Pommranz C M, Schmidt F P, Mannheim J G, Diebold S J, Tenzer C, Santangelo A, Pichler B J
Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University Tuebingen, Roentgenweg 13, D-72076 Tuebingen, Germany.
Institute for Astronomy and Astrophysics, Eberhard Karls University Tuebingen, Sand 1, D-72076 Tuebingen, Germany.
Phys Med Biol. 2023 Feb 28;68(5). doi: 10.1088/1361-6560/acba77.
. Three different breast positron emission tomography (PET) insert geometries are proposed for integration into an existing magnetic resonance imaging (MRI) breast coil (Breast Biopsy Coil, NORAS MRI products) to be used inside a whole-body PET/MRI scanner (Biograph mMR, Siemens Healthineers) to enhance the sensitivity and spatial resolution of imaging inside the breast.. Monte Carlo simulations were performed to predict and compare the performance characteristics of the three geometries in terms of the sensitivity, spatial resolution, scatter fraction, and noise equivalent count rate (NECR). In addition, the background single count rate due to organ uptake in a clinical scan scenario was predicted using a realistic anthropomorphic phantom.. In the center of the field of view (cFOV), absolute sensitivities of 3.1%, 2.7%, and 2.2% were found for Geometry A (detectors arranged in two cylinders), Geometry B (detectors arranged in two partial cylinders), and Geometry C (detectors arranged in two half cylinders combined with two plates), respectively. The full width at half maximum spatial resolution was determined to be 1.7 mm (Geometry A), 1.8 mm (Geometry B) and 2.0 mm (Geometry C) at 5 mm from the cFOV. Designs with multiple scintillation-crystal layers capable of determining the depth of interaction (DOI) strongly improved the spatial resolution at larger distances from the transaxial cFOV. The system scatter fractions were 33.1% (Geometries A and B) and 32.3% (Geometry C). The peak NECRs occurred at source activities of 300 MBq (Geometry A), 310 MBq (Geometry B) and 340 MBq (Geometry C). The background single-event count rates were 17.1 × 10cps (Geometry A), 15.3 × 10cps (Geometry B) and 14.8 × 10cps (Geometry C). Geometry A in the three-layer DOI variant exhibited the best PET performance characteristics but could be challenging to manufacture. Geometry C had the lowest impact on the spatial resolution and the lowest sensitivity among the investigated geometries.. Geometry B in the two-layer DOI variant represented an effective compromise between the PET performance and manufacturing difficulty and was found to be a promising candidate for the future breast PET insert.
提出了三种不同的乳腺正电子发射断层扫描（PET）插入式几何结构，用于集成到现有的磁共振成像（MRI）乳腺线圈（乳腺活检线圈，NORAS MRI产品）中，以便在全身PET/MRI扫描仪（Biograph mMR，西门子医疗）内使用，以提高乳腺内部成像的灵敏度和空间分辨率。进行了蒙特卡罗模拟，以预测和比较这三种几何结构在灵敏度、空间分辨率、散射分数和噪声等效计数率（NECR）方面的性能特征。此外，使用逼真的人体模型预测了临床扫描场景中由于器官摄取导致的背景单计数率。在视野中心（cFOV），几何结构A（探测器排列在两个圆柱体中）、几何结构B（探测器排列在两个部分圆柱体中）和几何结构C（探测器排列在两个半圆柱体与两个平板组合中）的绝对灵敏度分别为3.1%、2.7%和2.2%。在距cFOV 5 mm处，半高宽空间分辨率确定为1.7 mm（几何结构A）、1.8 mm（几何结构B）和2.0 mm（几何结构C）。具有能够确定相互作用深度（DOI）的多个闪烁晶体层的设计在距轴向cFOV较大距离处显著提高了空间分辨率。系统散射分数为33.1%（几何结构A和B）和32.3%（几何结构C）。峰值NECR出现在源活度为300 MBq（几何结构A）、310 MBq（几何结构B）和340 MBq（几何结构C）时。背景单事件计数率为17.1×10 cps（几何结构A）、15.3×10 cps（几何结构B）和14.8×10 cps（几何结构C）。三层DOI变体中的几何结构A表现出最佳的PET性能特征，但制造可能具有挑战性。在研究的几何结构中，几何结构C对空间分辨率的影响最小，灵敏度最低。两层DOI变体中的几何结构B代表了PET性能和制造难度之间的有效折衷，被发现是未来乳腺PET插入件的一个有前途的候选方案。
