背景:新型车载CBCT可以提高图像质量和Hounsfield单位精度。当与在线自适应工具相结合时,这可能有可能允许模拟和治疗在一个单独的会议中完成。
目的:研究高效放射治疗工作流程的可行性,而无需使用单独的会议进行模拟成像。剂量测定的准确性,整体效率,和技术可行性被用来评估无CT模拟自适应放疗的临床潜力。
方法:Varian的Ethos自适应放疗治疗平台采用新型CBCT系统升级,HyperSight可报告与标准扇形束CT相当的图像质量和Hounsfield单位精度规格。使用内部开发的MATLAB软件,将CBCT图像导入系统并用于规划。在配备有小体积离子室(交叉校准到ADCL可追溯剂量标准)的拟人化体模上完成了两个测试用例,以评估工作流程的可行性和准确性。计划进行一次8Gy的模拟姑息性脊柱治疗,计划以60Gy分20次进行完整的前列腺治疗。使用HyperSight以默认的胸部和骨盆成像协议采集CBCT,并使用带有散射去除的迭代算法进行重建,iCBCTAcuros。CBCT用于轮廓和规划,并且通过在线自适应工作流程提供治疗。此外,仅使用机载CBCT成像在端到端头颈部体模照射中完成了外部剂量学审核。
结果:可在12秒内采集扩展场CBCT,除了纵向桌子移位的时间之外,并在大约1分钟内重建。CBCT计划图像的上下范围为38.2cm,捕获了相关解剖结构的全部范围。脊柱和前列腺的轮廓和治疗计划在30和18分钟内完成,分别。离子室测量值与治疗计划之间的剂量学一致性在-1.4%至1.6%的范围内,平均值和标准偏差为0.41±1.16%。外部审计中使用的所有指标均符合通过标准,扇形束和CBCT技术之间的剂量学比较具有99.0%的伽马通过率,标准为2%/2毫米。
结论:使用内部工作流程,无CT模拟放射治疗被证明是可行的,具有可接受的工作流程效率和剂量准确性。这种方法可能特别适用于紧急姑息治疗。随着启用此工作流的软件的可用性,以及治疗适应的持续发展,对于某些临床适应症,单次放射治疗可能会取代当前的实践。
BACKGROUND: Novel on-board CBCT allows for improved image quality and Hounsfield unit accuracy. When coupled with online adaptive tools, this may have potential to allow for simulation and treatment to be completed in a single on-table session.
OBJECTIVE: To study the feasibility of a high-efficiency radiotherapy treatment workflow without the use of a separate session for simulation imaging. The dosimetric accuracy, overall efficiency, and technical feasibility were used to evaluate the clinical potential of CT simulation-free adaptive radiotherapy.
METHODS: Varian\'s Ethos adaptive radiotherapy treatment platform was upgraded with a novel CBCT system, HyperSight which reports image quality and Hounsfield unit accuracy specifications comparable to standard fan-beam CT. Using in-house developed MATLAB software, CBCT images were imported into the system and used for planning. Two test cases were completed on anthropomorphic phantoms equipped with small volume ion chambers (cross-calibrated to an ADCL traceable dose standard) to evaluate the feasibility and accuracy of the workflows. A simulated palliative spine treatment was planned with 8 Gy in one fraction, and an intact prostate treatment was planned with 60 Gy in 20 fractions. The CBCTs were acquired using HyperSight with default thorax and pelvis imaging protocols and reconstructed using an iterative algorithm with scatter removal, iCBCT Acuros. CBCTs were used for contouring and planning, and treatment was delivered via an online adaptive workflow. In addition, an external dosimetry audit was completed using only on-board CBCT imaging in an end-to-end head and neck phantom irradiation.
RESULTS: An extended-field CBCT acquisition can be acquired in 12 s, in addition to the time for longitudinal table shifts, and reconstructed in approximately 1 min. The superior-inferior extent for the CBCT planning images was 38.2 cm, which captured the full extent of relevant anatomy. The contouring and treatment planning for the spine and prostate were completed in 30 and 18 min, respectively. The dosimetric agreement between ion chamber measurements and the treatment plan was within a range of -1.4 to 1.6%, and a mean and standard deviation of 0.41 ± 1.16%. All metrics used in the external audit met the passing criteria, and the dosimetric comparison between fan-beam and CBCT techniques had a gamma passing rate of 99.0% with a criteria of 2%/2 mm.
CONCLUSIONS: Using an in-house workflow, CT simulation-free radiation therapy was shown to be feasible with acceptable workflow efficiency and dosimetric accuracy. This approach may be particularly applicable for urgent palliative treatments. With the availability of software to enable this workflow, and the continued advancement of on-treatment adaptation, single-visit radiation therapy may replace current practice for some clinical indications.