Département de radio-oncologie, Centre hospitalier universitaire de Sherbrooke (CHUS), Sherbrooke, Québec, J1H 5N4, Canada.
Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, J1H 5N4, Canada.
J Appl Clin Med Phys. 2020 Aug;21(8):173-182. doi: 10.1002/acm2.12940. Epub 2020 Jun 7.
To present an open-source software (https://github.com/CHUSRadOncPhys/FluoMV) for monitoring intrafraction motion that is based on the visualization of superimposed contours of projected region-of-interests from DICOM RTSTRUCT files on cine-MV images acquired and displayed in real-time during radiation therapy delivery. Clinical use with prostate gold fiducial markers is presented.
Projections of regions of interest (ROI) in the reference frame of the electronic portal imaging device are computed offline for different gantry angles before the first treatment fraction. During treatment delivery, the contrast of portal images is automatically adjusted using a histogram equalization algorithm. The projections associated with the current gantry angle are then superimposed on the images in real time. This allows the therapist to evaluate if the imaged structures of interest remain within their respective contours during treatment delivery and to potentially interrupt the treatment if deemed necessary. The spatial accuracy of the method was evaluated by imaging a ball bearing phantom in a set-up where the position of the projected ROI is highly sensitive to gantry angle errors. The visibility of fiducial markers during one fraction of seven different volumetric modulated arc therapy (VMAT) prostate treatments is characterized.
The geometric validation showed a negligible systematic error μ < 0.1 mm for the position of the projections. The random errors associated with the time accuracy of the gantry angle readout were characterized by standard deviations σ ≤ 0.6 mm. The VMAT clinical treatments showed that the fiducial markers were frequently visible, allowing for a meaningful clinical use.
The results demonstrate that the method presented is sufficiently accurate to be used for intrafraction monitoring of patients. The fact that this method could be implemented on many modern linacs at little to no cost and with no additional dose delivered to the patients makes this solution very attractive for improving patient care and safety in radiation therapy.
介绍一种开源软件（https://github.com/CHUSRadOncPhys/FluoMV），用于监测分次内运动，该软件基于在放射治疗过程中实时采集和显示的电影 MV 图像上叠加来自 DICOM RTSTRUCT 文件的投影感兴趣区域轮廓的可视化。介绍了前列腺金标记物的临床应用。
在第一次治疗前，针对不同的机架角度，离线计算感兴趣区域（ROI）的投影。在治疗过程中，使用直方图均衡化算法自动调整图像对比度。然后将与当前机架角度相关的投影实时叠加到图像上。这使治疗师能够评估在治疗过程中感兴趣的成像结构是否仍在其各自的轮廓内，并在必要时潜在地中断治疗。通过在一个设置中对球轴承体模进行成像，该设置中投影 ROI 的位置对机架角度误差高度敏感，评估了该方法的空间准确性。对七个不同容积调强弧形治疗（VMAT）前列腺治疗的一个分次中标记物的可见性进行了特征描述。
几何验证表明，投影位置的系统误差 μ < 0.1mm 可以忽略不计。与机架角度读数的时间精度相关的随机误差用标准差 σ ≤ 0.6mm 来表示。VMAT 临床治疗表明，标记物经常可见，允许进行有意义的临床应用。
结果表明，所提出的方法具有足够的准确性，可用于患者的分次内监测。该方法可以在许多现代直线加速器上以很少或无需额外成本实现，并且不会向患者额外提供剂量，这使得该解决方案在改善放射治疗中的患者护理和安全性方面非常有吸引力。
