Purpose: to compare lesion detectability of I-123 MIBG scintigraphy with that of high-dose I-131 MIBG and to evaluate incremental benefit of SPECT/CT over planar image for the detection and localization of the lesions in patients with I-131 MIBG therapy for malignant pheochromocytoma/paraganglioma and neuroblastoma.
Materials and methods: we retrospectively investigated 16 patients with malignant pheochromocytoma/paraganglioma and neuroblastoma, who were referred for I-131 MIBG therapy. We investigated the lesion detectability in 10 pairs of I-123 and high-dose I-131 MIBG studies of the same patient, obtained within 2 weeks. In 31 studies of I-123 MIBG scintigraphy in 16 patients and 17 studies of high-dose I-131 MIBG scintigraphy in 12 patients, we compared planar and SPECT/CT images for the lesion detectability and localization.
Results: the number of lesions detected by I-123 MIBG planer image and SPECT/CT and high-dose planer I-131 MIBG and SPECT/CT were 3.0 and 3.7, 7.3 and 7.7 per study, respectively. SPECT/CT images provided additional diagnostic information over planar images in 25 studies (81%) of 12 patients (75%) in I-123 MIBG scintigraphy and in 9 studies (53%) of 9 patients (75%) in high-dose I-131 MIBG scintigraphy.
Conclusion: post-therapy high-dose I-131 MIBG scintigraphy is superior to I-123 MIBG scintigraphy in lesion detectability even in comparison with I-123 MIBG SPECT/CT images and high-dose I-131 MIBG planar images in patients with malignant neuroendocrine tumors. SPECT/CT images are helpful for accurate identification of anatomic localization compared with planar images.