CT Online Course – Learn how to perform a Neck CTA exam – some of these instructions may vary depending on the equipment you are working on.
CT Online Course – Scanning the Neck CTA
CT Online Course – Neck CTA CT images are screen shots from the Virtual CT Trainer Software causing some degrading in the image quality.
Neck CTA
Exam Prep:
- When scanning the CTA Neck, attach the head unit and position the patient supine and head first in the scanner.
- Draw up 100 cc of IV contrast. NOTE: Most facilities will have two different IV contrasts (Example: Isovue 320 and Isovue 370). Isovue 320 would be used for standard CT such as: CT Chest or CT Abdomen/Pelvis. Isovue 370 would be used for Angio studies such as: Neck CTA, Head CTA(C.O.W), PE Study, Run Off.
- Start an IV if not already placed by the ED. Always test the IV with saline flush to verify it can handle the rapid injection. The CTA neck will require an 18g to 20g IV to be placed due to the rapid injection of contrast at 4 – 5 cc/second.
CT Online Course – Positioning the Patient:
- Position the patient on the table and center the patient at the level just above the diaphragm or just above the xiphoid process in the gantry, using the laser lights.
- Adjust the table height until the horizontal light is midway between the neck
- Turn off the positioning light
CT Online Course – 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.
Setting the ROI scan area:
- Move the ROI (Region of Interest) scout line located below the mandible (on our example) down to the arrow midway through the aortic arch. (NOTE: This line may not be located below the mandible on your scanner; it could be located anywhere on the scout image.) This line represents the location where the ROI will be placed on the patients anatomy.
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 CTA Neck place your lines or box to cover from above the skull base to midway through the aortic arch.
- When the lines or box are positioned from just above the skull base to midway though the aortic arch and your ROI scan area is properly placed, press the confirm button.
Scanning for the ROI Placement:
- Scan for the ROI. Press the scan button – This scan is the line that was placed across the aortic arch on the scout images. Generally, 1-2 slices are taken at this level to get the best image of the aortic arch for the proper placement of the ROI.
Placing the ROI in the Aortic Arch
- Place the ROI near the center of the aortic arch as seen above.
- NOTE: Be sure to place the ROI free from any plaque, as this can cause the ROI to read the density of the plaque and start the scan too early.
- Set your HU number (Hounsfield Units) at 140. (This number represents the contrast density that must be in the aortic arch before the scanner starts the scan).
- NOTE: See your facility protocol for your scanner settings and your average Hounsfield setting on a CTA neck study.
- Select the proper injector protocol and arm the injector.
- Injection rate of the CTA Neck is 4.0 – 5.0 ml/sec.
CT Online Course – Scanning the Patient:
- When you have your scan area covering the needed anatomy from above the skull base, through middle of aortic arch and you have your injector rate and you have your ROI set up properly – Push the injector start button and the scan button at the same time to start the scan.
- The ROI within the aortic arch will begin measuring the density of the contrast as it increases.
- When the contrast density reaches the set ROI of 140 HU it will automatically start the scan. (See your facility protocol for the ROI settings when scanning a CTA Neck.)
Completing the Exam:
- Look through your images to verify you have all of the needed anatomy for the contrast enhanced CTA Neck. Remove the IV if placed by you and help the patient off of the scanner table.
- Some facilities or radiologist may require a 3D work up of the carotid arteries using MIP (Maximum Intensity Projection).
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Disclaimer: This training does not replace formal hands on CT training, either on the job or academic schooling. Do not perform CT on an actual patient without additional training.
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