| Objective:To evaluate the enhancement effect of personalized contrast agent injection program,to explore the relationship between comprehensive low dose technique and image quality and the possibility that the energy spectrum CT GSI scan mode combined with low dosage contrast agents for reducing the radiation and contrast agent dose by the development of personalized contrast agent injection program and the integrated use of technology to reduce the radiation dose,which is compared with conventional contrast agent injection program and scanning program.Methods:(1)A total of 160 patients underwent coronary angiography were randomly divided into two groups,constant-dose contrast agent(5.5 mL/s and 80 mL)was used in the conventional injection program,while the contrast agent dose and flow speed was adjusted to the patient’s weight in the personalized injection program.4 subgroups in both groups with 20 cases each,the contrast agent doses were 300 mg/mL,320 mg/mL,350 mg I/mL and 370 mg/mL,respectively.The CT values of the ascending aorta,the left ventricle and the branches of the coronary artery were measured,respectively,and the difference of CT values between the two groups was analyzed by one-way ANOVA.(2)60 patients with suspected coronary heart disease were randomly divided into three groups to perform coronary CT angiography,each group had 20 cases.350mgI/ml contrast agent for 120kVp prospective ECG gated scan was performed in the control group,the experimental groups were given 350mgI/ml and 270mgI/ml contrast agent for GSI scanning,respectively,and 5 subgroups were divided into 1～5 subgroup by adjusting the different levels of keV for 60,65,70,75,80keV.CT values and aortic sinus noises of aortic sinus(AS),proximal left anterior descending branch(LAD-p),proximal left circumflex branch(LCX-p),proximal right coronary artery(RCA-p)and pericardial fat were measured,the signal-to-noise ratio(SNR)and contrast to noise ratio(CNR)were calculated.The objective evaluation indexes of group A and subgroups B1-5 were compared by one-way ANOVA,and LSV method was used to compare the two groups for selecting optimal keV.The difference of the optimal keV indexes between group A and C was compared by t test.(3)First,104 patients were prospectively divided into A and B groups according to the random number table method.There were 58 cases in group A and 46 cases in group B,prospective ECG gated scanning mode combined adaptive tube current modulation technique were selected for treating in both group A and B,100kV tube voltage was selected for group A as low tube voltage group,while 120kv was in group B as conventional tube voltage group.The objective image quality,subjective evaluation and radiation dose were compared between the two groups;secondly,218 patients who were performed coronary CT angiography in our hospital were divided into experiment and control groups according to the different tube current modulation modes,165 cases were in the experiment group,prospective ECG gated scanning mode with BMI tube current modulation mode was adopted,the tube voltage was 100kv;53 cases were in the control group,prospective ECG gated scanning mode and adaptive tube current modulation was adopted,the tube voltage was 100kv.Among the experiment group,group A,B,C,D were divided according to the BMI,and 48 cases were in group A,BMI<24 kg/m2,tube current was 240 mAs;50 cases were in group B,24<BMI≤26 kg/m2,tube current was 260 mAs;35 cases were in group C,26<BMI≤28 kg/m2,tube current was 300 mAs;32 cases were in group D,28<BMI ≤30 kg/m2,tube current was 320 mAs;the objective image quality,subjective evaluation and radiation dose were compared among the four groups.Result:(1)Under the personalized injection program,the CT values of the ascending aorta,the left ventricle and the branches of the coronary artery were compared according to the contrast agent dose and patient’s weight,the difference was not statistically significant(all P>0.05).While under the conventional injection program,contrast enhancement of left ventricle,left circumflex coronary artery,right coronary artery,right coronary artery and distal descending branch with 370 mg/mL was higher than those in the 300 mg/mL group(all P>0.05).The average dosage of contrast agent(62.83 vs.80.00,P<0.001)and flow rate(5.21 vs.5.50,P<0.001)under the personalized injection program were lower than those of the conventional group.(2)When using the same dosage of contrast agent(350mgl/ml),the CT value of each target vessel in group B1 and B2 was higher than that in the group A(P<0.05),and the noise did not decrease(P>0.05);the CT value of each target vessel in group A and B3 was similar(P>0.05),while the noise decreased(P= 0.009);SNR and CNR in group B1-5 were higher than those in group A,and the difference was statistically significant(P<0.05);among them,CNR was optimal in group B2(65 keV)and B3(70 keV),that was,the 65 and 70 keV were the optimal ones.CT values and image noise,SNR,CNR in targeted vessels AS,LMA,LAD,LCX,RCA in group C2(270 mg/ml contrast agent,65 keV GSI scanning)were compared with those in group A,the differences were not statistically significant(P>0.05).(3)CT values of targeted vessels(P<0.05)and the noise(P<0.05)in 100 kv tube voltage combined adaptive tube current modulation were higher,while the radiation dosage(P<0.05)was lower compared with those in 120 kv tube voltage;there was no significant difference between the two groups in subjective score(P>0.05);under 100 kv tube voltage,and according to the comparison between BMI adjusted tube cuurent and adaptive current,CT value and the noise were lower in the experiment group of 28<BMI<30 kg/m2,320 mAs tube current compared with those in the control group(P<0.05);there was no significant difference between the two groups in subjective score(P>0.05);the radiation dosage increased with the gradual increase of BMI and tube current,and there was no significant difference between the experiment group and control group only when BMI<24 kg/m2,tube current was 240 mAs(P>0.05).Conclusion:Compared with the constant-dose of contrast agent program,the coronary artery homogeneous enhancement effect can be obtained from personalized injection program based on body weight for different dosages of contrast agents.There was no significant difference in the degree of coronary artery enhancement among different weight groups under the personalized injection program,which indicated that the contrast agent enhanced scanning program was obtained according to the standardized design of this study,which was not affected by the weight of the patients.The average dosage of contrast agent and the average flow rate were lower than those of the conventional group.Therefore,the standardized injection program may reduce the adverse reaction of contrast agent and the occurrence of contrast agent nephropathy.When the 350mgI/ml contrast GSI scan was used,CT values in the target vessels in the coronary artery CT angiography as well as the noise decreased with the increase of single energy level,therefore,the best single energy level can be determined according to the CT value and noise of the target vessel.The best single energy level in this study was 65 keV.When the 270mgI/ml contrast agent CCTA examination was used,similar objective image quality can be obtained in both 65 keV GSI scan and 120 kVp front control scan,which could reduce the incidence of contrast agent nephropathy while meeting clinical diagnostic needs.Gem energy CT GSI scan mode was the same as the prospective ECG gated scan mode,and data was collected in a specific timeframe.The patient’s heart rate was more stringent,but it can also reduce the dose of radiation received by the patient.Application of dual-source CT prospective ECG gated scan,100kv tube voltage combined with adaptive tube current regulation,can improve the degree of enhancement of the target blood vessels,and did not increase the noise compared with those of the tube voltage 120kv,so that the image quality could meet the diagnostic requirements.The enhancement degree of target vessel decreased and the noise was uncertain with the increase of BMI and tube current in 100kv tube voltage combined with BMI tube current regulation.The radiation dose was higher in 100kv tube voltage combined with BMI tube current regulation compared with that of adaptive tube current regulation,only when BMI<24kg/m2,could achieve the goal of reducing the radiation dose consistent with the adjustment of the adaptive tube current. |
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