CT扫描及重建参数对放疗图像质量影响的研究

Effect of CT scanning and reconstruction parameters on the quality of imaging for radiation therapy

目的探讨CT模拟定位扫描协议中各项参数对CT图像质量的影响,为确定精确放疗定位图像的扫描协议参数提供依据。方法采用Philips16排大孔径螺旋CT模拟定位机扫描Catphan600模体和Philips图像校准模体,改变扫描及重建参数获取不同的图像序列,分析其对图像噪声、均匀度、不同物质的CT值、高对比度分辨力及低对比度分辨力等的影响。结果管电压、扫描部位及滤过器影响物质的CT值;管电压、管电流、重建层厚、滤过器及滤过器增强则影响图像的噪声;扫描部位影响图像的均匀度。图像高对比度分辨力与滤过器、滤过器增强相关,而低对比度分辨力则与噪声相关。结论通过全面系统的模体测试可充分了解CT扫描协议中各项参数对图像质量的影响,有利于确定精确放疗CT模拟定位扫描协议参数和设定CT值-电子密度曲线以确保精准放射治疗的实施。

Objective To investigate the impact of CT scanning and reconstructed parameters on the quality of CT image, in order to provide basis for establishing the standard of high quality image for precision radiation therapy. Methods Catphan600 phantom and Philips image calibration phantom were scanned by Philips Big-Bore Brilliance CT.Images were acquired at different protocols varying scan and reconstruction parameters. The impact of scanning and reconstruction parameters on image noise, uniformity, the CT values, high and low contrast resolution were analyzed. Results The CT value of image was influenced by tube voltage, scanning site and filters used during scanning. The image noise was affected by tube voltage, tube current, reconstruction thickness, filter and filter enhancement. The uniformity of image was affected by the scanning site and scanning resolution. High contrast resolution was affected by filter, filter enhancement and image matrix, while low contrast resolution was affected by image noise. Conclusion Through the investigation of CT scanning protocol and reconstructed parameters on the quality of CT image may help establish the standard of high quality of image for precision radiation therapy.