Desmonts Cédric, Lasnon Charline, Jaudet Cyril, Aide Nicolas
Nuclear Medicine Department, University Hospital of Caen, Avenue de La Côte de Nacre, 14033, Caen Cedex 9, France.
Normandy University, UNICAEN, INSERM 1086 ANTICIPE, Caen, France.
EJNMMI Phys. 2023 Oct 7;10(1):61. doi: 10.1186/s40658-023-00583-2.
Small-animal PET imaging is an important tool in preclinical oncology. This study evaluated the ability of a clinical SiPM-PET camera to image several rats simultaneously and to perform quantification data analysis.
Intrinsic spatial resolution was measured using 18F line sources, and image quality was assessed using a NEMA NU 4-2018 phantom. Quantification was evaluated using a fillable micro-hollow sphere phantom containing 4 spheres of different sizes (ranging from 3.95 to 7.86 mm). Recovery coefficients were computed for the maximum (Amax) and the mean (A50) pixel values measured on a 50% isocontour drawn on each sphere. Measurements were performed first with the phantom placed in the centre of the field of view and then in the off-centre position with the presence of three scattering sources to simulate the acquisition of four animals simultaneously. Quantification accuracy was finally validated using four 3D-printed phantoms mimicking rats with four subcutaneous tumours each. All experiments were performed for both 18F and 68Ga radionuclides.
Radial spatial resolutions measured using the PSF reconstruction algorithm were 1.80 mm and 1.78 mm for centred and off-centred acquisitions, respectively. Spill-overs in air and water and uniformity computed with the NEMA phantom centred in the FOV were 0.05, 0.1 and 5.55% for 18F and 0.08, 0.12 and 2.81% for 68Ga, respectively. Recovery coefficients calculated with the 18F-filled micro-hollow sphere phantom for each sphere varied from 0.51 to 1.43 for Amax and from 0.40 to 1.01 for A50. These values decreased from 0.28 to 0.92 for Amax and from 0.22 to 0.66 for A50 for 68 Ga acquisition. The results were not significantly different when imaging phantoms in the off-centre position with 3 scattering sources. Measurements performed with the four 3D-printed phantoms showed a good correlation between theoretical and measured activity in simulated tumours, with r values of 0.99 and 0.97 obtained for 18F and 68Ga, respectively.
We found that the clinical SiPM-based PET system was close to that obtained with a dedicated small-animal PET device. This study showed the ability of such a system to image four rats simultaneously and to perform quantification analysis for radionuclides commonly used in oncology.
小动物正电子发射断层扫描（PET）成像是临床前肿瘤学中的一项重要工具。本研究评估了一款临床硅光电倍增管（SiPM）PET相机同时对多只大鼠进行成像以及进行定量数据分析的能力。
使用18F线源测量固有空间分辨率，并使用NEMA NU 4-2018体模评估图像质量。使用一个可填充的微空心球体模进行定量评估，该体模包含4个不同尺寸（范围从3.95至7.86毫米）的球体。针对在每个球体上绘制的50%等剂量轮廓上测量的最大（Amax）和平均（A50）像素值计算恢复系数。首先将体模置于视野中心进行测量，然后将其置于偏心位置，并存在三个散射源以模拟同时采集四只动物的情况。最后使用四个3D打印的体模进行验证，每个体模模拟一只带有四个皮下肿瘤的大鼠。所有实验均针对18F和68Ga放射性核素进行。
使用点扩散函数（PSF）重建算法测量的径向空间分辨率，对于中心采集和偏心采集分别为1.80毫米和1.78毫米。当NEMA体模位于视野中心时，18F在空气中和水中的溢出率以及均匀性分别为0.05%、0.1%和5.55%，68Ga分别为0.08%、0.12%和2.81%。使用填充18F的微空心球体模计算的每个球体的恢复系数，Amax从0.51至1.43不等，A50从0.40至1.01不等。对于68Ga采集，这些值对于Amax从0.28降至0.92，对于A50从0.22降至0.66。在存在三个散射源的偏心位置对体模进行成像时，结果无显著差异。使用四个3D打印体模进行的测量表明，模拟肿瘤中的理论活性与测量活性之间具有良好的相关性，18F和68Ga的r值分别为0.99和0.97。
我们发现基于临床SiPM的PET系统的性能与专用小动物PET设备相近。本研究表明，该系统能够同时对四只大鼠进行成像，并对肿瘤学中常用的放射性核素进行定量分析。
