管电压对PET/CT中CT剂量及图像质量影响的模体研究

摘要

目的：在保证图像质量的前提下，为降低PET/CT中CT扫描部分的辐射剂量提供数据依据。方法：用GE Discovery ST16型号PET/CT系统，在管电压分别为80 kV、100 kV、120 kV及140 kV条件下，对CT剂量模体和Catphan®500CT性能模体进行扫描。测量在各种管电压下的CT加权剂量指数(CTDIw)，计算给定螺距下的CT容积剂量指数(CTDIvol)；测量CT图像的相关性能指标；分析CT图像质量与CT剂量的关系。结果：CTDIvol随管电压的增加而线性增加；CT图像高对比度分辨力不受管电压影响；CT图像的低对比度分辨力、CT图像均匀性及噪声性能均随管电压的增加而提高，而性能提高规律并非线性。结论：CT图像性能均随剂量的增加而提高，而性能提高规律并非线性，当剂量达到一定值时，其图像性能随剂量的增加幅度变缓，因此，在保证一定的CT图像质量的条件下，可以通过降低管电压适当降低PET/CT检查中CT部分的辐射剂量。%Objective:To examine how to decrease of radiation dose caused by CT in PET/CT while ensuring quality of CT image. Methods:CT dose phantom(DCT 10) and CT performance phantom (Catphan® 500) were scanned in the tube voltage 80kV, 100kV, 120kV and 140kV with PET/CT(GE Discovery ST16). The image quality was evaluated by high contrast resolution, low contrast resolution, uniformity and noise. CTDIw and CTDIvol were calculated. The relationship between CT image quantity and CT dose was analyzed. Results:CT dose increased linearly with the tube voltage. The high contrast resolution of CT image was independent of the tube voltage. The performances of CT image, low contrast resolution, uniformity and noise, improved with increasing tube voltage, and it was nolinear. Conclusion: The performances of CT image improved with increasing CT dose. It improved more slowly when the CT dose reach to a certain value. The radiation dose by CT in PET/CT could be decreased appropriately under the guarantee of the quality of the CT image.