| Objective:1.To investigate the influence of reducing the contrast agent dose on the imaging quality and radiation dose in 256-slice CT coronary angiography.2 Effect of reducing the scanning range on the radiation dose and diagnostic results of 256 slice spiral CT coronary angiography.Methods:1.From February 2016 to January 2017,120 patients with 256-slice of CT coronary artery examination in our hospital were selected and randomly divided into the observation group and the control group,60 cases respectively.A retrospective ECG gated coronary artery imaging technique was applied.The observation group was injected with contrast agent(body weight×1ml/kg-10)ml,and the control group was injected with contrast agent according to body weight,Measurement of the two groups of the left aortic stem(AO),the left anterior descending branch of proximal and distal parts(LADp,LADd),right coronary artery proximal and distal parts(RCAp,RCAd),LCX proximal and distal parts(LCXp,LCXd);according to the American Heart Association of 16 coronary artery segments were evaluated for coronary artery segments analysis;left ventricle,interventricular septum and right ventricle display;record the dose length product and CT radiation dose index,effective radiation dose calculation.The data were analyzed by SPSS17.0 software package,and the average number and rate were compared by t test andχ2 test.2 From February 2016 to October 2017,100 patients with CT coronary artery examination were randomly divided into group A and group B,each with 50 cases in our hospital.Coronary angiography with retrospective ECG gated coronary angiography,A group of scanning range selection to the lower edge of the bifurcation of the trachea heart1cm;B group received low dose scan,according to the plain image defined as the scanning range,on the edge of the coronary artery tree edge to the 1cm,the lower edge of the apex of pericardial disappearing level.Simultaneous coronary angiography(CAG)examination in group B.Measurement of the two groups of the left anterior descending branch of proximal and distal parts(LADp,LADd),right coronary artery proximal and distal parts(RCAp,RCAd),LCX proximal and distal parts(LCXp,LCXd);and to evaluate the coronary artery segments;record the dose length product(DLP),CT radiation dose index(CTDIvol),effective radiation dose calculation.The data were analyzed by SPSS17.0 software package,and the average number and rate were compared by t test andχ~2 test.Results:1.All the cases successfully completed the CT xamination,the CT values of LCXp、LCXd、RCAp、RCAd、LADp、LADd were(382.44±67.63)HU、(384.20±56.25)HU、(408.91±47.15)HU、(409.82±39.41)HU、(392.54±54.06)HU、(393.61±52.22)HU in the observ-ation group,they were(389.23±65.75)HU、(387.52±52.62)HU、(406.71±46.31)HU、(407.43±37.72)HU、(390.63±52.11)HU、(392.58±51.69)HU in the control group,there was no significant difference between the two groups(P>0.05).The observation group showed 762 segments of coronary artery and 757 segments of the control group.The excellent and good rates of coronary artery segments in two groups were 92.65%and 92.60%,respectively.There was no significant difference between the two groups(P>0.05).The image quality scores were 1,2,3,4 and 5 segments,the observation group was 3,6,47,154 and 552,respectively,and the control group was 4、7、45、150、551 respectively.There was no significant difference in image quality between the two groups(P>0.05).The left ventricular wall showed a good and general proportion,was68.33%and 31.67%in the observation group,respectively,and was 45%and 50%in the control group,respectively.The ratio of left ventricular wall in the observation group was significantly higher than that in the control group,the difference was statistically significant(P<0.05).The ratio of interventricular septum display was clear and acceptable,was 56.67%and 38.33%respect-tively in the observation group,was 35%and 63.33%respectively in the control group.The ratio of the interventricular septum display in the observation group was significantly higher than that in the control group(P<0.05).Superior vena cava and right ventricular artifact showed that the proportions of grade 0 and grade 1 in the observation group were 71.67%and 28.33%,respectively,while those in the control group were 51.67%and 48.33%,respectively.The proportion of 0 in the observation group was significantly higher than that in the control group(P<0.05).The dosage of contrast agent,DLP,and effective radiation dose in the observation group were(53.81±7.09)ml,and(64.07±8.54)ml in the control group,all the observation group were lower than the control group,and the difference was statistically significant(P<0.05).2 The blood vessels to strengthen the level of image quality,LCXp,LCXd,coronary artery RCAp,RCAd,LADp,LADd,CT,A group respectively(419.77±53.21)HU,(420.17±49.39)HU,(429.82±63.22)HU,(430.47±41.52)HU,(431.09±51.78)HU and(432.17±50.52)HU,B group respectively(421.21±56.09)HU,(423.07±51.52)HU,(431.61±59.46)HU,(432.76±43.23)HU,(433.76±53.44)HU,(434.31±49.07)HU,with no significant differ-ence between two groups(P>0.05).The image quality of coronary artery segments,A group showed coronary artery in 647,B group showed 654,two groups of image quality score,A group 1,2,3,4,5 segments were 3,4,32,127,481,B group were 2,4,28,124,496,two groups had no statistically significant difference(P>0.05).The number of evaluable segments and the number of good segments in the A group were 97.84%,93.66%,and 98.01%,94.65%in the B group,and there was no significant difference between the two groups(P>0.05).The scanning range,CTDIvol,DLP,and effective radiation dose in group A respectively were(15.43±2.41)cm,(1.92±0.61)m Gy,(983.63±34.76)m Gy·cm,(13.79±1.17)m Sv,and(13.72±2.66)cm,(1.53±0.74)m Gy,(798.15±31.42)mGy·cm,(11.18±1.05)m Sv in group B,Group B was less than group A,and the difference was statistically significant(P<0.05).In the 641 segment of the coronary artery image of B group,256 slice spiral CT and CAG were consistent with the diagnosis results of 616 segments of blood vessels(K value=0.922).Taking CAG as the gold standard,sensitivity,specificity,positive predictive value,negative predictive value,diagnostic coincidence rate was 96.33%,95.86%,96.04%,96.17%,96.10%.Conclusion:1.In the 256-slice CT coronary angiography,reducing the dose of contrast agent can significantly reduce the radiation dose,and the image quality can also meet the diagnostic requirements.At the same time,the left ventricle and ventricular septum can be clearly displayed,which is beneficial to the evaluation of cardiac function.2 In the 256 slice CT coronary angiography,we can control the scanning range properly by scanning the image and covering the whole heart or all coronary artery tree,which can effectively reduce the radiation dose. |
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