Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada
Section Radiation, Detection and Medical Imaging, Delft University of Technology, Delft, The Netherlands.
J Nucl Med. 2014 Aug;55(8):1368-74. doi: 10.2967/jnumed.113.136663. Epub 2014 Jun 5.
PET imaging of rodents is increasingly used in preclinical research, but its utility is limited by spatial resolution and signal-to-noise ratio of the images. A recently developed preclinical PET system uses a clustered-pinhole collimator, enabling high-resolution, simultaneous imaging of PET and SPECT tracers. Pinhole collimation strongly departs from traditional electronic collimation achieved via coincidence detection in PET. We investigated the potential of such a design by direct comparison to a traditional PET scanner.
Two small-animal PET scanners, 1 with electronic collimation and 1 with physical collimation using clustered pinholes, were used to acquire data from Jaszczak (hot rod) and uniform phantoms. Mouse brain imaging using (18)F-FDG PET was performed on each system and compared with quantitative ex vivo autoradiography as a gold standard. Bone imaging using (18)F-NaF allowed comparison of imaging in the mouse body. Images were visually and quantitatively compared using measures of contrast and noise.
Pinhole PET resolved the smallest rods (diameter, 0.85 mm) in the Jaszczak phantom, whereas the coincidence system resolved 1.1-mm-diameter rods. Contrast-to-noise ratios were better for pinhole PET when imaging small rods (<1.1 mm) for a wide range of activity levels, but this reversed for larger rods. Image uniformity on the coincidence system (<3%) was superior to that on the pinhole system (5%). The high (18)F-FDG uptake in the striatum of the mouse brain was fully resolved using the pinhole system, with contrast to nearby regions equaling that from autoradiography; a lower contrast was found using the coincidence PET system. For short-duration images (low-count), the coincidence system was superior.
In the cases for which small regions need to be resolved in scans with reasonably high activity or reasonably long scan times, a first-generation clustered-pinhole system can provide image quality in terms of resolution, contrast, and the contrast-to-noise ratio superior to a traditional PET system.
正电子发射断层扫描（PET）成像在临床前研究中越来越多地被使用，但由于图像的空间分辨率和信噪比的限制，其应用受到限制。最近开发的一种临床前 PET 系统使用了集束型小孔准直器，能够实现 PET 和单光子发射计算机断层扫描（SPECT）示踪剂的高分辨率、同时成像。小孔准直与传统的通过符合探测实现的电子准直有很大的不同。我们通过与传统的 PET 扫描仪进行直接比较，研究了这种设计的潜力。
使用两台小型动物 PET 扫描仪，一台具有电子准直，一台使用集束型小孔进行物理准直，从 Jaszczak（热棒）和均匀的体模中获取数据。对每台系统进行（18）F-FDG PET 小鼠脑成像，并与定量的体外放射自显影作为金标准进行比较。使用（18）F-NaF 进行骨骼成像，允许比较小鼠体内的成像。使用对比度和噪声的测量值对图像进行视觉和定量比较。
小孔 PET 分辨出了 Jaszczak 体模中最小的棒（直径为 0.85 毫米），而符合系统则分辨出了 1.1 毫米直径的棒。在成像小棒（<1.1 毫米）时，对于广泛的活性水平，小孔 PET 的对比度噪声比更好，但对于较大的棒则相反。符合系统的图像均匀性（<3%）优于小孔系统（5%）。使用小孔系统，完全分辨出了小鼠脑纹状体的高（18）F-FDG 摄取，与放射自显影相比，与附近区域的对比度相等；而符合 PET 系统的对比度较低。对于短时间的图像（低计数），符合系统具有优势。
在需要在具有合理高活性或合理长扫描时间的扫描中分辨小区域的情况下，第一代集束型小孔系统可以在分辨率、对比度和对比度噪声比方面提供优于传统 PET 系统的图像质量。
