Department of Biomedical Engineering, University of California-Davis, One Shields Avenue, Davis, CA 95616, USA.
Phys Med Biol. 2010 Jan 21;55(2):N63-74. doi: 10.1088/0031-9155/55/2/N04. Epub 2009 Dec 21.
Improvements to current small animal PET scanners can be made by improving the sensitivity and the spatial resolution of the scanner. In the past, efforts have been made to minimize the crystal dimensions in the axial and transaxial directions to improve the spatial resolution and to increase the crystal length to improve the sensitivity of the scanner. We have designed tapered PET detectors with the purpose of reducing the gaps between detector modules and optimizing the sensitivity of a future-generation small animal PET scanner. In this work, we investigate spatial resolution and sensitivity of a scanner based on tapered detector elements using Monte Carlo simulations. For tapered detector elements more scintillation material is used per detector resulting in a higher sensitivity of the scanner. However, since the detector elements are not uniform in size, degradation in spatial resolution is also expected. To investigate characteristics of tapered PET detectors, the spatial resolution and sensitivity of a one-ring scanner were simulated for a system based on traditional cuboid detectors and a scanner based on tapered detectors. Additionally, the effect of depth of interaction (DOI) resolution on the spatial resolution for the traditional and tapered detectors was evaluated. All simulations were performed using the Monte Carlo simulation package GATE. Using the tapered arrays, a 64% improvement in the sensitivity across the field of view was found compared with traditional detectors for the same ring diameter. The level of DOI encoding was found to be the dominating factor in determining the radial spatial resolution and not the detector shape. For all levels of DOI encoding, no significant difference was found for the spatial resolution when comparing the tapered and the cuboid detectors. Detectors employing the tapered crystal design along with excellent DOI resolution will lead to PET scanners with higher sensitivity and uniform spatial resolution across the field of view.
通过提高扫描仪的灵敏度和空间分辨率，可以改进当前的小动物 PET 扫描仪。过去，人们努力将轴向和横向的晶体尺寸最小化，以提高空间分辨率，并增加晶体长度以提高扫描仪的灵敏度。我们设计了锥形 PET 探测器，目的是减少探测器模块之间的间隙，并优化下一代小动物 PET 扫描仪的灵敏度。在这项工作中，我们使用蒙特卡罗模拟研究了基于锥形探测器元件的扫描仪的空间分辨率和灵敏度。对于锥形探测器元件，每个探测器使用的闪烁材料更多，从而提高了扫描仪的灵敏度。但是，由于探测器元件的尺寸不均匀，预计空间分辨率也会下降。为了研究锥形 PET 探测器的特性，我们针对基于传统长方体探测器的系统和基于锥形探测器的系统，对一环扫描仪的空间分辨率和灵敏度进行了模拟。此外，还评估了深度分辨率对传统和锥形探测器空间分辨率的影响。所有模拟均使用蒙特卡罗模拟软件 GATE 进行。与传统探测器相比，使用锥形探测器阵列可使整个视野的灵敏度提高 64%，而环直径相同。发现深度分辨率的水平是决定径向空间分辨率的主要因素，而不是探测器的形状。在所有深度分辨率水平下，比较锥形和长方体探测器时，空间分辨率没有明显差异。具有出色深度分辨率的锥形晶体设计探测器将使 PET 扫描仪具有更高的灵敏度和整个视野内均匀的空间分辨率。
