Babka Viktor, Rehounek Lubos, Jakubcova Iva, Sirak Igor, Paluska Petr, Kašaová Linda, Vosmik Milan, Grepl Jakub
Department of Oncology and Radiotherapy, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic.
Department of Nuclear Medicine, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic.
Rep Pract Oncol Radiother. 2025 Aug 7;30(3):298-305. doi: 10.5603/rpor.105857. eCollection 2025.
This study evaluates the quality of synthetic computed tomography (sCT) images for MR-only radiotherapy in prostate cancer using gamma analysis. A software tool, MRGamma, was developed to address challenges like the absence of electron density maps and registration uncertainties between magnetic resonance imaging (MRI) and planning CT (pCT).
Aplication developed in MATLAB assesses Hounsfield units (HU) discrepancies between CT and sCT images via 2D and 3D gamma analysis (GA). GA computes a gamma index (γ) for each voxel based on HU differences and distance to agreement (DTA). The study analyzed prostate cancer patients using the MRCAT algorithm to generate sCT images. Preprocessing included registration, resampling, and cropping to standardize image dimensions. GA was performed with thresholds of 100 HU and 70 HU for HU differences and 3 mm for DTA to evaluate image quality.
Aplication demonstrated high agreement between sCT and CT images. For 3D GA (100 HU, 3 mm), 95.5 ± 1.8% of voxels passed the threshold, with slightly lower rates for 70 HU. Discrepancies were most pronounced at tissue interfaces and air cavities, where HU variations were more significant. Mean γ values for 3D GA were 0.19 ± 0.04 (milder parameters) and 0.23 ± 0.05 (stricter parameters), showing consistent trends in 2D GA. Maximum γ values confirmed good overall agreement.
Aplication effectively evaluates sCT quality, supporting the feasibility of MR-only radiotherapy. By providing detailed HU comparisons, the tool enhances MR-based treatment planning, reducing costs and ionizing radiation exposure. Its implementation may improve workflow efficiency and patient safety in clinical practice.
本研究使用伽马分析评估用于前列腺癌磁共振成像（MRI）引导放疗的合成计算机断层扫描（sCT）图像的质量。开发了一种软件工具MRGamma，以应对诸如缺乏电子密度图以及磁共振成像（MRI）与计划计算机断层扫描（pCT）之间的配准不确定性等挑战。
在MATLAB中开发的应用程序通过二维和三维伽马分析（GA）评估CT图像与sCT图像之间的亨氏单位（HU）差异。GA基于HU差异和一致性距离（DTA）为每个体素计算伽马指数（γ）。该研究使用MRCAT算法分析前列腺癌患者以生成sCT图像。预处理包括配准、重采样和裁剪，以标准化图像尺寸。使用HU差异阈值100 HU和70 HU以及DTA阈值3 mm进行GA，以评估图像质量。
该应用程序显示sCT图像与CT图像高度一致。对于三维GA（100 HU，3 mm），95.5±1.8%的体素通过阈值，70 HU时通过率略低。差异在组织界面和空气腔处最为明显，此处HU变化更为显著。三维GA的平均γ值为0.19±0.04（较宽松参数）和0.23±0.05（较严格参数），在二维GA中显示出一致趋势。最大γ值证实了总体一致性良好。
该应用程序有效评估了sCT质量，支持了仅基于MRI放疗的可行性。通过提供详细的HU比较，该工具增强了基于MRI的治疗计划，降低了成本和电离辐射暴露。其实施可能会提高临床实践中的工作流程效率和患者安全性。
