Imaging Gastro Intestinal Bleeding in Nuclear Medicine
- Tiffany MaGill, student nuclear medicine technologist,
- Medical College of Georgia
- Cherry Lim, NMT, Aiken Regional Hospital, Aiken, SC
- Mary Anne Owen, M.H.E., RT(N)
- Program Director, Nuclear Medicine Technology,
- Medical College of Georgia
- Deborah Gibbs, B.S., CNMT, RT(N)
- Clinical Education Coordinator, Nuclear Medicine Technology
- Medical College of Georgia
Findings (from radiologist’s reports)
The radiologist noted an area of hyperemia (what is this?) in the right upper quadrant on the flow images. On the pool images, there were several focal areas of activity noted. In frame 17, there is a focal area in the right lower quadrant and right upper quadrant. In frame 18, there is one in the left upper quadrant and right lower quadrant. In frame 19, all three areas show high activity. Frames 20 and 21 don’t definitely demonstrate any focal areas of activity. In frames 22 through 24, there is an area of focal activity in the right upper quadrant, and in the 25th, the left upper quadrant area reappears as well as the right lower quadrant area. In the last 3 frames, there is an area of intense activity in the right upper quadrant with linear configuration suggestive of transverse colon. Delayed images demonstrated focal areas in the right upper and lower quadrants. Overall impression was that this was a positive GI bleed scan. Though the pictures were confusing, they were very suggestive of right colonic focus, which could be cecum or near the hepatic flexure. The radiologist was confident that vasopressin injection should cover both those regions. The patient was immediately taken in for a visceral angiogram to more accurately locate and treat the bleeding. While a pinpoint bleed was not located, an area of hyperemia was found in a short segment of bowel near the hepatic flexure, which corresponded with the location noted on the GI bleed scan pool pictures, and could represent inflammation angiodysplasia (an abnormal growth or formation of blood vessels). An 80% stenosis of the right common femoral artery was also found during the angiogram, which can be seen somewhat on pool pictures as well.
Patient History
The patient had a recent polypectomy, and it was suspected that the bleeding could be coming from the areas where polyps were removed. The patient was admitted one day prior for rectal bleeding. On the morning of the GI bleed scan, the patients hemoglobin and hematocrit levels were both below the normal range. What is considered normal range?
Radiopharmacy
The radiopharmaceutical used for this GI bleed scan was Tc99m UltraTag RBCs. It is ideal for GI bleed imaging because is localizes via compartmentalization to the blood vessels and areas of GI bleeding (Shackett). The tagging process is accomplished when Tc99m pertechnetate diffuses across the RBC membrane and is reduced by intracellular stannous ions that are injected into the reaction vial from the first syringe in the kit. After the Tc99m pertechnetate has been reduced, it cannot diffuse back out of the cell (UltraTag Package Insert). What happens if air is not vented from the reaction vial? What tagging deficiency will occur from this occurrence? How can this phenomenon be demonstrated on the patient scan?
Normal biodistribution includes the spleen (which is the critical organ), bladder, kidneys, blood, heart, and liver. Increased uptake in the spleen can indicate blood lysis during the tagging process, which could be due to handling the blood too roughly while mixing (Debra Gibbs). A positive scan will show increased activity within the intestinal lumen.
Patient
Preparation
Patient
preparation included first drawing a 1-3mL blood sample for tagging.
In this case, the in-patient had an existing IV access, which was used to
draw the blood. The blood is then
tagged with 20-50mCi of Tc99m Pertechnetate.
Directly before the scan, the patient is positioned and then the tagged
blood is injected back into the patient, in this case using the existing IV
access. This particular patient
received a 24.5mCi dose. Flow and
pool images are then acquired, and sometimes delay images may be requested by
the radiologist.
Instrumentation
The Picker PrismXP Gamma Camera was positioned over the patient’s abdomen as close as possible to optimize image resolution. The Odyssey software protocol for a Tc99m GI Bleed scan was selected. Energy window is 20%, collimators are low energy high resolution parallel hole. Dynamically acquired planar flow images are set at 16 frames at 4 seconds each, and dynamically acquired planar pool images are set at 12 frames at 5 minutes each. If delayed images are needed, the Odyssey protocol for GI Bleed Delays is selected, and views are set at 5 minutes each. Patient position is the same as the flow and pool images.
Positioning
The
patient was positioned supine on the table and covered with a blanket since it
was very cold in the room. The
patient was instructed not to move, but was asleep through most of the scan, so
movement wasn’t a problem.
Processing
Images were not adjusted or rescaled for intensity. The images were presented with flows first, then pools, and delays on a separate film. The radiologist reading the pictures also came into the scan room to view the cine view of the flow and pool pictures to get a better idea of where the activity was traveling.
October 2001