Carotid arterial stenosis: evaluation at CT angiography with the volume-rendering technique.

PURPOSE: To determine whether computed tomographic (CT) angiography with the volume-rendering technique (VRT) can be used to accurately quantify carotid arterial stenosis and to identify occlusions. MATERIALS AND METHODS: Spiral CT was performed in 23 patients who were referred for carotid stenosis evaluation. VRT images and shaded-surface display (SSD) images of 46 carotid arterial bifurcations were compared with findings from digital subtraction angiography (DSA). RESULTS: Agreement on stenosis category between VRT CT angiography and DSA was found in 39 (85%) of the 46 carotid arteries studied. VRT CT angiography was 92% (49 of 53) sensitive and 96% (82 of 85) specific for the detection of grade 2-3 stenoses (> or = 70% stenosis). Agreement on stenosis category between SSD CT angiography and DSA was found in 38 (83%) of the 46 carotid arteries studied. SSD CT angiography was 91% (48 of 53) sensitive and 93% (79 of 85) specific for the detection of grade 2-3 stenoses. Calcified stenoses were correctly graded at VRT CT angiography in 10 of the 10 cases with heavy mural calcified plaques, while eight of the 10 stenoses were accurately quantified at SSD CT angiography. CONCLUSION: These results indicate that VRT CT angiography is as accurate as SSD CT angiography in the evaluation of carotid arterial bifurcations.     

Detection of intracranial aneurysms with multislice CT: comparison with conventional angiography

We assessed the diagnostic accuracy of multislice CT in detection of intracranial aneurysms in patients presenting with subarachnoid or intracranial haemorrhage. Multislice CT and multiplanar digital subtraction angiography (DSA) images were obtained in 50 consecutive patients presenting with subarachnoid (SAH) and/or intracranial haemorrhage and reviewed by three neuroradiologists for the number, size and site of any aneurysms. The CT data were assessed using multiplanar reformats (MPR), maximum-intensity projections (MIP), surface-shaded display (SSD) and volume-rendering (VRT). In conventional angiography 51 aneurysms were detected in 41 patients. CT angiography (CTA) showed up to 48 aneurysms in 39 patients, depending on the observer. The overall sensitivity of multislice CT was 83.3% for small (<4 mm), 90.6% for medium-size (5–12 mm) and 100% for large (>13 mm) aneurysms. The sensitivity of multislice CTA to medium-size and large intracranial aneurysm is within the upper part of the range reported for helical single-slice CT. However, as small aneurysms may not be found, DSA remains the standard technique for investigation of SAH.     

64层螺旋CT血管成像对下肢动脉系统疾病的应用价值

目的:探讨64层螺旋CT血管成像术在下肢动脉疾病中的应用价值及技术优势。方法:对21例疑有下肢动脉疾病患者行64层螺旋CT增强扫描,扫描范围从肾动脉水平达足底。薄层重建横断面图像传入Wizard工作站,进行血管三维重建。其中21例结合常规血管造影评价64层螺旋CT血管成像术(CTA)的准确性。结果:在441个动脉节段中,435个节段在CTA与DSA均可以显示,在DSA图像上,狭窄闭塞的节段共130个(轻度狭窄16段,中度狭窄12段,重度狭窄22段,闭塞80段),最大密度投影(MIP)显示中度以上狭窄的敏感性、特异性及准确性分别为:99.1%、99.7%、99.5%。结论:64层CT血管成像是一种高度准确、非侵袭性的成像技术,在评估下肢动脉疾病方面与常规血管造影结果无明显差别,是下肢动脉疾病较好的影像学检查手段。     

Value of the CT angiography in the diagnosis of common carotid artery bifurcation disease: CT angiography versus digital subtraction angiography and color flow Doppler

OBJECTIVE: assessment of the degree of stenosis is the central point in the treatment of carotid stenosis. The purpose of our study was to assess whether invasive CT angiography (CTA) is a feasible alternative to the current invasive gold standard carotid digital subtraction angiography (DSA) and the current non-invasive gold standard color flow doppler. SUBJECTS AND METHODS: about 178 patients with cerebrovascular disease underwent digital subtraction angiography (DSA), CFD and CTA. CTA was performed on a Somatom plus 4 (Siemens, Erlangen Germany). CT was performed with 2/3/2 (collimation/table feed/reconstruction interval) or 2/3/1 mm, start delay 15-20 s, flow 2.5-3.0 ml/s, using 120 ml non-ionic contrast medium (300 mg J/ml). Quantification of degree of stenosis was based on the perfused area in the axial slices. Plaque morphology (soft and hard) and ulceration were evaluated. RESULTS: CTA detected nine cases of significant stenosis, which had been underestimated by DSA. CTA failed in two cases of a membraneous stenosis, which were underestimated, and in two cases with teeth artifacts. Calcifications were more readily appreciated by CTA than in CFD. In this respect, both methods were superior to DSA. CFD, DSA and CTA had a sensitivity of 100% for occlusions, respectively. CONCLUSION: CT angiography is useful in case of inconclusive CFD in the pre- and postoperative phase, and as a third modality in case of disagreement between DSA and CFD.     

16层螺旋CT在下肢动脉闭塞性疾病中的应用价值

目的:探讨16层螺旋CT血管成像术在诊断下肢动脉闭塞性疾病中的应用价值。方法:对42例临床疑为外周动脉闭塞性疾病的患者行下肢动脉16层螺旋CT血管造影(CTA),扫描范围从肾动脉水平达足底。薄层重建横断面图像传入HP xw8000工作站,进行血管三维重建。所有患者于CTA检查前或后2周内行数字减影血管造影(DSA)。以DSA为金标准,评价CTA诊断的准确性。结果:在882个动脉节段中,870个节段在CTA与DSA均可以显示,在DSA图像上,狭窄闭塞的节段共260个(轻度狭窄32段,中度狭窄24段,重度狭窄44段,闭塞160段),最大密度投影(MIP)显示中度以上狭窄的敏感性、特异性及准确性分别为99.1%、99.7%、99.5%。结论:16层螺旋CT在评估下肢动脉闭塞性疾病方面与常规血管造影结果无明显差别,是下肢动脉闭塞性疾病理想的影像学检查手段,可部分替代DSA检查。     

64层螺旋CT血管成像技术分析

目的探讨64层螺旋CT血管成像扫描技术,分析多种图像后处理方法的应用价值。方法应用64层螺旋CT,对45例患者行全身各部位CTA检查,其中胸主动脉4例,腹主动脉15例,肺动脉10例,共29例是通过对比剂智能跟踪兴趣区监测来确定扫描延迟时间;颅脑血管4例,颈部血管6例及双下肢动脉6例,共16例采用对比剂智能跟踪目测观察手动触发确定扫描延迟时间。原始图像应用多平面重组(MPR)、曲面重建(CPR)、最大密度投影(MIP)、表面遮盖法(SSD)及立体容积漫游技术(VRT)进行图像后处理重建。结果依据图像质量评定标准,图像质量为优的有37例,为良的有8例,无图像质量为差的病例,并且应用智能跟踪自动触发和手动触发技术的CTA图像均能满足诊断要求。结论就大血管疾病诊断而言,64层螺旋CTA完全可取代DSA,MIP及VRT是2种非常重要的血管后处理方法。     

Spiral CT angiography of renal arteries: comparison with angiography

A prospective study was carried out to determine the accuracy of spiral CT angiography (CTA) in the detection of renal artery stenosis (RAS). Eighty-two patients with arterial hypertension underwent CTA and digital subtraction angiography (DSA) to exclude RAS. For CTA a contrast medium bolus of 100–150 ml (flow rate 3 ml/s) was injected. A 24 or 40 s CTA was started at the origin of the superior mesenteric artery after a delay time determined by test bolus injection (collimation = 2 mm, pitch = 1/1.5). For stenosis detection transverse images supported by maximum intensity projections (MIP) or multiplanar reconstruction projections were used. Of 197 renal arteries examined (including 33 accessory arteries), 34 RAS were visualized using DSA. With CTA, one hemodynamic RAS was missed and one additional hemodynamic RAS was found. Sensitivity/specificity was calculated to be 94 %/98 %. For hemodynamically relevant RAS (> 50 %) the sensitivity/specificity was 96 %/99 %. CTA additionally depicted five adrenal masses. The high accuracy rate of RAS detection thus allows the use of CTA as a screening method in patients with arterial hypertension to exclude a renovascular cause. Received: 23 June 1997; Revision received: 6 January 1998; Accepted: 29 April 1998     

Carotid bifurcation CT angiography: assessment of interactive volume rendering.

PURPOSE: The purpose of this study was to compare the accuracy of CT angiography (CTA) for the assessment of carotid bifurcation stenosis, using interactive volume rendering (VR), maximum intensity projection (MIP), and 2D transverse CT technique (t-CT). METHOD: Nineteen consecutive patients were prospectively studied with CTA and selective digital subtraction angiography (DSA). There were 13 men and 6 women from 51 to 84 years old (mean 70 years). Results of DSA were compared with those of interactive VR, MIP, and conventional t-CT results, using North American Symptomatic Carotid Endarterectomy Trial criteria for stenosis grading. RESULTS: There were a total of 38 carotid bifurcations studied, with 9 mild, 10 moderate, and 15 severe stenoses and 4 occlusions. Overall agreement with DSA for VR was achieved in 76%. Eighty percent of the severe stenoses were correctly predicted by VR. The overall agreement between t-CT and DSA was 89%. MIP images, when analyzed independently, showed an overall agreement with angiography of only 71%. VR was not significantly different from MIP (p = 0.60). The difference between VR and t-CT had borderline significance (p = 0.09). MIP had significantly poorer agreement with angiography than t-CT (p = 0.02). CONCLUSION: CTA has a high degree of accuracy for the assessment of carotid artery disease compared with catheter angiography. Interactive VR increases the accuracy of diagnosing carotid stenosis and decreases the number of unsatisfactory studies as compared with MIP. Further advances in computation speeds and improvements in software may dramatically alter the future use of VR for the communication of results to clinicians; however, careful analysis of transverse sections is essential to accurate CT interpretation.     

CT angiographic analysis of carotid artery stenosis: comparison of manual assessment, semiautomatic vessel analysis, and digital subtraction angiography

BACKGROUND AND PURPOSE: To compare multisection CT angiography (CTA) analyzed with source/maximum intensity projection (MIP) images as well as semiautomated vessel analysis software with intra-arterial digital subtraction angiography (DSA) in detection and grading of carotid artery bifurcation stenosis. METHODS: Consecutive patients with sonography evidence of a marked internal carotid artery stenosis underwent both carotid CTA and DSA (37 patients, 73 vessels). In CTA, the grade of stenosis was determined using axial source and MIP images as well as vessel analysis. The scans were blind-analyzed by 2 neuroradiologists using the NASCET criteria. RESULTS: Correlation of CTA source/MIP images versus DSA estimates of stenosis (R = 0.95) was higher than for the vessel analysis method versus DSA (R = 0.89). Compared with DSA, CTA source/MIP images underestimated high (78.2% versus 86.4%, P < .05) and moderate grades of stenosis (57.3% versus 63.1%, P < .05) to a lesser extent than the vessel analysis method (68.5% versus 83.5% and 51.8% versus 63.1%, P < .05). For a high-grade stenosis, sensitivity and specificity of source/MIP image CTA were 75% and 96%, respectively, whereas for the vessel analysis method, they were 47% and 96%, respectively. For moderate stenosis, the source/MIP image CTA sensitivity and specificity were 88% and 82%, respectively, and for vessel analysis method, 62% and 82%, respectively. CTA detected all 4 occlusions. CONCLUSION: In evaluation of carotid stenosis, CTA provides an adequate, less invasive alternative with a high correlation to conventional DSA, though it tends to underestimate clinically relevant grades of stenosis. Its accuracy is not improved by semiautomated analysis. The data support the use of CTA in confirming carotid occlusion.     

CT angiography with three-dimensional techniques for the early diagnosis of intracranial aneurysms. Comparison with intra-arterial DSA and the surgical findings

INTRODUCTION: Cerebral CT angiography (CTA) is an established method applied to both the detection and treatment planning of intracranial aneurysms. The aim of our study was to compare CTA and digital subtraction angiography (DSA) findings with the surgical results mainly in patients with acute SAH and to evaluate the clinical usefulness of CTA. MATERIALS AND METHODS: During the last 2 years, 82 consecutive patients were admitted under clinical symptoms and signs suggestive of harboring an intracranial aneurysm. CT angiography performed immediately afterwards the plain CT, while DSA was performed within the first 48 h of admission. All aneurysms detected were confirmed during surgery or endovascular embolization. Repeat DSA was performed in all patients having both the initial CTA and the DSA 15 days after the onset of symptoms negative. CT angiograms and conventional angiographies were studied by a consensus of two radiologists for each technique, who performed aneurysm detection, morphological features characterization and evaluation of the technique. RESULTS: Surgical or/and endovascular treatment was performed in 45 patients and 53 aneurysms were confirmed. Using 3D-CT angiography, we detected 47 aneurysms in 42 patients. Conventional angiography depicted 43 aneurysms in 39 patients. The sensitivity of CTA for the detection of all aneurysms versus surgery was 88.7%, the specificity 100%, the positive predictive value (PPV) 100%, the negative predictive value (NPV) 80.7% and the accuracy 92.3%. Accordingly, the sensitivity of DSA was 87.8%, the specificity 98%, the PPV 97.7%, the NPV 89.1% and the accuracy 92.9%. Considering aneurysms > or =3 mm, CTA showed a sensitivity ranging from 93.3 to 100%, equal to that of DSA. CONCLUSION: Cerebral CT angiography has an equal sensitivity to DSA in the detection of intracranial aneurysms >3 mm. It has also 100% detection rate in AcoA and MCA bifurcation aneurysms, while some locations, like posterior communicating artery aneurysms, remain problematic. The delineating features of each aneurysm are better depicted with CTA due to 3D visualization. The use of digital subtraction angiography as a diagnostic tool can be limited in equivocal cases.     

CT血管造影对脑动脉瘤的临床应用价值

目的 评价ＣＴ血管造影（ＣＡＴ）对脑动脉瘤的诊断价值。方法 脑动脉瘤,１９例行ＤＳＡ检查,１８例手术。用最大强度投影（ＭＩＰ）法进行血管重建。结果 ２０例患者中ＤＳＡ及手术发现２１个动脉瘤,ＣＴＡ发现０个。１９例为单发,１９例为单发,１例为多发（２个）,ＤＳＡ示位于基底动脉和左后交通动脉,ＣＴＡ未能显示后者动脉径为３～３３ｍｍ。１例有血管。靶重建、ＣＴＡ像与原始图像后交通动脉,ＣＴＡ像与原有显始图     

64层螺旋CT与数字减影血管造影对颅内动脉瘤诊断的比较

目的 通过64层螺旋CT的CT血管造影(CTA)及CT数字减影血管造影(CTDSA)技术与数字减影血管造影(DSA)的比较研究,评价64层螺旋CT在颅内动脉瘤诊断中的临床应用价值。方法 26例临床怀疑颅内动脉瘤的患者实施64层CT和DSA检查,对64层CT图像进行了CTA和DSCTA两种方式的后处理。CTA后处理技术包括容积再现(VR),最大密度投影(MIP)和多平面重建(MPR),在CTA图像基础上用增强数据逐层减去平扫数据,自动去除骨与脑组织,获得CTDSA影像。比较3种技术(DSA、CTA和CTDSA)的特征。结果 26例可疑患者中,DSA和CTDSA发现31个动脉瘤,CTA发现29个动脉瘤。CTA漏掉的2个动脉瘤,直径小于3mm。结论 CTDSA是检查颅内动脉瘤的高度敏感的影像学方法,具有与DSA相当的价值。     

Infundibular dilation and aneurysm at the origin of the posterior communicating artery: differential diagnosis by CT angiography

Introduction

Infundibular dilation (ID) and aneurysm at the internal carotid artery (ICA)–posterior communicating artery (PComA) junction can be difficult to distinguish but may differ in clinical significance. The aim of this study was to evaluate the utility of CT angiography (CTA) in differentially diagnosing IDs and small unruptured aneurysms at the ICA–PComA junction.

Methods

This retrospective study comprised 88 patients diagnosed with 107 protrusions (70 IDs and 37 aneurysms <5 mm; 19 bilateral lesions) at the ICA–PComA junction who underwent both CTA and digital subtraction angiography (DSA). Two neuroradiologists independently reviewed CTA and DSA images according to these criteria: (a) size (maximum dimension <3 or ≥3 mm), (b) shape (triangular or round/oval/irregular), (c) aneurysmal neck (absent or present), (d) horizontal direction (posteriomedial or posteriolateral), and (e) PComA origin (apex, no PComA, or base). The intermodality (between CTA and DSA) and interobserver (between the two readers) agreement were determined for each finding. We also evaluated the sensitivity and specificity of CTA for distinguishing ID and aneurysm, using DSA as the reference standard.

Results

The mean κ values of intermodality agreement for the size, shape, aneurysmal neck, horizontal direction, and PComA origin were 0.88, 0.87, 0.84, 0.71, and 0.56, respectively. All interobserver agreements of CTA and DSA were excellent. The sensitivity, specificity, and accuracy of CTA for differentiating aneurysms from IDs were 94.6, 100, and 98.0 %, respectively.

Conclusion

CTA may be a useful noninvasive modality for differential diagnosis of ID and aneurysm at the ICA–PComA junction.     

64层3D-CTA与3D-DSA对颅内动脉瘤评价的对比研究

目的 对比评价64层螺旋CT三维血管造影(3D-CTA)与三维数字减影血管造影(3D-DSA)对颅内动脉瘤的诊断价值.方法 28例临床怀疑颅内动脉瘤的患者均行64层螺旋CT血管造影和DSA,CT三维后处理主要包括容积重建(VR)及最大密度投影(MIP).常规二维DSA检查后,对可疑病变血管行旋转DSA检查,应用三维工作软件行3D后处理,比较3D-CTA与3D-DSA对动脉瘤显示的价值.结果 28例病例中22例CTA和DSA均显示动脉瘤并经手术或栓塞证实,其中1例CTA和DSA显示单个动脉瘤,手术证实为2个动脉瘤,1例CTA显示假阳性.3D-CTA与3D-DSA均能清楚显示动脉瘤形状、瘤径指向、瘤体直径、瘤颈、载瘤动脉、瘤体穿动脉情况,两者无明显差异.结论 64层3D-CTA在颅内动脉瘤诊断及细节显示上与3D-DSA无明显差异,一定程度上应能替代血管造影,指导临床治疗.     

64层螺旋CT脑血管造影在颅内动脉瘤诊断中的应用

目的:与DSA相对照,探讨64层螺旋CT脑血管造影在颅内动脉瘤中的诊断价值。方法:对29例临床怀疑颅内动脉瘤的患者行64层螺旋CT脑血管造影(CTA)和DSA检查,使用GE64层Lightspeed VCT获得原始图像,所有病例均采用多层面重建(multiplanar reconstruction,MPR)、容积再现(volume rendering,VR)、薄层块最大密度投影(thin-slab maximumintensity projectjon,TS MIP)。后处理图像及DSA图像由2位放射科医生共同评估。结果:29例患者中,DSA证实25例共27个动脉瘤,其中2例为2个动脉瘤。与DSA结果相对照,CTA共检出25例26个动脉瘤,漏诊了1个颈出动脉瘤。CTA清晰显示了动脉瘤的形态、大小及载瘤动脉,3例动脉瘤瘤颈DSA未显示,CTA显示了全部动脉瘤的瘤颈。结论:64层CTA在颅内动脉瘤的诊断中具有极高价值,特别在显示动脉瘤瘤颈方面具有独特的优势,对临床治疗具有指导意义。     

Infrarenal aortic and lower-extremity arterial disease: diagnostic performance of multi-detector row CT angiography

PURPOSE: To compare multi-detector row spiral computed tomographic (CT) angiography with digital subtraction angiography (DSA) in evaluation of the infrarenal aorta and lower-extremity arterial system. MATERIALS AND METHODS: Fifty patients with peripheral arterial occlusive disease were evaluated with multi-detector row CT angiography and DSA. Arteries depicted at CT angiography and DSA were graded separately for degree of stenosis as 23 anatomic segments (infrarenal aorta, right and left common iliac artery, internal iliac artery, external iliac artery, common femoral artery, superficial femoral artery, deep femoral artery, popliteal artery, anterior tibial artery, tibioperoneal trunk, posterior tibial artery, and peroneal artery). Grades included the following: 1, normal patency; 2, moderate (< or =50%) stenosis; 3, focal severe (>50%) stenosis; 4, multiple severe stenoses; and 5, occlusion. Three readers independently interpreted the images, and statistical analysis was performed. The results of image interpretation were evaluated for strength of agreement by using Cohen kappa statistics. On the basis of consensus readings, sensitivity, specificity, and accuracy for detection of stenotic lesions were calculated, with findings at DSA used as the reference standard. RESULTS: Substantial to almost perfect interobserver agreement was achieved in all cases. At DSA, 349 diseased segments were found among the 1,137 segments evaluated. Sensitivity, specificity, and accuracy, based on a consensus reading of multi-detector row CT angiograms, were 96%, 93%, and 94%, respectively. A statistically significant difference (P <.05) between DSA and multi-detector row CT angiography was present only in arteries graded 1 or 2. Interobserver agreement was almost perfect among the three readers for treatment recommendations based on findings at CT angiography and DSA. CONCLUSION: Multi-detector row CT angiography appears consistent and accurate in the assessment of patients with peripheral arterial occlusive disease.     

Sixty-four-row multisection CT angiography for detection and evaluation of ruptured intracranial aneurysms: interobserver and intertechnique reproducibility

BACKGROUND AND PURPOSE: The purpose of this work was to assess intertechnique and interobserver reproducibility of 64-row multisection CT angiography (CTA) used to detect and evaluate intracranial aneurysms. MATERIALS AND METHODS: From October 2005 to November 2006, 54 consecutive patients with nontraumatic subarachnoid hemorrhage (SAH) underwent both CTA and digital substraction angiography (DSA). Four radiologists independently reviewed CT images, and 2 other radiologists reviewed DSA images. Aneurysm diameter (D), neck width (N), and the presence of a branch arising from the sac were assessed. RESULTS: DSA revealed 67 aneurysms in 48 patients and no aneurysm in 6 patients. Mean sensitivity and specificity of CTA for the detection of intracranial aneurysms were, respectively, 94% and 90.2%. For aneurysms less than 3 mm, CTA had a mean sensitivity of 70.4%. Intertechnique and interobserver agreements were good for the detection of aneurysms (mean kappa = 0.673 and 0.732, respectively) and for the measurement of their necks (mean kappa = 0.753 and 0.779, respectively). Intertechnique and interobserver agreements were excellent for the measurement of aneurysm diameters (mean kappa = 0.847 and 0.876, respectively). In addition, CTA was accurate in determining the N/D ratio of aneurysms and adjacent arterial branches. However, the N/D ratio was overestimated by all of the readers at CTA. CONCLUSION: Sixty-four-row multisection CTA is an imaging method with a good interobserver reproducibility and a high sensitivity and specificity for the detection and the morphologic evaluation of ruptured intracranial aneurysms. It may be used as an alternative to DSA as a first-intention imaging technique in patients with SAH.     

Spiral CT angiography: study of stenoses and calcification at the origin of the vertebral artery

The origin of the vertebral artery may be difficult to show on sonography or conventional angiography. Our aim was to evaluate the accuracy of CT angiography (CTA) in detecting arteriosclerotic changes in the first segment (V1) of the vertebral artery. We performed CTA and intra-arterial digital subtraction angiography (DSA) on 24 patients with vertebrobasilar insufficiency. The ostium and the V1 segment were examined. Stenosis was assessed on a three-grade scale, and calcification and the degree of kinking were recorded. DSA and CTA results were compared. The ostium of the artery was seen in all cases on CTA and in 33 of 47 cases with DSA. All ostial stenoses diagnosed on DSA were seen with CTA. CTA revealed 4 stenoses in cases in which angiography proved inadequate, 11 zones of calcification and 5 cases of luminal reduction due to calcified plaques undetected on DSA. In the V1 segment DSA and CTA showed 3 stenoses, 9 cases of kinking, 1 of coiling and 4 stenoses due to kinking. CTA also demonstrated 4 additional stenoses, 2 cases of kinking and 3 stenoses due to kinking. Received: 21 June 1995 Accepted: 6 December 1995     

双源64排螺旋CT血管成像对下肢动脉狭窄及闭塞性病变的诊断价值

目的：通过双源64排螺旋CT血管成像（CTA）与数字减影血管造影（DSA）进行比较,探讨双源64排螺旋CTA对下肢动脉狭窄及闭塞性病变的诊断价值。方法采用德国西门子公司生产的双源64排螺旋CT对30例临床怀疑下肢动脉狭窄及闭塞性病变的患者进行双下肢动脉血管成像检查,扫描范围自腹主动脉下段至足底,扫描层厚0．75 mm,管电压120 kV,管电流250 mAs,将原始图像送入工作站进行图像后处理,主要包括容积再现（VR）、最大密度摄影（MIP）、多平面重建（MPR）、曲面重建（CPR）,并结合原始图像进行分析,所有患者1周后行DSA检查,以DSA作为参考标准,对诊断一致性、敏感性、特异性和狭窄部位的检出准确率进行计算。结果在720个动脉节段中,700个节段在CTA和DSA均可以显示,以DSA作为诊断标准,双源64排螺旋CTA诊断下肢动脉闭塞的敏感性、特异性、准确性分别为99.3％、97．8％、97．8％;对于显示中度以上的狭窄,双源64排螺旋CTA的敏感性、特异性、准确性分别为99．7％、97．6％、95．6％;双源64排螺旋CTA在诊断下肢动脉狭窄及闭塞性病变与DSA结果一致性好（kappa值＝0．937）。结论双源64排螺旋CTA可以作为下肢动脉狭窄及闭塞性病变的首选检查手段,对临床具有重要的指导价值。     

Standardized volume rendering for magnetic resonance angiography measurements in the abdominal aorta

Purpose: To compare three methods for standardizing volume rendering technique (VRT) protocols by studying aortic diameter measurements in magnetic resonance angiography (MRA) datasets.

Material and Methods: Datasets from 20 patients previously examined with gadolinium-enhanced MRA and with digital subtraction angiography (DSA) for abdominal aortic aneurysm were retrospectively evaluated by three independent readers. The MRA datasets were viewed using VRT with three different standardized transfer functions: the percentile method (Pc-VRT), the maximum-likelihood method (ML-VRT), and the partial range histogram method (PRH-VRT). The aortic diameters obtained with these three methods were compared with freely chosen VRT parameters (F-VRT) and with maximum intensity projection (MIP) concerning inter-reader variability and agreement with the reference method DSA.

Results: F-VRT parameters and PRH-VRT gave significantly higher diameter values than DSA, whereas Pc-VRT gave significantly lower values than DSA. The highest interobserver variability was found for F-VRT parameters and MIP, and the lowest for Pc-VRT and PRH-VRT. All standardized VRT methods were significantly superior to both MIP and F-VRT in this respect. The agreement with DSA was best for PRH-VRT, which was the only method with a mean error below 1 mm and which also had the narrowest limits of agreement (95% of cases between 2.1 mm below and 3.1 mm above DSA).

Conclusion: All the standardized VRT methods compare favorably with MIP and VRT with freely selected parameters as regards interobserver variability. The partial range histogram method, although systematically overestimating vessel diameters, gives results closest to those of DSA.