Evaluation of global and regional myocardial uptake of MIBG-I123 with multimodality acquisition

2518 Objectives Aim of the study was to evaluate uptake and bio-distribution of MIBG-I123 to identify the timing to calculate H/M, washout rate in LV dysfunction. Methods We studied 22 pts [17 M; 5 F] with LV dysfunction [EF 31.9+ 3.4%], NYHA II-III. All pts underwent dynamic dual-phase acquisition [1st 5”frames x 60sec; 2nd 10”frames x10min], followed by whole body scan+ 3 static images[10min each] at 15min, 2hrs, 4hrs later in Anterior view [MTX 128x128pxls, Zoom 1.43]. Specific ROIs [myocardium, mediastinum, lung, liver] were drawn on dynamic, static images to obtain their time-activity curves. Total counts of whole body scan was used as input function. Heart/Mediastinum, wash-out rate, and Heart/Whole Body were calculated at 15min, 2hrs, 4hrs. Only for 4hrs static image we also drew 3 ROIs on remote, bordeline and infarcted myocardium. All pts underwent also stress-test G-SPECT to assess extent of perfusion defect and LV ventricular dysfunction. Results Early dynamic phase showed fast wash-out from blood, prompt uptake in myocardium, lung and liver. On time slow wash-out was observed in the liver and lung while myocardial uptake was variable depending on preserved tissue innervation. Values of H/M, washout rate were more stable at 4hrs which represents the correct timing. Uptake in remote myocardium was higher, in infarcted area lower, while in borderline showed more variability. Conclusions The early myocardial uptake of MIBG-I123 is relatively fast and represents initial vascular and cellular phase. Late 4hrs static imaging represents effective pre-synaptic pool, often unrelated to extent of scar, ischaemia and LV dysfunction. The repeatability of all indexes is strongly dependent on positioning of ROIs: therefore a specific and standardized software is needed