Enhanced megavoltage imaging for radiotherapy by light-field imaging of scintillators

超过50%的患者接受放射治疗（RT），以管理其 RT是成功的癌症治疗的重要组成部分。近年来，kV和 MV成像由于采用图像引导的放射治疗技术而大大增加。 MV治疗射束开启时肿瘤位置的直接成像具有改善的潜力。 肿瘤靶向，导致更好的患者结果和减少健康组织的辐射。一个 另一种方法采用实时kV荧光镜跟踪来执行3D肿瘤位置跟踪。 然而，这种方法只能用于短时间内，因为过量的成像剂量可以快速地 超过患者皮肤剂量耐受水平。 MV电子射野成像设备（EPID）具有明显的优势， 通过使用实际MV治疗射束执行实时肿瘤跟踪来消除该过量成像剂量。 然而，MV EPID通常遭受差的图像质量。典型地，薄（<1 mm）的 闪烁体用于将X射线转换成可见光，然后由阵列非晶硅检测 (aSi)光电探测器这些薄的量子阱具有非常低的探测量子效率（DQE），并且导致 对比度与噪声比差的图像。 我们建议通过增加光子探测层来克服EPID对比度障碍 到10- 50 mm，然后使用专门的 设计光学摄像系统。假设是通过分析捕获的4D光场， 从透明闪烁体，沿着MV射束方向的焦点对准2D平面沿着可以是 有效重建。由于对比度与吸收效率成线性比例， 与探测器厚度成线性比例，该技术有可能通过以下方式增加DQE： 一个数量级超过传统技术。该提案的目的是： 目标1 -开发用于模拟和处理MV光场的算法。 目标2 -基于MV的光场相机的实验评估。 如果成功，该方法将实现实时和/或自适应图像引导的放射治疗 而不添加非目标千伏剂量。

With more than 50% of all patients receiving radiation therapy (RT) for the management of their cancers, RT is an essential part of a successful cancer treatment. In recent years, the use of kV and MV imaging has greatly increased due to the adoption of image-guided radiation therapy techniques. Direct imaging of the tumor position while the MV treatment beam is ON has potential for improving tumor targeting, leading to better patient outcomes and reduced irradiation of healthy tissues. An alternative method employs real-time kV fluoroscopic tracking to perform 3D tumor-position tracking. However, this method can only be used for short periods of time as excess imaging dose can quickly exceed patient skin-dose tolerance levels. MV electronic portal imaging devices (EPID) have the distinct advantage that they can avoid this excess imaging dose by performing real-time tumor tracking using the actual MV treatment beam. However, MV EPIDs generally suffer from poor image quality. Typically, a thin (<1 mm) layer of scintillator is used to convert x-rays to visible light that is then detected by an array amorphous silicon (aSi) photodectors. These thin scintillators have very low detective quantum efficiency (DQE) and lead to images with poor contrast-to-noise ratios. We propose to overcome the EPID contrast obstacle by increasing the photon detection layer to 10-50mm using a transparent scintillator and then capturing its 4D light field using a specially designed optical camera system. The hypothesis is that by analyzing the 4D light field captured from a transparent scintillator, in-focus 2D planes along the MV beam direction can be effectively reconstructed. As contrast is linearly proportional to absorption efficiency, and absorption is linearly proportional to detector thickness, this technique has the potential to increase DQE by an order of magnitude over conventional techniques. The aims of the proposal are: Aim 1 – Development of algorithms for simulating and processing MV based light fields. Aim 2 – Experimental evaluation of a MV based light field camera. If successful, the approach will enable realtime and/or adaptive image-guided radiation therapy without addition of untargeted kilovoltage dose.