Department of Radiation Oncology, University Hospital, LMU Munich, Marchioninistraße 15, 81377, Munich, Germany.
Strahlenther Onkol. 2018 Jul;194(7):664-674. doi: 10.1007/s00066-018-1286-2. Epub 2018 Mar 9.
To evaluate the impact of shorter treatment times on intra-fractional motion of the prostate during external beam radiotherapy.
53 h of intra-fractional motion of the prostate were recorded in real-time by 4D ultrasound (4DUS) during 720 fractions in 28 patients, 14 of which whom treated with step-and-shoot intensity-modulated radiotherapy (IMRT) and 14 of whom were treated with volumetric arc therapy (VMAT).
The average VMAT fraction was recorded for 2 min 43 s and was substantially shorter than the average step-and-shoot IMRT fraction at 6 min 13 s. Average radial displacement of the prostate per fraction was substantially and significantly reduced from 1.31 ± 1.28 mm (n = 357 step-and-shoot IMRT fractions) to 0.96 ± 1.04 mm (n = 363 VMAT fractions), p = 0.00004. Radial, vertical, and longitudinal root-mean-square (r. m. s.) error per fraction was reduced from 1.55 to 1.12 mm (-28%, p < 0.0001), from 1.16 to 0.77 mm (-34%, p < 0.0001), and from 0.79 to 0.56 mm (-29%, p = 0.0002), respectively. Lateral intra-fractional motion was generally small and did not differ significantly. The prostate remained during 95% of fraction time within 4.55 mm of the isocenter in case of step-and-shoot IMRT and within 2.45 mm in case of VMAT. The variance of displacements increased linearly with time, and the rate was the same for both step-and-shoot IMRT and VMAT patients.
The position of the prostate changed less during shorter fractions, limiting fraction-average and end-of-fraction variance. This substantially and significantly reduced the impact of intra-fractional motion during shorter VMAT fractions as compared to longer step-and-shoot IMRT fractions.
评估缩短治疗时间对体外放射治疗中前列腺内部分运动的影响。
通过 4D 超声（4DUS）实时记录 28 名患者的 720 个分次中的前列腺内部分运动，共记录 53 小时。其中 14 例采用分步射击强度调制放疗（IMRT）治疗，14 例采用容积弧形治疗（VMAT）治疗。
VMAT 平均分次时间为 2 分 43 秒，明显短于分步射击 IMRT 平均分次时间 6 分 13 秒。前列腺的平均径向位移从 1.31±1.28mm（n=357 个分步射击 IMRT 分次）显著降低至 0.96±1.04mm（n=363 个 VMAT 分次），p=0.00004。每分次的径向、垂直和纵向均方根（r.m.s.）误差分别从 1.55mm 降低至 1.12mm（减少 28%，p<0.0001）、从 1.16mm 降低至 0.77mm（减少 34%，p<0.0001）、从 0.79mm 降低至 0.56mm（减少 29%，p=0.0002）。侧向的分次内运动通常较小，差异无统计学意义。在分步射击 IMRT 的情况下，前列腺在 95%的分次时间内保持在等中心 4.55mm 以内，在 VMAT 的情况下保持在 2.45mm 以内。位移的方差随时间线性增加，分步射击 IMRT 和 VMAT 患者的速率相同。
较短的分次中前列腺的位置变化较小，限制了分次平均和分次末方差。与较长的分步射击 IMRT 分次相比，这显著降低了较短 VMAT 分次中内部分运动的影响。
