Normal Uptake on WBI

Fig. 1  Whole body iodine, 10 days post administration of a therapeutic dose of I-131.

Whole body iodine (WBI) imaging was performed on a patient who was administered 3.7GBq of I-131 ten days prior for papillary carcinoma.  A total thyroidectomy was also performed as part of the treatment process earlier in the year.

For the most part the thyroid bed was unremarkable as well as the rest of the image, except for a focal uptake in the right upper quadrant.  Generally the technologists are fairly cautious at our facility, since a metastatic survey was being performed, a SPECT/CT of the area was also included in the study.

Fig. 2 Coronal section of the SPECT/CT, noting the uptake within the liver.  Most likely being gallbladder uptake of the I-131.

Fig. 3  Transaxial CT used in conjuction with the SPECT to localise the I-131 uptake.

Fig. 4  Fused transaxial SPECT/CT, confirming the uptake of the radioactive iodine is inside  the gallbladder.

Why is this interesting?  Well for one thing, this is something that we do not normally see on our WBI images.  Normally we see diffuse liver uptake in this area,  but it is not totally uncommon to visualise the gallbladder.  This is well documented in the literature and the article does discuss some possibilities of what can potentially cause this normal uptake.  Conditions such as cholecystitis, hypokinetic gallbladder function due to stones or an abnormal gallbladder morphology are just some of the potential reasons.  Most often an ultrasound is ordered to confirm or correlate if there are any underlying issues that may be involved with the gallbladder.

Bottomline, gallbladder uptake is normal.  It is not commonly seen, but from a technical perspective we would rather be "safe than sorry" by performing extra imaging such as a SPECT/CT.  Iodine is not the best isotopes to image with and with high energy collimators, it would have been tough to identify based on static images.