Breathing variations during 4D CT imaging often manifest as geometric irregularities known as respiratory-induced image artifacts and ultimately effect radiotherapy treatment efficacy. To reduce such image artifacts we developed Respiratory Adaptive Computed Tomography (REACT) to trigger CT acquisition during periods of regular breathing. For the first time, we integrate REACT with clinical hardware and hypothesize that REACT will reduce respiratory-induced image artifacts ≥ 4 mm compared to conventional 4D CT. 4D image sets were acquired using REACT and conventional 4D CT on a Siemens Somatom scanner. Scans were taken for 13 respiratory traces (12 patients) that were reproduced on a lung-motion phantom. Motion was observed by the Varian RPM system and sent to the REACT software where breathing irregularity was evaluated in real-time and used to trigger the imaging beam. REACT and conventional 4D CT images were compared to a ground truth static-phantom image and compared for absolute geometric differences within the region-of-interest. Breathing irregularity during imaging was retrospectively assessed using the root-mean-square error of the RPM measured respiratory signal during beam on (RMSE_Beam_on) for each phase of the respiratory cycle. REACT significantly reduced the average frequency of respiratory-induced image artifacts ≥ 4 mm by 70% for the tumor (p = 0.003) and 76% for the lung (p = 0.0002) compared to conventional 4D CT. Volume reductions of 10% to 6% of the tumor and 2% to 1% of the lung compared to conventional 4D CT were seen. Breathing irregularity during imaging (RMSE_Beam_on) was significantly reduced by 27% (p = 0.013) using the REACT method. For the first time, REACT was successfully integrated with clinical hardware. Our findings support the hypothesis that REACT significantly reduced respiratory-induced image artifacts compared to conventional 4D CT. These experimental results provide compelling evidence for further REACT investigation, potentially providing clearer images for clinical use.

中文翻译：

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从源头上减少4D CT成像伪影：来自呼吸适应计算机断层扫描（REACT）系统的第一批实验结果。

4D CT成像期间的呼吸变化通常表现为几何异常，称为呼吸诱发的图像伪影，最终影响放射治疗的疗效。为了减少此类图像伪影，我们开发了呼吸自适应计算机断层扫描（REACT），以在常规呼吸期间触发CT采集。我们首次将REACT与临床硬件相集成，并假设REACT与传统的4D CT相比将减少≥4 mm的呼吸诱发图像伪影。使用REACT和常规的4D CT在Siemens Somatom扫描仪上获取4D图像集。扫描了在肺部运动体模上复制的13条呼吸道（12例患者）。通过Varian RPM系统观察运动，并将其发送到REACT软件，在该软件中实时评估呼吸不规则状况并用于触发成像光束。将REACT和常规4D CT图像与地面真实静态幻像图像进行比较，并比较感兴趣区域内的绝对几何差异。使用呼吸周期的每个阶段在电子束开启期间（RMSE_Beam_on）期间RPM测量的呼吸信号的均方根误差，回顾性评估成像过程中的呼吸不规则性。与传统的4D CT相比，REACT显着降低了肿瘤引起的呼吸诱发图像伪影的平均频率，≥4 mm降低了70％（p = 0.003），肺部76％（p = 0.0002）。与传统的4D CT相比，肿瘤体积缩小了10％至6％，肺部缩小了2％至1％。使用REACT方法，成像期间的呼吸不规则（RMSE_Beam_on）显着降低了27％（p = 0.013）。REACT首次成功地与临床硬件集成。我们的发现支持以下假设：与传统的4D CT相比，REACT显着减少了呼吸诱发的图像伪影。这些实验结果为进一步进行REACT研究提供了有力的证据，可能为临床使用提供更清晰的图像。