Crash course in nuclear medicine for radiology exam preparation

A quick fire review of nuclear medicine for radiology part II exam candidates.

What a whirlwind lecture that was! Apologies it went quite quickly and was quite dense – but there was a lot to get through. This was the first time I have run a lecture on nuclear medicine in such a way and was a good learning experience. I might look at teasing out and expanding some of the higher yield sections in future.

To review a few points that did not come across so clearly…

- Parathyroid adenomas will retain 99mTc-sestamibi while the remainder of the thyroid washes out. Hyperfunctioning nodules mimic adenomas, however will be very hot on the subsequent pertecnetate thyroid scan. On SPECT/CT they will be within the thyroid gland anatomically.

- Prior to radioiodine treatment or imaging, intravenous contrast should be avoided for 4 weeks. IV contrast floods the residual thyroid tissue or metastases with iodine and will reduce the uptake of radioiodine for treatment purposes.

- Rights and lefts can be trick as they are sometimes flipped. Anything acquired from the posterior detector, will be flipped to normal radiological anatomy. This includes native renal studies, posterior acquisitions in bone scans, and palmar or plantar views of the hands and feet. Ideally, if there is ambiguity it will be labelled. A pitfall is that renal transplants are imaged from the anterior detector as they are situated anteriorly in the abdomen.

- Renal tracers – we spend through this, but it is important.
o Dynamic renal scintigraphy is performed with DTPA or MAG3 to allow assessment of perfusion, renal cortical extraction and excretion.
o DTPA is a glomerular agent and MAG3 is a tubular agent. For ATN or transplant rejection, MAG3 is the tracer of choice. If you would like to concurrently measure GFR, DTPA is the tracer of choice.

- Babies scanned with HIDA/DISIDA for biliary atresia will have no demonstrated excretion of tracer into the small bowel. In a normal study, including in cases of neonatal hepatitis, there will be movement of biliary excreted tracer into the small bowel – however this may be delayed due to decreased hepatocyte function.