| The first part: Application of four different tube voltage scanning mode combined with individual dosage of iodine contrast agent in the carotid CT angiography.Objective : To investigate the advantages of low tube voltage and gemstone spectral imaging with iodine contrast agent in carotid CT angiography using different tube voltage combined with individual dosage of iodine contrast agent.Materials and methods: 320 patients were prospectively collected for carotid CT angiography in the gemstone spectral CT.According to the sequential design,all patients were randomly divided into group A(120kv-5ml/s),group B(100kv-4ml/s),group C(80kv-4ml/s)and group D(GSI-3ml/s),80 cases in each group.Group A(120kv-5ml/s): 80 patients were scanned with 120 k V tube voltage,480 m A tube current,0.625 mm slice thickness,0.625 mm slice interval,0.5s rotation time,1.375 pitch,filtered back projection reconstruction,and the injection velocity of the contrast medium was 5ml/s.Group B(100kv-4ml/s): 80 patients were scanned with 100 k V tube voltage,480 m A tube current,0.625 mm slice thickness,0.625 mm slice interval,0.5s rotation time,1.375 pitch,fifty percent of adaptive statistical iterative reconstruction,and the injection velocity of the contrast medium was 4ml/s.Group C(80kv-4ml/s): 80 patients were scanned with 80 k V tube voltage,480 m A tube current,0.625 mm slice thickness,0.625 mm slice interval,0.5s rotation time,1.375 pitch,sixty percent of adaptive statistical iterative reconstruction,and the injection velocity of the contrast medium was 4ml/s.Group D(GSI-3ml/s): 80 patients were scanned with GSI(Gemstone spectral imaging),480 m A tube current,0.625 mm slice thickness,0.625 mm slice interval,0.5s rotation time,1.375 pitch,fifty percent of adaptive statistical iterative reconstruction,60 ke V monochromatic images,and the injection velocity of the contrast medium was 3ml/s.The parameters such as sex,age,height,weight,iodine contrast agent dosage,CTDIvol,DLP were recorded.The subjective evaluation and objective evaluation of image quality were carried out on the GE AW4.5 workstation,and the statistical analysis was performed.The contrast dose of each patient was calculated by using the format:(Ttest-bolus peak time +2s-5s)× injection velocity.Results: 1.Radiation dose(CTDIvol?DLP?ED): the radiation dose of the four groups were the group A [13.49(13.37,13.90),518.28(504.01,537.07),3.06(2.97,3.17)],the group B [10.52(10.50,10.57),403.71(397.33,404.15),2.38(2.34,2.38)],the group C[5.59(5.59,5.61),214.93(214.78,232.24),1.27(1.27,1.37),the group D [12.72(12.72,12.72),487.80(472.68,510.85),2.88(2.79,3.01)],respectively.Among the four scan protocols,the group A was the highest,the group C was the lowest,the group B and the group D had no statistically significant,but the differences between the other groups were statistically significant(P < 0.001).2.Iodine contrast agent dosage: the dosage of the four groups were the group A(69.63±12.92)ml,the group B(61.20±11.81)ml,the group C(59.50±13.25)ml,the group D(50.93±8.13)ml,respectively.Among the four scan protocols,the group A was the highest,the group D was the lowest,the group B and the group C had no statistically significant,but the differences between the other groups were statistically significant(P < 0.001).3.Background noise: the noise of the four groups were the group A(12.94±3.55)HU,the group B(9.17±2.73)HU,the group C(6.87±2.53)HU,the group D(8.64±3.51)HU,respectively.Among the four scan protocols,the group A was the highest,the group C was the lowest,the group B and the group D had no statistically significant,but the differences between the other groups were statistically significant(P < 0.001).4.CT value of carotid artery: the value of the four groups were the group A(376.80±59.14)HU,the group B(440.67±92.26)HU,the group C(549.33±86.87)HU,the group D(387.62±72.12)HU,respectively.Among the four scan protocols,the group C was the highest,the group A was the lowest,the group A and the group D had no statistically significant,but the differences between the other groups were statistically significant(P < 0.001).5.SNR and CNR of Carotid artery: the value of the four groups were the group A(31.50±11.59,40.06±13.92),the group B(53.19±21.78,66.57±26.26),the group C(91.40±39.38,112.32±46.98),the group D(50.60±19.86,64.87±24.12),respectively.Among the four scan protocols,the group C was the highest,the group A was the lowest,the group B and the group D had no statistically significant,but the differences between the other groups were statistically significant(P < 0.001).6.Mean CT value of three major vessels in the aortic arch(truncus brachiocephalicus,left common carotid artery,left subclavian artery): the value of the four groups were the group A(328.87±54.95)HU,the group B(397.78±83.58)HU,the group C(497.53±83.94)HU,the group D(387.71±68.41)HU,respectively.Among the four scan protocols,the group C was the highest,the group A was the lowest,the group B and the group D had no statistically significant,but the differences between the other groups were statistically significant(P < 0.001).7.SNR and CNR of three major vessels in the aortic arch:the value of the four groups were the group A(27.25±9.12,35.81±11.42),the group B(47.78±18.96,61.16±23.45),the group C(82.85±36.57,103.77±44.15),the group D(50.47±19.10,64.73±23.45),respectively.Among the four scan protocols,the group C was the highest,the group A was the lowest,the group B and the group D had no statistically significant,but the differences between the other groups were statistically significant(P < 0.001).8.In the subjective score of the artifacts of the venae brachiocephalica,the artifacts of the Subclavian vein and the image quality of the carotid artery,there were no significant differences between the different groups(P>0.05).Conclusion: 1.In carotid CT angiography,gemstone spectral CT combined with 100 k V tube voltage,80 k V tube voltage can not only ensure the image quality,but also effectively reduce the dose of ionizing radiation.Among them,the radiation dose was the lowest when 80 k V tube voltage scan scheme was used.2.Under the condition of low contrast agent dosage and low injection velocity,the use of GSI associated with ASIR reconstruction technique can not only reduce the image noise effectively,but also obtain high image quality.The second part: Application of the improved scheme of the individual dosage of iodine contrast agent in the carotid CT angiography.Objective :To explore the feasibility of the improved scheme of the individual dosage of iodine contrast agent in the carotid CT angiography,in order to further reduce the dosage of contrast agent and reduce the risk of the examination.Materials and methods: 120 patients were prospectively collected for carotid CT angiography in the gemstone spectral CT.According to the sequential design,all the patients were randomly divided into group E(The improved 120kv-5ml/s)and group F(The improved 100kv-4ml/s),60 cases in each group.Group E(The improved 120kv-5ml/s):60 patients were scanned with 120 k V tube voltage,480 m A tube current,0.625 mm slice thickness,0.625 mm slice interval,0.5s rotation time,1.375 pitch,filtered back projection reconstruction,and the injection velocity of the contrast medium was 5ml/s.Group F(The improved 100kv-4ml/s): 60 patients were scanned with 100 k V tube voltage,480 m A tube current,0.625 mm slice thickness,0.625 mm slice interval,0.5s rotation time,1.375 pitch,fifty percent of adaptive statistical iterative reconstruction,and the injection velocity of the contrast medium was 4ml/s.The rest of the scanning parameters were the same.The parameters such as sex,age,height,weight,iodine contrast agent dosage,CTDIvol,DLP were recorded.On GE AW4.5 workstation,the image quality was evaluated subjectively and objectively,and the statistical analysis was performed.The contrast dose of each patient was calculated by using the format:(T test-bolus peak time + 2S – T initial time)× injection velocity.Results: 1.Comparison results of the scanning strategy between the group E(The improved 120kv-5ml/s)and group F(The improved 100kv-4ml/s):1.1 Radiation dose(CTDIvol?DLP ? ED): the radiation dose of the group E [13.49(13.37,13.83),518.28(499.54,536.06),3.06(2.95,3.16)] was higher than that of the group F [10.43(10.43,10.44),401.26(401.13,401.37),2.37(2.37,2.37)],the differences between the two groups were statistically significant(P < 0.001).1.2 Iodine contrast agent dosage: the dosage of the group E(49.83±10.29)ml was higher than that of the group F(42.47±7.76)ml,the differences between the two groups were statistically significant(P < 0.001).1.3 Background noise: the noise of the group E(11.99±1.70)HU was higher than that of the group F(8.81±1.62)HU,the differences between the two groups were statistically significant(P < 0.001).1.4 CT value of carotid artery: compared with the group E(393.49±58.60)HU and group F(398.56±56.27)HU,the differences between the two groups were not statistically significant(P > 0.05).1.5 SNR and CNR of Carotid artery: the value of the group F [(47.03±12.26)HU,(59.16±14.36)HU] was higher than that of the group E[(33.19±5.01)HU,(41.74±5.90)HU],the differences between the two groups were statistically significant(P < 0.001).1.6 Mean CT value of three major vessels in the aortic arch(truncus brachiocephalicus,left common carotid artery,left subclavian artery):compared with the group E(359.15±60.20)HU and the group F(361.98±47.31)HU,the differences between the two groups were not statistically significant(P > 0.05).1.7 SNR and CNR of three major vessels in the aortic arch:the value of the group F(42.79±11.39,54.92±13.64)was higher than that of the group E(30.20±4.53,38.75±5.35),the differences between the two groups were statistically significant(P < 0.001).1.8 In the subjective score of the artifacts of the venae brachiocephalica,the artifacts of the Subclavian vein and the image quality of the carotid artery,There were no significant differences between the two groups(P>0.05).2.Comparison results of scanning strategy between the group A'(120kv-5ml/s)and group E(The improved 120kv-5ml/s): In the dosage of iodine contrast agent and the average noise value of three vessels of the aortic arch,the group A'was higher than that of the group E,and the differences between the two groups were statistically significant(P < 0.001).The mean CT value of three major vessels in the aortic arch of group E was higher than that of the group A',and the difference was statistically significant(P=0.011).In radiation dose,background noise,CT value of carotid artery,SNR and CNR of carotid artery,SNR and CNR of three major vessels in the aortic arch,the differences between the two groups had no statistical significance(P > 0.05).In the subjective score of the artifacts of the venae brachiocephalica and the artifacts of the Subclavian vein,the group E was better than that of the group A'(P<0.05).There was no significant difference in carotid artery image quality between the two groups(P > 0.05).3.Comparison results of scanning strategy between the group B'(100kv-4ml/s)and group F(The improved 100kv-4ml/s): In the dosage of iodine contrast agent,CT value of carotid artery,mean CT value of three major vessels in the aortic arch,the group B'were higher than those in the group F,and the differences between the two groups were statistically significant(P < 0.001,=0.013 P,=0.022 P).In radiation dose,background noise,SNR and CNR of Carotid artery,SNR and CNR of three major vessels in the aortic arch,the differences between the two groups had no statistical significance(P > 0.05).In the subjective score of the artifacts of the venae brachiocephalica,the artifacts of the Subclavian vein and the image quality of the carotid artery,There were no significant differences between the two groups(P>0.05).Conclusion: Compared with the original plan,the improved scheme of the individual dosage of iodine contrast agent has certain advantages in carotid CT angiography,especially when the patient's arterial peak time and initial time is longer,the improved scheme has more advantages.When the contrast agent flow rate was 5ml/s and 4ml/s,the improved scheme of iodine contrast agent can not only significantly reduce the iodine contrast agent dosage,but also can effectively reduce the artifacts of the venae brachiocephalica and Subclavian venous,better meet the requirement of the clinical diagnosis. |
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