Ashamalla Hani, Tejwani Ajay, Parameritis Ioannis, Swamy Uma, Luo Pei Ching, Guirguis Adel, Lavaf Amir
New York Methodist Hospital, Brooklyn, NY, USA. ; Leading Edge Radiation Oncology (LEROS), Weill Medical College of Cornell University, Brooklyn, NY, USA.
Radiat Oncol J. 2013 Jun;31(2):104-10. doi: 10.3857/roj.2013.31.2.104. Epub 2013 Jun 30.
Intensity modulated arc therapy (IMAT) is a form of intensity modulated radiation therapy (IMRT) that delivers dose in single or multiple arcs. We compared IMRT plans versus single-arc field (1ARC) and multi-arc fields (3ARC) IMAT plans in high-risk prostate cancer.
Sixteen patients were studied. Prostate (PTV P ), right pelvic (PTV RtLN ) and left pelvic lymph nodes (PTV LtLN ), and organs at risk were contoured. PTV P , PTV RtLN , and PTV LtLN received 50.40 Gy followed by a boost to PTV B of 28.80 Gy. Three plans were per patient generated: IMRT, 1ARC, and 3ARC. We recorded the dose to the PTV, the mean dose (D MEAN ) to the organs at risk, and volume covered by the 50% isodose. Efficiency was evaluated by monitor units (MU) and beam on time (BOT). Conformity index (CI), Paddick gradient index, and homogeneity index (HI) were also calculated.
Average Radiation Therapy Oncology Group CI was 1.17, 1.20, and 1.15 for IMRT, 1ARC, and 3ARC, respectively. The plans' HI were within 1% of each other. The D MEAN of bladder was within 2% of each other. The rectum D MEAN in IMRT plans was 10% lower dose than the arc plans (p < 0.0001). The GI of the 3ARC was superior to IMRT by 27.4% (p = 0.006). The average MU was highest in the IMRT plans (1686) versus 1ARC (575) versus 3ARC (1079). The average BOT was 6 minutes for IMRT compared to 1.3 and 2.9 for 1ARC and 3ARC IMAT (p < 0.05).
For high-risk prostate cancer, IMAT may offer a favorable dose gradient profile, conformity, MU and BOT compared to IMRT.
调强弧形放疗（IMAT）是调强放射治疗（IMRT）的一种形式，可通过单弧或多弧进行剂量输送。我们比较了高危前列腺癌患者的IMRT计划与单弧野（1ARC）和多弧野（3ARC）IMAT计划。
对16例患者进行研究。勾勒出前列腺（PTV P）、右盆腔（PTV RtLN）和左盆腔淋巴结（PTV LtLN）以及危及器官的轮廓。PTV P、PTV RtLN和PTV LtLN接受50.40 Gy的剂量，随后对PTV B给予28.80 Gy的追加剂量。为每位患者制定了三个计划：IMRT、1ARC和3ARC。我们记录了PTV的剂量、危及器官的平均剂量（D MEAN）以及50%等剂量线覆盖的体积。通过监测单位（MU）和射束开启时间（BOT）评估效率。还计算了适形指数（CI）、帕迪克梯度指数和均匀性指数（HI）。
IMRT、1ARC和3ARC的平均放射肿瘤学组CI分别为1.17、1.20和1.15。各计划的HI相互之间相差在1%以内。膀胱的D MEAN相互之间相差在2%以内。IMRT计划中直肠的D MEAN比弧形计划低10%（p < 0.0001）。3ARC的梯度指数比IMRT高27.4%（p = 0.006）。IMRT计划的平均MU最高（1686），其次是1ARC（575）和3ARC（1079）。IMRT的平均BOT为6分钟，而1ARC和3ARC IMAT分别为1.3分钟和2.9分钟（p < 0.05）。
对于高危前列腺癌，与IMRT相比，IMAT可能具有良好的剂量梯度分布、适形性、MU和BOT。
