AIM To compare radiation dose and image quality of lowdose computed tomography(CT) protocol combined with hybrid-iterative reconstruction algorithm with standarddose CT examinations for follow-up of oncologic patients...AIM To compare radiation dose and image quality of lowdose computed tomography(CT) protocol combined with hybrid-iterative reconstruction algorithm with standarddose CT examinations for follow-up of oncologic patients. METHODS Fifty-one patients with known malignant diseases which underwent, during clinical follow-up, both standarddose and low-dose whole-body CT scans were enrolled. Low-dose CT was performed on 256-row scanner, with 120 kV and automated m A modulation, and iterative reconstruction algorithm. Standard-dose CT was performed on 16-rows scanner, with 120 kV, 200-400 m As(depending on patient weight). We evaluated density values and signal-to-noise ratio, along with image noise(SD), sharpness and diagnostic quality with 4-point scale.RESULTS Density values in liver, spleen and aorta were higher in lowdose images(liver 112.55 HU vs 103.90 HU, P < 0.001), as SD values in liver and spleen(liver 16.81 vs 14.41). Volumetric-Computed-Tomographic-Dose-Index(CTDIvol) and Dose-Length-Product(DLP) were significantly lower in low-dose CT as compared to standard-dose(DLP 1025.6 m Gy*cm vs 1429.2 m Gy*cm, P < 0.001) with overall dose reduction of 28.9%. Qualitative analysis did not reveal significant differences in image noise and diagnostic quality.CONCLUSION Automatic tube-current modulation combined with hybriditerative algorithm allows radiation dose reduction of 28.9% without loss of diagnostic quality, being useful in reducing dose exposure in oncologic patients.展开更多
AIM:To determine the influence of anthropomorphic parameters on the relationship between patient centering,mean computed tomography(CT) numbers and quantitative image noise in abdominal CT.METHODS:Our Institutional Re...AIM:To determine the influence of anthropomorphic parameters on the relationship between patient centering,mean computed tomography(CT) numbers and quantitative image noise in abdominal CT.METHODS:Our Institutional Review Board approved study included 395 patients(age range 21-108,years;male:female = 195:200) who underwent contrast-enhanced abdominal CT on a 16-section multi-detector row scanner(GE LightSpeed 16).Patient centering in the gantry isocenter was measured from the lateral localizer radiograph(off center S = patient off centered superior to isocenter;off center I = patient off centered inferior to isocenter).Mean CT numbers(Hounsfield Units:HU) and noise(standard deviation of CT numbers:SD) were measured in the anterior(aHU,aSD) and posterior(pHU,pSD) abdominal wall subcutaneous fat and liver parenchyma(LivHU,LivSD) at the level of the porta hepatis.Patients' age,gender,weight,body mass index and maximal anteroposterior diameter were recorded.The data were analyzed using linear regression analysis.RESULTS:Most patients(81%;320/395) were not correctly centered in the gantry isocenter for abdominal CT scanning.Mean CT numbers in the abdominal wall increased significantly with an increase in the offcentering distance,regardless of the direction of the off-center(P < 0.05).There was a substantial increase in pSD(P = 0.01) and LivSD(P = 0.017) with off-centering.Change in mean CT numbers and image noise along the off-center distance was influenced by the patient size(P < 0.01).CONCLUSION:Inappropriate patient centering for CT scanning adversely affects the reliability of mean CT numbers and image noise.展开更多
目的探讨64层CT自动管电流调节技术(ATCM)结合低电压在幼儿胸部低剂量扫描中的应用价值。方法搜集行64层CT ATCM胸部扫描的幼儿(≤2岁)48例,其中A组(管电压100 k V)30例,B组(管电压80k V)18例;并与既往采用固定管电流条件下的低剂量扫...目的探讨64层CT自动管电流调节技术(ATCM)结合低电压在幼儿胸部低剂量扫描中的应用价值。方法搜集行64层CT ATCM胸部扫描的幼儿(≤2岁)48例,其中A组(管电压100 k V)30例,B组(管电压80k V)18例;并与既往采用固定管电流条件下的低剂量扫描数据进行对比分析,对照组C组(100 k V/60 m As)30例;其余扫描参数一致。记录每次扫描的平均管电流(m As)、CT容积剂量指数(CTDIvol)、剂量长度值(DLP),计算出有效剂量(ED)及剂量减低比值(DR),并比较3组的剂量及图像质量。结果 A组CTDIvol为(1.11±0.19)m Gy,B组CTDIvol为(0.99±0.11)mGy,C组CTDIvol为(2.38±0.00)m Gy;3组数据两两比较差异均有统计学意义(P<0.05)。A组相对C组DR约51.07%,B组相对C组DR降低约58.20%。3组图像质量均满足诊断要求,差异无统计学意义(P=0.50)。结论低电压联合ATCM技术在幼儿胸部扫描中可以广泛应用,能够有效降低辐射剂量且不影响图像质量。展开更多
目的本文探讨了应用自动管电流调节技术(Automatic Tube Medical University,ATCM)行胸部CT扫描时,管电压的变化对图像质量及辐射剂量的影响。方法应用GE Optima CT680 CT机采用ATCM技术对胸部仿真模体行CT扫描。共进行3组扫描,其中A组...目的本文探讨了应用自动管电流调节技术(Automatic Tube Medical University,ATCM)行胸部CT扫描时,管电压的变化对图像质量及辐射剂量的影响。方法应用GE Optima CT680 CT机采用ATCM技术对胸部仿真模体行CT扫描。共进行3组扫描,其中A组管电压为80 k Vp,B组管电压为100 k Vp,C组管电压为120 k Vp,各组分别预设5个噪声指数(Noise Index,NI)级别(10、15、20、25和30)扫描体模。记录每组图像的容积CT剂量指数(Volumetric CT Dose Index,CTDIvol)和剂量长度乘积(Dose-Length Product,DLP)。测量并比较图像的客观噪声(Standard Deviation,SD),由两名有经验的放射科医生采用双盲法对磨玻璃密度结节(Ground Glass Nodules,GGN)进行主观评分。结果研究结果显示,除NI为10以外,在其他相同NI时,图像客观噪声无统计学差异。NI在15、20、25和30时,A组与C组比较时,DLP分别增加21.96,16.25、9.18和6.37 m Gy·cm。B组与C组比较时,DLP分别增加14.05、8.50、5.17和3.65 m Gy·cm。相同预设NI时不同管电压下对GGN主观评分无明显统计学差异,且两名观察者间的一致性中等或良好。结论应用ATCM技术,相同预设NI下管电压的变化对图像质量不会产生明显影响。患者的辐射剂量随着扫描管电压的增高而降低。展开更多
文摘AIM To compare radiation dose and image quality of lowdose computed tomography(CT) protocol combined with hybrid-iterative reconstruction algorithm with standarddose CT examinations for follow-up of oncologic patients. METHODS Fifty-one patients with known malignant diseases which underwent, during clinical follow-up, both standarddose and low-dose whole-body CT scans were enrolled. Low-dose CT was performed on 256-row scanner, with 120 kV and automated m A modulation, and iterative reconstruction algorithm. Standard-dose CT was performed on 16-rows scanner, with 120 kV, 200-400 m As(depending on patient weight). We evaluated density values and signal-to-noise ratio, along with image noise(SD), sharpness and diagnostic quality with 4-point scale.RESULTS Density values in liver, spleen and aorta were higher in lowdose images(liver 112.55 HU vs 103.90 HU, P < 0.001), as SD values in liver and spleen(liver 16.81 vs 14.41). Volumetric-Computed-Tomographic-Dose-Index(CTDIvol) and Dose-Length-Product(DLP) were significantly lower in low-dose CT as compared to standard-dose(DLP 1025.6 m Gy*cm vs 1429.2 m Gy*cm, P < 0.001) with overall dose reduction of 28.9%. Qualitative analysis did not reveal significant differences in image noise and diagnostic quality.CONCLUSION Automatic tube-current modulation combined with hybriditerative algorithm allows radiation dose reduction of 28.9% without loss of diagnostic quality, being useful in reducing dose exposure in oncologic patients.
基金Supported by Research funding from GE Healthcare (Waukesha,Wis) (to Kalra MK)
文摘AIM:To determine the influence of anthropomorphic parameters on the relationship between patient centering,mean computed tomography(CT) numbers and quantitative image noise in abdominal CT.METHODS:Our Institutional Review Board approved study included 395 patients(age range 21-108,years;male:female = 195:200) who underwent contrast-enhanced abdominal CT on a 16-section multi-detector row scanner(GE LightSpeed 16).Patient centering in the gantry isocenter was measured from the lateral localizer radiograph(off center S = patient off centered superior to isocenter;off center I = patient off centered inferior to isocenter).Mean CT numbers(Hounsfield Units:HU) and noise(standard deviation of CT numbers:SD) were measured in the anterior(aHU,aSD) and posterior(pHU,pSD) abdominal wall subcutaneous fat and liver parenchyma(LivHU,LivSD) at the level of the porta hepatis.Patients' age,gender,weight,body mass index and maximal anteroposterior diameter were recorded.The data were analyzed using linear regression analysis.RESULTS:Most patients(81%;320/395) were not correctly centered in the gantry isocenter for abdominal CT scanning.Mean CT numbers in the abdominal wall increased significantly with an increase in the offcentering distance,regardless of the direction of the off-center(P < 0.05).There was a substantial increase in pSD(P = 0.01) and LivSD(P = 0.017) with off-centering.Change in mean CT numbers and image noise along the off-center distance was influenced by the patient size(P < 0.01).CONCLUSION:Inappropriate patient centering for CT scanning adversely affects the reliability of mean CT numbers and image noise.
文摘目的探讨64层CT自动管电流调节技术(ATCM)结合低电压在幼儿胸部低剂量扫描中的应用价值。方法搜集行64层CT ATCM胸部扫描的幼儿(≤2岁)48例,其中A组(管电压100 k V)30例,B组(管电压80k V)18例;并与既往采用固定管电流条件下的低剂量扫描数据进行对比分析,对照组C组(100 k V/60 m As)30例;其余扫描参数一致。记录每次扫描的平均管电流(m As)、CT容积剂量指数(CTDIvol)、剂量长度值(DLP),计算出有效剂量(ED)及剂量减低比值(DR),并比较3组的剂量及图像质量。结果 A组CTDIvol为(1.11±0.19)m Gy,B组CTDIvol为(0.99±0.11)mGy,C组CTDIvol为(2.38±0.00)m Gy;3组数据两两比较差异均有统计学意义(P<0.05)。A组相对C组DR约51.07%,B组相对C组DR降低约58.20%。3组图像质量均满足诊断要求,差异无统计学意义(P=0.50)。结论低电压联合ATCM技术在幼儿胸部扫描中可以广泛应用,能够有效降低辐射剂量且不影响图像质量。
文摘目的研究自动管电流调制扫描及50%权重自适应性统计迭代重建算法（adaptive statistical iterative reconstruction,ASIR）重建时,不同噪声指数（noise index,NI）的设定对胸部CT扫描图像质量的影响,探索合适的NI以降低辐射剂量。方法前瞻性地连续纳入193例行胸部CT扫描的患者,随机分为6组,各组NI预设为15、18、21、24、27、30,并进一步根据患者的体质量指数（Body Mass Index,BMI）分为三个亚组：偏瘦及正常组（BMI≤23.9）、超重组（24≤BMI≤27.9）、肥胖组（BMI≥28）。所有患者均采用自动管电流调制技术扫描,50%权重的ASIR重建。由2位放射科医师采用盲法分别对图像质量进行主观评分（〈13分,良好;13~15分,临界;〉15分,不能接受）,测量肺重建及纵隔重建图像的噪声（脂肪）、信噪比（大血管-脂肪）、对比噪声比（大血管-脂肪）。记录各患者CT容积剂量指数（CT does index volume,CTDIvol）、剂量长度乘积（dose length product,DLP）、有效剂量（effective dose,ED）。另外记录每位患者纵隔重建图像管电流小于50m A的层面占所有层面的百分比。结果随着NI的升高,图像主观评分增高（质量下降）,信噪比及对比噪声比降低。各NI预设条件下胸部CT图像主观评分均≤15分,仅NI=30时,4例（4/34）患者图像主观评分为13~15分。NI=30时图像主观评分显著高于、信噪比低于NI为15~27图像（P〈0.05）。NI为24~30的辐射剂量显著低于NI为15~21（P〈0.05）。NI为27及30时,随着BMI增加,出现电流低于50m A层面百分比降低（P〈0.05）。在NI为30时,随着BMI增加,辐射剂量显著增加（P〈0.05）。结论自动管电流调制扫描及50%ASIR重建下,胸部CT扫描可以预设NI为30,在大幅降低辐射剂量的同时,图像质量也能满足诊断要求。
文摘目的本文探讨了应用自动管电流调节技术(Automatic Tube Medical University,ATCM)行胸部CT扫描时,管电压的变化对图像质量及辐射剂量的影响。方法应用GE Optima CT680 CT机采用ATCM技术对胸部仿真模体行CT扫描。共进行3组扫描,其中A组管电压为80 k Vp,B组管电压为100 k Vp,C组管电压为120 k Vp,各组分别预设5个噪声指数(Noise Index,NI)级别(10、15、20、25和30)扫描体模。记录每组图像的容积CT剂量指数(Volumetric CT Dose Index,CTDIvol)和剂量长度乘积(Dose-Length Product,DLP)。测量并比较图像的客观噪声(Standard Deviation,SD),由两名有经验的放射科医生采用双盲法对磨玻璃密度结节(Ground Glass Nodules,GGN)进行主观评分。结果研究结果显示,除NI为10以外,在其他相同NI时,图像客观噪声无统计学差异。NI在15、20、25和30时,A组与C组比较时,DLP分别增加21.96,16.25、9.18和6.37 m Gy·cm。B组与C组比较时,DLP分别增加14.05、8.50、5.17和3.65 m Gy·cm。相同预设NI时不同管电压下对GGN主观评分无明显统计学差异,且两名观察者间的一致性中等或良好。结论应用ATCM技术,相同预设NI下管电压的变化对图像质量不会产生明显影响。患者的辐射剂量随着扫描管电压的增高而降低。
