Department of Radiation Oncology, Dana-Farber/Brigham and Women's Cancer Center and Harvard Medical School, Boston, MA 02115, USA.
Int J Radiat Oncol Biol Phys. 2012 Jan 1;82(1):e99-105. doi: 10.1016/j.ijrobp.2010.12.060. Epub 2011 Mar 4.
The potential role of four-dimensional (4D) positron emission tomography (PET)/computed tomography (CT) in radiation treatment planning, relative to standard three-dimensional (3D) PET/CT, was examined.
Ten patients with non-small-cell lung cancer had sequential 3D and 4D [(18)F]fluorodeoxyglucose PET/CT scans in the treatment position prior to radiation therapy. The gross tumor volume and involved lymph nodes were contoured on the PET scan by use of three different techniques: manual contouring by an experienced radiation oncologist using a predetermined protocol; a technique with a constant threshold of standardized uptake value (SUV) greater than 2.5; and an automatic segmentation technique. For each technique, the tumor volume was defined on the 3D scan (VOL3D) and on the 4D scan (VOL4D) by combining the volume defined on each of the five breathing phases individually. The range of tumor motion and the location of each lesion were also recorded, and their influence on the differences observed between VOL3D and VOL4D was investigated.
We identified and analyzed 22 distinct lesions, including 9 primary tumors and 13 mediastinal lymph nodes. Mean VOL4D was larger than mean VOL3D with all three techniques, and the difference was statistically significant (p < 0.01). The range of tumor motion and the location of the tumor affected the magnitude of the difference. For one case, all three tumor definition techniques identified volume of moderate uptake of approximately 1 mL in the hilar region on the 4D scan (SUV maximum, 3.3) but not on the 3D scan (SUV maximum, 2.3).
In comparison to 3D PET, 4D PET may better define the full physiologic extent of moving tumors and improve radiation treatment planning for lung tumors. In addition, reduction of blurring from free-breathing images may reveal additional information regarding regional disease.
研究与标准三维（3D）正电子发射断层扫描（PET）/计算机断层扫描（CT）相比，四维（4D）PET/CT 在放射治疗计划中的潜在作用。
在放射治疗前，10 例非小细胞肺癌患者在治疗位置进行了连续的 3D 和 4D[18F]氟脱氧葡萄糖 PET/CT 扫描。使用三种不同的技术，通过一位经验丰富的放射肿瘤学家使用预定方案进行手动轮廓描绘，使用标准化摄取值（SUV）大于 2.5 的恒定阈值的技术以及自动分割技术，在 PET 扫描上描绘大体肿瘤体积和受累淋巴结。对于每种技术，通过将每个 5 个呼吸阶段单独定义的体积组合起来，在 3D 扫描（VOL3D）和 4D 扫描（VOL4D）上定义肿瘤体积。还记录了肿瘤运动的范围和每个病变的位置，并研究了它们对观察到的 VOL3D 和 VOL4D 之间差异的影响。
我们鉴定和分析了 22 个不同的病变，包括 9 个原发性肿瘤和 13 个纵隔淋巴结。使用所有三种技术，VOL4D 的平均值均大于 VOL3D 的平均值，且差异具有统计学意义（p<0.01）。肿瘤运动的范围和肿瘤的位置影响差异的大小。在一个病例中，三种肿瘤定义技术都在 4D 扫描（SUV 最大值为 3.3）上识别出在肺门区域具有中度摄取的约 1 毫升体积，但在 3D 扫描（SUV 最大值为 2.3）上未识别出。
与 3D PET 相比，4D PET 可以更好地定义移动肿瘤的完整生理范围，并改善肺癌的放射治疗计划。此外，减少自由呼吸图像的模糊可能会揭示有关区域疾病的更多信息。
