Department of Radiology, School of Medicine, West Virginia University, Morgantown, West Virginia, USA.
Department of Chemical and Biomedical Engineering, Benjamin M. Statler College of Engineering and Mineral Resources, West Virginia University, Morgantown, West Virginia, USA.
Med Phys. 2022 Dec;49(12):7489-7496. doi: 10.1002/mp.16033. Epub 2022 Oct 24.
Dedicated, breast-specific positron emission tomography (BPET)-cone-beam computed tomography (BPET/CT) systems have been developed to improve detection and diagnosis of cancer in women with indeterminate mammograms caused by radiodense breasts. The absorption of X-rays that often vexes mammography in this subset of women does not affect the detection of the high energy annihilation photons used in PET. PET imaging of the breast, however, is subject to limitations caused by their comparatively low spatial resolution (∼2 mm) and often moderate radiotracer uptake in lesions.
The purpose of this investigation is to explore the PET-based lesion detection capabilities of a BPET/CT scanner developed by the Department of Radiology Instrumentation group at West Virginia University.
The PET component of the system consists of a rotating pair of 96 × 72 arrays of 2 × 2 × 15 mm LYSO scintillator elements. The cone-beam-CT component utilized a pulsed X-ray source and flat panel detector operated in portrait orientation. The density maps created by the CT scanner were used to correct the BPET data for photon attenuation and Compton scattering. The nonuniform uptake of F-fluorodeoxyglucose (FDG) in normal breast tissue was emulated in a specially designed phantom consisting of an acrylic cylinder filled with a mixture of acrylic beads and liquid containing FDG. FDG-avid lesions were simulated with agar spheres (3, 4, 6, 8, and 10 mm diameters) containing vary amounts of FDG to produce target-to-background ratios (TBR) of 6:1, 8:1, and 10:1. The spheres also contained X-ray contrast agent to make even the smallest ones readily visible in CT images. Positions of all the lesions were identified in the CT images. These positions were used to extract signal present and signal absent sub-images from the PET images. The sub-images were then input to software that calculated areas-under-the-curve for two numerical model observers (Laguerre-Gauss channelized Hotelling observer and non-prewhitening matched filter).
The results showed that the smallest detectable lesion with this system is no smaller than ∼3 mm in diameter with a TBR of 6:1. Simulated lesions with diameters of 4 mm and greater were calculated to have good to excellent likelihood of detection for all TBRs tested.
The results from this investigation identified the detectability capabilities and limitations for a dedicated breast-PET/CT scanner. Its ability to detect relatively small simulated FDG-avid breast lesions for a range of TBRs indicates its potential for clinical application. Finally, the study used methodologies that could be applied to a detectability assessment of other PET/CT scanners.
为了提高对致密型乳腺所致乳腺 X 线摄影检查结果不明确的女性癌症的检出和诊断，开发了专用的、针对乳腺的正电子发射断层扫描（BPET）-锥形束计算机断层扫描（BPET/CT）系统。在这部分女性中，常使乳腺 X 线摄影检查感到困扰的 X 射线吸收并不会影响到正电子发射断层扫描中使用的高能湮没光子的检测。然而，由于其空间分辨率相对较低（约 2mm），并且病变中摄取的放射性示踪剂通常为中等水平，因此，乳腺的正电子发射断层扫描成像存在局限性。
本研究旨在探讨西弗吉尼亚大学放射学仪器组开发的专用乳腺 BPET/CT 扫描仪的基于正电子发射断层扫描的病变检出能力。
该系统的正电子发射断层扫描组件由一对旋转的 96×72 个 2×2×15mm 的 LYSO 闪烁体元件组成。锥形束 CT 组件使用脉冲 X 射线源和平板探测器，以纵向模式运行。CT 扫描仪创建的密度图用于校正正电子发射断层扫描数据的光子衰减和康普顿散射。使用一个特殊设计的、由充满丙烯珠和含有 FDG 的液体的丙烯酸圆柱体制成的体模，模拟正常乳腺组织中 F-氟脱氧葡萄糖（FDG）的不均匀摄取。使用含有不同 FDG 量的琼脂球（直径为 3、4、6、8 和 10mm）模拟 FDG 摄取阳性的病变，以产生靶标与背景的比值（TBR）为 6:1、8:1 和 10:1。球体内还含有 X 射线造影剂，以便在 CT 图像中能够轻易看到最小的球。所有病变的位置均在 CT 图像中确定。这些位置用于从正电子发射断层扫描图像中提取存在信号和不存在信号的子图像。然后，将子图像输入到软件中，该软件为两种数值模型观察者（拉盖尔-高斯通道化霍特林观察者和非预白化匹配滤波器）计算了曲线下面积。
结果表明，该系统可检测到的最小病变直径不小于约 3mm，TBR 为 6:1。对于所有测试的 TBR，直径为 4mm 及以上的模拟病变均被计算为具有良好至优秀的检出可能性。
本研究确定了专用乳腺 BPET/CT 扫描仪的检出能力和局限性。该系统能够检测到一系列 TBR 下的相对较小的模拟 FDG 摄取阳性乳腺病变，表明其具有临床应用的潜力。最后，该研究使用的方法可应用于其他正电子发射断层扫描/计算机断层扫描扫描仪的检出能力评估。
