Shoulder Imaging Optimizing Bone CT: General Bones S C H There are always 3 things technologists Radiographs can do to optimize Bone CT AP &
Download ReportTranscript 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 www.schreibman.info © 2014 Ken L Schreibman, PhD/MD 57/72 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 www.schreibman.info © 2014 Ken L Schreibman, PhD/MD “Schreibman Shrug” 58/72 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 www.schreibman.info © 2014 Ken L Schreibman, PhD/MD “Schreibman Shrug” C,B 83yoF 59/72 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 www.schreibman.info © 2014 Ken L Schreibman, PhD/MD 60/72 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 www.schreibman.info © 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 61/72 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 www.schreibman.info © 2014 Ken L Schreibman, PhD/MD 62/72 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 www.schreibman.info © 2014 Ken L Schreibman, PhD/MD 63/72 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 www.schreibman.info © 2014 Ken L Schreibman, PhD/MD 64/72 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 www.schreibman.info © 2014 Ken L Schreibman, PhD/MD 65/72 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 www.schreibman.info © 2014 Ken L Schreibman, PhD/MD 66/72 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 www.schreibman.info © 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 67/72 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 www.schreibman.info © 2014 Ken L Schreibman, PhD/MD R,D 58yoM: Cleaning gutters, fell from 6ft ladder. Fell on elbow, shoulder pain Post ORIF 68/72