Turk J Med Sci. 2015;45(1):129-35. doi: 10.3906/sag-1312-149.
BACKGROUND/AIM: To investigate the effect of positron emission tomography-computed tomography (PET/CT)-based contouring on dosimetric parameters in rectal cancer patients undergoing preoperative intensity-modulated radiation therapy (IMRT).
Preoperative radiation therapy plans with conformal radiotherapy (CRT) or IMRT were created and examined according to the CT- and PET/CT-based contouring of 20 rectal cancer patients, retrospectively.
The target volumes delineated with PET/CT were significantlylarger than the volumes created by CT (P= 0.043). Dose delivered to 98% of the planning target volume was high in IMRT planning contouring with CT and PET/CT compared with CRT planning, but the difference was not statistically significant (P = 0.056). Percent volumes receiving 105% of dose and 110% of dose were low in IMRT planning when compared with CRT (P < 0.0001 and P = 0.044, respectively). The volumes receiving 45 Gy for the small intestine, femur heads, and bladder and the maximum dose received by the bladder were significantly lower in IMRT.
We showed that the target volumes created with PET/CT are significantly larger than the target volumes created with CT and that IMRT provides lower radiation exposure to the tumor-free tissues compared to the CRT planning. The dosimetric results primarily favor IMRT planning in rectal cancer patients and consequently present the significant alteration in target volumes.
背景/目的：研究正电子发射断层扫描-计算机断层扫描（PET/CT）勾画在直肠癌患者术前调强放疗（IMRT）中的剂量学参数的影响。
回顾性分析了 20 例直肠癌患者的 CT 和 PET/CT 勾画的术前放射治疗计划，比较了适形放疗（CRT）和调强放疗（IMRT）的计划。
PET/CT 勾画的靶区体积明显大于 CT 勾画的体积（P=0.043）。与 CRT 相比，CT 和 PET/CT 勾画的 IMRT 计划中，98%的计划靶区接受的剂量较高，但差异无统计学意义（P=0.056）。与 CRT 相比，IMRT 计划中接受 105%和 110%剂量的体积百分比较低（P<0.0001 和 P=0.044）。小肠、股骨头和膀胱接受 45Gy 的体积和膀胱接受的最大剂量在 IMRT 中明显较低。
我们表明，与 CT 相比，PET/CT 勾画的靶区体积明显较大，与 CRT 相比，IMRT 对肿瘤无照射组织的辐射暴露较低。剂量学结果主要有利于直肠癌患者的 IMRT 计划，因此靶区体积有明显的改变。
