COMPARISON OF IODINE-123-EPIDEPRIDE AND IODINE-123-IBZM FOR DOPAMINE D2 RECEPTOR IMAGING

Although (123)1-IBZM is widely used as a D2 receptor imaging agent, im age quality is compromised by a relatively low target-to-nontarget rat io. Animal studies suggest that I-123-epidepride (K-d 0.024 nM) may be superior to I-123-IBZM, but this agent has not been systematically st udied in humans. Methods: We directly compared I-123-epidepride and I- 123-IBZM in five normal volunteers (age range 30-58 yr, mean 43 yr). B rain SPECT imaging was performed 2 hr after the I-123-IBZM injection ( average dose 153 MBq). lodine-123-epidepride scans were performed 1 hr (n = 3), 2 hr (n = 5) and 3 hr (n = 3) postinjection (average dose 14 9 MBq). Results: Both radiopharmaceuticals were well tolerated. Iodine -123-epidepride provided excellent visualization of the striatum. Perc ent specific striatum uptake at 2 hr (71.7 +/- 4.9%) was much greater than with I-123-IBZM (32.6 +/- 5.3%, p < 0.01). Conclusion: lodine-123 -epidepride is a new D2 receptor agent that exhibits excellent neuroim aging properties and has a much higher affinity for striatal uptake th an I-123-IBZM.