Cover Keith S, Lagerwaard Frank J, Senan Suresh
Department of Radiation Oncology, VU University Medical Center, Amsterdam, The Netherlands.
Int J Radiat Oncol Biol Phys. 2006 Mar 1;64(3):954-61. doi: 10.1016/j.ijrobp.2005.10.006.
Four-dimensional computerized tomography scans (4DCT) enable intrafractional motion to be determined. Because more than 1500 images can be generated with each 4DCT study, tools for efficient data visualization and evaluation are needed. We describe the use of color intensity projections (CIP) for visualizing mobility.
Four-dimensional computerized tomography images of each patient slice were combined into a CIP composite image. Pixels largely unchanged over the component images appear unchanged in the CIP image. However, pixels whose intensity changes over the phases of the 4DCT appear in the CIP image as colored pixels, and the hue encodes the percentage of time the tissue was in each location. CIPs of 18 patients were used to study tumor and surrogate markers, namely the diaphragm and an abdominal marker block.
Color intensity projections permitted mobility of high-contrast features to be quickly visualized and measured. In three selected expiratory phases ("gating phases") that were reviewed in the sagittal plane, gating would have reduced mean tumor mobility from 6.3 +/- 2.0 mm to 1.4 +/- 0.5 mm. Residual tumor mobility in gating phases better correlated with residual mobility of the marker block than that of the diaphragm.
CIPs permit immediate visualization of mobility in 4DCT images and simplify the selection of appropriate surrogates for gated radiotherapy.
四维计算机断层扫描（4DCT）能够确定分次治疗期间的运动情况。由于每次4DCT研究可生成1500多张图像，因此需要有效的数据可视化和评估工具。我们描述了使用颜色强度投影（CIP）来可视化运动情况。
将每个患者切片的四维计算机断层扫描图像组合成一张CIP合成图像。在各组成图像中基本未发生变化的像素在CIP图像中也保持不变。然而，在4DCT各相位中强度发生变化的像素在CIP图像中显示为彩色像素，并且色调编码组织处于每个位置的时间百分比。利用18名患者的CIP来研究肿瘤和替代标志物，即膈肌和腹部标志物块。
颜色强度投影能够快速可视化和测量高对比度特征的运动情况。在矢状面观察的三个选定呼气期（“门控期”）中，门控可使肿瘤平均运动从6.3±2.0毫米降至1.4±0.5毫米。门控期的残余肿瘤运动与标志物块的残余运动比与膈肌的残余运动相关性更好。
CIP能够立即可视化4DCT图像中的运动情况，并简化了门控放射治疗合适替代物的选择。
