Megavoltage cross-scatter rejection and correction using 2D antiscatter grids in kilovoltage CBCT imaging.
Megavoltage cross-scatter rejection and correction using 2D antiscatter grids in kilovoltage CBCT imaging.
复制标题
在千伏 CBCT 成像中使用 2D 抗散射网格进行兆伏交叉散射抑制和校正。
DOI：
10.1117/12.2611202
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Altunbas,Cem
中科院分区：
文献类型：
--
作者：
Bayat,Farhang;Eldib,MohamedElsayed;Altunbas,Cem
同时使用千伏（kV）和兆伏（MV）光束在锥形束计算机断层扫描（CBCT）引导的放射治疗中有许多潜在的应用，例如用于单次屏气扫描的快速MV+kV CBCT，在MV治疗过程中使用kV CBCT成像进行肿瘤定位，以及金属伪影抑制。然而，MV光束的引入会导致kV平板探测器（FPD）上出现较大的MV交叉散射，从而降低了低对比度显示和Hounsfield单位（HU）的精度。在这项工作中，我们提出了一种新的鲁棒方法来降低MV交叉散射的影响。首先，我们在检测器顶部实现了一个2D反散射网格，该网格可以抑制大部分MV交叉散射。这种基于硬件的方法虽然有效，但允许一小部分MV交叉散射传输到FPD，导致CBCT图像中的伪影和HU精度降低。因此，我们引入了一个数据校正步骤，旨在估计和校正剩余的MV交叉散射。这种方法被称为基于网格的散射采样，它利用二维反散射网格本身来测量和校正投影中剩余的MV交叉散射。我们在实验中通过同时获取kV CBCT和用临床直线器传递MV光束来研究所提出的方法的性能。实验结果表明，该方法可以有效地降低HU的不准确性，提高对比噪声比。我们的方法不需要同步千伏和中伏光束脉冲，也不需要降低千伏帧采集率，也不需要降低中伏剂量率，因此在放射治疗的临床环境中更实用。
Simultaneous use of kilovoltage (kV) and megavoltage (MV) beams has numerous potential applications in cone beam computed tomography (CBCT)-guided radiotherapy, such as fast MV+kV CBCT for single breath-hold scan, tumor localization with kV CBCT imaging during MV therapy delivery, and metal artifact suppression. However, the introduction of MV beams results in a large MV-cross scatter fluence incident on the kV Flat Panel Detector (FPD), and thus, deteriorating the low contrast visualization and Hounsfield Unit (HU) accuracy. In this work, we introduced a novel and robust method for reducing the effects of MV cross scatter. First, we implemented a 2D antiscatter grid atop the detector which rejects a large section of MV cross scatter. This hardware-based approach, while effective, allows a fraction of MV cross scatter to be transmitted to the FPD, resulting in artifacts and degraded HU accuracy in CBCT images. We thus introduced a data correction step, which aimed to estimate and correct the remaining MV cross scatter. This approach, referred to as Grid-Based Scatter Sampling, utilized 2D antiscatter grid itself to measure and correct remaining MV cross scatter in projections. We investigated the performance of the proposed approach in experiments by simultaneously acquiring kV CBCT and delivering MV beams with a clinical linac. The results show that the proposed method can substantially reduce HU inaccuracy and increase contrast-to-noise ratio (CNR). Our method does not require synchronization of kV and MV beam pulses, reduction of kV frame acquisition rate, or MV dose rate, and therefore, it is more practical to implement in radiation therapy clinical setting.