The Utility of 64 Channel Multidetector CT Angiography for Evaluating the Renal Vascular Anatomy and Possible Variations: a Pictorial Essay

The increased use of laparoscopic nephrectomy and nephron-sparing surgery has prompted the need for a more detailed radiological evaluation of the renal vascular anatomy. Multidetector CT angiography is a fast and accurate modality for assessing the precise anatomy of the renal vessels. In this pictorial review, we present the multidetector CT angiography appearances of the normal renal vascular anatomy and a spectrum of various anomalies that require accurate vascular depiction before undergoing surgical treatment.

The Impact of Warmed Intravenous Contrast Material on the Bolus Geometry of Coronary CT Angiography Applications

OBJECTIVE: This study was designed to investigate the effect of administration of warmed contrast material (CM) on the bolus geometry and enhancement as depicted on coronary CT angiography. MATERIALS AND METHODS: A total of 64 patients (42 men, 22 women; mean age, 56 years) were randomly divided into two groups. Group 1 included 32 patients administered CM (Omnipaque [Iohexol] 350 mg I/ mL; Nycomed, Princeton, NJ) saline solutions kept in an incubator at a constant temperature (37degrees C). Group 2 included 32 patients administered the CM saline solutions kept at constant room temperature (24degrees C). Cardiac CT scans were performed with a dual source computed tomography (DSCT) scanner. For each group, region of interest curves were plotted inside the ascending aorta, main pulmonary artery and descending aorta on test bolus images. Using enhancement values, time/enhancement diagrams were produced for each vessel. On diagrams, basal Hounsfield unit (HU) values were subtracted from sequentially obtained values. A value of 100 HU was accepted as a cut-off value for the beginning of opacification. The time to peak, the time required to reach 100 HU opacification, maximum enhancement and duration of enhancement above 100 HU were noted. DSCT angiography studies were evaluated for coronary vessel enhancement. RESULTS: Maximum enhancement values in the ascending aorta, descending aorta and main pulmonary artery were significantly higher in group 1 subjects. In the ascending aorta, the median time required to reach 100 HU opacification during the test bolus analysis was significantly shorter for group 2 subjects than for group 1 subjects. In the ascending aorta, the descending aorta and main pulmonary artery, for group 1 subjects, the bolus geometry curve shifted to the left and upwards as compared with the bolus geometry curve for group 2 subjects. CONCLUSION: The use of warmed CM yields higher enhancement values and a shorter time to reach maximum enhancement duration, resulting in a shift of the bolus geometry curve to the left that may provide optimized image quality.

Coronary Artery Stent Evaluation Using a Vascular Model at 64-Detector Row CT: Comparison between Prospective and Retrospective ECG-Gated Axial Scans

OBJECTIVE: We wanted to evaluate the performance of prospective electrocardiogram (ECG)-gated axial scans for assessing coronary stents as compared with retrospective ECG-gated helical scans. MATERIALS AND METHODS: As for a vascular model of the coronary artery, a tube of approximately 2.5-mm inner diameter was adopted and as for stents, three (Bx-Velocity, Express2, and Micro Driver) different kinds of stents were inserted into the tube. Both patent and stenotic models of coronary artery were made by instillating different attenuation (396 vs. 79 Hounsfield unit [HU]) of contrast medium within the tube in tube model. The models were scanned with two types of scan methods with a simulated ECG of 60 beats per minute and using display field of views (FOVs) of 9 and 18 cm. We evaluated the in-stent stenosis visually, and we measured the attenuation values and the diameter of the patent stent lumen. RESULTS: The visualization of the stent lumen of the vascular models was improved with using the prospective ECG-gated axial scans and a 9-cm FOV. The inner diameters of the vascular models were underestimated with mean measurement errors of -1.10 to -1.36 mm. The measurement errors were smaller with using the prospective ECG-gated axial scans (Bx-Velocity and Express2, p < 0.0001; Micro Driver, p = 0.0004) and a 9-cm FOV (all stents: p < 0.0001), as compared with the other conditions, respectively. The luminal attenuation value was overestimated in each condition. For the luminal attenuation measurement, the use of prospective ECG-gated axial scans provided less measurement error compared with the retrospective ECG-gated helical scans (all stents: p < 0.0001), and the use of a 9-cm FOV tended to decrease the measurement error. CONCLUSION: The visualization of coronary stents is improved by the use of prospective ECG-gated axial scans and using a small FOV with reduced blooming artifacts and increased spatial resolution.

Adventitial Cystic Disease of the Femoral Vein: a Case Report with the CT Venography

Fewer than 20 cases of adventitial cystic disease of the vein have been reported in the worldwide literature. This small number of reported cases may be due not only to the disease's low incidence, but also to the difficulty in making the proper diagnosis. Many techniques have been used to investigate this disease, but venography has been the traditional diagnostic tool. In this report we present a case of adventitial cystic disease that was well demonstrated by CT venography.

Radiological Findings in a Case of Multiple Focal Nodular Hyperplasia Associated with Portal Vein Atresia and Portopulmonary Hypertension

We present here the radiological findings of a rare case of multiple focal nodular hyperplasia that was associated with portal vein atresia and portopulmonary hypertension in a young woman. This case illustrates and supports the pathophysiological hypotheses that were previously proposed for the coexistence of these three abnormalities.

Evaluation of Deep Vein Thrombosis with Multidetector Row CT after Orthopedic Arthroplasty: a Prospective Study for Comparison with Doppler Sonography

OBJECTIVE: This prospective study evaluated the ability of indirect 16-row multidetector CT venography, in comparison with Doppler sonography, to detect deep vein thrombosis after total hip or knee replacement. MATERIALS AND METHODS: Sixty-two patients had undergone orthopedic replacement surgery on a total of 30 hip joints and 54 knee joints. The CT venography (scan delay time: 180 seconds; slice thickness/increment: 2/1.5 mm) and Doppler sonography were performed 8 to 40 days after surgery. We measured the z-axis length of the beam hardening artifact that degraded the image quality so that the presence of deep vein thrombosis couldn't be evaluated on the axial CT images. The incidence and location of deep vein thrombosis was analyzed. The diagnostic performance of the CT venograms was evaluated and compared with that of Doppler sonography as a standard of reference. RESULTS: The z-axis length (mean +/- standard deviation) of the beam hardening artifact was 4.5 +/- 0.8 cm in the arthroplastic knees and 3.9 +/- 2.9 cm in the arthroplastic hips. Deep vein thrombosis (DVT) was found in the popliteal or calf veins on Doppler sonography in 30 (48%) of the 62 patients. The CT venography has a sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 90%, 97%, 96%, 91% and 94%, respectively. CONCLUSION: The ability of CT venography to detect DVT was comparable to that of Doppler sonography despite of beam hardening artifact. Therefore, CT venography is feasible to use as an alternative modality for evaluating post-arthroplasty patients.

Assessment of the Image Quality and Diagnostic Accuracy of Coronary CT Angiography: Effect of Sublingual Administration of Nitroglycerin

PURPOSE: We wanted to investigate the effect of sublingual nitroglycerin (NTG) on improving the image quality and diagnostic accuracy of coronary computed tomographic angiography (CTA) for detecting atherosclerosis and significant stenosis. MATERIALS AND METHODS: We retrospectively assessed the data of 81 patients who underwent coronary CTA. Forty three patients underwent coronary CTA without medication (the non-administrated group), while 38 patients were given 0.6 mg NTG sublingually before coronary CTA (the administrated group). Image quality was assessed using a five-point grading scale. We evaluated the diagnostic performance of coronary CTA for assessing atherosclerosis and significant stenosis (> or = 50%) in the 42 patients who underwent invasive coronary angiography. RESULTS: The mean image-quality grades were 4.09+/-0.72 and 4.50+/-0.60 in the non-administrated and administrated groups, respectively (p=0.008). On the per-artery analysis, the accuracy percentages for detecting coronary CTA were 65 and 88% for atherosclerosis and 82 and 80% for significant stenosis in the non-administrated and administrated groups, respectively. On the per-patient analysis, the positive predictive values for coronary CTA were 80% and 100% for atherosclerosis and 77% and 88% for significant stenosis in the non-administrated and administrated groups, respectively. CONCLUSION: Coronary CTA with NTG administration improved the image quality. The accuracy of coronary CTA for detecting atherosclerosis was higher in the administrated group than in the non-administrated group.

Diagnosis of Arteriovenous Fistulas following a Lumbar Discectomy

PURPOSE: To evaluate the relevant clinical and radiographical findings for the diagnosis of an arteriovenous fistula after a lumbar discectomy. MATERIALS AND METHODS: Five patients with an arteriovenous fistula following a lumbar discectomy were preoperatively diagnosed and treated. We retrospectively evaluated the level of surgery, injured vessels, clinical symptoms, physical findings, and the interval between surgery and treatment. Effective and fast diagnostic methods for determining the presence of a postoperative arteriovenous fistula were evaluated. RESULTS: All of the arteriovenous fistulas resulted from operative injuries of the iliac arteries and veins. They were diagnosed after a mean time of 22 months (range 2 months-4 years) in spite of various symptoms and signs shortly after surgery. The arteriovenous fistulas were confirmed with angiography and were treated by surgery for 3 patients and by insertion of a stent-graft in 2 patients. Postoperative CT angiography showed the complete occlusion of the fistula tract and the normal blood flow. CONCLUSION: Essential clinical information and radiological examination, especially CT angiography with 3D reconstruction, is necessary to obtain to diagnose an arteriovenous fistula after a lumbar discectomy.

Contrast Extravasation into an Acute Spontaneous Intracerebral Hematoma: Multidetector CT Angiographic Findings and Clinical Implications

PURPOSE: The purpose of this study was to evaluate multidetector row CT (MDCT) angiographic findings and their clinical significance for contrast extravasation into a spontaneous intracerebral hematoma (ICH). MATERIALS AND METHODS: MDCT angiographic studies and clinical records of 115 patients with spontaneous ICH were retrospectively reviewed. Cases were divided into two groups according to the presence or absence of contrast extravasation. The cases in the two groups were compared to determine the differences in radiological and clinical findings. The contrast extravasation group was divided into two subgroups according to radiological findings as follows: single or multiple dot-like contrast extravasation (Type A) and beaded-tubular (with or without dot-like extravasation) contrast extravasation (Type B). RESULTS: Contrast extravasation was seen in 38 patients (33%). It was associated with a larger hematoma volume, more frequent intraventricular hemorrhage (IVH) and subarachnoid hemorrhage (SAH), a shorter time interval from onset to the time of the CT scan, lower Glasgow coma scale (GCS), and a higher mortality rate. Type A and B contrast extravasation were observed in 16 (42%) and 22 (58%) patients, respectively. The rate of IVH and the clinical outcome of patients with Type B showed a significant correlation. CONCLUSION: Two types of contrast extravasation into an ICH show a significant difference in the rate of IVH and in clinical outcome. Detecting the presence of contrast extravasation and classifying them according to the morphologic patterns are important in predicting a prognosis.

Coronary CT Angiography: Focus on a New Algorithm as Diagnostic Tool in Routine Clinical Practice

Various invasive and non-invasive imaging techniques have been used for the diagnosis of coronary artery disease. Despite several limitations, coronary CTA may soon emerge as the initial diagnostic modality of choice for patients with suspected coronary artery disease. However, in routine clinical practice, the role of coronary CTA is not clearly defined even though promising diagnostic accuracy has been demonstrated compared with that of the other non-invasive tests. Herein, we suggest a new paradigm for coronary CTA as an emerging diagnostic tool in routine clinical practice on the basis of our experience and published data.

Coronary Arteriovenous Fistula Complicated with Dilated Pulmonary Sinus Confirmed by Multidetector-row CT

Congenital coronary arteriovenous fistula (CAVF) is a rare condition which is characterized by abnormal communication of the coronary artery with the right ventricle, right atrium, left atrium, left ventricle or pulmonary artery. In this paper, we report a case of a 68-year-old woman complaining of resting chest pain for one week. Initially, after performing a coronary arteriogram, the case was diagnosed as a CAVF combined with a pulmonary artery aneurysm. However, a multidetector-row CT (MDCT) was also performed, and the structure initially diagnosed as a pulmonary artery aneurysm was identified as a dilated pulmonary sinus. Subsequently, the patient was treated successfully with a simple ligation.

Three-Dimensional Computed Tomographic Angiography with Volume Rendering Technique in the Evaluation of Intracranial Aneurysms: Comparison with Three-Dimensional Digital Subtraction Angiography

PURPOSE: The author compared three-dimensional computed tomographic angiography with combined volume rendering technique (3D-CTA VR) with three-dimensional digital subtraction angiography (3D-DSA) in the detection and characterization of intracranial aneurysms, in order to assess the diagnostic capability of 3D-CTA VR. MATERIALS AND METHODS: This study included 50 patients with suspected intracranial aneurysm who underwent both 3D-CTA VR and 3D-DSA, and who were subsequently confirmed as having aneurysms by intracranial operation or other neurointerventional procedures. The detectability and the characteristics of the aneurysms, such as their aneurysmal neck, direction, and vasospasm of the adjacent vessels, were evaluated retrospectively. RESULTS: Sixty-five intracranial aneurysms were detected through surgery or other interventional procedures. 3D-DSA was more sensitive (96.92%) than 3D-CTA VR in the detection of the aneurysms. All of the aneurysms that were more than 3mm in size were detected with both techniques. 3D-DSA failed to reveal one posterior communicating artery aneurysm, while 3D-CTA VR missed three aneurysms. The aneurysmal necks were clearly visualized in 58 of 61 aneurysms (95.1%) on 3D-CTA VR, but all of the aneurysmal necks(100%) were clearly identified on 3D-DSA. CONCLUSION: 3D-CTA combined with VR technique showed good sensitivity for the depiction of intracranial aneurysms greater than 3 mm in size, and its usefulness in characterizing the aneurysms for surgical or endovascular treatment planning was equal to or less than that of 3D-DSA.

Role of CT Venography in the Diagnosis and Treatment of Benign Thoracic Central Venous Obstruction

OBJECTIVE: To evaluate the role of CT venography in the diagnosis and treatment of benign thoracic central venous obstruction. MATERIALS AND METHODS: Eighteen patients who had undergone both CT venography and digital subtraction venography were prospectively enrolled in this study. The following features were analyzed by two observers: the cause, degree, and extent of venous obstruction; associated thrombosis; and implications for the planning of treatment. CT venography and digital subtraction venography were compared in defined venous segments, and the degree of obstruction, and correlation was expressed using Spearman's rank correlation coefficient. RESULTS: In all patients, CT venography depicted the causes of obstruction, including extrinsic compression of the left brachiocephalic vein, and mediastinal inflammatory pseudotumor. Interobserver agreement regarding classification of the degree of obstruction was judged as good for CT venography (k=0.864), and in evaluating this, there was significant correlation between CT venography and digital subtraction venography (reader 1: Rs = 0.58, p < 0.01; reader 2: Rs = 0.56, p < 0.01). In evaluating the status of central veins proximal to long segmental obstruction, and associated thrombosis, CT venography was superior to digital subtraction venography. In half of all patients, the findings of CT venography led to changes in the treatment plan. CONCLUSION: The findings of CT venography correlated closely with those of digital subtraction venography, and the former accurately depicted the degree and extent of benign venous obstruction.

Influence of Anatomical, Scanning, and Reconstructing Parameters on Image Quality of CT Angiography: Vascular Phantom Study

PURPOSE: To investigate the image quality of CT angiograms obtained with various anatomical, scanning, and reconstruction parameters using a phantom with small vessels, and to determine the technique appropriate to a specific vascular anatomy. MATERIALS AND METHODS: The vascular phantom consisted of three pairs of parallel tubes with a luminal size of 1, 2, and 3 mm. Using the phantom, CT scans were obtained at three inter-tubal distances (1, 2, and 3 mm), three angles of inclination relative to the z-axis (0 degree, 45 degree, and 90 degree), three collimation widths (1, 3, and 5 mm) and two pitch factors (1 and 2). Using axial images obtained at 1-, 2-, and 3-mm reconstruction intervals, two types of three-dimensional images were rendered, and the quality of 972 such images was subjectively graded in terms of edge definition and artifact by three radiologists. RESULTS: All vessels parallel to the z-axis showed good image quality irrespective of other factors. A pair of vessels separated by 1 mm appeared to be stuck to each other. As collimation width and reconstruction interval increased, image quality decreased significantly and artifact increased. The quality of images obtained at 3 mm collimation and with a 6 mm increment was significantly better where collimation and increment were both 5 mm (p=0.001). Vessels 1 mm in size suffered artifactual degradation, especially in the case of SSD images. Most obliquely oriented vessels showed stair-step artifact, which tended to be severe when the reconstruction interval was large. CONCLUSION: In small vessels perpendicular to or inclined relative to the z-axis, a smaller collimation width and reconstruction interval lessens image degradation. When wider scan coverage is intended, a larger pitch rather than a larger collimation width is recommended. To lessen the artifacts occurring where vessels are obliquely oriented, the reconstruction interval should be reduced.

Comparison of CT Angiography and Digital Subtraction Angiography in the Evaluation of Intracranial Aneurysmal Neck

PURPOSE: To compare the usefulness of three-dimensional multislice CT angiography(CTA) and digital subtraction angiography (DSA) in the evaluation of intracranial aneurysmal neck. MATERIALS AND METHODS: Nineteen patients with intracranial aneurysm (23 cases) underwent DSA and subsequent CTA. Using a multislice CT scanner and the SSD(shaded surface display) technique, clipping, cutting and the MPR technique, three-dimensional images were obtained. These were (a) external, (b) internal, from the direction of the parent artery, (c) internal, from the direction of the aneurysmal dome, and (d) an aneurysmal cutting image. The CTA findings were retrospectively compared with the DSA images. RESULTS: Twenty aneurysms were small and three were large. In eleven cases aneurysm neck was small, in nine it was wide, and in three it was relatively wide. For aneurysnal neck evaluation, CTA was superior to DSA in six of nine wide-neck aneurysms and all three large-sized wide-neck aneurysms. In small neck aneurysms 8 of 11 cases and in relatively wide neck all 3 cases showed similarly good images by both modalities. Of the 23 cases demonstrated by four different images, 14 cases showed the best image in internal image from parent artery direction and 6 cases showed similarly good image in both aneurysmal cutting image and internal image from parent artery direction. In the evaluation of wide neck aneurysms, 7 of 9 cases showed the best image at internal image from parent artery direction, compared with other three different images. In two cases of aneurysms, calcification was visible in the aneurysmal wall, so it was difficult to evaluate the aneurysmal neck. CONCLUSION: CTA was superior to DSA in the evaluating the intracranial aneurysmal neck. CTA maybe an additional available modality to evaluate the aneurysmal neck which is difficult to detect by the DSA. And the information of intracranial aneurysmal neck through CTA will be of value in surgical and endovascular treatment.

Intrahepatic Venous Anato my on Three-Dimensional Spiral CT during Arterial Portography

PURPOSE: To evaluate the intrahepatic anatomy of the hepatic vein and right portal venous system, as seen on 3-D CTAP, and to assess the avascular zone between the anterior and posterior segments of the right lobe in relation to the right hepatic vein. MATERIALS AND METHODS: Fifteen patients in whom nodular hepatocellular was suspected underwent spiral C-TAP. 3-D images of the portal and hepatic vein were obtained using the maximal intensity projection technique. We examined the portal venous branching pattern and the draining pattern of the hepatic venous system to the inferior vena cava, as well as variation of the right hepatic vein and the avascular zone between the anterior and posterior segments of the right lobe. RESULTS: In 13 patients, three hepatic veins were clearly visualized, and in ten, the middle and left hepatic veins conjoined before draining to the IVC. In three patients, three hepatic veins drained separately into the IVC. Two right hepatic veins were seen in three patients. The right portal venous system was clearly visualized in 13 patients a classical branching pattern in 11, trifurcation in one, and four simultaneous branching patterns in one. Lateral projection showed that the angle of the avascular zone declined posteriorly by 26 degree - 64 degree ( 47.5 degree) in relation to the right hepatic vein. CONCLUSION: We observed the drainage pattern of the hepatic vein and variation of the right portal venous system on 3-D image, and confirmed that since the avascular zone declined posteriorly, the right hepatic vein is an inappropriate landmark for right hepatic segmentation.

Intrahepatic Venous Anato my on Three-Dimensional Spiral CT during Arterial Portography

PURPOSE: To evaluate the intrahepatic anatomy of the hepatic vein and right portal venous system, as seen on 3-D CTAP, and to assess the avascular zone between the anterior and posterior segments of the right lobe in relation to the right hepatic vein. MATERIALS AND METHODS: Fifteen patients in whom nodular hepatocellular was suspected underwent spiral C-TAP. 3-D images of the portal and hepatic vein were obtained using the maximal intensity projection technique. We examined the portal venous branching pattern and the draining pattern of the hepatic venous system to the inferior vena cava, as well as variation of the right hepatic vein and the avascular zone between the anterior and posterior segments of the right lobe. RESULTS: In 13 patients, three hepatic veins were clearly visualized, and in ten, the middle and left hepatic veins conjoined before draining to the IVC. In three patients, three hepatic veins drained separately into the IVC. Two right hepatic veins were seen in three patients. The right portal venous system was clearly visualized in 13 patients a classical branching pattern in 11, trifurcation in one, and four simultaneous branching patterns in one. Lateral projection showed that the angle of the avascular zone declined posteriorly by 26 degree - 64 degree ( 47.5 degree) in relation to the right hepatic vein. CONCLUSION: We observed the drainage pattern of the hepatic vein and variation of the right portal venous system on 3-D image, and confirmed that since the avascular zone declined posteriorly, the right hepatic vein is an inappropriate landmark for right hepatic segmentation.

Diagnostic Accuracy of Three-dimensional CT Angiography in Intracranial Aneurysms

PURPOSE: To determine the accuracy of three-dimensional CT angiography(CTA) in the diagnosis of intracranialaneurysms. MATERIALS AND METHODS: 3D-CTA was performed in 46 consecutive patients with subarachnoid hemorrhage orsuspected intracranial aneurysm. Images were obtained using a helical CT scanner and the SSD techinque. 3D CTAfindings were reviewed retrospectively and independently in blind fashion by two neuroradiologists. Digitalsubtraction angiography(DSA) was used as the reference standard. RESULTS: DSA revealed, in 36 patients, 40aneurysms ranging from 2mm to 12mm in maximal diameter, and negative findings in 10 patients. For observer 1, theaccuracy of 3D-CTA for all aneurysms and all patients was 85.2% and 82.7%, respectively. For observer 2, therespective figures were 94.6% and 91.9%. The agreement rates between the two observers were 86% for all aneurysmsand 87% for all patients (Kappa value 0.58, 0.59). CONCLUSION: Three-dimensional CTA is a useful imagingtechnique for the diagnosis of intracranial aneurysms, with an accuracy of over 85%

Prediction of Parent Artery of Anterior Communicating Artery Aneurysm on CT Angiography

PURPOSE: To determine whether CT angiography can predict the parent artery of an anterior communicating aneurysm on the basis of characteristics of the aneurysm and precommunicating anterior cerebral artery. MATERIALS AND METHODS: Eighteen patients with anterior communicating aneurysm were studied prospectively using CT angiography and conventional angiography. The parent artery of an aneurysm was predicted by evaluating aneurysm neck location, direction of aneurysm projection, and size of the precommunicating anterior cerebral artery, as seen on CT angiography. A somatom Plus-4 spiral CT scanner was used and shaded-surface display three-dimensional images were constructed. RESULTS: Aneurysm neck was located near the parent artery in 12 cases(66.7%), and aneurysm projection was against the parent artery in 11 cases(61.1 %). The parent artery of the anterior cerebral artery was larger in 15 cases (8 3 .3 %), including ten cases of hypoplasia or agenesis of the contralateral anterior cerebral artery. In 17 of 18 aneurysms(94.4%) the parent artery seen on DSA was correctly predicted by CT angiography. CONCLUSION: Teh parent artery of an anterior communicating aneurysm can be predicted by evaluating a-neurysm neck location, direction of aneurysm projection, and precommunicating anterior cerebral artery, as seen on CT angiography.

Spiral CT Venography in Central Venous Obstruction

PURPOSE: To determine the clinical usefulness of spiral computed tomographic (CT) venography for theevaluation of central venous obstruction. MATERIALS AND METHODS: The authors prospectively performed a total of29 spiral CT venography procedures in 25 consecutive patients with suspected central venous obstruction. Dilutedcontrast media were directly injected into the peripheral veins of the hand or the foot. Scan parameters were 3 mmX-ray beam collimation, table speed of 4-6 cm/sec, scan time of 32-40 sec, and injection delay of 20 sec. Axialimages were reconstructed at 2-mm intervals, and using shaded surface display (SSD), maximum intensity projection(MIP), and multiplanar reformation (MPR), 3-D reconstruction was performed. In all cases, ascending venograp-hy(n=13) and/or direct catheter venography (n=21) was performed within 2 days of CT venography. With regard to site,extent, extent, severity, and cause of obstruction and collateral circulation, we compared the results of CT andcontrast venography. RESULTS: In 24 patients, a total of 56 sites of central venous obstruction or stenosis(>50%) were demonstrated. The causes of obstruction were venous thrombosis (n=6), malignant tumors (n=4),arteriovenous fistula for hemodialysis (n=5), extrinsic compression (n=2), coincidence of extrinsic compressionand arteriovenous fistula (n=1), pacemaker (n=1), mediastinal inflammatory pseudotumor (n=1), spinal tuberculosis(n=1), membranous obstruction of the hepatic inferior vena cava (n=1), Behcet's disease (n=1), or unknown cause(n=1). When compared with ascending venography (n=13), CT venography was superior for evaluation of the extent andcause of obstruction and collateral circulation in two, four and one case(s), respectively. For the evaluation ofsite and severity of obstruction, CT venography was equal to ascending venography. In two cases, direct cathetervenography (n=21) was superior to CT venography for evaluating the obstruction site, but in three, five and onecase(s) respectively, CT venography was superior to direct catheter venograp-hy for evaluating the extent andcause of obstruction and collateral circulation. For the evaluation of severity of obstruction, CT and directcatheter venography were equal. CONCLUSION: In patients with suspected central venous obstruction, spiral CTvenography can be an alternative to replace not only conventional CT but also direct contrast venography.