| ObjectiveTo explore the feasibility of cranio-cervical CTA scan for common body weight and body mass index(BMI)population under the condition of ultra-low contrast agent dosage and low radiation dose by dual source CT using the technology of Optimization for scanning speed combined CareDose 4D.Materials and methodsThis study was divided into three parts.Part 1:Ten patients who were going to take the examination of hepatic portal vein CTV in our hospital were recruited as volunteers.On the premise of ensuring the successful examination of CTV for volunteers by relying on experience,the scanning sequence is adjusted and improved.We added Bolus Tracking trigger to the scan sequence of hepatic portal vein CTV.After obtaining the topography,the trigger position was selected at the aortic arch level.After obtaining the pre-monitoring image,we placed the region of interest(ROI)at the after part of aortic arch.We set the trigger threshold to the highest value of800 Hu,the monitoring interval of ROI to 1 second,and the monitoring voltage to 100 KV.We performed 15 seconds monitoring scans after contrast injection to collect time-density incremental data in the ROI of the aortic arch within 15 seconds,and then we started CTV scan manually.Combined the CT value of ROI on the pre-monitoring image without contrast and the time-density incremental data with contrast,we figured out Time density curve(TDC).The time-density curve data were analyzed to find out the appropriate trigger time point to ensure that the CT value of aortic arch in the examination of cranio-cervical CTA could arrive at 200 Hu and the images could meet the diagnostic requirements.Collect the data of the increments of CT value which were 3s earlier to the time point of the CT value in ROI arriving at 200 Hu,and then statistical analysis was carried out to get the confidence interval of 95% of the data.Then we could calculate the appropriate trigger threshold value to ensure the success of cranio-cervical CTA examination.Part 2:Forty cases of cranio-cervical CTA were randomly divided into experimental group and control group,with 20 cases in each group.In the experimental group,the trigger threshold was set to 56 Hu,the pitch was set to 1.2,the rotation time of the spherical tube was set to 0.33 s,and the scanning delay was 3s after triggering.In the control group,the trigger threshold was set to 100 Hu,the pitch was set to 0.7,the rotation time of the spherical tube was set to 0.5s,and the scanning delay was 2s after triggering.Cases in both of the two groups were injected with 50 ml contrast agent and 50 ml saline.The other scanning parameters of the experimental group and the control group were the same,the tube voltage was set to 100 KV,and the tube current was automatically adjusted by CareDose 4D technology(Quality ref m As175),ROI was placed at the after part of aortic arch.The monitoring interval was set to 1s,and the voltage was set to 100 KV.Adjust the injection rate of contrast agent and saline according to body weight.Subjective score of the images and enhancement level of the artery in both of the two groups were compared.Part 3:Eighty cases of cranio-cervical CTA were randomly divided into experimental group and control group,with 40 cases in each group.The key parameters of the experimental group were set as follows: the trigger threshold was set to 56 Hu,the pitch was 1.2,the tube rotation time was 0.33 s,delayed 3 seconeds before starting of the scan after firing,and the volume of the contrast agent was within the range of 26 ml to 32 ml.Differently from the experimental group,the key parameters of the control group were set as follows: the trigger threshold was set to 100 Hu,the pitch was 0.7,the tube rotation time was 0.5seconds,delayed 2 seconeds before starting of the scan after firing,and the volume of the contrast agent was set to 50 ml.The remaining scanning parameters between the two groups were set to the same value.We compared the image quality between the two groups,including the subjective evaluations such as the concentration of the contrast agent in right subclavian vein and brachiocephalic vein,the imaging effect of arterial,and also including the objective evaluation indexs such as the CT values in sigmoid sinus and every part of arteries,signal-to-noise ratio(SNR),contrast-to-noise ratio(CNR).We also compared the radiation dose indexes produced by the Head Angio sequence scanning between the two groups,including CT volume dose index(CTDIvol),dose length product(DLP)and effective radiation dose(ED).Then we compared the dosage of contrast agent between the two groups.Results Part 1:The increment of CT value in ROI of aortic arch in 10 volunteers 3s before the time of CT value above 200 Hu was(25.7 ±15.18)Hu.The confidence interval of 95% estimated by percentile method was(-13.15-55.45)Hu,and we set 56 Hu as the trigger threshold refered to the upper limit of the confidence interval of 95%.Part 2:The minimum enhancement of each segment of the head and neck arteries in the experimental group and the control group were 276 Hu and 284 Hu respectively,which met the requirements of image diagnosis.The enhancement of aortic arch,left common carotid artery,right common carotid artery,left internal carotid artery and right internal carotid artery in the experimental group were(337.30±47.27)Hu,(367.70±64.23)Hu,(377.61±63.59)Hu,(415.40 ±69.36)Hu,(378.40 ±60.01)Hu,respectively.In the control group,the enhancement of aortic arch,left common carotid artery,right common carotid artery,left internal carotid artery and right internal carotid artery were(387.5±50.136)Hu,(526.10±77.71)Hu,(527.3±82.59)Hu,(466.45±68.94)Hu,(501.75±48.43)Hu,respectively.The enhancement of aortic arch,bilateral common carotid artery and internal carotid artery in the experimental group was significantly lower than that in the control group(P< 0.05).The enhancement degree of left middle cerebral artery and right middle cerebral artery in the experimental group were(424.50±56.18)Hu and(449.25±57.67)Hu,respectively.The enhancement degree of left middle cerebral artery and right middle cerebral artery in the control group were(376.2±68.70)Hu and(383.10±56.62)Hu,respectively.The enhancement of bilateral middle cerebral artery in the experimental group was significantly higher than that in the control group(P< 0.05).The subjective scores of head and carotid artery imaging in experimental group and control group were(1.25±0.55)and(1.10±0.31)respectively,and there was no significant difference between the two groups(P> 0.05).Part 3:The subjective scores of contrast concentration in the right subclavian vein and the brachial vein in the experimental group(1.70±0.56 points)was lower than that in the control group(2.50±0.72 points),P< 0.05.The SNR values and CNR values of the bilateral internal carotid artery in experimental group were higher than the control group(P< 0.05),while the values of SNR and CNR in the aortic arch,bilateral carotid artery and bilateral middle cerebral artery were lower than the control group(P< 0.05),despite this case,the subjective evaluations of arterial imaging quality between the experimental group and the control group was no statistically significant difference(1.30±0.52 points,1.21±0.41 points,P> 0.05).The CT values in the sigmoid sinus of the experimental group was significantly lower than that in the control group(58.89±11.68 Hu,244.92±49.81 Hu,P<0.05).The CT values of the arteries in the experimental group were all lower than those in the control group,but all of the CT values were greater than that of270 Hu,which met the diagnostic requirements.The values of radiation dose of the experimental group was significantly lower than that of the control group,CTDIvol(13.86±2.82,27.09±3.28,P < 0.05),DLP(532.49±113.24,1008.75±126.53,P < 0.05),and ED value(1.22,1.22,1.22,P<0.05),The values of CTDIvol in the experimental group was about 48.85% less than that in the control group,and the values of DLP and ED decreased by about 47.21% compared to the control group.The dosage of contrast agent in the experimental group was significantly lower than that of the control group(29.07±2.05 ml,50ml),and the amount of contrast agent used in the experimental group was about 41.86% less than that in the control group.Conclusions1.If the examination of cranio-cervical CTA for common weight people was carried by dual-source CT,the CT value of aortic arch obtained after 3 seconds of the start of scanning would be higher than 200 Hu by setting the trigger threshold to 56 Hu,and the image could meet the requirements of post-processing.2.If the examination of cranio-cervical CTA for common weight people was carried by dual-source CT,the examination would success by setting the trigger threshold to 56 Hu combined the rotation time of the tube was set to 0.33 s and the pitch was set to 1.2.Moreover,this technology has the possibility of further reducing the dosage of contrast agent.3.Dual-source CT with low trigger threshold combined scan speed optimization and the technology of CareDose4 D could perform low contrast agent dosage and low radiation dose cranio-cervical CTA for common weight people.and the images could meet the diagnostic requirements.4.Optimizing scanning speed,adopting appropriate trigger threshold and applying low dose contrast agent could reduce venography on the premise of ensuring the success of cranio-cervical CTA,which could be conducive to the observation of arteries. |
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