Coded-aperture Compton scatter imaging for real-time tumor motion tracking during ablative radiotherapy

项目摘要/摘要 立体定向全身放射治疗(SBRT)是一种侵袭性、消融性的局部治疗方法，可以 有效治疗许多难以治疗的肿瘤，如胰腺癌、非小细胞肺癌 癌症、黑色素瘤和肾癌。通过在少数情况下提供大剂量、烧蚀剂量的辐射 在治疗中，SBRT显著改善了局部控制。然而，这两者之间有一个权衡 在腹部提供侵入性剂量的放射治疗，具有SBRT和剂量限制副作用。一位少校 问题是，呼吸诱导的腹部运动是不稳定的，使传统的 运动管理的方法效果不佳。 为了使这些肿瘤能够安全有效地增加剂量，我们提出了一种新的成像系统。 它测量植入患者体内的基准标记的位置。这个系统被称为编码孔径 散射成像(CASI)，在治疗过程中被动测量肿瘤的位置，不需要额外的 辐射剂量。在放射治疗过程中，一束大容量的x射线被对准肿瘤，其中一些 这些光子在患者体内经历散射相互作用。这些光子更有可能在 密度高、原子序数高的基准标记，提供可以通过 成像器垂直于梁放置。我们建议使用编码孔径成像来解码 这些基准标记是实时的。编码孔径技术，用于天文学和 核医学，可以帮助在广泛的背景下识别微弱的点源。 CASI在临床上很有吸引力，有几个原因。这种被动技术提供实时运动 不需要额外成像剂量的信息，因为它使用来自 治疗梁。CASI很容易在任何现有的临床直线加速器上实现，因为所有现代的 直线加速器配备了一个与治疗波束垂直放置的千伏成像面板。基准标记是 通常被植入这些肿瘤中，唯一需要的额外硬件是编码孔径本身， 它可以简单地放置在患者和检测器之间。最后，通过测量肿瘤的运动 在治疗过程中，可以提高治疗的准确性，这可以使更有效， 剂量递增治疗，以避免对正常组织的毒性。这项工作的目标是设计、制造、 并测试用于CASI引导放射治疗的优化孔径。

Project Summary/Abstract Stereotactic Body Radiation Therapy (SBRT) is an aggressive, ablative local therapy that can be an effective treatment for many hard-to-treat tumors, such as pancreatic adenocarcinoma, non-small cell lung cancer, melanoma, and renal cell carcinoma. By delivering large, ablative doses of radiation in a small number of treatments, SBRT leads to significantly improved local control. However, there is a trade-off between delivering aggressive doses of radiation in the abdomen with SBRT and dose-limiting side-effects. A major problem is that the breathing-induced motion of the abdomen is erratic and unstable, rendering traditional methods of motion management ineffective. To enable safe and effective dose escalation for these tumors, we are proposing a novel imaging system that measures the position of fiducial markers implanted inside the patient. This system, called Coded Aperture Scatter Imaging (CASI), passively measures the position of tumors during treatment with no additional radiation dose. During radiotherapy, a beam of megavoltage x-rays is directed towards the tumor, and some of those photons undergo scattering interactions within the patient. These photons are more likely to interact in the dense, high-atomic-number fiducial markers, providing a differential signal that can be measured by an imager placed orthogonal to the beam. We propose to use coded aperture imaging to decode the location of these fiducial markers in real time. The coded aperture technique, utilized in fields such as astronomy and nuclear medicine, can help identify faint point sources within a broad background. CASI is clinically attractive for several reasons. This passive technique provides real-time motion information with no additional imaging dose, since it forms an image using scattered photons from the treatment beam. CASI is easily implementable on any existing clinical linear accelerator, since all modern linacs are equipped with a kV imaging panel placed orthogonal to the treatment beam. Fiducial markers are commonly implanted in these tumors, and the only additional hardware needed is the coded aperture itself, which can simply be placed between the patient and the detector. Finally, by measuring the motion of tumors during treatment one could increase the accuracy of treatment delivery, which could enable more effective, dose-escalated treatments that avoid toxicity to normal tissues. The goal of this work is to design, fabricate, and test an optimized aperture for CASI-guided radiotherapy.