Marks L B, Spencer D P, Bentel G C, Ray S K, Sherouse G W, Sontag M R, Coleman R E, Jaszczak R J, Turkington T G, Tapson V
Dept. of Radiation Oncology, Duke University Medical Center, Durham, NC 27710.
Int J Radiat Oncol Biol Phys. 1993 Jul 15;26(4):659-68. doi: 10.1016/0360-3016(93)90285-4.
Three-dimensional single photon emission computed tomography lung perfusion scans (SPECT) provide a unique quantitative 3-dimensional map of the distribution of functioning pulmonary vascular/alveolar subunits, information not provided by other imaging modalities. This report describes our initial experience utilizing these scans to assist in the design of radiation treatment beams and to assess changes in regional lung function following irradiation.
Patients were immobilized and scanned in the treatment position with appropriate fiducial markers. Four millicuries of technetium 99M microaggregated albumin were injected and SPECT images of the lung were generated. Pre-treatment SPECT images were used to help design radiation beams to minimize irradiation of functioning lung. Pre- and post-treatment scans were compared to assess changes in regional function. These changes in function were then correlated with the regional radiation dose.
Pre-radiotherapy SPECT scans were obtained in 18 patients (11 with lung cancer). Marked variations in regional function were frequently noted. In patients with primary lung tumors, these variations were not necessarily immediately adjacent to the tumor volume. In general, patients with poor pulmonary function pre-treatment, in whom one would like to spare as much normal lung as possible, had the most non-uniform distribution throughout the lung of functioning vascular/alveolar subunits. In these cases, pre-treatment scans were most useful in designing radiation portals to minimize irradiation of functioning lung. SPECT scans were also used to detect changes in regional lung function secondary to radiotherapy in four patients. With doses in excess of 40 Gy, reductions in regional function were noted 1-6 months following completion of radiotherapy. These reductions were not necessarily accompanied by reductions in conventional pulmonary function tests, which are assessments of whole lung function and may not reflect regional lung injury if the volume affected is small.
SPECT lung scans provide an excellent means of assessing regional lung function, superior to that obtainable with planar images. The functional data provided by the SPECT images is useful in designing "optimal" radiation treatment beams and in assessing the effect of radiotherapy on regional lung functions. Efforts are continuing in our laboratory to develop a dose response curve for regional lung damage using the tools of SPECT scanning and 3-dimensional dose calculations.
三维单光子发射计算机断层扫描肺灌注扫描（SPECT）可提供功能正常的肺血管/肺泡亚单位分布的独特定量三维图谱，这是其他成像方式所无法提供的信息。本报告描述了我们利用这些扫描来辅助放射治疗束设计以及评估放疗后肺区域功能变化的初步经验。
患者在治疗体位固定，并使用适当的基准标记进行扫描。注入4毫居里的锝99m微聚合白蛋白，生成肺部的SPECT图像。治疗前的SPECT图像用于帮助设计放射束，以尽量减少对功能正常肺组织的照射。比较治疗前和治疗后的扫描结果，以评估区域功能的变化。然后将这些功能变化与区域放射剂量相关联。
18例患者（11例肺癌患者）进行了放疗前SPECT扫描。经常观察到区域功能存在明显差异。在原发性肺肿瘤患者中，这些差异不一定紧邻肿瘤体积。一般来说，治疗前肺功能较差的患者，即希望尽可能保留更多正常肺组织的患者，其功能正常的血管/肺泡亚单位在全肺的分布最不均匀。在这些情况下，治疗前扫描对于设计放射野以尽量减少对功能正常肺组织的照射最为有用。SPECT扫描还用于检测4例患者放疗后肺区域功能的变化。剂量超过40 Gy时，放疗完成后1 - 6个月观察到区域功能下降。这些下降不一定伴有传统肺功能测试结果的下降，传统肺功能测试是对全肺功能的评估，如果受影响的体积较小，可能无法反映区域肺损伤。
SPECT肺扫描是评估肺区域功能的极佳方法，优于平面图像。SPECT图像提供的功能数据有助于设计“最佳”放射治疗束，并评估放疗对肺区域功能的影响。我们实验室正在继续努力，利用SPECT扫描和三维剂量计算工具，绘制区域肺损伤的剂量反应曲线。
