Clinical Application Of 16-slice Spiral CT In The Diagnosis Of Acute Main Thoracic Artery Diseases

[Objective]1,To retrospectively evaluate clinical application of 16-slice spiral CT for diagnosisaorta dissection (AD).1.1 To evaluate application of 16-slice spiral CT in displaying intimal tear oftypical aorta dissection(TAD).1.2 To discuss CT findings for differential diagnosis of aortic intramuralhematoma(AIH) and aotic aneurysm(AA) with mural thrombus.2,To retrospectively evaluate clinical application of 16-slice spiral CT fordiagnosis pulmonary embolism(PE).2.1 To evaluate the visibility of peripheral pulmonary arteries by 1.25mm collimationusing 16-slice spiral CT pulmonary angiography(CTPA).2.2 To evaluate the sensitivity and specificity of 16-slice spiral CT for diagnosispulmonary embolism.2.3 To investigate a possible correlation between clot appearance of PE in 16-slicespiral CTPA and the effect of thrombolytic therapy.[Material and Method]1. Subjects According to the criterion of cases selected, collected 43 cases during2005.9～2007.3, who were suspected aortic dissection or aortic aneurysm, and allpatients underwent 16-slice spiral CT non-contrast scan and 16-slice spiral CTangiography(CTA) examination. Retrospectively collected 19 cases during2002.10～2005.9, who were diagnosed AD by magnetic resonance image(MRI), andreceived (DSA) examination or surgical therapy. Another collected AIH 10 cases andAA with mural thrombus 9 cases during the same period, all patients were examined bySiemens plus4 CT scanner.Collected 39 cases, who were suspected PE by physician. All patients underwent16-slice spiral CT Non-contrast scan and 16-slice spiral CT pulmonaryangiography(CTPA).Groups of study as follow:1.1 The study of displaying intimal tear of TAD①16SCTA compare with MR: group of 16SCTA include 21 cases, group of MRinclude 19 cases.②To compare the visibility of intimal tear of 5 kinds of image reconstructtechnic: Images of all cases underwent 16SCTA were reconstructed by MPR, CPR,MIP, VR, CTVE. According to the method of reformat, 5 groupes were defined,every group included 21 cases.Golden criterion of intimal tear: The results of surgery or digital substructangiography(DSA).Criterion of cases selected: Cases were diagnosis TAD by 16SCTA or MRI, andhad results of surgery or DSA.1.2 Differential diagnosis between AIH and AA with mural thrombus:Group AIH included 23 cases; Group AA with mural thrombus included 18 cases. Criterion: In coincident with the diagnosis criterion of AIH or AA with muralthrombus of CTA.1.3 The sudy of clinical application of 16-slice spiral CT for diagnosis PE①To evaluate the visibility of peripheral pulmonary arteries and diagnosisaccuracy of PE by 16-slice spiral CT pulmonary angiography(CTPA): Included 39cases.Criterion of cases selected:Patientas did not undergo surgery of thoracic, withoutmass of lung or mediastinum, without serious pneumonophthisis.②To investigate possible correlation between clot appearance of PE in CTPAand the effect of thrombolytic therapy: Included 24 cases.Criterion of cases selected: In coincidence with diagnostic criteria for PE , andaccepted thrombolytic therapy, underwent CTPA examination after therapy.2 EquipmentLightspeed 16 spiral CT scanner (GE company. USA) with AW4.2 workstation forpost-processing. An automatic single tube syringe controlled by mico-computer(medradcorp. USA); Siemens 1.5T magnetic resonance scanner. Siemens plus4 CT scanner.3 Examination technique3.1 Patient preparation: Test about allergic response of contrast material; Breath holdingtraining. Venous access at the arm;Patient installation: Arm above the head.3.2 Acquisition protocolNon-contrast thoracic aquisition first.Acquisition protocol of CTA : 90～100ml of contrast material (CM) at theconcentration of 300mg of iodine/ml at the injection rate of 3.5～4.0ml/s.Using bolustracking technology to monitor the dense of region of interest(ROI). Reference axialtransverse section at the level of the ascending aorta.. Visualization of the sequentialsections and manual start of the acquisition if the ROI is positioned in the false lumen with a delayed enhancement.rotation time 0.5s, slice thickness 7.5mm, collimation1.25mm, reconstruction thickness 1.25mm, pitch1.375:1, tube voltage :120KV, tubecurrent 250～280mA, FOV35cm.Range of scan: acquisition from the 2～3cm above the arch aortic to the commonfemoral arteries.Acquisition protocol of CTPA : 70～80ml of contrast material (CM) at theconcentration of 300mg of iodine/ml at the injection rate of 3.5～4.0ml/s.Using bolustracking technology to monitor the dense of region of interest(ROI). Reference axialtransverse section at the level of the right pulmonary artery. Visualization of thesequential sections and manual start of the acquisition if the ROI is positioned in thethrombus with a delayed enhancement.Rotation time 0.6s, slice thickness 7.5mm,collimation 1.25mm, reconstruction thickness 1.25mm, pitch1.375:1, tubevoltage :120KV, tube current 250～280mA.Range of scan: acquisition from theapex of lung to the basis of lung.4 Image processingAll image were transported to AW4.2 workstation. Reformat in MPR (Multiplannarreconstruction) , CPR(curved plannar reconstruction), MIP (Maximum intensityprojection) , VR (Volume rendering) , CTVE (Computed tomographic virtualendoscopy).5 Image evaluationAll images were read by two experienced radiologists. If they were disagreewith each other, the third radiologist read the image. Evaluated the images as follows:①Compare the visibility rate of intimal tear of TAD between 16SCTA and MRI.②Tocompare the visibility of intimal tear of 5 kinds of image postprocessing technology.Calculated the number of intimal tear displaying every reformat method.③Differentialdiagnosis between AIH and AA with mural thrombus: Measure the maximal diameter(D) and the longitude length(L) of the lesion of aorta. Compare calcifiedplaque position and inner margin of aortic wall of two groups.④To evaluate thevisibility of peripheral pulmonary arteries 16-slice spiral CT pulmonaryangiography(CTPA): record the visible number of the segment, subsegment, the fifthand the sixth pulmonary artery, and calculated the visible rate. Calculate theSensitivity(Se), Specificity(Sp) of 16SCTPA diagnosis PE .⑤Compare the effect ofthrombolytic therapy of PE with different clot appearence.6 Statistical analysisSPSS10.0 version software package.①K Independent Samples Test(α=0.05,p＜0.05);②Two Independent Samples Test(α=0.05, p＜0.05);③Crosstables Test(α=0.05, p＜0.05);④Independent-Samples T Test(α=0.05, p＜0.05).[Results]1. Results for chapterⅠ1.1 The accuracy of displaying intimal tear of 16SCTA and MR was 82.6% and84.2%respectively.There was no significant difference between 16SCTA and MR fordisplaying intimal tear.1.2 MPR and CPR could displaying intimal tear more clearly and accurately than otherreformat technologies; CTVE could display 59.1% intimal tear, but isn't reliable. Theintimal tear visibility of MIP is poor.1.3 The L/D ratio,calcified plaque position and inner margin of aortic wall smooth ornot had significant difference between AIH and AA with mural thrombus.But calcifiedplaque position and smooth degree of aortic wall inner margin were not the absolutpoint for differential diagnosis.2. Results for chapterⅡ 2.1 The displaying rate of segmental, subsegmental, the fifth, the sixth pulmonaryatery by 1.25mm collimation use 16SCTPA were 94.6%, 84.8%,64.3%,18.2%respectively.2.2 16SCTPA diagnosis PE Se=100%,Sp=64.3%.2.3 There was significant difference of the effect of thrombolytic therapy among the sixtypes of clot of PE. TypeⅠhad the best effect of therapy; TypeⅢhad the worst effectof therapy.[Conclusions]1. 16SCTA has the same accurency of displaying intimal tear with MR, can be used asthe first line examination of AD in preoperation evaluation.2. MPR and CPR are the best image reconstruction techniques for displaying intimaltear of AD; MIP is almost useless in displaying intimal tear of AD; CTVE is a excellenttechnique for displaying intimal tear from lumen of blood vessel, but it's not reliable.3. The L/D ratio, calcified plaque position and inner margin of aortic wall smooth ornot are all the important pointsfor distinguish AIH from AA with mural thrombus.4. 16SCTPA with 1.25mm collimation could reveal 74.1% pulmonary artery of3～5grade, also could reveal 18.2% the sixth pulmonary artery. 16SCTPA enablesdiagnosis 100% of PE cases, but the specificity is low, so the cases excluded PE by16SCTPA is safe withhold thrombolytic therapy.5. The prediction of the thrombolytic therapy effect is possible according to themorphology of PE in 16SCTPA.