Iodine-123-MIBG imaging of neuroblastoma: Utility of SPECT and delayed imaging

Possible incremental diagnostic benefits of SPECT and delayed planar imaging with [123I]MIBG in neuroblastoma have not yet been fully established. Methods: Whole-body delayed planar [123I]MIBG imaging at 48 hr and SPECT imaging of the chest-abdomen or other suspected sites obtained at 24 hr were compared with routine planar imaging at 24 hr in 83 studies of 29 children with neuroblastoma. The sensitivity for each of the [123I]MIBG imaging methods was calculated on a study-by-study and on a lesion-by-lesion basis. Results: Fifty-one planar imaging studies were performed in 20 patients with evidence of disease which was detected in 48 studies by 24-hr imaging (94.1% sensitivity) and in 44 studies by 48-hr imaging (86.3% sensitivity). On a lesion-by-lesion basis, sensitivity was 88.8% for the 24-hr scan, 86.7% for the 48-hr scan and 92.2% for a combination of the two (p = ns). Forty-three SPECT studies were performed in 20 patients with evidence of disease in the field of view of the SPECT camera. Disease was detected in 40 SPECT studies (93% sensitivity), in 38 planar scans at 24 hr (84.4% sensitivity) and in 37 planar scans at 48 hr (86.0% sensitivity). On a lesion-by-lesion basis, sensitivity was 83.6% for the 24-hr planar scan, 86.1% for the 48-hr planar scan, 88.2% for a combination of the two planar scans and 97.9% for SPECT (p < 0.001 compared with planar). The anatomic locations of tumors were clearer on SPECT in 15 studies. Conclusion: Delayed 48-hr planar scanning may occasionally depict more lesions than 24-hr imaging, but it may also miss lesions with rapid washout. SPECT imaging significantly increases the number of lesions detected and better defines anatomic location of tumors.