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首页> 美国卫生研究院文献>Current Oncology >Impact of geometric uncertainties on dose distribution during intensity modulated radiotherapy of head-and-neck cancer: the need for a planning target volume and a planning organ-at-risk volume
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Impact of geometric uncertainties on dose distribution during intensity modulated radiotherapy of head-and-neck cancer: the need for a planning target volume and a planning organ-at-risk volume

机译：头颈癌调强放射治疗期间几何不确定性对剂量分布的影响：需要计划目标体积和计划中危险器官的体积

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We assessed the effect of geometric uncertainties on target coverage and on dose to the organs at risk (oars) during intensity-modulated radiotherapy (imrt) for head-and-neck cancer, and we estimated the required margins for the planning target volume (ptv) and the planning organ-at-risk volume (prv). For eight head-and-neck cancer patients, we generated imrt plans with localization uncertainty margins of 0 mm, 2.5 mm, and 5.0 mm. The beam intensities were then applied on repeat computed tomography (ct) scans obtained weekly during treatment, and dose distributions were recalculated.The dose–volume histogram analysis for the repeat ct scans showed that target coverage was adequate (V100 ≥ 95%) for only 12.5% of the gross tumour volumes, 54.3% of the upper-neck clinical target volumes (ctvs), and 27.4% of the lower-neck ctvs when no margins were added for ptv. The use of 2.5-mm and 5.0-mm margins significantly improved target coverage, but the mean dose to the contralateral parotid increased from 25.9 Gy to 29.2 Gy. Maximum dose to the spinal cord was above limit in 57.7%, 34.6%, and 15.4% of cases when 0-mm, 2.5-mm, and 5.0-mm margins (respectively) were used for prv.Significant deviations from the prescribed dose can occur during imrt treatment delivery for head-and-neck cancer. The use of 2.5-mm to 5.0-mm margins for ptv and prv greatly reduces the risk of underdosing targets and of overdosing the spinal cord.
机译：我们评估了头颈癌调强放疗（imrt）期间几何不确定性对靶标覆盖率和高风险器官（桨）剂量的影响，并估算了规划目标量（ptv）所需的余量）和规划机构的风险量（prv）。对于八位头颈癌患者，我们生成了imrt计划，定位不确定性余量为0 mm，2.5 mm和5.0 mm。然后将光束强度应用于治疗期间每周进行的重复计算机断层扫描（ct）扫描，并重新计算剂量分布。重复ct扫描的剂量-体积直方图分析表明，仅对目标覆盖率足够（V100≥95％）当未增加ptv的余量时，肿瘤总体积的12.5％，上颈临床目标体积（ctvs）的54.3％和下颈ctvs的27.4％。使用2.5 mm和5.0 mm切缘可显着改善靶标覆盖范围，但对侧腮腺的平均剂量从25.9 Gy增加到29.2 Gy。分别使用0毫米，2.5毫米和5.0毫米切缘的情况下，脊髓的最大剂量超过限制的57.7％，34.6％和15.4％。发生在头颈癌的IMRT治疗期间。 ptv和prv使用2.5毫米至5.0毫米的页边距可大大降低靶标剂量不足和脊髓剂量过量的风险。

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