Quantitative analysis with ¹²³I-MIBG SPECT/CT for pheochromocytoma and paraganglioma

Objectives In ¹²³I- MIBG scintigraphy, an inline SPECT/CT system allows us to get attenuation corrected SPECT images easily using CT data. The purpose of this retrospective study was to evaluate the diagnostic performance of quantitative analysis of ¹²³I-MIBG-SPECT/CT in patients with suspected pheochromocytoma or paraganglioma.

Methods We analyzed 60 patients who were clinically suspected of having pheochromocytoma or paraganglioma, and underwent ¹²³I-MIBG SPECT/CT scan between September 2009 and November 2014. Patients got an intravenous injection of 111 to 222 MBq ¹²³I-MIBG, and SPECT/CT was performed at 6-h post-injection, in addition to obtaining planar images at 6-h and 24-h post-injection. A low-dose unenhanced CT was used for attenuation correction. On SPECT images, we measured SUVmax of retroperitoneal tumors, including pheochromocytoma, paraganglioma and normal organs using newly-developed software. We compared the SUVmax of pheochromocytoma and paraganglioma with that of other retroperitoneal lesions and physiological uptake of adrenal glands. In addition, the diagnostic performance of this technique was assessed by ROC analysis.

Results The mean ± standard deviation of SUVmax of pheochromocytomas and paragangliomas was 12.5±5.76, which was significantly higher (p<0.05) than that of other retroperitoneal lesions (4.46±1.63) and normal adrenal (4.60±1.40). The SUVmax of physiological uptake in parotid glands, submandibular glands, thyroid, heart, liver and adrenal glands was ranging from 7.55±4.38, 5.41±3.48, 9.31±4.23, 8.03±3.23, 14.7±5.06, and 4.60±1.40, respectively. When applying 7.9 as the optimal cut-off value, the sensitivity, specificity, and accuracy were 82.2%, 98.2% and 95.6%, respectively, with the area under the curve of 0.880.

Conclusions Quantitative approach in ¹²³I-MIBG SPECT/CT was clinically feasible, and it demonstrated reasonably high diagnostic performance in differentiating pheochromocytoma and paraganglioma from other retroperitoneal pathology or physiological uptake in adrenal gland.

Research Support We have no research support.