Parameters of dynamic and static iodine-123-MIBG cardiac imaging

Dynamic and static 123I-MIBG studies were used to investigate various parameters with regard to their usefulness in evaluating cardiac disorders.

Four patient groups and one control group were included in this study. Dynamic study was acquired immediately after injection at 1 frame/sec for 2 min and at 1 frame/6 sec for the next 30 min using a 64 x 64 matrix format. Static study consisted of planar images at the anterior and left anterior oblique 45 degrees views in a 512 x 512 matrix format for 1 min. The early and delayed planar images were acquired soon after dynamic acquisition and approximately 4 hr after injection, respectively. Net injection dose was calculated as the difference in syringe counts before and after injection. From the dynamic and static studies, the heart uptake ratios at 3 min and 30 min, early uptake ratio and delayed uptake ratio were calculated at various intervals. Early and delayed clearance rates, Ke and Kd, respectively were also determined. These parameters were compared and correlated with each other.

Three-minute heart uptake ratios were significantly higher than early or delayed uptake ratios or uptake ratios at 30 min in all groups. All uptake ratios in hemodialysis patients were significantly higher than those in other groups. The Kd values in dilated cardiomyopathy, doxorubicin therapy and vasospastic angina patients were significantly higher than those in hemodialysis patients and normal controls. At least bi-exponential clearance patterns of MIBG from the heart were observed in all groups.

Three-minute and delayed heart uptake ratios calculated from dynamic and static studies are helpful in elucidating the uptake at nonvesicular sites, which reflect the severity of sympathetic nervous system abnormalities in the heart.