European Nuclear Medicine Guide
These are non-absorbable compounds which are used to show gastrointestinal transit over a period of days. There is no significant tracer uptake, and all activity is excreted in the faeces.
Colonic transit is measured as part of assessment of gastrointestinal motility disorders such as chronic constipation and irritable bowel syndrome.
Pregnancy is a relative contra-indication.
There is extensive literature on methodology and clinical studies of colonic transit in various conditions. It is used in adjunct with other manometric and radiological examinations of the gastrointestinal tract. Objective assessment of the extent of constipation and colonic transit delay is particularly important if surgery is being considered for severe colonic transit delay.
The suggested activities to administer are
No recommendations are given for paediatric nuclear medicine.
The effective dose for [67Ga] Ga-citrate is 100-120 µSv/MBq [1], [109]
The effective dose for 111In-non absorbable markers is: 300-320 µSv/MBq [1].
“Effective Dose” is a protection quantity that provides a dose value related to the probability of health detriment to an adult reference person due to stochastic effects from exposure to low doses of ionizing radiation. It should not be used to quantify the radiation risk for a single individual associated with a particular nuclear medicine examination. It is used to characterize a certain examination in comparison to alternatives, but it should be emphasized that if the actual risk to a certain patient population is to be assessed, it is mandatory to apply risk factors (per mSv) that are appropriate for the gender, the age distribution and the disease state of that population."
Various methods have been used to assess colonic transit. The simplest method is visual assessment, but this is usually accompanied by calculation of percent remaining activity in various segments of the colon at various time points, and one would expect 70% excretion by 48 h in normal transit [110]. Another method used in calculation of geometric centre to quantify the progression of the bolus activity [111].
Patients should ideally be off any medication affecting the gut motility one week before the test until the end of the test period.
Joint SNMMI-EANM guidelines are available at https://jnm.snmjournals.org/content/54/11/2004.
3-10 MBq of In-111 chloride or 3 MBq of Ga-67 citrate is administered orally either as a liquid or in enteric coated capsule designed to release the activity in small the bowel. Frequent imaging can be performed first day if assessing small bowel transit. For colonic transit measurements, anterior and posterior images are acquired daily for up to 10 days, stopped earlier when most of the activity is excreted. Geometric mean of each pair of image is used to calculate remaining activity in the entire colon and well as within regions. The percentage of excreted activity at each time point, as well as the pattern of progression is assessed. The pattern can be assessed either by looking at percent administered activity in each region, or by calculation of geometric center for each day. Geometric center is the sum of proportion of activity in each region x region number.