Iodine-123 metaiodobenzylguanidine imaging and carbon-11 hydroxyephedrine positron emission tomography compared in patients with left ventricular dysfunction

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