Objective To evaluate the feasibility of using a low concentration of contrast medium(Visipaque 270 mg I/m L), low tube voltage, and an advanced image reconstruction algorithm in head and neck computed tomography angi...Objective To evaluate the feasibility of using a low concentration of contrast medium(Visipaque 270 mg I/m L), low tube voltage, and an advanced image reconstruction algorithm in head and neck computed tomography angiography(CTA).Methods Forty patients(22 men and 18 women; average age 48.7 ± 14.25 years; average body mass index 23.9 ± 3.7 kg/m2) undergoing CTA for suspected vascular diseases were randomly assigned into two groups. Group A(n = 20) was administered 370 mg I/m L contrast medium, and group B(n = 20) was administered 270 mg I/m L contrast medium. Both groups were administered at a rate of 4.8 m L/s and an injection volume of 0.8 m L/kg. Images of group A were obtained with 120 k Vp and filtered back projection(FBP) reconstruction, whereas images of group B were obtained with 80 k Vp and 80% adaptive iterative statistical reconstruction algorithm(ASi R). The CT values and standard deviations of intracranial arteries and image noise on the corona radiata were measured to calculate the contrast-to-noise ratio(CNR) and signal-to-noise ratio(SNR). The beam-hardening artifacts(BHAs) around the skull base were calculated. Two readers evaluated the image quality with volume rendered images using scores from 1 to 5. The values between the two groups were statistically compared.Results The mean CT value of the intracranial arteries in group B was significantly higher than that in group A(P < 0.001). The CNR and SNR values in group B were also statistically higher than those in group A(P < 0.001). Image noise and BHAs were not significantly different between the two groups. The image quality score of VR images of in group B was significantly higher than that in group A(P = 0.001). However, the quality scores of axial enhancement images in group B became significantly smaller than those in group A(P< 0.001). The CT dose index volume and dose-length product were decreased by 63.8% and 64%, respectively, in group B(P < 0.001 for both).Conclusion Visipaque combined with 80 k Vp and 80% ASi R provided similar image quality in intracranial CTA with 64% radiation dose reduction compared with the use of Iopamidol, 120 k Vp, and FBP reconstruction.展开更多
Background Currently there is a trend towards reducing radiation dose while maintaining image quality during computer tomography （CT） examination.This results from the concerns about radiation exposure from CT and t...Background Currently there is a trend towards reducing radiation dose while maintaining image quality during computer tomography （CT） examination.This results from the concerns about radiation exposure from CT and the potential increase in the incidence of radiation induced carcinogenesis.This study aimed to investigate the lowest radiation dose for maintaining good image quality in adult chest scanning using GE CT equipment.Methods Seventy-two adult patients were examined by Gemstone Spectral CT.They were randomly divided into six groups.We set up a different value of noise index （NI） when evaluating each group every other number from 13.0 to 23.0.The original images were acquired with a slice of 5 mm thickness.For each group,several image series were reconstructed using different levels of adaptive statistical iterative reconstruction （ASIR） （30％,50％,and 70％）.We got a total of 18 image sequences of different combinations of NI and ASIR percentage.On one hand,quantitative indicators,such as CT value and standard deviation （SD）,were assessed at the region of interest.The signal-to-noise ratio （SNR） and contrast-to-noise ratio （CNR） were calculated.The volume CT dose index （CTDI） and dose length product （DLP） were recorded.On the other hand,two radiologists with ＞5 years of experience blindly reviewed the subjective image quality using the standards we had previously set.Results The different combinations of noise index and ASIR were assessed.There was no significant difference in CT values among the 18 image sequences.The SD value was reduced with the noise index＇s reduction or ASIR＇s increase.There was a trend towards gradually lower SNR and CNR with an NI increase.The CTDI and DLP were diminishing as the NI increased.The scores from subjective image quality evaluation were reduced in all groups as the ASIR increased.Conclusions Increasing NI can reduce radiation dose.With the premise of maintaining the same image quality,using a suitable percentage of ASIR can increase the value of NI.To assure image quality,we concluded that when the NI was set at 17.0 and ASlR was 50％,the image quality could be optimal for not only satisfying the requirements of clinical diagnosis,but also achieving the purpose of low-dose scanning.展开更多
目的:探讨在头颈部CT血管成像(CTA)中,以患者体重指数(BMI)为基础的低剂量扫描方案实施前后对图像质量及辐射剂量的影响。方法:连续选取拟行头颈CTA检查患者186例,按检查先后分为,A组:采用管电压120 k V,滤波反投影法(FBP)重建;B组:采...目的:探讨在头颈部CT血管成像(CTA)中,以患者体重指数(BMI)为基础的低剂量扫描方案实施前后对图像质量及辐射剂量的影响。方法:连续选取拟行头颈CTA检查患者186例,按检查先后分为,A组:采用管电压120 k V,滤波反投影法(FBP)重建;B组:采用管电压100k V,自适应性迭代重建(ASi R)。A、B组根据患者的BMI进一步分组,A1组和B1组:BMI<24kg/m2;A2组和B2组:24kg/m2≤BMI<28kg/m2;A3组和B3组:BMI≥28kg/m2。对各组的辐射剂量、客观图像质量评价采用两独立样本t检验。由两名有经验的放射科医师对两组图像质量进行主观评价,并对两名医师的阅片结果进行Kappa检验。结果:B1组、B2组及B3组的CT容积剂量指数(CTDIvol)较A1组、A2组及A3组分别下降29.29%、32.70%及40.24%(均P<0.05);B1组、B2组及B3组的剂量长度乘积(DLP)较A1组、A2组及A3组分别下降32.44%、35.10%和40.98%(均P<0.05)。头部,颈部以及胸廓入口处的血管CT值B组各分组较A组对应组均增高,图像噪声均减低,信噪比(SNR)和对比噪声比(CNR)均增高,差异均有统计学意义(均P<0.05)。B组各分组的主观评分较A组对应组均高(均P<0.05),B1组、B2组及B3组图像质量的一致性(Kappa值=0.634,0.644,0.628,均P<0.05)分别高于A1组、A2组及A3组(Kappa值=0.476,0.566,0.595,均P<0.05)。结论:不同BMI患者行头颈CTA检查,采用100k V管电压结合ASi R迭代重建扫描方案,可以降低辐射剂量(尤其是肥胖患者),并且可获得满意的图像质量。展开更多
文摘Objective To evaluate the feasibility of using a low concentration of contrast medium(Visipaque 270 mg I/m L), low tube voltage, and an advanced image reconstruction algorithm in head and neck computed tomography angiography(CTA).Methods Forty patients(22 men and 18 women; average age 48.7 ± 14.25 years; average body mass index 23.9 ± 3.7 kg/m2) undergoing CTA for suspected vascular diseases were randomly assigned into two groups. Group A(n = 20) was administered 370 mg I/m L contrast medium, and group B(n = 20) was administered 270 mg I/m L contrast medium. Both groups were administered at a rate of 4.8 m L/s and an injection volume of 0.8 m L/kg. Images of group A were obtained with 120 k Vp and filtered back projection(FBP) reconstruction, whereas images of group B were obtained with 80 k Vp and 80% adaptive iterative statistical reconstruction algorithm(ASi R). The CT values and standard deviations of intracranial arteries and image noise on the corona radiata were measured to calculate the contrast-to-noise ratio(CNR) and signal-to-noise ratio(SNR). The beam-hardening artifacts(BHAs) around the skull base were calculated. Two readers evaluated the image quality with volume rendered images using scores from 1 to 5. The values between the two groups were statistically compared.Results The mean CT value of the intracranial arteries in group B was significantly higher than that in group A(P < 0.001). The CNR and SNR values in group B were also statistically higher than those in group A(P < 0.001). Image noise and BHAs were not significantly different between the two groups. The image quality score of VR images of in group B was significantly higher than that in group A(P = 0.001). However, the quality scores of axial enhancement images in group B became significantly smaller than those in group A(P< 0.001). The CT dose index volume and dose-length product were decreased by 63.8% and 64%, respectively, in group B(P < 0.001 for both).Conclusion Visipaque combined with 80 k Vp and 80% ASi R provided similar image quality in intracranial CTA with 64% radiation dose reduction compared with the use of Iopamidol, 120 k Vp, and FBP reconstruction.
文摘Background Currently there is a trend towards reducing radiation dose while maintaining image quality during computer tomography （CT） examination.This results from the concerns about radiation exposure from CT and the potential increase in the incidence of radiation induced carcinogenesis.This study aimed to investigate the lowest radiation dose for maintaining good image quality in adult chest scanning using GE CT equipment.Methods Seventy-two adult patients were examined by Gemstone Spectral CT.They were randomly divided into six groups.We set up a different value of noise index （NI） when evaluating each group every other number from 13.0 to 23.0.The original images were acquired with a slice of 5 mm thickness.For each group,several image series were reconstructed using different levels of adaptive statistical iterative reconstruction （ASIR） （30％,50％,and 70％）.We got a total of 18 image sequences of different combinations of NI and ASIR percentage.On one hand,quantitative indicators,such as CT value and standard deviation （SD）,were assessed at the region of interest.The signal-to-noise ratio （SNR） and contrast-to-noise ratio （CNR） were calculated.The volume CT dose index （CTDI） and dose length product （DLP） were recorded.On the other hand,two radiologists with ＞5 years of experience blindly reviewed the subjective image quality using the standards we had previously set.Results The different combinations of noise index and ASIR were assessed.There was no significant difference in CT values among the 18 image sequences.The SD value was reduced with the noise index＇s reduction or ASIR＇s increase.There was a trend towards gradually lower SNR and CNR with an NI increase.The CTDI and DLP were diminishing as the NI increased.The scores from subjective image quality evaluation were reduced in all groups as the ASIR increased.Conclusions Increasing NI can reduce radiation dose.With the premise of maintaining the same image quality,using a suitable percentage of ASIR can increase the value of NI.To assure image quality,we concluded that when the NI was set at 17.0 and ASlR was 50％,the image quality could be optimal for not only satisfying the requirements of clinical diagnosis,but also achieving the purpose of low-dose scanning.
文摘目的探讨前置基于多模型的自适应统计迭代重建(ASiR-V)技术对胸部CT辐射剂量和图像质量的影响。方法采用GE Revolution CT对胸部仿真体模和120例胸部CT平扫患者(分为6组,每组20例)分别设定前置ASiR-V权重为0、20%、40%、60%、80%、100%进行扫描。管电压120kV,管电流采用自动毫安(Smart mA 10-500)技术,噪声指数设为11。记录胸部体模及各组患者扫描的剂量长度乘积,计算并比较各组有效剂量(ED)。以胸部体模不同组织结构(肺组织、脊柱旁软组织、主动脉和椎体)的CT值和标准差(SD)作为客观指标,结合对各组患者的图像主观评分,比较图像质量的组间差异。结果随着前置ASiR-V权重的增加,体模及患者的ED均呈对数降低,体模不同组织CT值、图像噪声均未见明显改变。ASiR-V权重为40%时纵隔窗和肺窗的主观评分开始下降;60%时纵隔窗和肺窗图像主观评分相对40%时出现明显下降(P<0.05)。ASiR-V权重为40%,ED降至ASiR-V权重为0时的57.21%。结论前置ASiR-V可以降低辐射剂量,同时又不影响图像客观指标;前置ASiR-V权重为40%时,图像仍可保证临床诊断需求,且辐射剂量明显降低,临床应用价值最高。
