Abstract Cancer is the second leading cause of death in the world, and therefore, there is an undeniable need to ensure early screening and detection systems worldwide. The aim of this project was to study the feasibility of a Cone Beam Computed Tomography (CBCT) scanner for simultaneous breast and lung lesion imaging. Additionally, the development of reconstruction algorithms and the study of their impact to the image quality was considered. Monte Carlo (MC) simulations were performed using the PENELOPE code system. A geometry model of a CBCT scanner was implemented for energies of 30 keV and 80 keV for hypothetical scanning protocols. Microcalcifications were inserted into the breast and lung of the computational phantom (ICRP Adult Female Reference), used in the simulations for dose assessment and projection acquisition. Dosimetric and imaging performances were evaluated through Computed Tomography Dose Index and Catphan phantoms, respectively. Reconstructed images were analyzed in terms of Contrast-to-Noise Ratio (CNR) and dose calculations were performed for two protocols, using a normalization factor of 2 mGy in the breast and another with 5 mGy in the lungs. MC geometry model and reconstruction algorithm were validated by means of on-field measurements and data acquisition in a clinical center. Results indicate that for both protocols, the absorbed dose in both organs is the same, allowing the optimization of protocol strategies regarding radiosensitive organs. The best implementation of the reconstruction algorithm was achieved with 80 keV, using linear interpolation and hanning filter. More specifically for a spherical lung lesion (r = 7 mm) a 30% CNR gain was found when the number of projections varied from 12 to 36 (corresponding to a dose increase of a factor of 3). This study suggests the applicability of a CBCT modulated beam scanner for imaging simultaneously breast and lung lesions while ensuring dose reduction without compromising image quality as a possibility.

中文翻译：

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同步乳腺和肺部 CT 成像中的剂量评估和重建算法优化。

摘要 癌症是世界上第二大死因，因此不可否认，在全球范围内确保早期筛查和检测系统是不可否认的。该项目的目的是研究锥形束计算机断层扫描 (CBCT) 扫描仪用于同时进行乳房和肺部病变成像的可行性。此外，还考虑了重建算法的开发及其对图像质量影响的研究。Monte Carlo (MC) 模拟是使用 PENELOPE 代码系统进行的。CBCT 扫描仪的几何模型是针对 30 keV 和 80 keV 的能量实现的，用于假设扫描协议。微钙化被插入到计算体模（ICRP 成年女性参考）的乳房和肺中，用于剂量评估和投影采集的模拟。剂量学和成像性能分别通过计算机断层扫描剂量指数和 Catphan 体模进行评估。根据对比度噪声比 (CNR) 分析重建图像，并针对两种方案进行剂量计算，使用乳房中的 2 mGy 和另一个肺部 5 mGy 的归一化因子。MC几何模型和重建算法通过临床中心的现场测量和数据采集进行了验证。结果表明，对于两种方案，两个器官的吸收剂量相同，从而可以优化有关辐射敏感器官的方案策略。重构算法的最佳实现是在 80 keV 下实现的，使用线性插值和汉宁滤波器。更具体地，对于球形肺病变 (r = 7 mm)，当突出数从 12 变化到 36（对应于 3 倍的剂量增加）时，发现 CNR 增加了 30%。这项研究表明 CBCT 调制光束扫描仪可用于同时对乳房和肺部病变进行成像，同时确保减少剂量而不影响图像质量。