Radiation Oncology Department, Northern Sydney Cancer Centre, St Leonards, New South Wales, Australia.
Clin Oncol (R Coll Radiol). 2011 Oct;23(8):503-11. doi: 10.1016/j.clon.2011.02.002. Epub 2011 Mar 11.
Volumetric-modulated arc therapy (VMAT) allows rapid delivery of radiotherapy. The aim of this planning study was to evaluate VMAT and dynamic intensity-modulated radiotherapy (IMRT) using a simultaneous integrated boost technique
Planning computed tomography data from 10 patients with locoregionally advanced oropharynx or nasopharynx carcinoma were selected. The prescription dose was 70, 63 and 56Gy to the high-dose, intermediate-dose and low-dose planning target volume (PTV), respectively, and planning parameters were according to Radiation Therapy Oncology Group IMRT protocols. VMAT and IMRT plans were calculated, and dose-volume histograms were created for plan evaluation and comparison.
Clinically acceptable plans were achieved for both IMRT and VMAT plans, although IMRT plans typically required three times the number of monitor units. The coverage of 95% of the PTV70 was between 96 and 100% of the prescribed dose for IMRT plans and 100% for all VMAT plans. There was a trend of improved dose conformity for IMRT plans. Both IMRT and VMAT achieved acceptable plans in terms of sparing of the spinal cord and brainstem. Contralateral parotid sparing was improved with VMAT, with a mean dose of 25.08Gy (range 21.35-30.02Gy) for oropharynx and 31.37Gy (range 23.47-35.52Gy) for nasopharynx cases.
Simultaneous integrated boost VMAT achieved comparable plans to dynamic IMRT in complex head and neck cases and used two-thirds less monitor units.
容积旋转调强放疗（VMAT）可实现放疗的快速递送。本研究旨在通过同时整合增敏技术，评估 VMAT 和动态调强放疗（IMRT）。
选择 10 例局部晚期口咽或鼻咽癌患者的计划 CT 数据。高剂量、中剂量和低剂量计划靶区（PTV）的处方剂量分别为 70、63 和 56Gy，计划参数根据放射治疗肿瘤学组（RTOG）的 IMRT 协议。计算了 VMAT 和 IMRT 计划，并创建了剂量体积直方图，用于计划评估和比较。
虽然 IMRT 计划通常需要三倍的机器跳数，但对于 IMRT 和 VMAT 计划都获得了可接受的临床计划。PTV70 的 95%覆盖范围分别为 IMRT 计划的处方剂量的 96%至 100%和所有 VMAT 计划的 100%。IMRT 计划的剂量适形性有改善的趋势。IMRT 和 VMAT 均在保护脊髓和脑干方面实现了可接受的计划。VMAT 可改善对侧腮腺的保护，口咽病例的平均剂量为 25.08Gy（范围 21.35-30.02Gy），鼻咽病例为 31.37Gy（范围 23.47-35.52Gy）。
在复杂的头颈部病例中，同时整合增敏 VMAT 可实现与动态 IMRT 相当的计划，且使用的机器跳数减少三分之二。
