Qi Chi, Sui Xiuli, Yu Haojun, Wang Siyang, Hu Yan, Sun Hongyan, Yang Xinlan, Wang Yihan, Zhou Yun, Shi Hongcheng
Department of Nuclear Medicine, Zhongshan Hospital, Fudan University, No. 180 in Fenglin Road, Shanghai, 200032, People's Republic of China.
Institute of Nuclear Medicine, Fudan University, Shanghai, 200032, People's Republic of China.
EJNMMI Phys. 2024 Feb 15;11(1):17. doi: 10.1186/s40658-023-00597-w.
Conventional PET/CT imaging reconstruction is typically performed using voxel size of 3.0-4.0 mm in three axes. It is hypothesized that a smaller voxel sizes could improve the accuracy of small lesion detection. This study aims to explore the advantages and conditions of small voxel imaging on clinical application.
Both NEMA IQ phantom and 30 patients with an injected dose of 3.7 MBq/kg were scanned using a total-body PET/CT (uEXPLORER). Images were reconstructed using matrices of 192 × 192, 512 × 512, and 1024 × 1024 with scanning duration of 3 min, 5 min, 8 min, and 10 min, respectively.
In the phantom study, the contrast recovery coefficient reached the maximum in matrix group of 512 × 512, and background variability increased as voxel size decreased. In the clinical study, SUV, SD, and TLR increased, while SNR decreased as the voxel size decreased. When the scanning duration increased, SNR increased, while SUV, SD, and TLR decreased. The SUV was more reluctant to the changes in imaging matrix and scanning duration. The mean subjective scores for all 512 × 512 groups and 1024 × 1024 groups (scanning duration ≥ 8 min) were over three points. One false-positive lesion was found in groups of 512 × 512 with scanning duration of 3 min, 1024 × 1024 with 3 min and 5 min, respectively. Meanwhile, the false-negative lesions found in group of 192 × 192 with duration of 3 min and 5 min, 512 × 512 with 3 min and 1024 × 1024 with 3 min and 5 min were 5, 4, 1, 4, and 1, respectively. The reconstruction time and storage space occupation were significantly increased as the imaging matrix increased.
PET/CT imaging with smaller voxel can improve SUV and TLR of lesions, which is advantageous for the diagnosis of small or hypometabolic lesions if with sufficient counts. With an F-FDG injection dose of 3.7 MBq/kg, uEXPLORER PET/CT imaging using matrix of 512 × 512 with 5 min or 1024 × 1024 with 8 min can meet the image requirements for clinical use.
传统PET/CT成像重建通常在三个轴向上使用3.0 - 4.0毫米的体素大小。据推测，较小的体素大小可以提高小病灶检测的准确性。本研究旨在探讨小体素成像在临床应用中的优势和条件。
使用全身PET/CT（uEXPLORER）对NEMA IQ体模和30例注射剂量为3.7 MBq/kg的患者进行扫描。分别使用192×192、512×512和1024×1024矩阵重建图像，扫描时间分别为3分钟、5分钟、8分钟和10分钟。
在体模研究中，对比恢复系数在512×512矩阵组中达到最大值，且背景变异性随着体素大小的减小而增加。在临床研究中，随着体素大小的减小，SUV、SD和TLR升高，而SNR降低。当扫描时间增加时,SNR升高，而SUV、SD和TLR降低。SUV对成像矩阵和扫描时间的变化更不敏感。所有512×512组和1024×1024组（扫描时间≥8分钟）的平均主观评分均超过3分。在扫描时间为3分钟的512×512组、扫描时间为3分钟和5分钟的1024×1024组中分别发现1例假阳性病灶。同时，在扫描时间为3分钟和5分钟的192×192组、扫描时间为3分钟的512×512组以及扫描时间为3分钟和5分钟的1024×1024组中发现的假阴性病灶分别为5个、4个、1个、4个和1个。随着成像矩阵的增加，重建时间和存储空间占用显著增加。
较小体素的PET/CT成像可以提高病灶的SUV和TLR，如果计数足够，有利于小病灶或代谢减低病灶的诊断。在注射剂量为3.7 MBq/kg的18F-FDG时，使用512×512矩阵、扫描时间为5分钟或使用1024×1024矩阵、扫描时间为8分钟的uEXPLORER PET/CT成像可以满足临床使用的图像要求。
