHR)…
Ax & WP
…if available on your CT scanner
Y & ACJ
On any CT scanner, resolution degrades
AC Injury
GH Dislocate dramatically as you move away from center
This will always be an issue with shoulders
Anterior
Posterior Hi Res uses fluctuating focal spot position
Minimizes off-center sharpness degradation
CT
Particularly useful for shoulders
Final Case
Conclusion
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Shoulder Imaging
Optimizing Bone CT: Shoulder
Bones S C H 3) Optimize Reformats
Radiographs Angle slices relative to ANATOMY Not relative to table
AP &aggressive
Obl
Overly
shrugs:
Coronal slices angled
AxAngle
& WPaxial reformats
perpendicular to GHJ
Y & ACJ
Slices should not be
AC Injury
coronal to the table
GH Dislocate
Anterior
Posterior
Also, all these
CT
Sagittal slices angled
annotations
should be turned off
Final Case
parallel to GHJ
Conclusion
CT:
AP Scout
CT: Axial image through GHJ
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Shoulder Imaging
Optimizing Bone CT: Shoulder
Bones S C H 3b)Optimize 3-D Reformats
Radiographs
Series of 36 rotating images, 10° intervals
AP & Obl
Rotate around both vertical and horizontal axes
Disarticulate humerus/scapula
Ax & WP
Y & ACJ
AC Injury
GH Dislocate
Anterior
Posterior
CT
Final Case
Conclusion
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Shoulder Imaging
Case CT: 2D Reformats
AP
Bones S C H CT: Axial slice
16:05
Radiographs through GHJ
AP & Obl
Ax & WP
Y & ACJ
AC Injury
GH Dislocate
Anterior
Posterior
CT
Final Case
Conclusion
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© 2014 Ken L Schreibman, PhD/MD
CT: Coronal Reformat
(Perpendicular to GHJ)
AP: CT scout
17:39
Bankart Fx
CT: Sagittal Reformat
(Parallel to GHJ)
Coracoid
Fx
Bankart Fx
R,D 58yoM: Cleaning gutters, fell from 6ft ladder.
Fell on elbow, shoulder pain
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Shoulder Imaging
CT: 3D Reformats
Sagittal
36 Images:
Ribs
Reoriented
Removed
&
Clavicle
onlyto
Vertical
Horizontal
better
Removed
Rotation
show
Rotation
GHAxis
Joint
Axis Reformat
Bones S C H Scapula
(Parallel to GHJ)
Radiographs
Coracoid
Fx
AP & Obl
Ax & WP
Y & ACJ Bankart Fx
AC Injury
Coronal Reformat
GH Dislocate
(Perpendicular to GHJ)
Anterior
Posterior
CT
Final Case
Humerus only
Conclusion
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© 2014 Ken L Schreibman, PhD/MD
R,D 58yoM: Cleaning gutters, fell from 6ft ladder.
Fell on elbow, shoulder pain
Post ORIF
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