de Figueiredo Bénédicte Henriques, Antoine Mikael, Trouette Renaud, Lagarde Philippe, Petit Adeline, Lamare Frédéric, Hatt Mathieu, Fernandez Philippe
Radiat Oncol. 2014 Dec 23;9:300. doi: 10.1186/s13014-014-0300-9.
The aim of this study was to assess if FDG-PET could guide dose prescription heterogeneity and decrease arbitrary location of hotspots in SBRT.
For three patients with stage I lung cancer, a CT-simulation and a FDG-PET were registered to define respectively the PTVCT and the biological target volume (BTV). Two plans involving volumetric modulated arc therapy (VMAT) and simultaneous integrated boost (SIB) were calculated. The first plan delivered 4 × 12 Gy within the PTV(CT) and the second plan, with SIB, 4 × 12 Gy and 13.8 Gy (115% of the prescribed dose) within the PTV(CT) and the BTV respectively. The Dmax-PTV(CT) had to be inferior to 60 Gy (125% of the prescribed dose). Plans were evaluated through the D95%, D99% and Dmax-PTV(CT), the D2 cm, the R50% and R100% and the dice similarity coefficient (DSC) between the isodose 115% and BTV. DSC allows verifying the location of the 115% isodose (ideal value = 1).
The mean PTV(CT) and BTV were 36.7 (±12.5) and 6.5 (±2.2) cm3 respectively. Both plans led to similar target coverage, same doses to the OARs and equivalent fall-off of the dose outside the PTV(CT). On the other hand, the location of hotspots, evaluated through the DSC, was improved for the SIB plans with a mean DSC of 0.31 and 0.45 for the first and the second plans respectively.
Use of PET to decrease arbitrary location of hotspots is feasible with VMAT and SIB for lung cancer.
本研究的目的是评估氟代脱氧葡萄糖正电子发射断层扫描（FDG-PET）是否能够指导立体定向体部放疗（SBRT）中的剂量处方异质性，并减少热点的随意定位。
对于3例I期肺癌患者，分别进行CT模拟和FDG-PET检查以定义计划靶区（PTVCT）和生物靶区（BTV）。计算了两个涉及容积调强弧形放疗（VMAT）和同步整合加量（SIB）的计划。第一个计划在PTV(CT)内给予4×12 Gy，第二个计划采用SIB，在PTV(CT)和BTV内分别给予4×12 Gy和13.8 Gy（处方剂量的115%）。PTV(CT)的最大剂量（Dmax-PTV(CT)）必须低于60 Gy（处方剂量的125%）。通过D95%、D99%和Dmax-PTV(CT)、D2 cm、R50%和R100%以及115%等剂量线与BTV之间的骰子相似性系数（DSC）对计划进行评估。DSC可用于验证115%等剂量线的位置（理想值=1）。
PTV(CT)和BTV的平均体积分别为36.7（±12.5）cm³和6.5（±2.2）cm³。两个计划导致相似的靶区覆盖、对危及器官的相同剂量以及PTV(CT)外剂量的等效下降。另一方面，通过DSC评估，SIB计划的热点定位得到改善，第一个和第二个计划的平均DSC分别为0.31和0.45。
对于肺癌，使用PET减少热点的随意定位在VMAT和SIB中是可行的。
