Image quality and lesion detectability in simulated [¹²⁴I]MIBG cardiac imaging across 3-generation PET/CT scanners...

Cardiac sympathetic imaging with iodine-labeled metaiodobenzylguanidine (MIBG) is clinically relevant for assessing autonomic dysfunction and arrhythmic risk in heart failure. The development of positron-emitting ¹²⁴I-MIBG and new-generation PET/CT systems, particularly long axial field-of-view (LAFOV) scanners, may improve image quality and regional defect assessment while enabling protocol optimization. This study compared simulated cardiac ¹²⁴I-MIBG image quality and lesion detectability across three PET/CT generations, analog standard axial field-of-view (SAFOV), digital SAFOV, and LAFOV, and explored the potential for acquisition-time and activity reduction.

An anthropomorphic torso phantom with cardiac insert was prepared to simulate physiologic ¹²⁴I-MIBG biodistribution. Two configurations were studied: a pathological model with a transmural defect (TD) and a non-transmural defect (NTD), and a normal model with homogeneous myocardial uptake. Acquisitions were performed on three PET/CT systems: analog SAFOV (Biograph mCT), digital SAFOV (Biograph Vision Edge 600), and LAFOV (Biograph Vision Quadra). List-mode data were acquired for 10 min and reconstructed to simulate 1-, 5-, and 10-min acquisitions, yielding nine datasets. Qualitative assessment included lesion detectability and overall image quality scored on 5-point Likert scales by two experienced readers. Quantitative analysis included signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Exploratory pairwise Wald-type comparisons were performed using propagated measurement uncertainty.

LAFOV PET/CT showed the best qualitative and quantitative performance overall. Lesion detectability was highest on LAFOV at all acquisition times, with digital SAFOV intermediate and analog SAFOV lowest. Image quality likewise favored LAFOV, especially at 5 and 10 min. In the pathological phantom, SNR increased from 25.9 to 75.1 on LAFOV, from 18.7 to 41.8 on digital SAFOV, and from 15.5 to 17.1 on analog SAFOV. At 10 min, exploratory uncorrected pairwise comparisons showed nominally higher SNR on LAFOV than on analog SAFOV PET/CT (75.1 vs 17.1, p = 0.028). For the transmural defect, CNR also increased most on LAFOV, with a nominally higher value versus analog SAFOV at 10 min (67.6 vs 14.5, p = 0.044). By contrast, for the low-contrast non-transmural defect, CNR was numerically higher on LAFOV at longer acquisition times, but the absolute inter-scanner differences were smaller and did not reach statistical significance.

LAFOV PET/CT provides superior image quality and lesion detectability for simulated cardiac ¹²⁴I-MIBG imaging and supports shorter acquisitions and potentially lower administered activity. However, the advantage was most pronounced for high-contrast transmural defects, whereas the benefit for low-contrast non-transmural defects was less robust. Reliable detection of subtle partial innervation defects remains challenging and requires dedicated clinical validation.