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目的通过对CT模拟定位机质量控制模体的测试,对CT模拟定位机的各项指标进行质量控制,分析影响图像质量的因素,保证图像质量。方法利用PHILIPS大孔径CT模拟定位机分别对Catphan504模体四大部分进行头部标准质量控制方案轴向扫描,测试其层厚、CT值线性、均匀性、噪声、空间分辨率、密度分辨率。层厚测试扫描条件为120 kV,280 mAs,层厚9.0、6.0、3.0、1.5 mm,旋转时间0.75 s,算法采用EB;CT值线性扫描条件为120 kV,280 mAs,层厚9.0 mm,旋转时间0.75 s,算法EB、B;均匀性、噪声、空间分辨率扫描条件均为120 kV,280 mAs,层厚9.0 mm,旋转时间0.75 s,算法EB;密度分辨率扫描条件为120 kV,220 mAs、240 mAs、260 mAs、280 mAs,层厚9.0 mm,旋转时间0.75 s,算法EB。结果 9.0 mm、6.0 mm、3.0 mm、1.5 mm标称层厚的测试结果分别为8.82 mm、5.80 mm、2.95 mm、1.55 mm;对于CT值线性,EB、B两种算法的对比度标度分别为1.79×10~(-4) cmHu~(-1)、1.93×10~(-4) cmHu~(-1);均匀性为3.9 Hu;噪声水平为0.34%;空间分辨率为6 LP/cm;220 mAs、240 mAs、260 mAs、280 mAs条件下,密度分辨率分别为4 mm@1%、3 mm@1%、2 mm@1%、2 mm@1%。CT值线性在EB算法条件下,对比度标度近似等于参考值下限值,密度分辨率在220 mAs、240 mAs条件下,其测量值低于参考值,其他测试项目结果均符合要求。结论通过对各项目的检测可保证影像质量最优化,进而保证精确放射治疗的实施。
OBJECTIVE Through the test of the quality control module of CT simulation positioning machine, the quality control of each index of the CT simulation positioning machine is analyzed, the factors affecting the image quality are analyzed to ensure the image quality. Methods The head of the four parts of Catphan504 phantom were scanned axially by PHILIPS large aperture CT simulation positioning machine to test the thickness, CT value, linearity, uniformity, noise, spatial resolution and density resolution. The scanning conditions of layer thickness were 120 kV, 280 mAs, layer thickness 9.0, 6.0, 3.0, 1.5 mm, rotation time 0.75 s, EB was used in the algorithm. The CT scanning conditions were 120 kV, 280 mAs, Time 0.75s, algorithm EB, B; uniformity, noise, spatial resolution scanning conditions are 120 kV, 280 mAs, layer thickness 9.0 mm, rotation time 0.75 s, EB algorithm; density resolution scanning conditions of 120 kV, 220 mAs, 240 mAs, 260 mAs, 280 mAs, layer thickness 9.0 mm, rotation time 0.75 s, algorithm EB. Results The test results of 9.0 mm, 6.0 mm, 3.0 mm and 1.5 mm nominal layer thicknesses were 8.82 mm, 5.80 mm, 2.95 mm and 1.55 mm, respectively. The contrast scales of EB and B algorithms for CT value linearity were 1.79 × 10 -4 cmHu -1 and 1.93 × 10 -4 cmHu -1; the uniformity is 3.9 Hu; the noise level is 0.34%; the spatial resolution is 6 LP / cm The density resolution was 4 mm @ 1%, 3 mm @ 1%, 2 mm @ 1%, 2 mm @ 1% at 220 mAs, 240 mAs, 260 mAs and 280 mAs, respectively. Under the EB algorithm, the contrast scale is approximately equal to the lower reference value. The density resolution is lower than the reference value under the conditions of 220 mAs and 240 mAs. The results of other test items meet the requirements. Conclusion Through the detection of various projects to ensure the optimization of image quality, thus ensuring the implementation of accurate radiotherapy.