Significance of oral administration of sodium perchlorate in planning liver-directed radioembolization.

(99m)Tc-macroaggregated albumin ((99m)Tc-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 (99m)Tc-MAA and in scanning protocols, the images frequently show a gastric concentration of free (99m)Tc-pertechnetate, hindering accurate evaluation of the gastroduodenal region. Our aim was to evaluate whether oral administration of sodium perchlorate (NaClO(4)) before (99m)Tc-MAA scanning will improve its accuracy by blocking free (99m)Tc-pertechnetate gastric uptake. In 144 patients, 171 diagnostic hepatic angiograms combined with a (99m)Tc-MAA scan were performed; 86 angiograms were performed after oral administration of NaClO(4), and 85 were performed without this premedication. Clinical follow-up, esophagogastroduodenoscopy, and angiography served as reference standards. (99m)Tc-MAA studies showed tracer uptake in the gastric region of 25 patients who did not receive NaClO(4). The uptake was interpreted as a free (99m)Tc-pertechnetate concentration in 21 studies and as a (99m)Tc-MAA accumulation in 4 studies. In 5 patients with a free (99m)Tc-pertechnetate concentration, aberrant vessels were detected in angiographic reexamination, and 3 patients developed gastrointestinal ulcer. In 7 studies, gastric findings viewed pretherapeutically as free (99m)Tc-pertechnetate were retrospectively classified as equivocal. Of the patients receiving NaClO(4), 2 showed gastric accumulation of (99m)Tc-MAA but no equivocal or free (99m)Tc-pertechnetate. Oral administration of NaClO(4) 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. Oral administration of NaClO(4) before the test angiogram with (99m)Tc-MAA resulted in effective avoidance of free (99m)Tc-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.