van der Have Frans, Ivashchenko Oleksandra, Goorden Marlies C, Ramakers Ruud M, Beekman Freek J
Section Radiation, Detection and Medical Imaging, Delft University of Technology, Mekelweg 15, 2629 JB, Delft, The Netherlands; MIlabs B.V., Heidelberglaan 100 STR 4.105, 3584, CX, Utrecht, The Netherlands; Department for Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584, CG, Utrecht, The Netherlands.
Section Radiation, Detection and Medical Imaging, Delft University of Technology, Mekelweg 15, 2629 JB, Delft, The Netherlands; MIlabs B.V., Heidelberglaan 100 STR 4.105, 3584, CX, Utrecht, The Netherlands; Department for Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584, CG, Utrecht, The Netherlands.
Nucl Med Biol. 2016 Aug;43(8):506-11. doi: 10.1016/j.nucmedbio.2016.05.015. Epub 2016 Jun 1.
High-resolution pre-clinical (131)I SPECT can facilitate development of new radioiodine therapies for cancer. To this end, it is important to limit resolution-degrading effects of pinhole edge penetration by the high-energy γ-photons of iodine. Here we introduce, optimize and validate (131)I SPECT performed with a dedicated high-energy clustered multi-pinhole collimator.
A SPECT-CT system (VECTor/CT) with stationary gamma-detectors was equipped with a tungsten collimator with clustered pinholes. Images were reconstructed with pixel-based OSEM, using a dedicated (131)I system matrix that models the distance- and energy-dependent resolution and sensitivity of each pinhole, as well as the intrinsic detector blurring and variable depth of interaction in the detector. The system performance was characterized with phantoms and in vivo static and dynamic (131)I-NaI scans of mice.
Reconstructed image resolution reached 0.6mm, while quantitative accuracy measured with a (131)I filled syringe reaches an accuracy of +3.6±3.5% of the gold standard value. In vivo mice scans illustrated a clear shape of the thyroid and biodistribution of (131)I within the animal. Pharmacokinetics of (131)I was assessed with 15-s time frames from the sequence of dynamic images and time-activity curves of (131)I-NaI.
High-resolution quantitative and fast dynamic (131)I SPECT in mice is possible by means of a high-energy collimator and optimized system modeling. This enables analysis of (131)I uptake even within small organs in mice, which can be highly valuable for development and optimization of targeted cancer therapies.
高分辨率临床前（131）I单光子发射计算机断层显像（SPECT）有助于开发新的癌症放射性碘疗法。为此，限制碘的高能γ光子对针孔边缘穿透的分辨率降低效应很重要。在此，我们介绍、优化并验证了使用专用高能簇状多孔径准直器进行的（131）I SPECT。
一个带有固定伽马探测器的SPECT-CT系统（VECTor/CT）配备了一个带有簇状针孔的钨准直器。使用基于像素的有序子集期望最大化（OSEM）算法进行图像重建，使用专用的（131）I系统矩阵，该矩阵对每个针孔的距离和能量依赖性分辨率及灵敏度、探测器固有模糊以及探测器内相互作用的可变深度进行建模。通过体模以及对小鼠进行体内静态和动态（131）I-碘化钠（NaI）扫描来表征系统性能。
重建图像分辨率达到0.6毫米，而用装有（131）I的注射器测量的定量准确度达到金标准值的+3.6±3.5%的准确度。体内小鼠扫描显示出动物体内甲状腺的清晰形状以及（131）I的生物分布。通过动态图像序列的15秒时间帧和（131）I-NaI的时间-活度曲线评估了（131）I 的药代动力学。
借助高能准直器和优化的系统建模，在小鼠中实现高分辨率定量和快速动态（131）I SPECT是可行的。这使得即使在小鼠的小器官内也能分析（131）I摄取情况，这对于靶向癌症治疗的开发和优化可能具有极高价值。
