Keall P J, Starkschall G, Shukla H, Forster K M, Ortiz V, Stevens C W, Vedam S S, George R, Guerrero T, Mohan R
Department of Radiation Oncology, Virginia Commonwealth University, Richmond, Virginia, USA.
Phys Med Biol. 2004 May 21;49(10):2053-67. doi: 10.1088/0031-9155/49/10/015.
Respiratory motion degrades anatomic position reproducibility during imaging, necessitates larger margins during radiotherapy planning and causes errors during radiation delivery. Computed tomography (CT) scans acquired synchronously with the respiratory signal can be used to reconstruct 4D CT scans, which can be employed for 4D treatment planning to explicitly account for respiratory motion. The aim of this research was to develop, test and clinically implement a method to acquire 4D thoracic CT scans using a multislice helical method. A commercial position-monitoring system used for respiratory-gated radiotherapy was interfaced with a third generation multislice scanner. 4D cardiac reconstruction methods were modified to allow 4D thoracic CT acquisition. The technique was tested on a phantom under different conditions: stationary, periodic motion and non-periodic motion. 4D CT was also implemented for a lung cancer patient with audio-visual breathing coaching. For all cases, 4D CT images were successfully acquired from eight discrete breathing phases, however, some limitations of the system in terms of respiration reproducibility and breathing period relative to scanner settings were evident. Lung mass for the 4D CT patient scan was reproducible to within 2.1% over the eight phases, though the lung volume changed by 20% between end inspiration and end expiration (870 cm3). 4D CT can be used for 4D radiotherapy, respiration-gated radiotherapy, 'slow' CT acquisition and tumour motion studies.
呼吸运动在成像过程中会降低解剖位置的可重复性，在放射治疗计划中需要更大的边界，并在放疗过程中导致误差。与呼吸信号同步采集的计算机断层扫描（CT）可用于重建4D CT扫描，其可用于4D治疗计划以明确考虑呼吸运动。本研究的目的是开发、测试并临床应用一种使用多层螺旋方法采集4D胸部CT扫描的方法。将用于呼吸门控放疗的商业位置监测系统与第三代多层扫描仪连接。对4D心脏重建方法进行了修改以允许进行4D胸部CT采集。该技术在不同条件下的体模上进行了测试：静止、周期性运动和非周期性运动。还对一名肺癌患者实施了4D CT并进行了视听呼吸指导。对于所有病例，均成功从八个离散呼吸阶段采集了4D CT图像，然而，该系统在呼吸可重复性和相对于扫描仪设置的呼吸周期方面存在一些局限性。4D CT患者扫描的肺肿块在八个阶段内的再现性在2.1%以内，尽管肺体积在吸气末和呼气末之间变化了20%（870 cm³）。4D CT可用于4D放射治疗、呼吸门控放疗、“慢速”CT采集和肿瘤运动研究。
