Functional Characterization of Adrenal Lesions Using [123I] IMTO-SPECT/CT

Context: Adrenal tumors are highly prevalent and represent a wide range of different pathological entities. Conventional imaging often provides only limited information on the origin of these lesions. Novel specific imaging methods are, therefore, of great clinical interest. Objective: We evaluated [I-123] iodometomidate ([(123)] IMTO) imaging for noninvasive characterization of adrenal masses. Design/Setting: This was a prospective monocentric diagnostic study in a tertiary care center. Patients and Intervention: A total of 51 patients with an adrenal lesion underwent [(123)] IMTO imaging after injection of 185 MBq of [(123)] IMTO. Sequential planar whole-body scans until 24 hours postinjection and single photon emission computed tomography (SPECT)/computed tomography imaging 4 to 6 hours postinjection were performed. Main Outcome Measure: Sensitivity and specificity of [(123)] IMTO imaging for the noninvasive characterization of adrenal lesions were measured. Results: Adrenocortical tissue showed high and specific tracer uptake with a short investigation time and low radiation exposure. Qualitative analysis of SPECT/computed tomography data resulted in a sensitivity of89% anda specificity of85% for differentiating adrenocortical tumors from lesions of nonadrenocortical origin. Receiver-operating characteristic analysis of semiquantitative data revealed a sensitivity of 83% and a specificity of 86% for identification of adrenocortical lesions at a cutoff value of tumor to liver ratio of 1.3. Conclusions: [(123)] IMTO is a highly specific radiotracer for imaging of adrenocortical tissue with a short investigation time and low radiation exposure. Because of the general availability of SPECT technology, [(123)] IMTO scintigraphy has the potential to become a widely used tool to noninvasively characterize the biology of adrenal lesions. (J Clin Endocrinol Metab 98: 1508-1518, 2013)