Clinical performance and radiation dosimetry of no-carrier-added vs carrier-added 123I-metaiodobenzylguanidine (MIBG) for the assessment of cardiac sympathetic nerve activity.
OBJECTIVE
We hypothesized that assessment of myocardial sympathetic activity with no-carrier-added (nca) (123)I-meta-iodobenzylguanidine (MIBG) compared to carrier-added (ca) (123)I-MIBG would lead to an improvement of clinical performance without major differences in radiation dosimetry.


METHODS
In 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 (123)I-MIBG. The subjects were given both nca and ca (123)I-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.


RESULTS
Both early and late H/M were higher for nca (123)I-MIBG (ca (123)I-MIBG early H/M 2.46 +/- 0.15 vs nca (123)I-MIBG 2.84 +/- 0.15, p = 0.001 and ca (123)I-MIBG late H/M 2.69 +/- 0.14 vs nca (123)I-MIBG 3.34 +/- 0.18, p = 0.002). Myocardial washout showed a longer retention time for nca (123)I-MIBG (p < 0.001). The effective dose equivalent (adult male model) for nca (123)I-MIBG was similar to that for ca (123)I-MIBG (0.025 +/- 0.002 mSv/MBq vs 0.026 +/- 0.002 mSv/MBq, p = 0.055, respectively).


CONCLUSIONS
No-carrier-added (123)I-MIBG yields a higher relative myocardial uptake and is associated with a higher myocardial retention. This difference between nca (123)I-MIBG and ca (123)I-MIBG in myocardial uptake did not result in major differences in estimated absorbed doses. Therefore, nca (123)I-MIBG is to be preferred over ca (123)I-MIBG for the assessment of cardiac sympathetic activity.
Verberne
Hein J
HJ
Department of Nuclear Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. h.j.verberne@amc.uva.nl
Sokole
Ellinor Busemann
EB
van Moerkerken
Astrid F
AF
Deeterink
Joop H W M
JH
Ensing
Geert
G
Stabin
Michael G
MG
Somsen
G Aernout
GA
van Eck-Smit
Berthe L F
BL
D019797:3-Iodobenzylguanidine / Q000008:administration & dosage / Q000493:pharmacokinetics*; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging; D006329:Heart Conduction System; D006801:Humans; D007267:Injections; D007457:Iodine Radioisotopes / Q000008:administration & dosage / Q000493:pharmacokinetics*; D007700:Kinetics; D008297:Male; D011877:Radionuclide Imaging; D012016:Reference Values; D013564:Sympathetic Nervous System / Q000000981:diagnostic imaging*; D014018:Tissue Distribution; D014916:Whole-Body Irradiation / Q000379:methods
D007457:Iodine Radioisotopes; D019797:3-Iodobenzylguanidine