目的探讨256层螺旋CT应用低管电流联合迭代重建技术在腹部低剂量增强扫描的可行性。方法对160例拟行腹部CT扫描患者随机分成8组(A^H组),每组20例。A组采用120 k V、250 m As条件进行腹部常规剂量扫描,图像应用滤波反投影重建。B^H组采...目的探讨256层螺旋CT应用低管电流联合迭代重建技术在腹部低剂量增强扫描的可行性。方法对160例拟行腹部CT扫描患者随机分成8组(A^H组),每组20例。A组采用120 k V、250 m As条件进行腹部常规剂量扫描,图像应用滤波反投影重建。B^H组采用固定管电压120 k V,管电流于250~70 m As之间每次间隔30m As减低扫描条件行上腹部低剂量扫描,图像采用迭代重建。采用方差分析比较各组图像噪声、对比噪声比、CT剂量指数、CT剂量长度乘积及有效辐射剂量的差异。并对各组图像分别进行质量评分,确定等同于A组图像质量并满足临床诊断要求最低剂量组。图像噪声与体重指数、腹围相关性采用Pearson相关分析。结果采用迭代算法重建图像的低剂量B^H组主动脉、肝脏、脾脏、胰腺噪声为10.7~23.0 HU,B^F组均较常规剂量组A组图像噪声[(13.8~16.8)HU]低,而G、H组图像噪声均明显高于A组。B^E组图像平均噪声与A组比较,差异无统计学意义(P>0.05),F^H组图像噪声与A组比较,差异有统计学意义(P<0.05)。低剂量组对比噪声比为3.1~14.7,B^E组对比噪声比均高于A组(3.4~7.6),但差异无统计学意义(P>0.05)。F^H组对比噪声比出现不同程度下降,部分低剂量组对比噪声比已低于常规剂量A组。低剂量组B^E组图像质量评分均≥3分,并与常规剂量组A组比较差异无统计学意义。F^H组主观图像质量随管电流减低而明显降低,与常规剂量组A组比较差异有统计学意义(P<0.05)。B^H组辐射剂量差异有统计学意义(P<0.01),A组与B组比较,辐射剂量无统计学意义(P>0.05)。E组为图像质量等同于常规剂量扫描最适低剂量组,辐射剂量降低约35%。图像噪声与体重指数低度相关(r^2=0.316),与腹围高度相关(r^2=0.817)结论迭代重建可以显著降低图像噪声、辐射剂量,提高图像质量,辐射剂量降低35%仍可得到与常规剂量滤波反投影重建相当的图像质量。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 inc展开更多
文摘目的探讨256层螺旋CT应用低管电流联合迭代重建技术在腹部低剂量增强扫描的可行性。方法对160例拟行腹部CT扫描患者随机分成8组(A^H组),每组20例。A组采用120 k V、250 m As条件进行腹部常规剂量扫描,图像应用滤波反投影重建。B^H组采用固定管电压120 k V,管电流于250~70 m As之间每次间隔30m As减低扫描条件行上腹部低剂量扫描,图像采用迭代重建。采用方差分析比较各组图像噪声、对比噪声比、CT剂量指数、CT剂量长度乘积及有效辐射剂量的差异。并对各组图像分别进行质量评分,确定等同于A组图像质量并满足临床诊断要求最低剂量组。图像噪声与体重指数、腹围相关性采用Pearson相关分析。结果采用迭代算法重建图像的低剂量B^H组主动脉、肝脏、脾脏、胰腺噪声为10.7~23.0 HU,B^F组均较常规剂量组A组图像噪声[(13.8~16.8)HU]低,而G、H组图像噪声均明显高于A组。B^E组图像平均噪声与A组比较,差异无统计学意义(P>0.05),F^H组图像噪声与A组比较,差异有统计学意义(P<0.05)。低剂量组对比噪声比为3.1~14.7,B^E组对比噪声比均高于A组(3.4~7.6),但差异无统计学意义(P>0.05)。F^H组对比噪声比出现不同程度下降,部分低剂量组对比噪声比已低于常规剂量A组。低剂量组B^E组图像质量评分均≥3分,并与常规剂量组A组比较差异无统计学意义。F^H组主观图像质量随管电流减低而明显降低,与常规剂量组A组比较差异有统计学意义(P<0.05)。B^H组辐射剂量差异有统计学意义(P<0.01),A组与B组比较,辐射剂量无统计学意义(P>0.05)。E组为图像质量等同于常规剂量扫描最适低剂量组,辐射剂量降低约35%。图像噪声与体重指数低度相关(r^2=0.316),与腹围高度相关(r^2=0.817)结论迭代重建可以显著降低图像噪声、辐射剂量,提高图像质量,辐射剂量降低35%仍可得到与常规剂量滤波反投影重建相当的图像质量。
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 inc
