Department of Radiation Oncology, University of Florida, Jacksonville, FL, USA.
Int J Radiat Oncol Biol Phys. 2011 Nov 1;81(3):880-7. doi: 10.1016/j.ijrobp.2010.07.1978. Epub 2010 Oct 8.
To evaluate the setup, interfraction, and intrafraction organ motion error distributions and simulate intrafraction intervention strategies for prostate radiotherapy.
A total of 17 patients underwent treatment setup and were monitored using the Calypso system during radiotherapy. On average, the prostate tracking measurements were performed for 8 min/fraction for 28 fractions for each patient. For both patient couch shift data and intrafraction organ motion data, the systematic and random errors were obtained from the patient population. The planning target volume margins were calculated using the van Herk formula. Two intervention strategies were simulated using the tracking data: the deviation threshold and period. The related planning target volume margins, time costs, and prostate position "fluctuation" were presented.
The required treatment margin for the left-right, superoinferior, and anteroposterior axes was 8.4, 10.8, and 14.7 mm for skin mark-only setup and 1.3, 2.3, and 2.8 mm using the on-line setup correction, respectively. Prostate motion significantly correlated among the superoinferior and anteroposterior directions. Of the 17 patients, 14 had prostate motion within 5 mm of the initial setup position for ≥91.6% of the total tracking time. The treatment margin decreased to 1.1, 1.8, and 2.3 mm with a 3-mm threshold correction and to 0.5, 1.0, and 1.5 mm with an every-2-min correction in the left-right, superoinferior, and anteroposterior directions, respectively. The periodic corrections significantly increase the treatment time and increased the number of instances when the setup correction was made during transient excursions.
The residual systematic and random error due to intrafraction prostate motion is small after on-line setup correction. Threshold-based and time-based intervention strategies both reduced the planning target volume margins. The time-based strategies increased the treatment time and the in-fraction position fluctuation.
评估前列腺放射治疗中的摆位、分次间和分次内器官运动误差分布，并模拟分次内干预策略。
共 17 例患者在放射治疗过程中接受了治疗摆位，并使用 Calypso 系统进行监测。平均而言，每位患者的前列腺跟踪测量在 28 个分次中，每个分次进行 8 分钟。对于患者床位移数据和分次内器官运动数据，从患者群体中获得了系统和随机误差。使用 van Herk 公式计算计划靶区边界。使用跟踪数据模拟了两种干预策略：偏差阈值和周期。介绍了相关的计划靶区边界、时间成本和前列腺位置“波动”。
仅使用皮肤标记进行摆位时，左右、上下和前后方向所需的治疗边界分别为 8.4、10.8 和 14.7mm，使用在线摆位校正时分别为 1.3、2.3 和 2.8mm。前列腺运动在上下和前后方向之间具有显著相关性。在 17 例患者中，有 14 例患者的前列腺运动在总跟踪时间的 91.6%以上保持在初始摆位位置的 5mm 内。当采用 3mm 阈值校正时，治疗边界分别减少至 1.1、1.8 和 2.3mm，当采用每 2 分钟校正时，治疗边界分别减少至 0.5、1.0 和 1.5mm，左右、上下和前后方向。周期性校正显著增加了治疗时间，并增加了在瞬态漂移期间进行摆位校正的次数。
在线摆位校正后，由于分次内前列腺运动引起的残余系统和随机误差较小。基于阈值和基于时间的干预策略均降低了计划靶区边界。基于时间的策略增加了治疗时间和分次内位置波动。
