Iodine-123 Metaiodobenzylguanidine Imaging and Carbon-11 Hydroxyephedrine Positron Emission Tomography Compared in Patients With Left Ventricular Dysfunction

Background-Although both I-123-metaiodobenzylguanidine (I-123-MIBG) imaging and C-11-hydroxyephedrine (C-11-HED) positron emission tomography (PET) are used for assessing cardiac sympathetic innervation, their relationship remains unknown. The aims were to determine whether I-123-MIBG parameters such as heart-to-mediastinum ratio (H/M) are associated with quantitative measures by C-11-HED PET and to compare image quality, defect size, and location between I-123-MIBG single-photon emission computed tomography (SPECT) and C-11-HED PET. Methods and Results-Twenty-one patients (mean left ventricular ejection fraction, 39 +/- 15%) underwent I-123-MIBG imaging and C-11-HED PET. Early (15-minute), late (3-hour) H/M, and washout rate (WR) were calculated for I-123-MIBG. Myocardial retention and WR was calculated for C-11-HED. Using a polar map approach, defect was defined as the area with relative activity <60% of the maximum. Both the early (r = 0.76) and late (r = 0.84) I-123-MIBG H/M were correlated with C-11-HED retention. I-123-MIBG WR was correlated with C-11-HED WR (r = 0.57). Defect size could not be measured in 3 patients because of poor quality I-123-MIBG SPECT, whereas C-11-HED defect was measurable in all patients. Although defect size measured by early or late I-123-MIBG SPECT was closely correlated with that by C-11-HED PET (early: r = 0.94; late: r = 0.88), the late I-123-MIBG overestimated defect size particularly in the inferior and septal regions. Conclusions-I-123-MIBG H/M gives a reliable estimate of cardiac sympathetic innervation as measured by C-11-HED PET. Furthermore, despite the close correlation in defect size, C-11-HED PET appears to be more suitable for assessing regional abnormalities than does I-123-MIBG SPECT. (Circ Cardiovasc Imaging. 2010;3:595-603.)