Department of Oncology, Aarhus University Hospital , Aarhus , Denmark.
Acta Oncol. 2013 Oct;52(7):1437-44. doi: 10.3109/0284186X.2013.813638. Epub 2013 Jul 23.
To investigate the stability of target motion amplitude and motion directionality throughout full stereotactic body radiotherapy (SBRT) treatments of tumors in the liver.
Ten patients with gold markers implanted in the liver received 11 courses of 3-fraction SBRT on a conventional linear accelerator. A four-dimensional computed tomography (4DCT) scan was obtained for treatment planning. The time-resolved marker motion was determined throughout full treatment field delivery using the kV and MV imagers of the accelerator. The motion amplitude and motion directionality of all individual respiratory cycles were determined using principal component analysis (PCA). The variations in motion amplitude and directionality within the treatment courses and the difference from the motion in the 4DCT scan were determined.
The patient mean (± 1 standard deviation) peak-to-peak 3D motion amplitude of individual respiratory cycles during a treatment course was 7.9 ± 4.1 mm and its difference from the 4DCT scan was -0.8 ± 2.5 mm (max, 6.6 mm). The mean standard deviation of 3D respiratory cycle amplitude within a treatment course was 2.0 ± 1.6 mm. The motion directionality of individual respiratory cycles on average deviated 4.6 ± 1.6° from the treatment course mean directionality. The treatment course mean motion directionality on average deviated 7.6 ± 6.5° from the directionality in the 4DCT scan. A single patient-specific oblique direction in space explained 97.7 ± 1.7% and 88.3 ± 10.1% of all positional variance (motion) throughout the treatment courses, excluding and including baseline shifts between treatment fields, respectively.
Due to variable breathing amplitudes a single 4DCT scan was not always representative of the mean motion amplitude during treatment. However, the motion was highly directional with a fairly stable direction throughout treatment, indicating a potential for more optimal individualized motion margins aligned to the preferred direction of motion.
研究肝脏肿瘤立体定向体部放疗（SBRT）治疗过程中靶区运动幅度和运动方向的稳定性。
10 名肝内植入金标记的患者接受了 11 次 3 分次 SBRT，采用传统直线加速器。治疗计划采用四维 CT（4DCT）扫描。使用加速器的千伏（kV）和兆伏（MV）成像仪，在整个治疗野传递过程中确定时间分辨标记运动。使用主成分分析（PCA）确定所有个体呼吸周期的运动幅度和运动方向。确定治疗过程中的运动幅度和方向变化，以及与 4DCT 扫描的运动差异。
患者在治疗过程中每个呼吸周期的 3D 运动幅度的平均（± 1 个标准差）峰值到峰值为 7.9 ± 4.1mm，与 4DCT 扫描的差异为-0.8 ± 2.5mm（最大为 6.6mm）。治疗过程中 3D 呼吸周期幅度的平均标准差为 2.0 ± 1.6mm。个体呼吸周期的运动方向平均偏离治疗方向 4.6 ± 1.6°。治疗过程的平均运动方向平均偏离 4DCT 扫描中的方向 7.6 ± 6.5°。一个单独的患者特定的斜向空间方向解释了治疗过程中所有位置变化（运动）的 97.7 ± 1.7%和 88.3 ± 10.1%，分别排除和包括治疗场之间的基线偏移。
由于呼吸幅度的变化，单次 4DCT 扫描并不总是代表治疗过程中的平均运动幅度。然而，运动方向具有很高的方向性，在整个治疗过程中方向相对稳定，表明有潜力为更优化的个体化运动边界提供更理想的运动方向。
