Localization of metastases from malignant pheochromocytoma in patients undergoing 131I-MIBG therapy with manually fused 123I-MIBG SPECT and CT images.

(131)I-metaiodobenzylguanidine (MIBG) has been used as a therapeutic agent for pheochromocytoma. Tumor localization and precise staging are essential for therapy with high-dose (131)I-MIBG. The sites and extent of (123)I-MIBG uptake are usually estimated to predict the effectiveness of therapy before administration. However, conventional scintigraphic images provide insufficient anatomic information. Therefore, we tried to manually superimpose (123)I-MIBG SPECT and CT images using free software.