Learn CT Protocol – Learn how to perform the Multi-Phase Liver CT exam – some of these instructions may vary depending on the equipment you are working on.
Learning CT Protocol – Scanning the Multi-Phase Liver
Multi-Phase Liver CT Protocol images are screen shots from the Virtual CT Trainer Software causing some degrading in the image quality.
Multi-Phase Liver
Exam Prep:
- When scanning the multi-phase liver, attach the foot holder and position the patient supine and feet first in the scanner.
- NOTE: This exam can be done either feet first or headfirst but is typically done feet first.
- A multi-phase exam typically consists of a scan without contrast, followed by an arterial, venous and delayed imaging.
Multi-Phase Liver CT Protocol – 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 to center the horizontal laser light midway between the anterior and posterior aspect of the abdominal cavity.
- Turn off the positioning light
Multi-Phase Liver CT Protocol – Scanning Scout Images:
- When the patient is properly positioned on the CT table – 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.
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).
- NOTE: You may need to set up the lines or box up to four(4) times if your protocol does not auto copy your set up. Remember you will be scanning a without contrast, an arterial phase, venous phase and a delay phase.
- Scan the multiphase liver in all phases from just above the diaphragm to the top of the iliac crest.
- When the lines or box are positioned over the desired anatomy and set up for all the required phases, press the confirm button.
- Push the scan start button to scan the multiphase liver without contrast.
Old school way to set up the scanner for the arterial, venous and delay scans:
- If you have an older scanner you may have to set up each of phases separately. One way to do that is to look through the scan without contrast that you just completed (each image will have a number assigned to it) Find an image 1-2 slices above the dome of the liver and 1-2 slices below the bottom of the liver. Take the assigned number of above the liver and enter the number into the protocol as the start location. Take the bottom of the liver number you found and enter it into the protocol as the end number.
- Do the above step for all the remaining phases – arterial, venous, and delay. Placing these numbers into the protocol tells the scanner that you want to start at the first location above the liver and end at your set location below the liver (this will reduce radiation exposure to the patient and all the scans will cover the same anatomy).
Multi-Phase Liver CT Protocol – Finding your start and end numbers
- The image location number for the starting slice above the liver (in this case 10) will be manually entered as the beginning slice of the first series. Now find the number of the image that is below the bottom of the liver (in this case 170) and enter it into the protocol manually as the ending slice of the first series.
- Take the same numbers that were entered as the beginning and ending points of the first series (arterial phase) and enter them into the beginning and end of the second series (venous phase). Series # 1 will be your arterial phase and series # 2 will be your venous phase.
- With the same location numbers in the arterial and venous phases, the scanner will scan the first series (arterial phase) after the proper delay. After the arterial phase has completed the patient will move back into the scanner and wait for the second delay to complete and scan the same area as the venous phase.
Arterial
Multi-Phase Liver CT Protocol – Scanning the Patient:
- NOTE: If you have a newer scanner you should not have to do the above manual set up but it is always good to know how to do it if needed.
- Select the proper injector protocol (typically the abdomen protocol – depends on your facility and radiologist requirements – arm the injector.
- Injection rate for the abdomen/liver is 2.0 – 2.5 ml/sec. (Dependent on Your Department)
- Push the injector start button and the scan button at the same time to start the scan.
- The first scan is the arterial phase which is achieved with a contrast delay of 25 – 30 seconds post the start of the contrast injection.
- The second scan is the venous phase which is achieved with a contrast delay of 60 – 70 seconds post start of the contrast injection.
Arterial
Venous
Delayed
- Typical delay for a Multiphase liver is 5 – 8 minutes post the start of the contrast injection. (See your department protocols for proper delay times).
Delayed
Multi-Phase Liver CT Protocol – Completing the Exam:
- Look through your images to verify you have all of the anatomy that is needed and no additional imaging is needed. Remove the IV if placed by you and help the patient off of the scanner table.
- Radiation safety is important to keep in mind when doing CT and becomes even more important on multi-phase exams where you are radiating the same tissue multiple times.
- Choosing to limit the scan to the area of interest, in this case the liver will reduce the radiation exposure to tissue that is not needed for the diagnosis.
- The concept of selecting a slice location above and below the anatomical area of interest keeps the radiation exposure limited to that anatomy only. The use of this concept decreases needless radiation exposure for multi-phase exams such as liver, kidney, pancreas or adrenals.
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