Data on myocardial kinetic of (123)I-meta-iodobenzylguanidine(MIBG) in vivo are scarce and obtained using planar acquisitions. We studied 6 anesthetized pigs (mean body weight: 37±4 Kg). Left ventricle myocardial perfusion and sympathetic innervation were assessed using (99m)Tc-Tetrofosmin (26±6 MBq), (123)I-MIBG (54±14 MBq) and a CZT camera (NM 530c, GE). A normal perfusion/function gated-SPECT was the inclusion criteria. Dynamic acquisition in list mode simultaneously started with the bolus injection of (123)I-MIBG and steps of 5 minutes for the first 20 min, at 30-60-90-120 min were collected. Each step was reconstructed using a dedicate software (Lister, GE) and reframed (60sec/frame). On the reconstructed transaxial slice with the best visualization of LV cavity, regions of interest were drawn to obtain myocardial and blood pool activities. Myocardial time-activity curves were generated interpolating data between contiguous acquisition steps, corrected for the radiotracer decay and the injected dose, and fitted to a bicompartimental model. Time to myocardial maximum signal intensity (MSI), MSI value, radiotracer retention index (RI, myocardial activity/blood pool integral) and wash-out rate were calculated. Mediastinum signal was measured and fitted to a linear model. Myocardial MSI of (123)I-MIBG was reached within 5.57±4.23 min (range 2-12 min). The mean MSI was 4.35±0.95?. Myocardial RI decreased with time and reached zero value at 176±31 min (range 140-229). The ratio between myocardial and mediastinum signal at 15, 125 min and extrapolated at 176 and 4h was 5.45±0.61%, 4.33±1.23% (P = ns vs 15min), 3.95±1.46% (P < 0.03 vs 125min) and 3.63±1.64% (P < 0.03 vs 176min). Mean global wash-out rate at 125min was 15±14% (range 0-34%) and extrapolated data at 176min and 4h were 18±20% (range 0.49-45%) and 22 ±25 % (range 1.7-56.2%; P = ns vs 176min). 3-D dynamic analysis of (123)I-MIBG suggests that myocardial peak uptake is reached faster than previously described. Myocardial RI decreases with time and, on average, 3 hours from the injection is null. The combination of an early peak and variations in delayed myocardial uptake could result in a wide physiological range of wash-out rates. Mediastinal activity appears constant with time and significantly lower than previously described in planar study, resulting in a higher H/M ratio.
Dynamic 3D-analysis of myocardial sympathetic innervation: an experimental study using 123Imeta- iodobenzylguanidine and a CZT camera.
Trivella MG;
2015
Abstract
Data on myocardial kinetic of (123)I-meta-iodobenzylguanidine(MIBG) in vivo are scarce and obtained using planar acquisitions. We studied 6 anesthetized pigs (mean body weight: 37±4 Kg). Left ventricle myocardial perfusion and sympathetic innervation were assessed using (99m)Tc-Tetrofosmin (26±6 MBq), (123)I-MIBG (54±14 MBq) and a CZT camera (NM 530c, GE). A normal perfusion/function gated-SPECT was the inclusion criteria. Dynamic acquisition in list mode simultaneously started with the bolus injection of (123)I-MIBG and steps of 5 minutes for the first 20 min, at 30-60-90-120 min were collected. Each step was reconstructed using a dedicate software (Lister, GE) and reframed (60sec/frame). On the reconstructed transaxial slice with the best visualization of LV cavity, regions of interest were drawn to obtain myocardial and blood pool activities. Myocardial time-activity curves were generated interpolating data between contiguous acquisition steps, corrected for the radiotracer decay and the injected dose, and fitted to a bicompartimental model. Time to myocardial maximum signal intensity (MSI), MSI value, radiotracer retention index (RI, myocardial activity/blood pool integral) and wash-out rate were calculated. Mediastinum signal was measured and fitted to a linear model. Myocardial MSI of (123)I-MIBG was reached within 5.57±4.23 min (range 2-12 min). The mean MSI was 4.35±0.95?. Myocardial RI decreased with time and reached zero value at 176±31 min (range 140-229). The ratio between myocardial and mediastinum signal at 15, 125 min and extrapolated at 176 and 4h was 5.45±0.61%, 4.33±1.23% (P = ns vs 15min), 3.95±1.46% (P < 0.03 vs 125min) and 3.63±1.64% (P < 0.03 vs 176min). Mean global wash-out rate at 125min was 15±14% (range 0-34%) and extrapolated data at 176min and 4h were 18±20% (range 0.49-45%) and 22 ±25 % (range 1.7-56.2%; P = ns vs 176min). 3-D dynamic analysis of (123)I-MIBG suggests that myocardial peak uptake is reached faster than previously described. Myocardial RI decreases with time and, on average, 3 hours from the injection is null. The combination of an early peak and variations in delayed myocardial uptake could result in a wide physiological range of wash-out rates. Mediastinal activity appears constant with time and significantly lower than previously described in planar study, resulting in a higher H/M ratio.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
