School of Mathematical and Physical Sciences, The University of Newcastle, Callaghan, NSW, Australia.
Department of Radiation Oncology, Calvary Mater Newcastle, Waratah, NSW, Australia.
Med Phys. 2018 Mar;45(3):1009-1017. doi: 10.1002/mp.12758. Epub 2018 Feb 19.
Breathing management can reduce breath-to-breath (intrafraction) and day-by-day (interfraction) variability in breathing motion while utilizing the respiratory motion of internal and external surrogates for respiratory guidance. Audiovisual (AV) biofeedback, an interactive personalized breathing motion management system, has been developed to improve reproducibility of intra- and interfraction breathing motion. However, the assumption of the correlation of respiratory motion between surrogates and tumors is not always verified during medical imaging and radiation treatment. Therefore, the aim of the study was to test the hypothesis that the correlation of respiratory motion between surrogates and tumors is the same under free breathing without guidance (FB) and with AV biofeedback guidance for voluntary motion management.
For 13 lung cancer patients receiving radiotherapy, 2D coronal and sagittal cine-MR images were acquired across two MRI sessions (pre- and mid-treatment) with two breathing conditions: (a) FB and (b) AV biofeedback, totaling 88 patient measurements. Simultaneously, the external respiratory motion of the abdomen was measured. The internal respiratory motion of the diaphragm and lung tumor was retrospectively measured from 2D coronal and sagittal cine-MR images. The correlation of respiratory motion between surrogates and tumors was calculated using Pearson's correlation coefficient for: (a) abdomen to tumor (abdomen-tumor) and (b) diaphragm to tumor (diaphragm-tumor). The correlations were compared between FB and AV biofeedback using several metrics: abdomen-tumor and diaphragm-tumor correlations with/without ≥5 mm tumor motion range and with/without adjusting for phase shifts between the signals.
Compared to FB, AV biofeedback improved abdomen-tumor correlation by 11% (p = 0.12) from 0.53 to 0.59 and diaphragm-tumor correlation by 13% (p = 0.02) from 0.55 to 0.62. Compared to FB, AV biofeedback improved abdomen-tumor correlation by 17% (p = 0.01) and diaphragm-tumor correlation by 15% (p < 0.01) while correcting 0.3 s (p = 0.54) and 0.2 s (p = 0.19) phase shifts, respectively. In addition, AV biofeedback with ≥5 mm tumor motion range, compared to FB improved abdomen-tumor correlation by 14% (p = 0.18) and diaphragm-tumor correlation by 17% (p = 0.01). The highest abdomen-tumor and diaphragm-tumor correlations were found using ≥5 mm tumor motion range and phase shifts, resulting in a 12% improvement in AV biofeedback.
Our results demonstrated that AV biofeedback improves the correlation of respiratory motion between surrogates and the tumor. This suggests a need for AV biofeedback for respiratory guidance utilizing respiratory surrogates during image-guided and MRI-guided radiotherapy in thoracic regions.
呼吸管理可以减少分次内（intrafraction）和分次间（interfraction）呼吸运动的变异性，同时利用内部和外部替代物的呼吸运动进行呼吸引导。视听（AV）生物反馈是一种交互式个性化呼吸运动管理系统，已被开发用于提高分次内和分次间呼吸运动的可重复性。然而，在医学成像和放射治疗过程中，替代物和肿瘤之间的呼吸运动相关性并不总是得到验证。因此，本研究的目的是检验以下假设，即在没有引导的自由呼吸（FB）和使用 AV 生物反馈进行自愿运动管理的情况下，替代物和肿瘤之间的呼吸运动相关性是相同的。
对 13 名接受放疗的肺癌患者，在两次 MRI 治疗过程中（治疗前和中期）使用两种呼吸条件（a）FB 和（b）AV 生物反馈共采集 88 个患者测量值，采集 2D 冠状和矢状面电影-MR 图像。同时，测量腹部的外部呼吸运动。从 2D 冠状和矢状面电影-MR 图像中回顾性测量膈肌和肺肿瘤的内部呼吸运动。使用 Pearson 相关系数计算替代物和肿瘤之间的呼吸运动相关性：（a）腹部与肿瘤（腹部-肿瘤）和（b）膈肌与肿瘤（膈肌-肿瘤）。使用以下几个指标比较 FB 和 AV 生物反馈之间的相关性：有无≥5mm 肿瘤运动范围的腹部-肿瘤和膈肌-肿瘤相关性，以及有无调整信号之间的相位差。
与 FB 相比，AV 生物反馈将腹部-肿瘤相关性提高了 11%（p=0.12），从 0.53 提高到 0.59，将膈肌-肿瘤相关性提高了 13%（p=0.02），从 0.55 提高到 0.62。与 FB 相比，AV 生物反馈将腹部-肿瘤相关性提高了 17%（p=0.01），将膈肌-肿瘤相关性提高了 15%（p<0.01），同时校正了 0.3s（p=0.54）和 0.2s（p=0.19）的相位差。此外，与 FB 相比，AV 生物反馈在≥5mm 肿瘤运动范围下，腹部-肿瘤相关性提高了 14%（p=0.18），膈肌-肿瘤相关性提高了 17%（p=0.01）。在≥5mm 肿瘤运动范围和相位差的情况下，腹部-肿瘤和膈肌-肿瘤的相关性最高，AV 生物反馈提高了 12%。
我们的结果表明，AV 生物反馈可以提高替代物和肿瘤之间呼吸运动的相关性。这表明在胸部区域的图像引导和 MRI 引导放疗中，需要使用 AV 生物反馈进行呼吸引导，利用呼吸替代物。
