Online CT Training – Head CTA

Online CT Training – Learn how to perform a head CTA exam – some of these instructions may vary depending on the equipment you are working on.

Online CT Training – Scanning the Head CTA

Online CT Training – Head CTA CT images are screen shots from the Virtual CT Trainer Software causing some degrading in the image quality.

Head CTA

Exam Prep:

• When scanning the CTA Head, 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.
• This CTA Head exam will demonstrate how to manually determine the delay time so the scanner starts when the contrast bolus is at the highest peak in arterial vessels of interest.
• The CTA head can also be scanned using the same ROI principle demonstrated in the CTA Neck exam. If you are using the ROI as a contrast trigger, place the ROI in the aortic arch for the best arterial enhancement of the Circle of Willis (C.O.W – Arterial Vessels in the Brain)
• NOTE: Most facilities will require a head without contrast before the head CTA exam is performed – see the head with and without contrast on how to perform a head without contrast.

Online CT Training – Scanning Scout Images:

• Position the patient on the table and center the patient until the positioning light is at the level of the chin.
• Adjust the table height until the horizontal light is just in front of the EAM as seen below.
• Turn off the positioning light

Online CT Training – 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.

Old way to determine contrast timing – For the modern ROI way see the CTA Neck.

• Move the single scout line (blue line) located over the mandible (on our example) up to the arrow just below the base of the skull. (NOTE: This line may not be located in the mandible on your scanner; it could be located anywhere on the scout image). This line is the location where the scanner will scan in the same anatomical area multiple times to determine the contrast timing.

Adjusting Your Lines or Box to Cover Desired Anatomy:

• Adjust the lines or box to cover from the base of the skull to the vertex of the head (lines or box depends on CT manufacture).
• Angle your lines or box to the same angle as the base of the skull. NOTE: Some facilities may not require the gantry to be angled. It should be angled to reduce the exposure to the eyes but that is up to your facility and radiologist.
• When the lines or box are positioned over the desired anatomy – press the confirm button.

• After the scan parameters are confirmed, the scanner will require you to angle the gantry to match the angle that was placed on your lines or box (if done at your facility) when the lines were initially set up on your scout images.

This is the Old School Way to Determine Contrast Delay Time

Modern Way is to use an ROI in the Aortic Arch – You should know both ways

*** ROI Settings for the CTA Head are the same as the Neck CTA – Click Here ***

Online CT Training – Test Bolus:

• The CTA head will require an 18g to 20g IV to be placed due to the rapid injection of contrast at 4 – 5 cc/sec.
• Looking at row 1 in the image above you see that the beginning and end of the scan are set at 15 and the image count is 24 and the rotation time is 1 second.
• Having the beginning and end of the scan set in the same location and a rotation time of 1 second will produce 24 images (can use less images to reduce exposure to the patient) in the exact same anatomical location that are 1 second apart.
• A test bolus of contrast of about 15 cc will be started at the same time the scanner is started using the parameters set above. We can then look at the 24 images and determine which image starts to have the brightest contrast in the carotid arteries. Looking at the image below we see image number 18 is beginning to get bright.
• What this data tells us is since each image is 1 second apart, the delay should be set at about 18 seconds.

Online CT Training – Scanning the Patient:

• Now that we have determined that the delay should be 18 seconds enter that into your delay time in the scanner software see image below.
• Select the proper injector protocol, and arm your injector.
• Press the scan and injector start button at the same time. After the 18 sec delay has completed the scanner will start automatically.

Completing the Exam:

• Look through your images to verify that all of the desired anatomy is included. Remove the IV if it is not an ER patient. Help the patient off of the scanner table.
• NOTE: Most facilities will require 3D post processing of CTA exams.

Virtual CT Trainer Software – Learn More

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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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