Clinical performance and radiation dosimetry of no-carrier-added vs carrier-added 123I-metaiodobenzylguanidine (MIBG) for the assessment of cardiac sympathetic nerve activity.

Abstract

PurposeWe hypothesized that assessment of myocardial sympathetic activity with no-carrier-added (nca) 123I-meta-iodobenzylguanidine (MIBG) compared to carrier-added (ca) 123I-MIBG would lead to an improvement of clinical performance without major differences in radiation dosimetry.MethodsIn nine healthy volunteers, 15 min and 4 h planar thoracic scintigrams and conjugate whole-body scans were performed up to 48 h following intravenous injection of 185 MBq 123I-MIBG. The subjects were given both nca and ca 123I-MIBG. Early heart/mediastinal ratios (H/M), late H/M ratios and myocardial washout were calculated. The fraction of administered activity in ten source organs was quantified from the attenuation-corrected geometric mean counts in conjugate views. Radiation-absorbed doses were estimated with OLINDA/EXM software.ResultsBoth early and late H/M were higher for nca 123I-MIBG (ca 123I-MIBG early H/M 2.46 ± 0.15 vs nca 123I-MIBG 2.84 ± 0.15, p = 0.001 and ca 123I-MIBG late H/M 2.69 ± 0.14 vs nca 123I-MIBG 3.34 ± 0.18, p = 0.002). Myocardial washout showed a longer retention time for nca 123I-MIBG (p < 0.001). The effective dose equivalent (adult male model) for nca 123I-MIBG was similar to that for ca 123I-MIBG (0.025 ± 0.002 mSv/MBq vs 0.026 ± 0.002 mSv/MBq, p = 0.055, respectively).ConclusionNo-carrier-added 123I-MIBG yields a higher relative myocardial uptake and is associated with a higher myocardial retention. This difference between nca 123I-MIBG and ca 123I-MIBG in myocardial uptake did not result in major differences in estimated absorbed doses. Therefore, nca 123I-MIBG is to be preferred over ca 123I-MIBG for the assessment of cardiac sympathetic activity.