Department of Biomedical Engineering, University of California Davis, Sacramento, CA 95817, United States of America.
Department of Radiology, University of California Davis, Sacramento, CA 95817, United States of America.
Phys Med Biol. 2020 Dec 18;65(23):235032. doi: 10.1088/1361-6560/abc306.
The purpose of this study was to compare various multisource configurations applied to cone beam CT (CBCT) using phantom imaging and Monte Carlo simulations. Image quality, scatter, and dose were evaluated in both overlapping (large cone angle) and collimated (small cone angle) configurations for CBCT. Four x-ray tube configurations were considered: traditional one source, three source overlapping, six source overlapping, and six source collimated. Image quality was evaluated on a prototype breast CT system using the following five phantoms: a Defrise phantom, a previously reported CBCT QA phantom (Corgi), a polyethylene cylinder, and two anthropomorphic phantoms (hand and knee). Scatter contamination and radiation dose were evaluated using Monte Carlo simulations of a voxelized polyethylene cylinder. The modulation of the Defrise phantom disks on average was 2.7X greater for the six source collimated configuration than the six source overlapping configuration. The data lost from cone beam artifact (spatial domain) and the null cone (frequency domain) in the overlapping configuration were completely recovered using the collimated configuration. The maximum scatter-to-primary ratio (SPR) for the overlapping configuration was 0.81 and the maximum SPR for the collimated configuration was 0.26. The average dose and maximum dose was 4X less in the collimated six source configuration when compared with the overlapping configurations. The maximum dose for the overlapping configurations (one, three & six) remained constant, but the average dose for the multisource (three & six source) overlapping configurations increased 25% when compared to the one source configuration. Use of a collimated multisource x-ray tube configuration was shown to provide significant improvements in image quality throughout the cone-beam geometry field-of-view, reduction in scatter contamination, and more efficient use of dose in comparison to both the traditional CBCT geometry with a single source and the overlapping multisource configurations.
本研究旨在通过体模成像和蒙特卡罗模拟比较应用于锥形束 CT（CBCT）的各种多源配置。在重叠（大锥角）和准直（小锥角）配置下，对 CBCT 的图像质量、散射和剂量进行了评估。考虑了四种 X 射线管配置：传统单源、三源重叠、六源重叠和六源准直。使用以下五种体模评估了原型乳腺 CT 系统的图像质量：Defrise 体模、先前报道的 CBCT QA 体模（Corgi）、聚乙烯圆柱和两个拟人体模（手和膝盖）。使用体素化聚乙烯圆柱的蒙特卡罗模拟评估了散射污染和辐射剂量。六源准直配置的平均调制比六源重叠配置高 2.7 倍。重叠配置中从锥形束伪影（空域）和空锥形（频域）丢失的数据完全可以使用准直配置来恢复。重叠配置的最大散射与原始射线比值（SPR）为 0.81，准直配置的最大 SPR 为 0.26。与重叠配置相比，准直六源配置的平均剂量和最大剂量减少了 4 倍。重叠配置（一、三、六源）的最大剂量保持不变，但与单源配置相比，多源（三、六源）重叠配置的平均剂量增加了 25%。与传统的具有单源的 CBCT 几何形状和重叠多源配置相比，使用准直多源 X 射线管配置可在整个锥形束几何视场中提供显著改善的图像质量、减少散射污染和更有效地利用剂量。
