Nano Tomi F, Capaldi Dante P I, Yeung Timothy, Chuang Cynthia F, Wang Lei, Descovich Martina
Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, 94143, USA.
Department of Radiation Oncology, Stanford University, Stanford, CA, 94305-6104, USA.
Med Phys. 2020 Dec;47(12):6163-6170. doi: 10.1002/mp.14537. Epub 2020 Oct 28.
To investigate the effects of CT protocol and in-room x-ray technique on CyberKnife (Accuray Inc.) tracking accuracy by evaluating end-to-end tests.
End-to-end (E2E) tests were performed for the different tracking methods (6D skull, fiducial, spine, and lung) using an anthropomorphic head phantom (Accuray Inc.) and thorax phantom (CIRS Inc.). Bolus was added to the thorax phantom to simulate a large patient and to evaluate the performance of lung tracking in a more realistic condition. The phantoms were scanned with a Siemens Sensation Open 24 slice CT at low dose (120 kV, 70 mAs, 1.5 mm slice thickness) and high dose (120 kV, 700 mAs, 1.5 mm slice thickness) to generate low-dose and high-dose digitally reconstructed radiographs (DRRs). The difference in initial phantom alignment, Δ(Align), and in total targeting accuracy, E2E, were obtained for all tracking methods with low- and high-dose DRRs. Additionally, Δ(Align) was determined for different in-room x-ray imaging techniques (0.5 to 50 mAs and 100 to 140 kV) using a low-dose lung tracking plan.
Low-dose CT scans produced images with high noise; however, for these phantoms the targets could be easily delineated on all scans. End-to-end results were less than 0.95 mm for all tracking methods and all plans. The greatest difference in initial alignment Δ(Align) and E2E results between low- and high-dose CT protocols was 0.32 and 0.24 mm, respectively. Similar results were observed with a large thorax phantom. Tracking using different in-room x-ray imaging techniques (mAs) corresponding to low exposures (resulting in high image noise) or high exposure (resulting in image saturation) had alignment accuracy Δ(Align) greater than 1 mm.
End-to-end targeting accuracy within tolerance (<0.95 mm) was obtained for all tracking methods using low-dose CT protocols, suggesting that CT protocol should be set by target contouring needs. Additionally, high tracking accuracy was achieved for in-room x-ray imaging techniques that produce high-quality images.
通过评估端到端测试，研究CT协议和室内X射线技术对射波刀（Accuray公司）跟踪精度的影响。
使用拟人化头部模型（Accuray公司）和胸部模型（CIRS公司），对不同的跟踪方法（6D颅骨、基准点、脊柱和肺部）进行端到端（E2E）测试。在胸部模型中添加 bolus 以模拟大型患者，并在更真实的条件下评估肺部跟踪的性能。使用西门子Sensation Open 24层CT对模型进行低剂量（120 kV，70 mAs，1.5 mm层厚）和高剂量（120 kV，700 mAs，1.5 mm层厚）扫描，以生成低剂量和高剂量数字重建射线照片（DRR）。获得所有跟踪方法在低剂量和高剂量DRR下的初始模型对齐差异Δ(Align)和总靶向精度E2E。此外，使用低剂量肺部跟踪计划，确定不同室内X射线成像技术（0.5至50 mAs和100至140 kV）的Δ(Align)。
低剂量CT扫描产生的图像噪声较高；然而，对于这些模型，目标在所有扫描中都能轻松勾勒出来。所有跟踪方法和所有计划的端到端结果均小于0.95 mm。低剂量和高剂量CT协议之间初始对齐Δ(Align)和E2E结果的最大差异分别为0.32和0.24 mm。在大型胸部模型中也观察到了类似结果。使用对应于低曝光（导致高图像噪声）或高曝光（导致图像饱和）的不同室内X射线成像技术（mAs）进行跟踪时，对齐精度Δ(Align)大于1 mm。
使用低剂量CT协议的所有跟踪方法均获得了公差范围内（<0.95 mm）的端到端靶向精度，这表明CT协议应根据目标轮廓需求进行设置。此外，对于产生高质量图像 的室内X射线成像技术，实现了高跟踪精度。
