GI Didactic Test Out

What two energies are used in a dual isotope gastric emptying study?

Tc-99m Sulfur Colloid - 140 keV

In-111 DTPA - 172, 247 keV

What is the protocol for a gastric reflux scan?

use liquid mixture of 300 uCi of Tc-99m SC in 150 ml of orange juice and 150 ml hydrochloric acid orally, may rinse excess activity down with water

drink solution and attach binder to patient

30 second static images are taken anteriorly while patient is sitting upright

patient lays down and static images repeated, then pressure is increased stepwise in 5-20 mmHg increments to 100 mmHg

during the time that the binder is being pumped up the patient is continually imaged and the data is saved on the computer for 30 seconds per pressure stop

draw ROI around stomach and esophagus

calculate reflux

normal is

What is the protocol for an esophageal motility/transit scan?

patients should be NPO for 6-8 hours and no contrast studies before

camera is placed anteriorly

rehearse swallowing before images

patient takes a single swallow of a drink then dry swallows every 15 seconds up to 4-10 minutes

evaluate it as a dynamic 1-2 sec/frame study in the computer

testing starts with the camera over the thorax

technique involves the patient swallowing 300 uCi of Tc-99m SC in 15 mls of water (the RPx is given via straw and as a single swallow)

after the patient has swallowed they are asked to dry swallow every 15 seconds for the next 4-10 minutes

for the first 2 minutes of the study, rapid 2 second images are acquired and stored on the computer

draw either ROI around entire esophagus or over equal regions to localize problems

calculate the % of esophageal transit time

normally the transit is very rapid with no activity showing in the esophagus by 5-10 seconds after the swallow, and a >90% transit by 8 swallows

What is the best RPx for canvernous hemangioma?

Tc-99m RBC

What regions do you include in the ROI for an adult patient for a gastric reflux scan?

stomach and esophagus

When imaging for GI bleeding with SC, what are the RPx used?

5-10 mCi Tc-99m SC

20-30 mCi of RBC Ultratag (preferred)

What are the imaging times for a gastric emptying scan?

Immediate after eating, 30 min, 1 hour, 2 hour, 3 hour, 4 hour

Why is it important to have a semi-solid or a consistent meal in gastric emptying?

imaging with solids is more sensitive for abnormalities

it also affects the rate of emptying

What is the best dose and RPx for a leveen shunt?

5 mCi of Tc-99m MAA

What is the pediatric prep for a meckels scan?

fasting for 3-4 hours prior

patient should void immediately prior to the start of the test

patient should NOT be actively bleeding when doing the exam

What are the clinical indications for doing a leveen shunt?

was designed to help manage patients with chronic ascites

the Leveen shunt is a periotneovenous shunt, intended to drain the ascites into the venous system

Why a nuc med GI bleed stidy over a CT or other scans?

we can localize smaller bleeds

What are advantages to using Ultratag?

more sensitive

can detect bleeds in the liver

patient does NOT have to be actively bleeding

What are disadvantages to using Ultratag?

TcO4- can cause false positives

dealing with blood so there is problems with handling it

What are advantages to using Tc-99m SC for GI bleeds?

cannot see bleeds in the liver

patient must be actively bleeding

What are disadvantages to using Tc-99m SC for GI bleeds?

SC has a short circulating half life of 3 minutes and an equally quick extraction by the RES system (liver, spleen, bone marrow)

much higher contrast to background ratio because of rapid clearance from blood

Where are GI bleeds normally located?

RLQ (cecum area, small bowel and large bowel connect)

most can be in the colon as well

What FOV is commonly imaged on infants 24 hours after a GER study?

the lung field

What range do you want blood glucose for diabetic patients for a gastric emptying study?

ideally less than 200 mg/dL or 70-200 mg/dL

What will affect the rate of gastric emptying?

pain meds like reglan (metochlopramide), opiates or antispasmodic agents

atropine, nifedipine, progesterone, octreotide, theophylline, benzo, and phentolamine

Why would rantidine be given for a Meckels study?

it is a histamine H2 blocker that reduces the secretion of the RPx, Tc-99m Pertechnetate, into the GI lumen

by blocking the secretion, ranitidine increases accumulation and detection of the radiotracer in any ectopic gastric mucosa within the meckels diverticulum significantly improving the scans sensitivity and accuracy

Why would you do a SPECT on a Meckels study?

it is helpful if the diverticulum is small or if there is interference from the bladder