PDF(Pubmed)
Abstract：
Objective. The concept of using kilovoltage (kV) and megavoltage (MV) beams concurrently has potential applications in cone beam computed tomography (CBCT) guided radiation therapy, such as single breath hold scans, metal artifact reduction, and simultaneous imaging during MV treatment delivery. However, MV cross-scatter generated during MV beam delivery degrades CBCT image quality. To address this, a 2D antiscatter grid and a cross-scatter correction method were investigated in the context of high dose MV treatment delivery.Approach. A 3D printed, tungsten 2D antiscatter grid prototype was utilized in kV CBCT scans to reduce MV cross-scatter fluence during concurrent MV beam delivery. Remaining cross-scatter in projections was corrected by using the 2D grid itself as a cross-scatter intensity sampling device, referred to as grid-based scatter sampling (GSS). To test this approach, kV CBCT acquisitions were performed while delivering 6 and 10 MV beams, mimicking high dose rate treatment delivery scenarios. kV and MV beam deliveries were not synchronized to eliminate MV beam delivery interruption. MV cross-scatter suppression performance of the proposed approach was evaluated in projections and CBCT images of phantoms.Main results. 2D grid reduced the intensity of MV cross-scatter in kV projections by a factor of 3 on the average, when compared to conventional antiscatter grid. Remaining cross scatter as measured by the GSS method was within 7% of measured reference intensity values, and subsequently corrected. CBCT image quality was improved substantially during concurrent kV-MV beam delivery. Median Hounsfield Unit (HU) inaccuracy was up to 182 HU without our methods, and it was reduced to a median 6.5 HU with our 2D grid and scatter correction approach. Our methods provided a factor of 2-6 improvement in contrast-to-noise ratio.Significance. This investigation demonstrates the utility of 2D antiscatter grids and grid-based scatter sampling in suppressing MV cross-scatter. Our approach successfully minimized the effects of MV cross-scatter in concurrent kV CBCT imaging and high dose MV treatment delivery scenarios. Hence, robust MV cross-scatter suppression is potentially feasible without MV beam delivery interruption or compromising kV image acquisition rate.
摘要：
Objective.同时使用千伏（kV）和兆伏（MV）束的概念在锥形束计算机断层扫描（CBCT）引导放射治疗中具有潜在的应用，比如单次屏气扫描，金属伪影减少，在MV治疗期间同时成像。然而,在MV光束传递期间生成的MV交叉散射降低了CBCT图像质量。为了解决这个问题，在高剂量MV治疗交付的背景下研究了2D抗散射网格和交叉散射校正方法。方法。3D打印,在kVCBCT扫描中使用了钨2D抗散射网格原型，以减少并发MV光束传输期间的MV交叉散射通量。通过使用2D网格本身作为交叉散射强度采样设备来校正投影中的剩余交叉散射。称为基于网格的散射采样(GSS)。为了测试这种方法，在提供6和10MV波束时执行kVCBCT采集，模仿高剂量率治疗交付方案。kV和中压梁输送不同步以消除中压梁输送中断。在幻像的投影和CBCT图像中评估了所提出方法的MV交叉散射抑制性能。主要结果。2D网格将kV投影中的MV交叉散射强度平均降低了3倍，与传统的抗散射网格相比。通过GSS方法测量的剩余交叉散射在测量的参考强度值的7%以内，随后纠正。在并发kV-MV波束传输期间，CBCT图像质量得到了显着改善。如果没有我们的方法，中位亨氏单位(HU)的不准确性高达182HU，通过我们的2D网格和散射校正方法，它被降低到中位数6.5HU。我们的方法在对比噪声比方面提供了2-6倍的改善。意义。这项研究证明了2D抗散射网格和基于网格的散射采样在抑制MV交叉散射中的实用性。我们的方法成功地将并发kVCBCT成像和高剂量MV治疗递送方案中的MV交叉散射的影响降至最低。因此，鲁棒的MV交叉散射抑制是潜在可行的没有MV光束传输中断或损害kV图像采集率。
