Su Z, Slopsema R, Flampouri S, Li Z
University of Florida, Jacksonville, FL.
Med Phys. 2012 Jun;39(6Part9):3702. doi: 10.1118/1.4735054.
To investigate dosimetric impact of prostate intra-fraction motion to five fraction hypofractionated proton treatment with uniform scanning (US) and double scattering (DS) techniques using real-time prostate tracking data from electromagnetic transponder system.
Prostate intra-fraction motion can have spatiotemporal interplay with proton treatment delivery. Five fraction (7.25Gy/fraction) prostate proton stereotactic body radiotherapy (SBRT) treatments were simulated for total 14 patients using in-house proton treatment simulation program. The US treatment was simulated by rigidly moving CTV through a series of temporal-spatial dose matrices indexed by energy layers, according to prostate motion traces. The CTV temporal doses of the whole treatment fraction were obtained and summed as final prostate CTV dose. The DS treatment was simulated by moving CTV through the energy layer summed dose matrix. For all patients, the fraction doses and the total dose to the CTV were presented for both DS and US treatments.
The CTV dose of different fractions indicated that its dose degradation depends on magnitude and direction of prostate intra-fraction motion and is patient specific. For one of the prostate motion traces investigated, only 70% of CTV received 100% prescribed dose for a simulated US treatment and 79% CTV had 100% dose for a DS treatment. Furthermore, DVH and isodose graphs of both treatments revealed that intra-fraction motion caused significant CTV cold and hot spots in US treatment whereas only cause CTV underdose in DS treatment.
Intra-fraction prostate motion causes dose uncertainty to CTV. In the 5 fraction prostate SBRT, prostate intra-fraction motion causes significant target dose degradation. In US treatment, spatiotemporal interplay between energy layers delivery and prostate motion leads to hot and cold spots in CTV for some patients with severe prostate intra-fraction motion. Further investigation of intra-fraction motion management and its impact on CTV dose is necessary.
利用电磁应答器系统的实时前列腺跟踪数据，研究前列腺分次内运动对采用均匀扫描（US）和双散射（DS）技术的五分次低分割质子治疗的剂量学影响。
前列腺分次内运动可能与质子治疗的实施存在时空相互作用。使用内部质子治疗模拟程序，对总共14例患者进行了五次分次（每次7.25Gy）的前列腺质子立体定向体部放射治疗（SBRT）模拟。根据前列腺运动轨迹，通过将临床靶体积（CTV）在一系列由能量层索引的时空剂量矩阵中进行刚性移动来模拟US治疗。获取整个治疗分次的CTV时间剂量并求和，作为最终的前列腺CTV剂量。通过将CTV在能量层求和剂量矩阵中移动来模拟DS治疗。对于所有患者，给出了DS和US治疗的分次剂量以及CTV的总剂量。
不同分次的CTV剂量表明，其剂量降低取决于前列腺分次内运动的幅度和方向，且具有患者特异性。对于所研究的一条前列腺运动轨迹，在模拟的US治疗中，只有70%的CTV接受了100%的处方剂量，而在DS治疗中，79%的CTV接受了100%的剂量。此外，两种治疗的剂量体积直方图（DVH）和等剂量线图显示，分次内运动在US治疗中导致了显著的CTV冷点和热点，而在DS治疗中仅导致CTV剂量不足。
前列腺分次内运动导致CTV剂量不确定。在五次分次的前列腺SBRT中，前列腺分次内运动导致显著的靶区剂量降低。在US治疗中，能量层照射与前列腺运动之间的时空相互作用导致一些前列腺分次内运动严重的患者的CTV出现热点和冷点。有必要进一步研究分次内运动管理及其对CTV剂量的影响。
