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

Abstract

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