Marianne Muckle

The Significance of 99mTc-MAA SPECT/CT Liver Perfusion Imaging in Treatment Planning for 90Y-Microsphere Selective Internal Radiation Treatment

Selective internal radiation therapy (SIRT), a catheter-based liver-directed modality for treating primary and metastatic liver cancer, requires appropriate planning to maximize its therapeutic response and minimize its side effects. 99mTc-macroaggregated albumin (MAA) scanning should precede the therapy to detect any extrahepatic shunting to the lung or gastrointestinal tract. Our aim was to compare the ability of SPECT/CT with that of planar imaging and SPECT in the detection and localization of extrahepatic 99mTc-MAA accumulation and to evaluate the impact of SPECT/CT on SIRT treatment planning and its added value to angiography in this setting. Methods: Ninety diagnostic hepatic angiograms with 99mTc-MAA were obtained for 76 patients with different types of cancer. All images were reviewed retrospectively for extrahepatic MAA deposition in the following order: planar, non–attenuation-corrected SPECT, and SPECT/CT. Review of angiograms and follow-up of patients with abdominal shunting served as reference standards. Results: Extrahepatic accumulation was detected by planar imaging, SPECT, and SPECT/CT in 12%, 17%, and 42% of examinations, respectively. The sensitivity for detecting extrahepatic shunting with planar imaging, SPECT, and SPECT/CT was 32%, 41%, and 100%, respectively; specificity was 98%, 98%, and 93%, respectively. The respective positive predictive values were 92%, 93%, and 89%, and the respective negative predictive values were 71%, 73%, and 100%. The therapy plan was changed according to the results of planar imaging, SPECT, and SPECT/CT in 7.8%, 8.9%, and 29% of patients, respectively. Conclusion: In pre-SIRT planning, 99mTc-MAA SPECT/CT is valuable for identifying extrahepatic visceral sites at risk for postradioembolization complications.

Significance of Oral Administration of Sodium Perchlorate in Planning Liver-Directed Radioembolization

99mTc-macroaggregated albumin (99mTc-MAA) scanning precedes radioembolization of the liver to detect extrahepatic shunting to the lung or gastrointestinal tract. Despite strict preventive measures in the production of 99mTc-MAA and in scanning protocols, the images frequently show a gastric concentration of free 99mTc-pertechnetate, hindering accurate evaluation of the gastroduodenal region. Our aim was to evaluate whether oral administration of sodium perchlorate (NaClO4) before 99mTc-MAA scanning will improve its accuracy by blocking free 99mTc-pertechnetate gastric uptake. Methods: In 144 patients, 171 diagnostic hepatic angiograms combined with a 99mTc-MAA scan were performed; 86 angiograms were performed after oral administration of NaClO4, and 85 were performed without this premedication. Clinical follow-up, esophagogastroduodenoscopy, and angiography served as reference standards. Results: 99mTc-MAA studies showed tracer uptake in the gastric region of 25 patients who did not receive NaClO4. The uptake was interpreted as a free 99mTc-pertechnetate concentration in 21 studies and as a 99mTc-MAA accumulation in 4 studies. In 5 patients with a free 99mTc-pertechnetate concentration, aberrant vessels were detected in angiographic reexamination, and 3 patients developed gastrointestinal ulcer. In 7 studies, gastric findings viewed pretherapeutically as free 99mTc-pertechnetate were retrospectively classified as equivocal. Of the patients receiving NaClO4, 2 showed gastric accumulation of 99mTc-MAA but no equivocal or free 99mTc-pertechnetate. Oral administration of NaClO4 increased the negative predictive value and accuracy of the test concerning the detection of gastric perfusion from 68% and 69%, respectively, to 93% and 94%, respectively. Conclusion: Oral administration of NaClO4 before the test angiogram with 99mTc-MAA resulted in effective avoidance of free 99mTc-pertechnetate concentration and, consequently, of equivocal findings in the gastroduodenal region. This technique increased test accuracy and reporter confidence, saved time in reviewing the angiograms, and can improve treatment planning and reduce therapeutic side effects.

I-MIBG SPECT/CT for Tumour Imaging

Metaiodobenzylguanidine (mIBG) is an aralkylguanidine norepinephrine analogue, which was clinically introduced in 1981 and developed to visualize tumours of the adrenal medulla [1]. It enters the neuroendocrine cells of postganglionic sympathetic neurons by an active uptake mechanism via the epinephrine transporter and is stored in the neurosecretory granule without being metabolized. This leads to a difference in the concentration compared to cells of other tissues [2, 3], whereas the storage intensity of mIBG-avid tissue is dependent on tissue uptake, and the storage capacity is proportional to the quantity of catecholamine-containing vesicles in the tumour and tracer turnover [4–6].

Appearance of extraosseous pelvic Ewing sarcoma on triphasic bone scan.

A 24-year-old man with extraosseous Ewing sarcoma in the pelvis underwent a triphasic bone scintigraphy to rule out bone metastases and local bone infiltration before chemotherapy. The bone scintigraphy showed tracer uptake in the tumor in all 3 phases.