智能最佳管电压调制技术胸部CT成像剂量优化滑块位置对图像质量及辐射剂量的影响

Effect of slider position of optimized dose of CT imaging of chest by CARE kV on image quality and radiation dosage

目的:探讨在利用智能最佳管电压调制(CARE kV)技术扫描胸部时剂量优化滑块不同位置对图像质量及辐射剂量的影响,以确定CARE kV技术扫描胸部时剂量优化滑块的最佳位置。方法:收集在医院行胸部平扫的180例成年患者,依据剂量优化滑块位置分为3档A组,7档B组,11档C组,每组60例。在图像客观评价中测量比较各组患者气管分叉层面降主动脉CT值与噪声值(SD),以及同层肺窗空气的CT值与SD值;比较各组容积CT剂量指数(CTDIvol)、剂量长度乘积(DLP)及计算有效剂量(ED),并对图像的主观评分值进行分析。结果:3档A组,7档B组和11档C组图像质量主观评分依次为(2.55±0.82)分、(2.47±0.73)分和(1.92±0.51)分,3档A组与7档B组两组评分比较无统计学差异,3组的主观评分比较,差异均有统计学意义(F=123.007,P<0.05);3档A组,7档B组和11档C组图像气管分叉层面降主动脉CT值分别为(42.7±5.4)HU、(43.9±6.3)HU和(44.6±6.7)HU,同层肺窗空气的CT值分别为(-980.0±42.6)HU、(-975.9±47.7)HU和(-969.9±46.3)HU,3组比较差异均无统计学意义;3档A组,7档B组和11档C组图像降主动脉SD值分别为(11.1±2.1)、(13.9±1.9)和(19.6±2.7),与空气的SD值比较依次明显增高,其差异有统计学意义(F=9.92,F=2.567;P<0.05);3档A组,7档B组和11档C组的CTDI_(vol)分别为(4.34±0.53)mGy、(3.47±0.47)mGy和(2.57±0.41)mGy,3组比较差异有统计学意义(F=3.88,P<0.05);DLP分别为(154.86±20.90)mGy·cm、(126.40±16.85)mGy·cm和(91.60±13.85)mGy·cm,3组比较差异有统计学意义(F=11.89,P<0.05);ED分别为(2.16±0.36)mSv、(1.69±0.33)mSv和(1.27±0.25)mSv,依次明显降低,3组比较差异有统计学意义(F=5.96,P<0.05)。结论:应用CARE kV技术扫描胸部时剂量调制因子选择7档,较3档k V逐渐降低,可以在保证图像质量的同时有效降低受检者的辐射剂量。

Objective:To explore the effect of different slider positions of the optimized dose on image quality and radiation dosage when used combined application to reduce exposure technique(CARE kv)scanned chest,so as to determine the optimal position of the slider with optimized dose when CARE kv technique scanned chest.Methods:A total of 180 adult patients who underwent plain scan on chest were selected,and random number method was adopted to divide them into three groups,which were respectively named as group A at 3 gear,group B at 7 gear and group C at 11 gear according to slider position of optimized dose.The computed tomography(CT)value and noise value(SD)of descending aorta at the tracheal bifurcation layer,and the CT value and SD value of the air of lung window of the same layer between two groups were measured and compared in the objective evaluation of images.And then,the volume CT dose index(CTDIvol),dose length product(DLP)and the effective doses(ED)among various groups were compared,and the subjective scoring values of the images were further analyzed.Results:The subjective scores of image quality of the three groups were successively(2.55±0.82)points,(2.47±0.73)points and(1.92±0.51)points.There was no significant difference in scores between group A at 3 gear and group B at 7 gear,but there was significant difference in subjective scores between each two groups(F=123.007,P<0.05).The CT values of descending aorta at the tracheal bifurcation layer of the three groups were respectively(42.7±5.4)HU,(43.9±6.3)HU and(44.6±6.7)HU,and the CT values of the air of lung window of the same layer were respectively(-980.0±42.6)HU,(-975.9±47.7)HU and(-969.9±46.3)HU,and there was no significant difference among the three groups.The SD values of the images of descending aorta of the three groups were(11.1±2.1),(13.9±1.9)and(19.6±2.7),which were significantly higher than those of the air(F=9.92,F=2.567,P<0.05).The CTDI_(vol) of the three groups were respectively(4.34±0.53)mGy,(3.47±0.47)mGy and(2.57±0.41)mGy,and the difference among three groups was statistically significant(F=3.88,P<0.05).The DLPs of them were respectively(154.86±20.90)mGy·cm,(126.40±16.85)mGy·cm and(91.60±13.85)mGy·cm,and there was significant differences among the three groups(F=11.89,P<0.05).The EDs of them were respectively(2.16±0.36)mSv,(1.69±0.33)mSv and(1.27±0.25)mSv,which decreased significantly in the order,and the difference of that among the three groups was statistically significant(F=5.96,P<0.05).Conclusion:Compared with the kV of 3 gear,the choice of the 7 gear of dose modulation factor gradually decreased when we apply the CARE kV to scan the chest,which can effectively reduce the radiation dosage of subjects when ensure the image quality.