容积旋转调强弧形治疗（VMAT）与固定野动态调强放疗（FF-DIMRT）治疗局部进展期鼻咽癌的剂量学比较
Dosimetry Comparison between Volumetric Modulated Arc Therapy with Rapid Arcand Fixed Field Dynamic IMRT for Local-Regionally Advanced Nasopharyngeal Carcinoma.
机构信息
Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Radiotherapy, Peking University School of Oncology, Beijing Cancer Hospital & Institute, Beijing 100142, China.
出版信息
Chin J Cancer Res. 2011 Dec;23(4):259-64. doi: 10.1007/s11670-011-0259-0.
OBJECTIVE
A dosimetric study was performed to evaluate the performance of volumetric modulated arc radiotherapy with RapidArc on locally advanced nasopharyngeal carcinoma (NPC).
METHODS
The CT scan data sets of 20 patients of locally advanced NPC were selected randomly. The plans were managed using volumetric modulated arc with RapidArc and fixed nine-field coplanar dynamic intensity-modulated radiotherapy (IMRT) for these patients. The dosimetry of the planning target volumes (PTV), the organs at risk (OARs) and the healthy tissue were evaluated. The dose prescription was set to 70 Gy to the primary tumor and 60 Gy to the clinical target volumes (CTV) in 33 fractions. Each fraction applied daily, five fractions per week. The monitor unit (MU) values and the delivery time were scored to evaluate the expected treatment efficiency.
RESULTS
Both techniques had reached clinical treatment's requirement. The mean dose (Dmean), maximum dose (Dmax) and minimum dose (Dmin) in RapidArc and fixed field IMRT for PTV were 68.4±0.6 Gy, 74.8±0.9 Gy and 56.8±1.1 Gy; and 67.6±0.6 Gy, 73.8±0.4 Gy and 57.5±0.6 Gy (P<0.05), respectively. Homogeneity index was 78.85±1.29 in RapidArc and 80.34±0.54 (P<0.05) in IMRT. The conformity index (CI: 95%) was 0.78±0.01 for both techniques (P>0.05). Compared to IMRT, RapidArc allowed a reduction of Dmean to the brain stem, mandible and optic nerves of 14.1% (P<0.05), 5.6% (P<0.05) and 12.2% (P<0.05), respectively. For the healthy tissue and the whole absorbed dose, Dmean of RapidArc was reduced by 3.6% (P<0.05), and 3.7% (P<0.05), respectively. The Dmean to the parotids, the spinal cord and the lens had no statistical difference among them. The mean MU values of RapidArc and IMRT were 550 and 1,379. The mean treatment time of RapidArc and IMRT was 165 s and 447 s. Compared to IMRT, the delivery time and the MU values of RapidArc were reduced by 63% and 60%, respectively.
CONCLUSION
For locally advanced NPC, both RapidArc and IMRT reached the clinic requirement. The target volume coverage was similar for the different techniques. The RapidArc technique showed some improvements in OARs and other tissue sparing while using reduced MUs and delivery time.
目的
本研究旨在评估容积旋转调强弧形放疗（RapidArc）治疗局部晚期鼻咽癌（NPC）的剂量学性能。
方法
本研究从局部晚期 NPC 患者中随机选择 20 例患者的 CT 扫描数据集。为这些患者使用容积旋转调强弧形和固定九野共面动态调强放疗（IMRT）进行计划管理。评估了计划靶区（PTV）、危及器官（OAR）和健康组织的剂量学。将剂量处方设置为 70 Gy 至原发肿瘤和 60 Gy 至临床靶区（CTV），共 33 个分数。每个分数每天应用一次，每周应用 5 次。记录监测器单位（MU）值和治疗时间，以评估预期的治疗效率。
结果
两种技术均达到临床治疗要求。RapidArc 和固定野 IMRT 治疗 PTV 的平均剂量（Dmean）、最大剂量（Dmax）和最小剂量（Dmin）分别为 68.4±0.6 Gy、74.8±0.9 Gy 和 56.8±1.1 Gy；67.6±0.6 Gy、73.8±0.4 Gy 和 57.5±0.6 Gy（P<0.05）。RapidArc 的均匀性指数为 78.85±1.29，IMRT 为 80.34±0.54（P<0.05）。两种技术的适形指数（CI：95%）均为 0.78±0.01（P>0.05）。与 IMRT 相比，RapidArc 使脑干、下颌骨和视神经的 Dmean 分别降低了 14.1%（P<0.05）、5.6%（P<0.05）和 12.2%（P<0.05）。对于健康组织和全身吸收剂量，RapidArc 的 Dmean 分别降低了 3.6%（P<0.05）和 3.7%（P<0.05）。腮腺、脊髓和晶状体的 Dmean 无统计学差异。RapidArc 和 IMRT 的平均 MU 值分别为 550 和 1379。RapidArc 和 IMRT 的平均治疗时间分别为 165 s 和 447 s。与 IMRT 相比，RapidArc 的治疗时间和 MU 值分别降低了 63%和 60%。
结论
对于局部晚期 NPC，RapidArc 和 IMRT 均达到了临床要求。不同技术的靶区覆盖相似。RapidArc 技术在保护 OAR 和其他组织方面有一些改进，同时减少了 MU 值和治疗时间。
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