Pollock Sean, Kipritidis John, Lee Danny, Bernatowicz Kinga, Keall Paul
Radiation Physics Laboratory, University of Sydney, Sydney, Australia.
Phys Med Biol. 2016 Sep 7;61(17):6485-501. doi: 10.1088/0031-9155/61/17/6485. Epub 2016 Aug 15.
Two interventions to overcome the deleterious impact irregular breathing has on thoracic-abdominal 4D computed tomography (4DCT) are (1) facilitating regular breathing using audiovisual biofeedback (AVB), and (2) prospective respiratory gating of the 4DCT scan based on the real-time respiratory motion. The purpose of this study was to compare the impact of AVB and gating on 4DCT imaging using the 4D eXtended cardiac torso (XCAT) phantom driven by patient breathing patterns. We obtained simultaneous measurements of chest and abdominal walls, thoracic diaphragm, and tumor motion from 6 lung cancer patients under two breathing conditions: (1) AVB, and (2) free breathing. The XCAT phantom was used to simulate 4DCT acquisitions in cine and respiratory gated modes. 4DCT image quality was quantified by artefact detection (NCCdiff), mean square error (MSE), and Dice similarity coefficient of lung and tumor volumes (DSClung, DSCtumor). 4DCT acquisition times and imaging dose were recorded. In cine mode, AVB improved NCCdiff, MSE, DSClung, and DSCtumor by 20% (p = 0.008), 23% (p < 0.001), 0.5% (p < 0.001), and 4.0% (p < 0.003), respectively. In respiratory gated mode, AVB improved NCCdiff, MSE, and DSClung by 29% (p < 0.001), 34% (p < 0.001), 0.4% (p < 0.001), respectively. AVB increased the cine acquisitions by 15 s and reduced respiratory gated acquisitions by 31 s. AVB increased imaging dose in cine mode by 10%. This was the first study to quantify the impact of breathing guidance and respiratory gating on 4DCT imaging. With the exception of DSCtumor in respiratory gated mode, AVB significantly improved 4DCT image analysis metrics in both cine and respiratory gated modes over free breathing. The results demonstrate that AVB and respiratory-gating can be beneficial interventions to improve 4DCT for cancer radiation therapy, with the biggest gains achieved when these interventions are used simultaneously.
为克服不规则呼吸对胸腹部四维计算机断层扫描（4DCT）产生的有害影响，有两种干预措施：（1）使用视听生物反馈（AVB）促进规律呼吸，以及（2）基于实时呼吸运动对4DCT扫描进行前瞻性呼吸门控。本研究的目的是比较AVB和门控对使用由患者呼吸模式驱动的4D扩展心脏躯干（XCAT）体模进行的4DCT成像的影响。我们在两种呼吸条件下对6例肺癌患者的胸壁和腹壁、胸段膈肌及肿瘤运动进行了同步测量：（1）AVB，以及（2）自由呼吸。XCAT体模用于模拟电影模式和呼吸门控模式下的4DCT采集。通过伪影检测（NCCdiff）、均方误差（MSE）以及肺和肿瘤体积的骰子相似系数（DSClung、DSCtumor）对4DCT图像质量进行量化。记录4DCT采集时间和成像剂量。在电影模式下，AVB使NCCdiff、MSE、DSClung和DSCtumor分别提高了20%（p = 0.008）、23%（p < 0.001）、0.5%（p < 0.001）和4.0%（p < 0.003）。在呼吸门控模式下，AVB使NCCdiff、MSE和DSClung分别提高了29%（p < 0.001）、34%（p < 0.001）、0.4%（p < 0.001）。AVB使电影模式下的采集时间增加了15秒，使呼吸门控模式下的采集时间减少了31秒。AVB使电影模式下的成像剂量增加了10%。这是第一项量化呼吸引导和呼吸门控对4DCT成像影响的研究。除呼吸门控模式下的DSCtumor外，与自由呼吸相比，AVB在电影模式和呼吸门控模式下均显著改善了4DCT图像分析指标。结果表明，AVB和呼吸门控可能是改善用于癌症放射治疗的4DCT的有益干预措施，同时使用这些干预措施时获益最大。
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