Focal MIBI uptake is a better indicator of active myeloma than diffuse uptake

: Purpose: Technetium‐99m 2‐methoxyisobutylisonitrile (MIBI) imaging has been proposed as a front‐line investigation to detect bone disease both before and after the treatment of myeloma. In this study, we have compared the pattern of MIBI uptake (focal and diffuse) between patients with proven myeloma and a cohort of patients without myeloma, in order to identify the uptake pattern that best correlates with disease activity. Methods: Nineteen scans were taken in 16 consecutive patients (nine males and seven females: aged 39–71 yr) with active myeloma. A further 20 scans (10 subjects having MIBI myocardial perfusion scintigraphy and 10 subjects having MIBI parathyroid adenoma localisation studies), comprised the control (non‐myeloma) cohort. Scans were evaluated in a double‐blinded fashion by two observers for any diffuse skeletal MIBI uptake (homogeneous uptake in spine, sternum and/or long bones), and/or abnormal focal uptake (patchy, focal or tubular uptake in the skeleton or soft tissues). Results: The pattern of MIBI uptake was significantly different in the myeloma‐positive subjects and the control cohort. Focal uptake was highly discriminatory, being seen in 15 of 19 (79%) scans of the myeloma‐positive group as opposed to one of 20 (5%) scans of the control group (P 50% myocardial activity), we demonstrated improved specificity from 45% to 100%, but significantly impaired sensitivity for presence of myeloma (79% vs. 37%, P = 0.02). Conclusion: Our study thus illustrates that the presence of any focal uptake of MIBI is useful in indicating active myeloma whereas diffuse uptake is not.