摘要
目的评估能谱CT智能匹配技术(GSI assist)在不同体质量指数(BMI)患者腹部CT扫描中的图像噪声和辐射剂量,并与120 kVp常规扫描进行对比研究。方法搜集行能谱CT全腹部增强扫描患者76例,扫描前记录每例患者的BMI。平扫采用120 kVp、自动管电流调制扫描,采用滤波反投影(FBP)、30%和50%自适应统计迭代重建(ASiR)3组图像;增强采用GSI成像模式,打开GSI assist并设置与平扫相同噪声指数,自动选择最佳能谱参数扫描,重建静脉期65 keV单能量图像。根据患者BMI将所有患者分为4组,A组:BMI<18.5 kg/m^2;B组:BMI18.5~23.9 kg/m^2;C组:BMI 24~28.9 kg/m^2;D组:BMI≥29 kg/m^2。记录各组患者常规120 kVp和GSI assist两种扫描模式的容积CT剂量指数(CTDIvol),并测量4组图像腹壁皮下脂肪和膀胱的图像噪声。采用配对t检验比较各组患者GSI assist模式扫描和常规120 kVp扫描的图像噪声和辐射剂量。结果 GSI assist模式扫描和常规120 kVp扫描的CTDIvol在各组分别为:A组:(8.2±2.3)mGy和(6.5±2.2)mGy;B组:(11.3±3.2)mGy和(10.8±3.4)mGy;C组:(17.9±3.7)mGy和(18.3±4.3)mGy;D组:(18.9±4.7)mGy和(20.4±5.6)mGy。GSI assist模式扫描CTDIvol在A组低于120 kVp常规扫描(P<0.05),在B组和C组与120 kVp常规扫描差异无统计学意义(P>0.05),在D组高于120 kVp常规扫描(P<0.05)。4组患者65 keV单能量图像皮下脂肪和膀胱噪声均低于120 kVp联合FBP图像(P<0.05),高于120 kVp联合50%ASiR图像(P<0.05),与120 kVp联合30%ASiR图像差异无统计学意义(P>0.05)。结论能谱CT智能匹配技术可以降低低BMI患者的辐射剂量;其65 keV单能量图像噪声与常规120 kVp扫描联合30%ASiR图像相当,低于常规扫描FBP重建图像。
Objective To evaluate the image noise and radiation dose of gemstone spectral imaging（ GSI） assist mode in abdominal CT based on the body mass index（ BMI） and to compare with conventional CT scan. Methods 76 patients underwent abdominal enhanced CT scans at our hospital. Plain CT scan was performed in the 120 kVp mode and automatic exposure control technique,and FBP,30% ASiR,50% ASiR were used to reconstruction. Keeping GSI mode and GSI assist on,the optimal GSI parameters were automatically selected for enhanced scan,and 65 keV monochromatic images in the venous phase were reconstructed. Patients were divided into four groups according to BMI,A： BMI 18. 5 kg/m^2; B：BMI 18. 5 - 23. 9 kg/m^2; C： BMI 24 - 28. 9 kg/m^2; D： BMI ≥29 kg/m^2. The volume CT dose index（ CTDIvol） of conventional scan and GSI assist mode were recorded,and the image noise of abdominal subcutaneous fat and bladder in each group were measured. The differences were compared by paired t-test. Results The CTDIvol（ mGy） of GSI assist mode and conventional mode at each BMI group were A：（ 8. 2 ± 2. 3） mGy and（ 6. 5 ± 2. 2） mGy; B：（ 11. 3 ± 3. 2） mGy and（ 10. 8 ± 3. 4） mGy; C：（ 17. 9 ± 3. 7） mGy and（ 18. 3 ± 4. 3） mGy; D：（ 18. 9 ± 4. 7） mGy and（ 20. 4 ± 5. 6） mGy,respectively. The CTDIvol of GSI assist mode was lower than the conventional mode in group A,higher than conventional mode in group D,and had no significant difference with conventional mode in group B and C. The image noises of fat and bladder on 65 keV images in each group were lower than 120 kVp with FBP images,higher than 120 kVp with 50% ASiR images,and had no significant difference with 120 kVp with 30% ASiR images. Conclusion GSI assist scanning mode can reduce radiation dose in patients with BMI under 18. 5 kg/m^2. The image noise of 65 keV monochromatic images is similar to that of conventional scan with 30% ASiR,and lower than conventional scan with FBP images.
出处
《临床放射学杂志》
CSCD
北大核心
2017年第7期1034-1037,共4页
Journal of Clinical Radiology
