The Study Of Volume Computed Tomographic Digital Subtraction Angiography In Cerebral Vessels

PART ONE ESTABLISHMENT AND OPTIMIZATION OF VOLUME COMPUTED TOMOGRAPHIC DIGITAL SUBTRACTION ANGIOGRAPHYObjective:To establish the method of volume computed tomographic digital subtraction angiography (VCTDSA), and optimize the protocol for scanning, contrast media injection and image post-processing methods by a series of study, as well as evaluate the value of VCTDSA in imaging of cerebral vessels by comparison with subtraction CTA in the literature.Methods:1) Establishment the method of VCTDSA:scanned the bone-vessel model of skull base with non-helical and helical CT 10 times; while obtaining two helical scanning in the same sequence 20 times with controlling the interval time of repeat exposure (TIRE) of X-ray tube in integer and non-integer of 0.4, which scanning time of 0.4 seconds for 360°rotation; after that subtracted images with the software of Add/Sub, then CT value of whole subtracted image were measured, and achievement ratio with 3-D reconstruction were assessed.2) Optimization of the protocol for scanning: Scanning performed with the same upper method, but using different mode: mA, kV(followed by synchronous changes and asynchronous changes), slice thickness and pitch, then subtracted images with the software of Add/Sub, and achievement ratio with 3-D reconstruction were assessed.3) Optimization of the protocol for injection of contrast medium:①study of contrast medium circulation time in intracranial and cervical vessel: time-density curve of artery enhancement by dynamic scan within 52 subjects which artery being adjacent to the fourth cervical vertebrae and 120 subjects at the level of the suprasellar cistern were analyzed, time to peak were measured;②study of delay scan time: time-density curve of administration of low-dose opposed to high-dose contrast medium in 47 subjects were analyzed, the time to peak were measured separately;③making a contrast research of Iodine concentration: Prospective study of different Iodine concentration as Ultravist370 and Iomeron400 with each 23 subjects: quality of reconstruction images in Cerebral Vessels and display of small vessels were analyzed.④study of injection vein: 60 chest scanning with plain and enhanced scan were analyzed, short diameter of left brachiocephalic vein spanning right brachiocephalic artery or the aortic arch, also of right brachiocephalic vein before draining into superior vena cava were measured, vein regurgitation were reviewed.4) Study of head movement influence: 44 subjects subtracted information with small dose test bolus injection and VCTDSA were analyzed. The type and extent of head movement, the shape and extent of image artifacts after subtracting were observed.5) Optimization of the protocol for the image post-processing methods:①contrast research of 3D VR between VCTDSA and conventional CTA: 96 cases intracranial aneurysms on detection rate, location, display grade of aneurysm neck, relationship with parent artery and size of aneurysm were analyzed②contrast research of removing bone reconstruction between VCTDSA and conventional CTA: 32 cases which had two methods to reconstruct cerebral vessel simultaneously were included in the research, post-processing time of two methods and the correlation between image quality after subtraction and post-processing time were analyzed.③contrast research of display with integrity, half cutting and region view in 3D VR and 3D MIP: 96 cases of aneurysms with integrity, half cutting and region view in 3D VR and 3D MIP were included in the research, detection rate, location, display grade of aneurysms neck, relation to parent artery and size of aneurysms were analyzed.6) Comparison with subtraction CTA in the literature: 8 papers about subtraction CTA were analyzed, then imaging quality of cerebral vessels, vascular displaying and the value of aneurysm detection were compared.Results:1) Establishment the method of VCTDSA: 100 percent success of subtraction with 10 time's non-helical scan. while 80 percent not success with 10 time's helical scan; if obtaining two scans in one sequence, and insuring matching for start point of X-ray tube exposure, all success with 10 time's helical scan, if not matching, none success.2) Optimization of the protocol for scanning: no effecting on image quality of subtraction with mA, kV, slice thickness and pitch, but effecting on image noise and image quality in variable degree. Dual-energy subtraction can decrease impact of image noise.3) Optimization of the protocol for injection of contrast media: The discrepancy of time to peak between common carotid artery and middle cerebral artery was 0.22 second, without statistically different, P>0.05. The circulation time of cerebral artery to vein was 6 seconds, while of cervical vessel was 8 seconds.②The discrepancy of time to peak between low dose and high dose test bolus was 7.43 seconds;③Demonstration of small cerebral vessel, Iomeron injection excelled Ultravist injection , also increasing the demonstration of lenticulostriate arteries.④Short diameter of left brachiocephalic vein spanning right brachiocephalic artery or the aortic arch was mostly less than the other side, with 26.7% stenosis, and 8.3% vein regurgitation after injection via left upper limbs vein, while the right brachiocephalic vein without stenosis and regurgitation.4) Three form of head movement without head fixation in single-level dynamic scan with test bolus: inner-plane, inter-plane and mixed movement with 77.3% 4.5% and 18.2%, respectively,most of them were little movement (65.9%). Image artifacts after subtracting decreased obviously, the proportion of image without artifact raised from 13.6% to 59.1%, proportion of little artifact declined from 47.7% to 11.4%.5) Optimization of the protocol for the image post-processing methods:①119 aneurysm were detected in 96 cases combining VCTDSA with conventional CTA, with sensitivity of 99.2%, 83.2%, respectively,both specificity of 100%. Detection of intracranial aneurysm with VCTDSA without skull interference by different view, the relationship between aneurysm and parent artery or surrounding vessels were showed vividly. Measurement of aneurysm with VCTDSA and conventional CTA had no difference.②Quality of reconstruction images in Cerebral Vessels with VCTDSA excelled conventional CTA in vascular integrality,arteriovenous display and remains of high-density. Time of removing bone reconstruction in VCTDSA was mostly shortened than conventional CTA. There were significant positive correlation between the post-processing time and the image quality after subtraction ( r=0.63,p<0.05).③Different detection rate with different view: Integrity view in 96.6%, half-cutting view in 97.5% and region view in 99.2%, 3D VR has characteristic with volume and three dimensional displaying, while 3D MIP has high density resolution, which can demonstrate the details of aneurysm when 3D VR had difficulty display.6) Comparing with subtraction CTA in the literature suggest that VCTDSA is superior to other subtraction CTA in high resolution of small vessels, integrity of cerebral vessels and imaging of whole cerebral vessels, moreover, in detection and character of intracranial aneurysm.Conclusion:1) Establishment the method of VCTDSA: Obtaining the non-enhanced and contrast-enhanced CT scan in the same sequence, to insure the matching for start point of X-ray tube exposure, subsequently subtracted images with the software of Add/Sub.2) Applying the double-energy, gathering wide collimation but thin thickness reconstructing, decreasing mAs and increasing pitch, while ensuring image quality and reducing the radiation dose.3) Ensuring the successful scan and image quality of VCTDSA by controlling the scan time, getting exactitude delay scan time, using high-concentration contrast medium and choosing injection via antecubital vein.4) The head movement studying proved the importance of head fixation and prepared for the research of the head fixation manner and the exploitation of software for correction.5) Research on image post-processing with VCTDSA established a suit of integrated program of image reconstruction and display, and constituted the criteria for clinical performance.6) VCTDSA is superior to other subtraction CTA in high resolution of small vessels, integrity of intracranial vessels, and imaging of whole cerebral vessels and detection of intracranial aneurysm.PART TWO VOLUME COMPUTED TOMOGRAPHIC DIGITAL SUBTRACTION ANGIOGRAPHY STUDY OF NORMAL CEREBRAL VESSELSObjective:To investigate the VCTDSA manifestation of normal circle of Willis, superior sagittal sinus and its tributaries, and establish standards of normal appearance.Methods: 1) 95 circle of Willis that matches clinical and image inclusion criteria in VCTDSA with cerebral vessels were analyzed. The circle of Willis was displayed with region view. The development condition, morphologic patterns, integrality and the perforating branch of the circle of Willis were studied, the size of each artery of the circle of Willis were measured.2) 32 subjects of superior sagittal sinus and tributaries that matches research inclusion criteria in VCTDSA with cerebral vessels were analyzed; the morphology of original point, output forms and the diameter of superior sagittal sinus, the number, appearance, size, the abouchement angle and location to superior sagittal sinus of bridging vein were studied. The number of tributaries veins, the anastomosis of superior sagittal sinus with other sinus, the location, size and relationship with bridging vein of arachnoid granulations were observed.Results:1) The dysplasia of the circle of Willis was displayed on each section, the incidence rate was L-PCoA (20%), R-PCoA (15.8%), R-ACA A1 (13.6%), R-PCA P1 (9.4%), L-PCA P1 (6.3%), ACoA (5.3%) and L-ACA A1 (3.2%). The artery absence was significant on R-PCoA (54.7%), L-PCoA (52.6%) and ACoA (13.6%). The dysplasia or absence of posterior cerebral circulation was 54.7%, the dysplasia or absence on both anterior and posterior cerebral circulation was 35.8%, and integrity circle was only 7.4% in 95 circles of Willis. There were 9 perforating branch of the circle of Willis, 0.87mm in mean diameter, and 14 recurrent artery of Heubner with mean diameter of 0.96mm in 95 circles of Willis.2)The original point of superior sagittal sinus was dead end accounting 41.5%, 59.5% was converged by veins. The output branching as superior sagittal sinus lateralization, straight-sinus type at most (50%), double branching type secondly (37.5%), and confluens sinus type (12.5%). There are 275 bridging veins in 32 subjects, which was significantly on middle (about 2 branches/per side), and least on posterior part (about 1 branch/per side).The anterior part mostly centralized nearby original point. There are three shapes of bridging vein: tube or ribbon shape (65.8%), significantly on anterior and posterior part; flat and irregularity shape (25.1%), significantly on middle; flat and ethmoidal foramen shape (9.1%), significantly on middle; Shape of bridging vein abouchement of superior sagittal sinus was mostly on sinus-basilar in the anterior part(84.4%), and sinus-central in the middle part(56.3%),while sinus-inferior in posterior part(90.6%). Abouchement angle of the bridging vein to superior sagittal sinus was mostly acute angle (79.2%~83.3%) on anterior part, straight angle (65.4%~68.4%) on middle part, and totally obtuse angle on posterior part. Trolard anastomosis in 35, Labbe anastomosis in 50, and anastomosis between superior sagittal sinus and falciform sinus, straight sinus through cerebral falx vein in 9 were detected. 32 arachnoid granulations were detected, all less than 5mm, mostly (68.8%) none relationship with bridging vein, partly (21.9%) on the stenosis of bridging vein.Conclusion:1) The circle of Willis displayed completely, clearly and in different view in VCTDSA. The hypoplasia or absence is mostly in normal circle of Willis, little circle of Willis is integrity, small vessels of the circle of Willis can be displayed. Therefore, VCTDSA is mostly efficient method in showing the circle of Willis.2) Superior sagittal sinus and its tributaries can display clearly and accurately with VCTDSA. The morphology of original point and output branching, bridging vein and its tributaries can display completely, clearly and in different view without interference of skull. VCTDSA is efficiently in invest the superior sagittal sinus and its tributaries in clinical. PART THREE THE CLINICAL APPLICATION OF VOLUME COMPUTED TOMOGRAPIC DIGITAL SUBTRACTION ANGIOGRAPHYObjective:To investigate aneurysms characteristics of the Circle of Willis with VCTDSA, and compare the diagnostic value between VCTDSA and DSA in aneurysm and cerebrovascular malformation.Methods:The clinical data including: 1) 84 aneurysms in 75 cases with circle of Willis conformed by DSA and/or by surgery. 2) 32 cases intracranial aneurysms with the data of VCTDSA and DSA. 3) 18 cases cerebrovascular malformation with the data of VCTDSA and DSA. The location, shape and size of the intracranial aneurysms and the cerebrovascular malformation were observed; the relationship between the aneurysm and the form of the circle of Willis, and the relationship between the aneurysm and the parent artery were analyzed. The supply artery and draining vein of the cerebrovascular malformation, signs of rupture of the aneurysm, intracranial vascular spasm and steal phenomenon were also observed.Results:1) The incidence of aneurysms in the circle of Willis was the highest at the PCoA and the ACoA, 53.6% and 35.7%, respectively. There are variations in all the circle of Willis Aneurysms, and the aneurysm in ACoA were in the main variation of typeⅣa in 90%. 96.7% of the long axis of the ACoA aneurysm had the same direction with the blood flow of the parent arteries. PCoA aneurysm was dysplasia or absent in bilateral posterior circulation in 86.7%, accompanied by variable degree of the anterior circulation with dysplasia or absent. 60% of the long axis of the PCoA aneurysm had the same direction with the blood flow of the parent artery, 26.7% with acute angle between the long axis of aneurysm and the direction of blood flow of the parent artery, and 13.3% with straight angle. Morphology of the aneurysm was saccular or cone in 98.8%. The microaneurysm can be detected by the VCTDSA in 14.3%, disruption sign of aneurysm were detected in 21.4% patients.2) The sensitivity and specificity of the VCTDSA to detect the aneurysm were 100% and 100%, respectively. For the DSA, the sensitivity and specificity were 76.2% and 100%, respectively. 15 cone or broad basilar aneurysms were displayed by VCTDSA, but only 2 by DSA. There were no significant differences in the display of the neck and intracranial arterial spasm. 3) Diagnosis of AVM and AVF, the lesions of AVM detection were all at 100% by VCTDSA and conventional DSA, while 100% and 87.5% in AVF. Supply arteries and draining veins of AVM detection were 100% and 93.3%, both 100%, while 100% and 93.3%, 100% and 75% in AVF. VCTDSA was not sensitive to steal phenomenon as conventional DSA.Conclusion:1) VCTDSA demonstrate the location and morphology of the aneurysms in the circle of Willis clearly, the incidence of aneurysms in the circle of Willis was the highest at the PCoA and the ACoA, the close correlation of ACoA aneurysm with variants of the circle of Willis and the direction of blood flow of the parent artery. It can early detect the micro-aneurysms, the ruptured aneurysm signs and the vascular spasm.2) In reflecting the aneurysm three-dimensional shape and spatial relations, VCTDSA is better than DSA, and higher than DSA in sensitivity and specificity of Aneurysm detection. VCTDSA can be a new standard for diagnosis of intracranial aneurysms.3) In the diagnosis of cerebral vascular malformation, VCTDSA with the three-dimensional and high spatial resolution can make accurate diagnosis to the nidus, fistula, supply arteries and draining veins of AVM and AVF, of which the sensitivity and specificity are higher than or equal to that of DSA, but VCTDSA is not sensitive to change in cerebral blood flow. Therefore, to understand the anatomic detail of cerebral vascular malformations, VCTDSA has obvious advantages, but to reflect the state of blood flow, DSA is better.