Abstract：
UNASSIGNED: Intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) are the main radiotherapy techniques for treating and managing rectal cancer. Collimator rotation is one of the crucial parameters in radiotherapy planning, and its alteration can cause dosimetric variations. This study assessed the effect of collimator rotation on the dosimetric results of various IMRT and VMAT plans for rectal cancer.
UNASSIGNED: Computed tomography (CT) images of 20 male patients with rectal cancer were utilized for IMRT and VMAT treatment planning with various collimator angles. Nine different IMRT techniques (5, 7, and 9 coplanar fields with collimator angles of 0°, 45°, and 90°) and six different VMAT techniques (1 and 2 full coplanar arcs with collimator angles of 0°, 45°, and 90°) were planned for each patient. The dosimetric results of various treatment techniques for target tissue (conformity index [CI] and homogeneity index [HI]) and organs at risk (OARs) sparing (parameters obtained from OARs dose-volume histograms [DVH]) as well as radiobiological findings were analyzed and compared.
UNASSIGNED: The 7-fields IMRT technique demonstrated lower bladder doses (V40Gy, V45Gy), unaffected by collimator rotation. The 9-fields IMRT and 2-arcs VMAT (excluding the 90-degree collimator) had the lowest V35Gy and V45Gy. A 90-degree collimator rotation in 2-arcs VMAT significantly increased small bowel and bladder V45Gy, femoral head doses, and HI values. Radiobiologically, the 90-degree rotation had adverse effects on small bowel NTCP (normal tissue complication probability). No superiority was found for a 45-degree collimator rotation over 0 or 30 degrees in VMAT techniques.
UNASSIGNED: Collimator rotation had minimal impact on dosimetric parameters in IMRT planning but is significant in VMAT techniques. A 90-degree rotation in VMAT, particularly in a 2-full arc technique, adversely affects PTV homogeneity index, bladder dose, and small bowel NTCP. Other evaluated collimator angles did not significantly affect VMAT dosimetrical or radiobiological outcomes.
UNASSIGNED: Computed tomography (CT) images of 20 male patients with rectal cancer were utilized for IMRT and VMAT treatment planning with various collimator angles. Nine different IMRT techniques (5, 7, and 9 coplanar fields with collimator angles of 0°, 45°, and 90°) and six different VMAT techniques (1 and 2 full coplanar arcs with collimator angles of 0°, 45°, and 90°) were planned for each patient. The dosimetric results of various treatment techniques for target tissue (conformity index [CI] and homogeneity index [HI]) and organs at risk (OARs) sparing (parameters obtained from OARs dose-volume histograms [DVH]) as well as radiobiological findings were analyzed and compared.
UNASSIGNED: The 7-fields IMRT technique demonstrated lower bladder doses (V40Gy, V45Gy), unaffected by collimator rotation. The 9-fields IMRT and 2-arcs VMAT (excluding the 90-degree collimator) had the lowest V35Gy and V45Gy. A 90-degree collimator rotation in 2-arcs VMAT significantly increased small bowel and bladder V45Gy, femoral head doses, and HI values. Radiobiologically, the 90-degree rotation had adverse effects on small bowel NTCP (normal tissue complication probability). No superiority was found for a 45-degree collimator rotation over 0 or 30 degrees in VMAT techniques.
UNASSIGNED: Collimator rotation had minimal impact on dosimetric parameters in IMRT planning but is significant in VMAT techniques. A 90-degree rotation in VMAT, particularly in a 2-full arc technique, adversely affects PTV homogeneity index, bladder dose, and small bowel NTCP. Other evaluated collimator angles did not significantly affect VMAT dosimetrical or radiobiological outcomes.
摘要：
■调强放射治疗（IMRT）和体积调强电弧治疗（VMAT）是治疗和管理直肠癌的主要放射治疗技术。准直器旋转是放射治疗计划中的关键参数之一,它的改变会导致剂量学变化。这项研究评估了准直器旋转对直肠癌各种IMRT和VMAT计划的剂量测定结果的影响。
■将20名男性直肠癌患者的计算机断层扫描（CT）图像用于各种准直器角度的IMRT和VMAT治疗计划。九种不同的IMRT技术（准直器角为0°的5、7和9共面场，45°,和90°）和六种不同的VMAT技术（准直器角度为0°的1和2个全共面弧，45°,和90°）为每位患者计划。分析并比较了靶组织（符合性指数[CI]和均匀性指数[HI]）和危险器官（OARs）保留（从OARs剂量-体积直方图[DVH]获得的参数）以及放射生物学结果的各种治疗技术的剂量测定结果。
■7场IMRT技术显示出较低的膀胱剂量（V40Gy，V45Gy),不受准直器旋转的影响。9场IMRT和2弧VMAT（不包括90度准直器）具有最低的V35Gy和V45Gy。2弧VMAT中的90度准直器旋转显着增加了小肠和膀胱V45Gy，股骨头剂量,和HI值。放射生物学,90度旋转对小肠NTCP有不良影响(正常组织并发症概率).在VMAT技术中，45度准直器旋转超过0或30度没有发现优越性。
■准直器旋转对IMRT计划中的剂量测定参数影响最小，但在VMAT技术中意义重大。在VMAT中旋转90度，特别是在双弧技术中，对PTV均匀性指数产生不利影响，膀胱剂量，和小肠NTCP。其他评估的准直器角度没有显着影响VMAT剂量或放射生物学结果。
■将20名男性直肠癌患者的计算机断层扫描（CT）图像用于各种准直器角度的IMRT和VMAT治疗计划。九种不同的IMRT技术（准直器角为0°的5、7和9共面场，45°,和90°）和六种不同的VMAT技术（准直器角度为0°的1和2个全共面弧，45°,和90°）为每位患者计划。分析并比较了靶组织（符合性指数[CI]和均匀性指数[HI]）和危险器官（OARs）保留（从OARs剂量-体积直方图[DVH]获得的参数）以及放射生物学结果的各种治疗技术的剂量测定结果。
■7场IMRT技术显示出较低的膀胱剂量（V40Gy，V45Gy),不受准直器旋转的影响。9场IMRT和2弧VMAT（不包括90度准直器）具有最低的V35Gy和V45Gy。2弧VMAT中的90度准直器旋转显着增加了小肠和膀胱V45Gy，股骨头剂量,和HI值。放射生物学,90度旋转对小肠NTCP有不良影响(正常组织并发症概率).在VMAT技术中，45度准直器旋转超过0或30度没有发现优越性。
■准直器旋转对IMRT计划中的剂量测定参数影响最小，但在VMAT技术中意义重大。在VMAT中旋转90度，特别是在双弧技术中，对PTV均匀性指数产生不利影响，膀胱剂量，和小肠NTCP。其他评估的准直器角度没有显着影响VMAT剂量或放射生物学结果。
