Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
Int J Radiat Oncol Biol Phys. 2011 Jul 1;80(3):909-17. doi: 10.1016/j.ijrobp.2010.08.011. Epub 2011 Apr 4.
To analyze tumor position reproducibility of feedback-guided voluntary deep inspiration breath-hold (FGBH) gating for cone beam computed tomography (CBCT)-based stereotactic body radiotherapy (SBRT).
Thirteen early-stage lung cancer patients eligible for SBRT with tumor motion of >1cm were evaluated for FGBH-gated treatment. Multiple FGBH CTs were acquired at simulation, and single FGBH CBCTs were also acquired prior to each treatment. Simulation CTs and treatment CBCTs were analyzed to quantify reproducibility of tumor positions during FGBH. Benefits of FGBH gating compared to treatment during free breathing, as well treatment with gating at exhalation, were examined for lung sparing, motion margins, and reproducibility of gross tumor volume (GTV) position relative to nonmoving anatomy.
FGBH increased total lung volumes by 1.5 times compared to free breathing, resulting in a proportional drop in total lung volume receiving 10 Gy or more. Intra- and inter-FGBH reproducibility of GTV centroid positions at simulation were 1.0 ± 0.5 mm, 1.3 ± 1.0 mm, and 0.6 ± 0.4 mm in the anterior-posterior (AP), superior-inferior (SI), and left-right lateral (LR) directions, respectively, compared to more than 1 cm of tumor motion at free breathing. During treatment, inter-FGBH reproducibility of the GTV centroid with respect to bony anatomy was 1.2 ± 0.7 mm, 1.5 ± 0.8 mm, and 1.0 ± 0.4 mm in the AP, SI, and LR directions. In addition, the quality of CBCTs was improved due to elimination of motion artifacts, making this technique attractive for poorly visualized tumors, even with small motion.
The extent of tumor motion at normal respiration does not influence the reproducibility of the tumor position under breath hold conditions. FGBH-gated SBRT with CBCT can improve the reproducibility of GTV centroids, reduce required margins, and minimize dose to normal tissues in the treatment of mobile tumors.
分析基于锥形束 CT（CBCT）的立体定向体部放疗（SBRT）中反馈引导的自主深吸气屏气（FGBH）门控的肿瘤位置再现性。
对 13 名适合 SBRT 治疗且肿瘤运动大于 1cm 的早期肺癌患者进行 FGBH 门控治疗评估。在模拟时获取多个 FGBH CT，并且在每次治疗前也获取单次 FGBH CBCT。对模拟 CT 和治疗 CBCT 进行分析，以量化 FGBH 期间肿瘤位置的再现性。比较了 FGBH 门控与自由呼吸治疗以及呼气时门控治疗在肺保护、运动边界以及相对于固定解剖结构的大体肿瘤体积（GTV）位置的再现性方面的优势。
与自由呼吸相比，FGBH 将总肺量增加了 1.5 倍，导致总肺量接受 10Gy 或更高剂量的比例下降。在模拟时，FGBH 内和 FGBH 之间的 GTV 质心位置的重现性在前后（AP）、上下（SI）和左右侧（LR）方向上分别为 1.0±0.5mm、1.3±1.0mm 和 0.6±0.4mm，而在自由呼吸时肿瘤运动超过 1cm。在治疗期间，GTV 质心相对于骨解剖结构的 FGBH 间重现性在 AP、SI 和 LR 方向上分别为 1.2±0.7mm、1.5±0.8mm 和 1.0±0.4mm。此外，由于消除了运动伪影，因此 CBCT 的质量得到了改善，即使肿瘤运动较小，该技术也适用于难以可视化的肿瘤。
在正常呼吸下肿瘤运动的程度不影响屏气条件下肿瘤位置的重现性。使用 CBCT 的 FGBH 门控 SBRT 可以提高 GTV 质心的重现性，减少所需的边界，并最大限度地减少移动肿瘤治疗中正常组织的剂量。
