Respiration-correlated spiral CT: A method of measuring respiratory-induced anatomic motion for radiation treatment planning
Respiration-correlated spiral CT: A method of measuring respiratory-induced anatomic motion for radiation treatment planning
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DOI：
10.1118/1.1531177
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发表时间：
2003-01-01
期刊：
影响因子：
3.8
通讯作者：
Ling, CC
中科院分区：
文献类型：
--
作者：
Ford, EC;Mageras, GS;Ling, CC
我们描述了一种方法，用于在多个呼吸相位与一个单一的螺旋CT扫描，称为螺旋相关螺旋CT（RCCT）的CT图像。RCCT依赖于外部患者监护仪提供的呼吸波形。在采集期间，该波形与CT扫描的起始时间一起沿着被记录，以便用呼吸周期的相位对每个重建的切片进行“时间标记”。通过选择适当的切片，在几个阶段生成完整的CT图像集，通常每个周期7-11个。选择CT参数以优化时间分辨率，同时最小化连续呼吸周期切片之间的空间间隙。使用0.5的节距、1.5 s的机架旋转周期和180度重建算法，对于典型的呼吸周期，在给定相位处产生类似于5 mm的切片间距，并且在每个切片内的呼吸运动是可接受的小的，特别是接近呼气末或吸气末，其中将发生门控放射治疗。我们已经进行了验证测量体模与移动球体设计来模拟呼吸引起的肿瘤运动。在4、5和6秒的呼吸周期对体模进行的RCCT扫描显示，球体的运动与在荧光透视成像下观察到的运动具有良好的一致性。RCCT和荧光透视之间球体质心的位置偏差在轴向方向上为1.1+/-0.9 mm（所有扫描在所有相位的平均值+/-1 s.d.）纵向为1.2+/-1.0mm。在所有情况下，重建的体积与基于静止体模扫描的预期体积匹配在5%以内。重建球的表面失真，从一个数学参考球的偏差量化，是类似于那些从一个固定的幻影扫描，并与幻影的速度。进行不规则运动的体模的RCCT扫描表明，即使呼吸不规则，也可以实现成功的重建。在我们当前的CT装置中，X射线管加热的限制将所使用的RCCT设置的扫描区域的长度限制为9 cm，尽管这对于多层扫描仪将不是限制。RCCT为当前呼吸触发轴向扫描方法提供了一种替代方法。使用RCCT对呼吸的多个相位进行成像，所需的扫描时间与使用触发轴向扫描对单个相位进行成像所需的扫描时间大致相同。RCCT扫描可与经门控治疗结合使用，以识别最小肿瘤运动的患者特定阶段，确定门控间隔内的残留肿瘤运动，并比较不同阶段的治疗计划。(C)2003年美国医学物理学家协会。
We describe a method for generating CT images at multiple respiratory phases with a single spiral CT scan, referred to as respiratory-correlated spiral CT (RCCT). RCCT relies on a respiration wave form supplied by an external patient monitor. During acquisition this wave form is recorded along with the initiation time of the CT scan, so as to "time stamp" each reconstructed slice with the phase of the respiratory cycle. By selecting the appropriate slices, a full CT image set is generated at several phases, typically 7-11 per cycle. The CT parameters are chosen to optimize the temporal resolution while minimizing the spatial gap between slices at successive respiratory cycles. Using a pitch of 0.5, a gantry rotation period of 1.5 s, and a 180degrees reconstruction algorithm results in similar to 5 mm slice spacing at a given phase for typical respiration periods, and a respiratory motion within each slice that is acceptably small, particularly near end expiration or end inspiration where gated radiotherapy is to occur. We have performed validation measurements on a phantom with a moving sphere designed to simulate respiration-induced tumor motion. RCCT scans of the phantom at respiratory periods of 4, 5, and 6 s show good agreement of the sphere's motion with that observed under fluoroscopic imaging. The positional deviations in the sphere's centroid between RCCT and fluoroscopy are 1.1+/-0.9 mm in the transaxial direction (average over all scans at all phases +/-1 s.d.) and 1.2+/-1.0 mm in the longitudinal direction. Reconstructed volumes match those expected on the basis of stationary-phantom scans to within 5% in all cases. The surface distortions of the reconstructed sphere, as quantified by deviations from a mathematical reference sphere, are similar to those from a stationary phantom scan and are correlated with the speed of the phantom. A RCCT scan of the phantom undergoing irregular motion, demonstrates that successful reconstruction can be achieved even with irregular respiration. Limitations from x-ray tube heating in our current CT unit restrict the length of the scan region to 9 cm for the RCCT settings used, though this will not be a limitation for a multislice scanner. RCCT offers an alternative to the current method of respiration-triggered axial scans. Multiple phases of respiration are imaged with RCCT in approximately the same scanning time required to image a single phase with a triggered axial scan. RCCT scans can be used in connection with respiratory-gated treatment to identify the patient-specific phase of minimum tumor motion, determine residual tumor motion within the gate interval, and compare treatment plans at different phases. (C) 2003 American Association of Physicists in Medicine.