Learning CT Free – PE Chest (Chest CTA)

Learning CT - PE Study - Chest CTA

Learning CT Free – Learn how to perform a PE Chest (Chest CTA) exam – some of these instructions may vary depending on your facility and the equipment you are working on.

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Learning CT Free – Scanning the PE Chest (Chest CTA)

Learning CT Free – PE Chest (CTA Chest) CT images are screen shots from the Virtual CT Trainer Software causing some degrading in the image quality.

PE Chest (Chest CTA)

Exam Prep:

  • When scanning the chest for a PE (Pulmonary Embolism), attach the foot board and position the patient supine, feet first in the scanner.
  • NOTE: This exam can be done either feet first or headfirst (this example exam is done feet first). Usually head first is easier, when doing the exam head first, place the injector head at the back of scanner and hook up the contrast with the patient in the scanner from the back side. Connecting the contrast to the patient from the back side of the scanner will allow for better movement of the contrast tubing, as the patient moves in and out of the scanner.
  • The PE study will require an 18g or 20g IV placed. NOTE: Do not use hand veins for any CTA exam if at all possible. Note: Always test IV using a saline flush before connecting the contrast.
Learning CT - PE Chest (CTA Chest) Computed Tomography 1

Learning CT – Positioning the Patient:

  • Move the patient into the scanner until the positioning light is just above the shoulders in the gantry as seen in the image below. Use the same positioning location if the patient is in the gantry head first.
  • Adjust the table height to center the horizontal laser light midway between the anterior and posterior aspect of the chest cavity.
  • Turn off the positioning light.
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Learning CT – Scanning Scout Images:

  • When have the patient in the scanner – press confirm
  • 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.
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Adjusting Your Lines or Box to Cover Desired Anatomy:

  • Move the ROI (Region Of Interest) scout line located in the upper chest (on our example) down to level of the carina or the level of the bronchial bifurcation. (NOTE: This line may not be located in the upper chest on your scanner; it could be located anywhere on the scout image.) This line represents the location where the ROI will be placed. The ROI will automatically start the scanner when the contrast bolus reaches the Hounsfield Unit (HU) number that was set in the protocol.
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PE (Chest CTA) Set Up

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  • When scanning a PE Study, place your lines or box to cover from above the lung apices through the lung bases. Adrenal glands are not usually required with a PE Study.
  • When the lines or box are positioned over the desired anatomy press the confirm button.

Learning CT – Scanning and Placing the ROI:

  • Now scan for the ROI (blue line above). This scan is the line that was placed at the carina on the scout images. Scan 1-2 slices at the level of the carina to achieve the best image of the pulmonary arteries for the proper placement of the ROI (Region Of Interest).
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  • Place the ROI in the pulmonary artery 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 80. NOTE: See your facility protocol for your scanner settings and your average Hounsfield setting on a PE Study.

Learning CT – Scanning the Patient:

  • Select the proper injector protocol and arm the injector. Your facility may have injector protocols set for different exams. If you have preset protocols, select the PE protocol or Angio protocol. If there are no preset protocols then set your injection rate at 4 ml/sec.
  • Injection rate of the PE chest is 4.0 – 5.0 ml/sec.
  • When you are ready to scan the patient, push the injector start button and the scan button at the same time. This will start the contrast flowing into the patient and the scanner to scan the ROI.
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  • The ROI within the pulmonary artery is measuring as the contrast density increases. You can see in image above that the pulmonary arteries are becoming brighter with contrast enhancement.
  • When the contrast density reaches the set ROI of 80 HU it will automatically start the scan. (See your facility protocol for the ROI settings when scanning a PE Study.)
  • Some technologist like to move the ROI out of scan field and manually start the scan when they see the contrast entering the pulmonary artery. Occasionally if the patient has plaque in the pulmonary arteries the ROI can read that as the selected contrast density and start the scan too early.
  • NOTE: Also keep in mind the speed of your scanner. If you scanner is slow by the time you start the scan and it scans through the pulmonary arteries you can be later and the pulmonary arteries are not at full enhancement.
  • A perfectly timed PE study (Chest CT) the pulmonary arteries are bright white and there is no contrast in the aorta. NOTE: If you see contrast in the aorta then you are late to some degree.
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Completing the Exam:

  • Look through your images to verify you have all of the needed anatomy for the contrast enhanced PE Study. 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 pulmonary arteries using MIP (Maximum Intensity Projection).
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Source of Header Image – https://commons.wikimedia.org/wiki/File:Pulmonary_Embolism.jpg