PDF(Pubmed)
Abstract：
OBJECTIVE: This study aimed to assess the margin for the planning target volume (PTV) using the Van Herk formula. We then validated the proposed margin by real-time magnetic resonance imaging (MRI).
METHODS: An analysis of cone-beam computed tomography (CBCT) data from early glottic cancer patients was performed to evaluate organ motion. Deformed clinical target volumes (CTV) after rigid registration were acquired using the Velocity program (Varian Medical Systems, Palo Alto, CA, USA). Systematic (Σ) and random errors (σ) were evaluated. The margin for the PTV was defined as 2.5 Σ + 0.7 σ according to the Van Herk formula. To validate this margin, we accrued healthy volunteers. Sagittal real-time cine MRI was conducted using the ViewRay system (ViewRay Inc., Oakwood Village, OH, USA). Within the obtained sagittal images, the vocal cord was delineated. The movement of the vocal cord was summed up and considered as the internal target volume (ITV). We then assessed the degree of overlap between the ITV and the PTV (vocal cord plus margins) by calculating the volume overlap ratio, represented as (ITV∩PTV)/ITV.
RESULTS: CBCTs of 17 early glottic patients were analyzed. Σ and σ were 0.55 and 0.57 for left-right (LR), 0.70 and 0.60 for anterior-posterior (AP), and 1.84 and 1.04 for superior-inferior (SI), respectively. The calculated margin was 1.8 mm (LR), 2.2 mm (AP), and 5.3 mm (SI). Four healthy volunteers participated for validation. A margin of 3 mm (AP) and 5 mm (SI) was applied to the vocal cord as the PTV. The average volume overlap ratio between ITV and PTV was 0.92 (range 0.85-0.99) without swallowing and 0.77 (range 0.70-0.88) with swallowing.
CONCLUSIONS: By evaluating organ motion by using CBCT, the margin was 1.8 (LR), 2.2 (AP), and 5.3 mm (SI). The margin acquired using CBCT fitted well in real-time cine MRI. Given that swallowing during radiotherapy can result in a substantial displacement, it is crucial to consider strategies aimed at minimizing swallowing and related motion.
METHODS: An analysis of cone-beam computed tomography (CBCT) data from early glottic cancer patients was performed to evaluate organ motion. Deformed clinical target volumes (CTV) after rigid registration were acquired using the Velocity program (Varian Medical Systems, Palo Alto, CA, USA). Systematic (Σ) and random errors (σ) were evaluated. The margin for the PTV was defined as 2.5 Σ + 0.7 σ according to the Van Herk formula. To validate this margin, we accrued healthy volunteers. Sagittal real-time cine MRI was conducted using the ViewRay system (ViewRay Inc., Oakwood Village, OH, USA). Within the obtained sagittal images, the vocal cord was delineated. The movement of the vocal cord was summed up and considered as the internal target volume (ITV). We then assessed the degree of overlap between the ITV and the PTV (vocal cord plus margins) by calculating the volume overlap ratio, represented as (ITV∩PTV)/ITV.
RESULTS: CBCTs of 17 early glottic patients were analyzed. Σ and σ were 0.55 and 0.57 for left-right (LR), 0.70 and 0.60 for anterior-posterior (AP), and 1.84 and 1.04 for superior-inferior (SI), respectively. The calculated margin was 1.8 mm (LR), 2.2 mm (AP), and 5.3 mm (SI). Four healthy volunteers participated for validation. A margin of 3 mm (AP) and 5 mm (SI) was applied to the vocal cord as the PTV. The average volume overlap ratio between ITV and PTV was 0.92 (range 0.85-0.99) without swallowing and 0.77 (range 0.70-0.88) with swallowing.
CONCLUSIONS: By evaluating organ motion by using CBCT, the margin was 1.8 (LR), 2.2 (AP), and 5.3 mm (SI). The margin acquired using CBCT fitted well in real-time cine MRI. Given that swallowing during radiotherapy can result in a substantial displacement, it is crucial to consider strategies aimed at minimizing swallowing and related motion.
摘要：
目的：本研究旨在使用VanHerk公式评估计划目标体积（PTV）的裕度。然后，我们通过实时磁共振成像（MRI）验证了所提出的界限。
方法：对早期声门癌患者的锥形束计算机断层扫描（CBCT）数据进行分析，以评估器官运动。使用Velocity程序（VarianMedicalSystems，帕洛阿尔托,CA,美国）。评估了系统误差(Σ)和随机误差(σ)。根据VanHerk公式，PTV的余量定义为2.5Σ+0.7σ。要验证此边距，我们培养了健康的志愿者。使用ViewRay系统(ViewRayInc.，奥克伍德村,OH,美国）。在获得的矢状图像中，声带被划定。总结声带的运动并将其视为内部目标体积（ITV）。然后，我们通过计算音量重叠比来评估ITV和PTV（声带加边距）之间的重叠程度，表示为(ITV_PTV)/ITV。
结果：对17例声门早期患者的CBCT进行分析。左右(LR)的Σ和σ分别为0.55和0.57，前后（AP）为0.70和0.60，上下级(SI)为1.84和1.04，分别。计算的余量为1.8mm(LR),2.2mm(AP),和5.3毫米（SI）。四名健康志愿者参与验证。将3mm(AP)和5mm(SI)的边缘应用于声带作为PTV。ITV和PTV之间的平均体积重叠比为0.92（范围0.85-0.99），吞咽时为0.77（范围0.70-0.88）。
结论：通过使用CBCT评估器官运动，利润率为1.8(LR)，2.2(AP),和5.3毫米（SI）。使用CBCT获得的边缘在实时电影MRI中拟合良好。鉴于放射治疗期间吞咽会导致大量位移，考虑旨在减少吞咽和相关运动的策略至关重要。
方法：对早期声门癌患者的锥形束计算机断层扫描（CBCT）数据进行分析，以评估器官运动。使用Velocity程序（VarianMedicalSystems，帕洛阿尔托,CA,美国）。评估了系统误差(Σ)和随机误差(σ)。根据VanHerk公式，PTV的余量定义为2.5Σ+0.7σ。要验证此边距，我们培养了健康的志愿者。使用ViewRay系统(ViewRayInc.，奥克伍德村,OH,美国）。在获得的矢状图像中，声带被划定。总结声带的运动并将其视为内部目标体积（ITV）。然后，我们通过计算音量重叠比来评估ITV和PTV（声带加边距）之间的重叠程度，表示为(ITV_PTV)/ITV。
结果：对17例声门早期患者的CBCT进行分析。左右(LR)的Σ和σ分别为0.55和0.57，前后（AP）为0.70和0.60，上下级(SI)为1.84和1.04，分别。计算的余量为1.8mm(LR),2.2mm(AP),和5.3毫米（SI）。四名健康志愿者参与验证。将3mm(AP)和5mm(SI)的边缘应用于声带作为PTV。ITV和PTV之间的平均体积重叠比为0.92（范围0.85-0.99），吞咽时为0.77（范围0.70-0.88）。
结论：通过使用CBCT评估器官运动，利润率为1.8(LR)，2.2(AP),和5.3毫米（SI）。使用CBCT获得的边缘在实时电影MRI中拟合良好。鉴于放射治疗期间吞咽会导致大量位移，考虑旨在减少吞咽和相关运动的策略至关重要。
