CT Scan of Knee / Other Lower Ext.

CT Scan of Knee - Knee CT and Other Lower Extremity CT Header

CT Scan of Knee – Learn how to perform a Knee CT / Other Lower Extremities exams – some of these instructions may vary depending on the equipment you are working on.

CT Scan of Knee - Virtual CT Trainer Software

CT Scan of Knee – Scanning the Knee / Other Lower Extremities

CT Scan of Knee – Knee CT images are screen shots from the Virtual CT Trainer Software causing some degrading in the image quality.

Knee

Exam Prep:

  • When scanning the knee, attach the foot holder and position the patient supine and feet first in the scanner.
  • Move the patient over on the table so their affected side is a close to the center of the table as possible.
  • The knee is typically done without IV contrast unless a mass is suspected.
  • You may occasionally get a CT Knee Arthrogram order. Contrast is injected into the joint using fluoroscopy and then scanned post injection. MRI has become the gold standard for the knee but the exam is still occasionally ordered as a CT procedure.
CT Scan of Knee - Knee Computed Tomography 1

CT Scan of Knee – Positioning the Patient:

  • Move the patient into the scanner until the positioning light is two to three inches above the patella.
  • Adjust the table height until the horizontal light is midway between the anterior and posterior aspect of the knee.
  • Turn off the positioning light
CT Scan of Knee - Knee Computed Tomography 2
CT Scan of Knee - Knee Computed Tomography 3

CT Scan of Knee – Scanning Scout Images:

  • When the patient is properly positioned – Press the confirm button
  • Prep the scanner (Scan button will be solid or a flashing light – depends on manufacture)
  • Scan your AP & Lateral scout images – Some manufacturers will require the patient to move back into the gantry to scan the second scout and some will move the patient back into the scanner as it acquires the second scout.
CT Scan of Knee - Knee Computed Tomography 4

Adjusting Your Lines or Box to Cover Desired Anatomy:

  • Adjust the lines or box to cover the anatomy to be scanned (lines or box depends on CT manufacture)
  • When scanning the knee, scan from about two inches above the patella down to about two inches below the head of the fibula.
  • When the lines or box are positioned over the desired anatomy, press the confirm button.
CT Scan of Knee - Knee Computed Tomography 5

CT Scan of Knee – Scanning the Patient:

  • When you have your scan area covering the needed anatomy from about two inches above the patella down to about two inches below the head of the fibula.
CT Scan of Knee - Knee Computed Tomography 6
CT Scan of Knee - Knee Computed Tomography 7

CT Scan of Knee – Completing the Exam:

  • Look through the images for any pathology that may need additional scanning or any possible patient motion and verify that you have covered all of the desired anatomy. Help the patient off of the scanner table.

Other Lower Extremities

The other lower extremities are scanned in the same way as the knee.

Hip

  • Position the patient supine and feet first in the scanner. Have the patient bring their heels apart and rotate the feet together. Use tape to hold their feet in position.
  • When scanning the hip include the entire bony pelvis
  • Move the patient into the scanner until the positioning light is about two inches above the iliac crest.
  • Adjust the table height until the horizontal light is midway between the anterior and posterior aspect of the pelvis.
  • Turn off the positioning light and zero out the scanner.
  • Scan your scouts of the pelvis/hip and set up the scan range using the lines or box.
  • Scan the pelvis/hip about one to two to inches above the iliac crest down through the lesser trochanters.
  • NOTE: Your radiologist may require MPR’s (Sagittal and Coronal reformations) done of just the affected hip.

Femur

  • Position the patient prone supine feet first in the scanner. Have the patient bring their heels apart and rotate the feet together. Use tape to hold their feet in position.
  • Move the patient into the scanner until the positioning light is about two to three inches above the hip joint.
  • Adjust the table height until the horizontal light is midway between the anterior and posterior aspect of the femur.
  • Turn off the positioning light and zero out the scanner.
  • Scan your scouts of the femur and set up the scan range using the lines or box.
  • Scan the femur about two inches above the acetabulum/hip joint and one to two inches below the knee joint. Include the entire knee joint.

Lower Leg

  • Position the patient supine and feet first in the scanner. Rotate the foot of the affected leg straight up and down.
  • Adjust the patient so the lower leg is as close to the center of the table as possible.
  • Move the patient into the scanner until the positioning light is about two to three inches above the knee joint.
  • Adjust the table height until the horizontal light is midway between the anterior and posterior aspect of the lower leg.
  • Turn off the positioning light and zero out the scanner.
  • Scan your scouts of the lower leg and set up the scan range using the lines or box.
  • Scan the lower leg about one to two inches above the knee joint and one to two inches below the distal tibia/fibula.

Ankle

  • Position the patient supine and feet first in the scanner. Rotate the foot of the affected ankle straight up and down.
  • Adjust the patient so the ankle is as close to the center of the table as possible.
  • Move the patient into the scanner until the positioning light is about two to three inches above the ankle joint.
  • Adjust the table height until the horizontal light is midway between the anterior and posterior aspect of the ankle.
  • Turn off the positioning light and zero out the scanner.
  • Scan your scouts of the ankle and set up the scan range using the lines or box.
  • Scan the ankle about two to three inches above the ankle joint through the planter surface of the foot.
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