| Part one: A study on the scan-delay-time after contrast medium administration in cervical and cerebral vascularities imaging with 64-detector spiral CT angiography.Purpose: To discuss the optimal scanning technology in predicting the scan-delay-time after contrast medium administration in cervical and cerebral vascularities imaging with 64-detector spiral CT angiography.Materials and Methods: 129 patients were divided into three groups, who had examined cervical and cerebral CT angiography based on the same iodine concentration,volume,injection rate of contrast medium. Group A: 43 cases were performed by the method of experience of 15 to 20 seconds as the scan-delay-time. Group B: 43 cases were performed by the time to peak in CT perfusion as the scan-delay-time during the combination scanning technology of CTP-CTA. Group C: 43 cases were performed by the time to peak in a test bolus injection as the scan-delay-time. One experienced radiologist measured and compared the enhancement value of CT in the left common carotid artery and left internal jugular vein adjacent to the fourth cervical vertebrace,the proximal M1 segment of left middle cerebral artery and superior sagittal sinus adjacent to suprasellar cistern, and then compared the differences between the arteries and the veins in the same layer of the three groups; meanwhile, recorded and compared the dose length product generated automatically during the scanning between group B and group C. The image quality of the three groups was separately compared by two experienced radiologists in a blind way.Results: The scan-dealy-time of group A,B,C was (17.12±1.52) seconds,(20.65±3.09) seconds,(18.33±5.34) seconds, respectively. By one-way analysis of variance (ANOVA), there were statistically significant difference of the scan-dealy-time between group B and group A,group B and group C(p<0.05) except between group A and group C ( p>0.05) , the scan-dealy-time of group B was longer than group A and group C. There were statistically significant difference of the enhancement value of CT in the left common carotid artery adjacent to the fourth cervical vertebrace,the proximal M1 segment of left middle cerebral artery adjacent to suprasellar cistern, and the differences between the arteries and the veins in the same layer between group A and group B,group A and group C(p<0.05) except between group B and group C ( p>0.05), the enhancement value of CT in the cervical and cerebral arteries and the resolving power between the arteries and the veins in the same layer of group B and group C were higher than those of group A. The average of the dose length product with group B and group C during the scanning was 2031.24mGy.cm,80.13 mGy.cm, respectively; the radiation exposure of group B was obviously higher than group C during the scanning. For the two experienced radiologists on the manifestation of cervical and cerebral arteries,the venous artifact, the Kappa value was respectively 0.889,0.872,0.882. By Mann-Whitney U-test, the grading score on the manifestation of cervical and cerebral arteries,the venous artifact between group A and group B,group A and group C had statistically significant difference( p<0.05)except between group B and group C ( p>0.05). The image quality of group B and group C were superior to group A.Conclusion: Test-bolus technique is the optimal scanning technology in predicting the scan-delay-time after contrast medium administration in cervical and cerebral vascularities imaging with 64-detector spiral CT angiography, it fully embodies the individualized and optimal principle, greatly increases the scanning successful ratio of multi-detector spiral CT angiography, and efficiently improves the image quality of three-dimensional reconstrcution of vascularities. Part two: Research on clinical applications of digital subtraction technique of 64-detector spiral CT angiography in cervical and cerebral vascularities imaging.Purpose: To apply the digital subtraction technique of 64-detector spiral CT angiography in cervical and cerebral vascularities imaging and introduce the Bone-Subtraction CT Angiography Tool software exploited by the medical company of neusoft for three-dimensional subtraction, so as to explore the feasibility of the new subtraction software and clinical applicative value.Materials and Methods: 71 patients were performed digital subtraction CT angiography in cervical and cerebral vascularities. Optimal scan-delay-time was determined by using the test-bolus technique, the pre-contrast and post-contrast scanning were executed in the same series , the scanning parameters and positions were all the same and the tube repetition exposure interval time was integrally divided by the rotation speed of 0.5×2 second. First, the Add/Sub software of workstation was used for two-dimensional subtraction, and then the Bone-Subtraction CT Angiography Tool software exploited by the medical company of neusoft was used for three-dimensional subtraction. One experienced radiologist recorded and compared the post-processing time of VR and MIP among conventional CT angiography,two-dimensional subtraction CT angiography,three-dimensional subtraction CT angiography; meanwhile, the image quality of cervical and cerebral arteries reconstructed from the raw CT data set of the three kinds of CT angiography techniques were separately compared by two experienced radiologists in a blind way. The three kinds of CT angiography techniques images of 49 patients were compared with those of the digital subtraction angiography (DSA). Paired designχ2-test was used for evaluating whether there were differences between the three kinds of CT angiography techniques and DSA for diagnosis of cervical and cerebral vascular diseases; meanwhile, the sensitivity,specificity,positive predictive value,negative predictive value and accurate ratio of the three kinds of CT angiography techniques for diagnosis of cervical and cerebral vascular diseases were analyzed.Results: By one-way analysis of variance (ANOVA), there were statistically significant difference of the post-processing time of VR and MIP among conventional CT angiography technique,two-dimensional subtraction CT angiography technique,three-dimensional subtraction CT angiography technique(p<0.05), the post-processing time of the three-dimensional subtraction CT angiography technique was shorter than the other two CT angiography techniques, and the conventional CT angiography technique was the longest one of the three. For the two experienced radiologists on the manifestation of cervical and cerebral arteries reconstructed from the raw CT data set of the three kinds of CT angiography techniques, the Kappa value was 0.845. By Mann-Whitney U-test, the grading score on the manifestation of cervical and cerebral arteries among the three kinds of CT angiography techniques had statistically significant difference (p<0.05), the image quality of the three-dimensional subtraction CT angiography technique were superior to the other two CT angiography techniques, and the conventional CT angiography technique was the poorest one of the three. By paired designχ2-test, there was no statistically significant difference between the three kinds of CT angiography techniques and DSA for diagnosis of cervical and cerebral vascular diseases in 49 cases ( p>0.05). The sensitivity,specificity,positive predictive value,negative predictive value and accurate ratio of conventional CT angiography was respectively 92.86%,71.43%,95.12%,62.50%,89.80% for diagnosis of cervical and cerebral vascular diseases in 49 cases with DSA as the reference standard. The sensitivity,specificity,positive predictive value,negative predictive value and accurate ratio of two-dimensional subtraction CT angiography and three-dimensional subtraction CT angiography were all the same and higher than those of conventional CT angiography for diagnosis of cervical and cerebral vascular diseases in 49 cases with DSA as the reference standard, they were respectively 92.86%,71.43%,95.12%,62.50%,89.80%.Conclusion: Digital subtraction technique of 64-detector spiral CT angiography obviously shortens the post-processing time and improves the image quality;it may displace DSA for diagnosis of cervical and cerebral vascular diseases. Especially, the clinical application of Bone-Subtraction CT Angiography Tool software exploited by the medical company of neusoft for three-dimensional subtraction is feasible;it has a wide application prospect as a new subtraction software.
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