No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Contrast-Related Flow Phenomena Mimicking Pathology on Thoracic Computed Tomography
Abstract
Flow phenomena occurring after the bolus injection of contrast material can simulate the presence of pathology on thoracic computed tomography. In a review of 50 dynamic scans performed after contrast medium injection, apparent filling defects in the superior vena cava were seen in 46. In four cases, retrograde filling of the azygos or hemiazygos veins occurred. In two cases, layering of contrast material within the descending aorta simulated dissection. In many cases, the dynamic series of scans helped in diagnosing these appearances as flow related.
... 1,2 An azygos valve is usually present in the middle of the arch 3 and its appearance on contrast enhanced computed tomography (CT) has been previously described. 4,5 Although the reflux from the SVC into the azygos arch has been shown to be a sign of right heart failure or SVC obstruction 6 and the azygos vein diameter has even been a predictor of mortality in patients with severe pulmonary embolism, 7 the clinical relevance of azygos valves is still unknown. As CTAs requiring high rate of contrast injections are on the increase, with contrast reflux into the azygos arch and subsequent visualization of azygos valves, it is important to be aware of their variability at CT, particularly for the evaluation of mediastinal pathology and for the differentiation of normal from pathological features. ...
... Furthermore, we could have missed some of the valves which were located at the junction of the SVC and the azygos valve due to streak artifacts, often visible with almost nondiluted highdensity contrast material within the SVC, addressed and described in the early days of contrast-enhanced CT and identified as a potential hazard in CTPAs. 6,8 Although there is not enough data available about the clinical relevance of azygos valves, radiologists should be aware of the high prevalence of azygos valves and flow phenomena around them. The natural 3-dimensional curvature of the azygos arch may not allow the whole azygos arch to be visualized in 1 section on an axial scan slice rendering the interpretation of the valve even more difficult. ...
... Reflux has also been explained by the effect of gravity on contrast material with higher physical density than blood. 6,16,17 Although gravity could be responsible for some of the cases with minimal reflux, its effect cannot explain some of the examinations in our study with reflux extending to the azygos vein inferior to the arch (Fig. 5) or even into the hemizygous vein which is almost horizontal in a supine position. ...
... 1,2 An azygos valve is usually present in the middle of the arch 3 and its appearance on contrast enhanced computed tomography (CT) has been previously described. 4,5 Although the reflux from the SVC into the azygos arch has been shown to be a sign of right heart failure or SVC obstruction 6 and the azygos vein diameter has even been a predictor of mortality in patients with severe pulmonary embolism, 7 the clinical relevance of azygos valves is still unknown. As CTAs requiring high rate of contrast injections are on the increase, with contrast reflux into the azygos arch and subsequent visualization of azygos valves, it is important to be aware of their variability at CT, particularly for the evaluation of mediastinal pathology and for the differentiation of normal from pathological features. ...
... Furthermore, we could have missed some of the valves which were located at the junction of the SVC and the azygos valve due to streak artifacts, often visible with almost nondiluted highdensity contrast material within the SVC, addressed and described in the early days of contrast-enhanced CT and identified as a potential hazard in CTPAs. 6,8 Although there is not enough data available about the clinical relevance of azygos valves, radiologists should be aware of the high prevalence of azygos valves and flow phenomena around them. The natural 3-dimensional curvature of the azygos arch may not allow the whole azygos arch to be visualized in 1 section on an axial scan slice rendering the interpretation of the valve even more difficult. ...
... Reflux has also been explained by the effect of gravity on contrast material with higher physical density than blood. 6,16,17 Although gravity could be responsible for some of the cases with minimal reflux, its effect cannot explain some of the examinations in our study with reflux extending to the azygos vein inferior to the arch (Fig. 5) or even into the hemizygous vein which is almost horizontal in a supine position. ...
To evaluate the prevalence of azygos arch valves and assess azygos valve insufficiency at computed tomography angiography (CTA) of the chest or body with high rate contrast material injection.
Three hundred twenty-one CTAs using high intravenous injection rates (3-5 mL/second) of 300 mgI/mL contrast material were retrospectively evaluated for the presence of contrast material reflux from the superior vena cava into the azygos vein. Among the patients with contrast material reflux, azygos valves were identified within the azygos arch. Age, sex, and site of contrast material injection were analyzed. Azygos valve insufficiency was considered to be present if there was contrast material within the azygos vein posterior to the azygos valve.
Of the 321 examinations, 191 (59.5%) showed reflux into the azygos vein. There was no significant difference in frequency of reflux into the azygos vein between right and left arm injection site (56.4% vs 63.5%, P = 0.20) or male and female patients (63.4% vs 55.0%, P = 0.12). No difference in mean age was noted between patients with reflux and those without it (P = 0.97). Azygos valves were identified in 124 (64.9%) of 191 CTA examinations with contrast reflux and pitfalls related to their appearance variety are discussed. No significant difference was found in valve frequency between male and female patients (66.0% vs 63.4%, P = 0.70). Contrast material posterior to the visible azygos valve was present in 66 (53.2%) of 124 examinations.
Azygos arch valves are a common finding on CTA. They come in various sizes and shapes, and many of them show features of insufficiency.
... Rather, other age-associated processes, such as increased prevalence of cardiopulmonary disease (tricuspid regurgitation, pulmonary hypertension) or altered venous compliance, likely predispose more elderly patients to retrograde reflux of contrast material into the collateral veins; further work in this area will be necessary to determine the predictors for increased observed contrast material reflux in older patients. Although authors of prior case reports have suggested that reflux of contrast material into the azygos vein may be a useful sign of abnormal right heart he-modynamics (23) such as may be seen in cardiac tamponade (24), our overall findings support the stance that limited azygos reflux is a nonspecific phenomenon (10,25). There are likely multiple factors that contribute to contrast material reflux into the azygos vein. ...
... There are likely multiple factors that contribute to contrast material reflux into the azygos vein. Presumably, the force of gravity contributes to contrast material reflux into the azygos vein (10). At 37°C, iohexol has a relatively high specific gravity of 1.406 (package insert, Nycomed, Princeton, NJ) compared with that of blood, which has an average specific gravity of 1.055 (26). ...
... At 37°C, iohexol has a relatively high specific gravity of 1.406 (package insert, Nycomed, Princeton, NJ) compared with that of blood, which has an average specific gravity of 1.055 (26). With the patient in a supine position, contrast material with high physical density may exhibit retrograde flow into the more dependent portions of the venous system along the azygos arch even if the flow of blood in this vessel is antegrade (10). ...
To evaluate the prevalence and appearance of azygos arch valves at intravenous contrast material-enhanced computed tomography (CT).
Findings of 309 intravenous contrast-enhanced spiral CT examinations of the chest were retrospectively reviewed. The presence of contrast material reflux into the azygos arch and of a focal bulge in the azygos arch was recorded. An azygos valve was considered present if contrast material with a curvilinear posterior contour was seen in the azygos arch. The chi2 test was used to compare the frequency of contrast material reflux into the azygos vein for high and low rates of contrast material injection and for right and left arm injection.
Reflux of contrast material into the azygos arch occurred at 154 (49.8%) of 309 examinations, and valves were seen on images of 105 (68.2%) examinations. A focal bulge was seen in the azygos arch on images of 86 (81.9%) of 105 examinations with an azygos valve. Contrast material refluxed more frequently into the azygos vein in examinations with high rates of injection (83 of 128 examinations, 64.8%) than in those with low rates of injection (71 of 181, 39.2%, P <.001). Among the patients with high rates of injection, contrast material refluxed more frequently into the azygos vein with the right arm injection than with left arm injection (53 of 70, 76% vs 30 of 58, 52%, P <.01). Refluxed contrast material appeared as discrete collections within cusps of the azygos valves on images of 69 (44.8%) of 154 examinations.
Valves in the azygos arch are common and more frequently seen at CT when high injection rates and right arm injections are used.
... The accessory hemiazygos vein descends on the left of T5 to T8, posterior to the descending aorta, before crossing to the right at T7 or T8 to join the azygos vein [3,4]. Contrast within the azygos system may be mistaken for pathology such as abnormal masses or lymph nodes [1,5,6]. Majority of reported cases describe contrast reflux from SVC into azygos veins in the context of CTPA as high contrast injection rates and short scan delays are associated factors [2]. ...
... Majority of reported cases describe contrast reflux from SVC into azygos veins in the context of CTPA as high contrast injection rates and short scan delays are associated factors [2]. The high density of contrast also allows retrograde venous flow, aided by gravity [6]. To our knowledge, this is the first report of residual contrast in the azygos vein during CTCA. ...
... Although CT phlebography shows the site and the extent of obstruction for visualizing collateral pathways, it has been reported that this technique is insufficient to diagnose the cause of obstruction [30]. Major technical [31]. MSCT or MDCT, with its multiplanar and 3D imaging, depicts mediastinal widening and identifies superimposed thrombosis, severity of SVC obstruction, and the level and extent of venous obstruction [32]. ...
Behçet’s disease (BD) causes vascular inflammation and necrosis in a wide range of organs and tissues. In the thorax, it may cause vascular complications, affecting the aorta, brachiocephalic arteries, bronchial arteries, pulmonary arteries, pulmonary veins, capillaries, and mediastinal and thoracic inlet veins. In BD, chest radiograph is commonly used for the initial assessment of pulmonary symptoms and complications and for follow-up and establishment of the response to treatment. With the advancement of helical or multislice computed tomography (CT) technologies, such noninvasive imaging techniques have been employed for the diagnosis of vascular lesions, vascular complications, and pulmonary parenchymal manifestations of BD. CT scan (especially, CT angiography) has been used to determine the presence and severity of pulmonary complications without resorting to more invasive procedures, in conjunction with gadolinium-enhanced three-dimensional (3D) gradient-echo magnetic resonance (MR) imaging with the subtraction of arterial phase images. These radiologic methods have characteristics that are complementary to each other in diagnosis of the thoracic complications in BD. 3D ultrashort echo time (UTE) MR imaging (MRI) could potentially yield superior image quality for pulmonary vessels and lung parenchyma when compared with breath-hold 3D MR angiography.
... Contrast-enhanced CT is able to depict anatomical changes in the azygos vein and disorders of the azygos system (Fig. 2) [7][8][9]. A few articles have reported reflux of CM into the azygos vein and artifacts to be caused by CM in the azygos vein [10,11]. In addition, previous case reports have suggested that refulx of CM into the azygos vein may be an indicator of abnormal right heart hemodynamics, such as cardiac tamponade [12,13]. ...
To evaluate the frequency and appearance of azygos arch valves after short and long scanning delays and high injection rates of contrast material (CM) using a 64-slice multi-detector-row computed tomography (MDCT).
We retrospectively reviewed the findings from 264 contrast-enhanced MDCT chest examinations. The rate of injection for 300 mg I/ml CM was 3.0 ml/sec; the short and long scanning delays were 20 and 180 sec, respectively. The presence of residual CM in the azygos arch valves and reflux of CM into the azygos arch were recorded. A chi-square test was used to compare the frequency of residual CM in azygos arch valves and reflux of CM into the azygos arch in both groups.
Of the 132 examinations with short scanning delays, 91 (68.9%) demonstrated residual CM in azygos arch valves and 103 (78.0%) demonstrated reflux of CM into the azygos arch. A significantly higher frequency of reflux of CM into the azygos arch and residual CM in azygos arch valves was seen with short scanning delays than with long scanning delays (P<0.05). However, no reflux of CM into azygos arch was seen with long scanning delays.
Both reflux of CM into azygos arch valve and residual CM in the azygos arch were frequently seen using short scanning delays.
Acute chest pain is a leading cause of Emergency Department visits. Computed tomography angiography plays a vital diagnostic role in such cases, but there are several common challenges associated with the imaging of acute chest pain, which, if unrecognized, can lead to an inconclusive or incorrect diagnosis. These imaging challenges fall broadly into 3 categories: (1) image acquisition, (2) image interpretation (including physiological and pathologic mimics), and (3) result communication. The aims of this review are to describe and illustrate the most common challenges in the imaging of acute chest pain and to provide solutions that will facilitate accurate diagnosis of the causes of acute chest pain in the emergency setting.
Purpose: Comparison between peripheral digital subtraction venography (DSV) and magnetic resonance venography (MRV) in planning for stent placement in malignant superior central venous obstruction. Method: 19 patients with malignant central vein obstruction were examined by DSV (n = 19) and MRV (n = 19). For each patient 12 segment-vessel-evaluation was performed to review for obstruction and then compared with the gold standard - selective catheter phlebography - performed at the time of stent insertion. Additionally, tumor extension and collateral venous outflow was noted. Results: Sensitivity, specificity, and accuracy amounted to 92%, 96%, and 95% for DSV and 98%, 100%, and 100%, respectively for MRV. The McNemar test revealed a significance between MR venography and DSV. Conclusions: With regard to planning of stent placement, a more exact evaluation was possible with MR venography than with DSV. Thus, MR venography can replace DSV as the method of choice for clarifying malignant superior central vein obstructions prior to stent placement.
Ziel: Vergleich zwischen peripherer digitaler Subtraktionsvenographie (DSV) und Magnetresonanz (MR)-Venographie zur Planung einer Stenteinlage bei maligner oberer zentralvenöser Einflußstauung. Methoden: 19 Patienten mit maligner oberer zentralvenöser Einflußstauung wurden mittels DSV (n = 19) und MRV (n = 19) untersucht. Pro Patient wurden jeweils 12 Gefäßabschnitte bezüglich Obstruktion beurteilt und mit der selektiven, anläßlich der Stenteinlage durchgeführten Katheterphlebographie als Goldstandard auf ihre Richtigkeit verglichen. Zudem wurden Tumorausdehnung und kollateralvenöse Abflüsse untersucht. Ergebnisse: Sensitivität, Spezifität und Genauigkeit betrugen für die DSV 92 %, 96 % und 95 %, und für die MR-Venographie 98 %, 100 % und 100 %. Der McNemar-Test zeigte einen signifikanten Unterschied zwischen MR-Venographie und DSV. Schlußfolgerungen: Hinsichtlich Planung einer Stenteinlage war mit der MR-Venographie eine exaktere Beurteilung möglich als mit der DSV, weshalb die MR-Venographie die DSV als Methode der Wahl bei der Abklärung einer malignen oberen zentralvenösen Obstruktion vor Stenteinlage ersetzen kann.
Summary
Purpose: Comparison between peripheral digital subtraction venography (DSV) and magnetic resonance venography (MRV) in planning for stent placement in malignant superior central venous obstruction. Method: 19 patients with malignant central vein obstruction were examined by DSV (n = 19) and MRV (n = 19). For each patient 12 segment-vessel-evaluation was performed to review for obstruction and then compared with the gold standard - selective catheter phlebography - performed at the time of stent insertion. Additionally, tumor extension and collateral venous outflow was noted. Results: Sensitivity, specificity, and accuracy amounted to 92 %, 96 %, and 95 % for DSV and 98 %, 100 %, and 100 %, respectively for MRV. The McNemar test revealed a significance between MR venography and DSV. Conclusions: With regard to planning of stent placement, a more exact evaluation was possible with MR venography than with DSV. Thus, MR venography can replace DSV as the method of choice for clarifying malignant superior central vein obstructions prior to stent placement.
Superior vena cava syndrome (SVCS) presents with a number of nonspecific symptoms that must be assessed rapidly to prevent
life-threatening sequelae such as cerebral edema and respiratory failure. To define the utility of computed tomography (CT)
in evaluating SVCS, we initiated a retrospective analysis of all emergent chest CT scans performed at our affiliated institutions
to rule out SVCS. Twenty-eight emergent chest CT scans were analyzed. In all 23 cases confirmed to have SVCS (true-positives),
CT depicted the nature and extent of the obstructing lesions. In 4 of 5 symptomatic cases (80%) proven not to have SVCS, CT
imaged the abnormalities responsible for the misleading clinical appearance. CT also outlined the extent and course of superficial
chest wall venous collaterals in all 23 true-positive cases and that of mediastinal collaterals in 18 cases. We also found
12 patients to have CT evidence of soft tissue edema of the upper thorax, an indicator of SVCS not previously detailed. A
large number of related, unsuspected lesions were also identified. Our study supports the emergent use of chest CT as the
imaging modality of choice in the work-up of patients presenting with the clinical suspicion of SVCS.
Image quality of gadofosveset trisodium-enhanced magnetic resonance venography (MRV) of the upper extremities was evaluated.
Imaging was performed using a 3D Fast Low Angle Shot gradient recalled echo sequence (3D FLASH) and 3D gradient echo Volumetric Interpolated Breath-hold Examination with fat suppression (3D VIBE FS). Image quality was evaluated by two raters.
3D FLASH sequences demonstrated good image quality for depiction of the central venous system; 3D VIBE FS sequences showed good image quality for peripheral veins.
MRV using Gadofosveset trisodium enables good quality depiction of the venous system of the upper extremities.
Films from 246 angiograms performed for acute trauma were reviewed for artifacts that mimic arterial pathology. The population studied was young (mean age 31.8 years), and preexisting arterial disease was uncommon. Thirty patients (12%) exhibited 35 artifactual abnormalities. Artifacts included stationary wave formation (15 patients), admixture in the leading edge of the contrast column (7 patients) or streaming from the inside aspect of an arterial curve (13 patients), Mach bands (8 patients), and abnormal densities caused by the mishandling of film (1 patient) or discharge of static electricity (1 patient). These artifacts have typical morphologic appearances and locations that allow differentiation from pathological processes that manifest as intraluminal filling defects or arterial wall irregularity.
To assess the accuracy of MR imaging in the evaluation of patients with suspected thoracic venous obstruction, hospital records and MR studies of 31 such patients were reviewed. Gradient-recalled echo, spin-echo, or cine MR techniques were used. In 26 of the 31 patients, venous obstruction was confirmed by CT, venography, sonography, surgery, or autopsy. Causes included tumor invasion, compression of veins, coagulopathy, or indwelling catheters. MR detected an abnormality of the superior vena cava in all 16 cases in which it was seen on other tests. Abnormality of the internal or external jugular veins was detected in all six cases in which other studies were abnormal. Abnormality of veins in the shoulder region was detected by MR in 10 of 12 patients in whom such disease was seen on other tests. The two interpretive errors were caused by nonocclusive clot, short (less than 2-cm) occlusions, and metallic artifact. Overall, MR correctly identified abnormality in 32 of 34 vessels (sensitivity, 94%). In all cases, a negative MR study was found to be a true negative (no false positives in 42 normal vessels; specificity, 100%). We conclude that MR is an accurate means of assessing patency of the thoracic inlet and mediastinal veins. Its noninvasive nature and multiplanar capability contribute to its usefulness in this clinical setting.
Opacification of thoracic collateral venous channels (CVC) on chest CT is considered a useful sign of superior vena cava (SVC) obstruction, although its lack of specificity has occasionally been emphasized. We compared the degree of opacification of six various thoracic CVC in a group of 36 patients with SVC syndrome and in a control group of 50 patients; a dynamic incremental CT technique with bolus injection was used. Opacification of at least one CVC is inaccurate for the diagnosis of SVC obstruction, with a false-positive and false-negative rate of 34 and 31%, respectively. Only the opacification of the subcutaneous anterior channel provides a good specificity (96%), significantly higher (p less than 0.05) than that observed for the posterior collateral channels. In patients in whom the clinical records and other direct CT signs of vena cava obstruction are doubtful or absent, opacification of a subcutaneous anterior channel on chest CT should lead to a suspicion of obstruction of the SVC and cavography should be performed.
Which imaging procedure is best for the diagnosis of the superior vena cava (SVC) syndrome is subject to considerable debate. Available imaging procedures include the plain chest film, SVC phlebography, scintiangiography, digital phlebography, CT digital phlebography, and CT. In our experience the combined technique of contrast enhanced CT axial images, followed by a CT digital phlebogram, is the most informative, cost-effective, and least invasive method available.
Fourteen patients with clinical and/or radiographic evidence of mediastinal or thoracic inlet venous obstruction were studied with magnetic resonance imaging (MRI) on a 0.35-T superconducting system using multislice spin-echo technique. The MRI examinations were retrospectively evaluated for their ability to provide information about the presence, level, and cause of venous obstruction, local extent of disease causing obstruction, and presence of collateral venous pathways. The results were compared to the information available from correlative studies including CT (11) and venography (four). In each instance, MRI provided detailed information about the precise site and extent of venous obstruction. The specific cause of the obstruction was suggested by MRI findings in one case of teratoma and in one case of postradiation fibrosis. Otherwise, all masses had relatively prolonged T1 T1 and T2 relaxation times and could not be differentiated on the basis of their and T2 relaxation times and could not be differentiated on the basis of their MRI appearances. Transaxial images most clearly and unequivocally depicted patent and obstructed superior vena cava (SVC). Enlarged venous collateral pathways were apparent in four cases. CT scans with intravenous contrast material in general provided information similar to that available with MRI, except in two cases where there was a discrepancy between CT and MRI concerning complete versus partial occlusion of the SVC. This initial study indicates that MRI can provide information about the presence, cause, and precise level of mediastinal and thoracic inlet venous obstruction.
In computerized tomography of the chest and abdomen in children, visualization of veins in the paravertebral musculature is indicative of superior inferior vena caval obstruction. This collateral circulation, while not a constant feature of vena caval obstruction, is not seen in normal children.
Involvement of the inferior vena cava (IVC) by testicular neoplasms is unusual and often clinically unsuspected. We present a patient with testicular seminoma that involved the IVC secondarily and caused multiple pulmonary emboli requiring the placement of a caval filter. The radiographic features of this phenomenon are presented with special emphasis on the computed tomographic (CT) appearance of caval thrombosis and pulmonary embolus. The characteristically low density lymphadenopathy of seminoma may obscure the diagnosis of caval thrombosis on CT. Although the findings are nonspecific, tumor invasion of the IVC should be suspected in all patients with testicular neoplasms who demonstrate caval thrombosis radiographically.
Four patients exhibited thoracic venous collateral circulation on CT of the chest. No clinical or CT evidence of venous obstruction was seen. Repeat CT in one patient following repositioning of the arms from hyperabducted to the anatomic position showed absence of collateral circulation. It appears that hyperabduction of the arms during performance of chest CT can occasionally cause transient obstruction of the subclavian vein and opacification of collateral venous channels.
Observations on computed tomography (CT) of 15 patients with compression of the superior vena cava (SVC) and its tributaries are reported and compared with clinical, radiographic and surgical findings. The site of compression in 14 patients was accurately determined by CT, which could delineate the presence of intraluminal clot and extrinsic compression of venous structures, as well as associated mediastinal masses. Collateral superficial vessels were identified in nine patients with contrast-enhanced scans. Contrast-enhanced mediastinal and chest CT was shown to provide detailed anatomic and physiologic information about the etiology of SVC syndrome.
Pseudothrombosis of the infra-renal vena cava is a frequent finding during post-contrast helical computed tomography (CT) studies of the abdomen. Three hundred consecutive patients undergoing contrast-enhanced helical studies were evaluated prospectively to document the incidence of pseudothrombosis. Typical CT findings are illustrated and a significant difference in incidence between the male and female population noted.
We evaluated findings on contrast-enhanced abdominal CT scans that suggest obstruction of the superior vena cava, brachiocephalic vein, or subclavian vein.
We conducted a retrospective review of 22 patients with superior vena caval, brachiocephalic vein, or subclavian vein obstruction and analyzed the upper abdominal images on a chest CT scan or an abdominal CT scan. We assessed collateral vessels in the upper abdomen to answer the following question: Did enhancement approach undiluted IV contrast or were there other findings? In the second part of our study, we conducted a prospective review of abdominal CT scans of 200 patients without known mediastinal disease or known upper extremity venous occlusion to determine the frequency of abnormal enhancement of these vessels in a healthy population.
The groups of collateral vessels revealed on abdominal CT scans were azygos or hemiazygos veins, internal mammary veins, lateral thoracic and superficial thoracoabdominal veins, vertebral venous plexus veins, and small mediastinal collateral veins. In the retrospective series, one patient had focal enhancement of the liver and early inferior vena caval enhancement due to collateral vessels. In the prospective series, abdominal CT scans of two patients (1%) revealed dense undiluted enhancement of one or more groups of collateral vessels: One patient had an ipsilateral pacemaker, and the other patient had an anterior neck phlegmon to the upper mediastinum. Both conditions may have been factors in the revealing of the collateral vessels. Two other patients (1%) in the prospective series had mild to moderate vessel enhancement that was less than that from undiluted contrast material. In one of these patients, the enhancement was related to abdominal wall hyperemia after surgery. In the other patient, enhancement may have been the result of ipsilateral axillary nodes.
On upper abdominal CT scans, dense undiluted contrast material in the collateral vessel groups that we studied suggests possible obstruction of the superior vena cava, brachiocephalic vein, or subclavian vein.
The purpose of this study was to determine the feasibility of helical CT phlebography of the superior vena cava (SVC) and to evaluate the role of this imaging technique in the diagnosis and treatment of SVC obstruction.
Twenty-three helical CT phlebograms were obtained of patients with clinical findings that were suggestive of SVC obstruction (n = 19) and of patients undergoing posttherapeutic evaluation for SVC obstruction (n = 4). CT examinations consisted of helical acquisitions obtained in the craniocaudal direction with simultaneous bilateral antecubital vein injection of 2 x 90 ml of 12% iodinated contrast material at 2 ml/sec. Combined analysis of axial, multiplanar, and maximum-intensity-projection reformatted images was used for all patients. Image quality, venous stenosis or obstruction, intraluminal thrombus, and collateral pathways were evaluated. Comparison with digital phlebographic data was available for 16 patients; this comparison was performed in a nonblinded manner.
CT phlebograms were considered technically optimal in 91% of the patients. In all these patients, helical CT phlebograms showed the venous obstruction: the site, extent, cause, and collateral pathways. CT phlebography appeared to be well correlated with digital phlebography in 16 patients regarding the degree of obstruction, the presence of collateral pathways, and the presence of thrombus.
Helical CT phlebography may be a useful technique for imaging the SVC and its tributaries. This imaging technique is simple to perform and can provide all the information necessary to diagnose and treat SVC obstruction.
To assess the usefulness of three-dimensional (3D) gadolinium-enhanced magnetic resonance (MR) venography for evaluation of thoracic central veins.
A retrospective study included 15 patients who underwent 3D gadolinium-enhanced subtraction MR venography with a spoiled gradient-echo sequence before and at multiple times after intravenous administration of 30-40 mL of contrast material. Maximum intensity projection and multiplanar reconstruction images were used to categorize central veins as patent, occluded, or narrowed. Results were compared with findings (in 12 patients) at conventional venography (n = 3), attempted central venous catheter placement (n = 3), or surgery (n = 6). Medical records were retrospectively reviewed to determine if patient care was affected by MR venographic findings.
By using MR venograms, an appropriate vessel could be identified for successful placement of a catheter, indwelling venous access device, or arteriovenous hemodialysis graft in all nine patients in whom placement was attempted. MR venography also was predictive of unsuccessful hemodialysis catheter placement in one patient. Conventional venographic findings confirmed MR venographic findings in three patients; in a fourth patient, conventional venography was unsuccessful due to inadequate access. MR venographic findings influenced treatment in 14 patients.
On the basis of these initial results, 3D gadolinium-enhanced MR venography may facilitate comprehensive evaluation of abnormalities of the central veins in the thorax, particularly with regard to selection of venous access sites.
To determine the usefulness of high-resolution three-dimensional (3D) gadolinium-enhanced magnetic resonance venography (MRV) in the evaluation of central venous thrombo-occlusive disease of the chest.
Prospective study.
University hospital.
Sixteen consecutive patients with clinically suspected thrombosis of the superior vena cava, subclavian, brachiocephalic/innominate, internal jugular, or axillary veins. Thirteen patients had a neoplasm, two patients had a connective tissue disease, and one patient had a history of strenuous exercise. Twelve of 16 patients had prior central venous catheter placement. MRI was correlated with color-coded duplex sonography (CCDS) in 7 of 16 patients, digital subtraction angiography (DSA) in 3 of 16 patients, and CT in 2 of 16 patients.
Contrast-enhanced MRV was performed in a total of 20 examinations. A 3D data set (gradient echo; time to repeat, 4.6 ms; time to echo, 1.8 ms; flip angle, 30 degrees; time of acquisition, 23 s; 512 matrix/64 partitions; slice thickness, 1.5 mm) was acquired in the arterial and venous phase. Overall image quality was assessed on a 5-point scale. The presence, site, and extent of thrombus, as well as presence of an intravascular device, were determined.
Overall image quality was rated very good (1 point) in 7 of 16 cases (44%) and good (2 points) in 9 of 16 cases (56%). Thrombus was detected in 16 of 16 patients, and complete extent of disease could be determined in 15 of 16 patients (94%). MRV did not miss any finding obtained by CCDS, DSA, or CT, and provided additional information in 6 of 16 examinations (38%).
Contrast-enhanced MRV is a fast and reliable noninvasive procedure with excellent results regarding detection and determination of the extent of thrombo-occlusive disease of the chest veins.
Venous thromboembolic events (VTE) in children are mostly related to central venous lines (CVL), and are located in the central upper venous system. The incidence of VTE in children with CVL is significant. However, the majority of CVL-related VTE do not present with typical symptoms or are not recognized due to underlying disease. Asymptomatic VTE still cause significant venous obstruction and are associated with short-term and long-term clinical complications. Because the clinical diagnosis of CVL-related VTE is unreliable, screening by objective radiographic testing is required. In the upper venous system, ultrasound is insensitive for the VTE in the central venous system and venography is not sensitive for jugular VTE. Therefore, a combination of ultrasound and venography is required for accurate diagnosis of CVL-related VTE in the upper venous system. Whether ultrasound alone is accurate for CVL-related VTE in the lower venous system is uncertain. Magnetic resonance venography will likely prove a valid alternative for diagnosis of VTE both in the upper and lower central venous system, and may be combined with magnetic resonance pulmonary angiography to screen for pulmonary embolism.
To investigate the diagnostic value of direct contrast-enhanced three dimensional magnetic resonance (3D MR) venography in mapping the deep venous system of the upper extremities and to plan potential interventional procedures.
Nineteen cases with the diagnoses of end-stage renal disease with multiple hemodialysis catheter access were examined. Direct contrast-enhanced 3D MR venograms were obtained with 1.5 Tesla device with 3D-FSPGR pulse sequence and using body coil following the manual injection of gadolinium solution prepared by diluting 20 ml of contrast substance in 200 ml saline with a proportion of 1:10 through intravenous access opened symmetrically in antecubital fossa. In the workstation, evaluation was performed on three-dimensional images, two-dimensional multiplanar reformats and maximum-intensity projection method obtained from the source images. Intravenous DSA was performed on all the patients, and two radiologists evaluated MR venograms and conventional angiograms independently from each other. Results of MR venography and conventional angiography were then compared.
In all cases, the MR venograms obtained were capable of supporting the diagnoses. Venous pathologies were found in 16 cases. In three cases central veins were evaluated to be patent. Results of MR venography and conventional angiography were consistent with each other (100% sensitivity and 100% specificity).
Direct contrast-enhanced 3D MR venography is a well-tolerated sensitive technique in explaining the cause of the malfunctioning arterio-venous fistulas and in pre-surgical planning before placing new catheters or creating fistulas. It is possible to obtain high-quality images with this technique as an alternative to invasive angiography.
To evaluate the frequency and appearance of the azygos arch valves on chest examinations using multidetector-row computed tomography (MDCT), we retrospectively reviewed findings from 194 contrast-enhanced MDCT examinations of the chest. Rate of injection of 300 mgI/ml contrast materials was low (2.0 ml/s) and high (3.0 ml/s). Scanning delay was 80 s on examination on low-rate injection of contrast material and 20 s on high-rate injection of contrast material. The presence of residual contrast material in the azygos arch valves and reflux of contrast material into the azygos arch were recorded. The Cochran-Armitage trend test was used to compare the frequency of residual contrast material in the azygos arch valves and reflux of contrast material into the azygos arch in both groups. Of 92 examinations of high-rate injection of contrast material, 63 (68.5%) demonstrated residual contrast material in the azygos arch valves and 71 (77.2%) demonstrated reflux of contrast material into the azygos arch. A significantly higher frequency of reflux of contrast material into the azygos arch and residual contrast material in the azygos arch valves was seen in the high-rate injection group than in the low-rate injection group (P < 0.05). Residual contrast material in the azygos arch valves was demonstrated more frequently when contrast material was administered in the right side of the arm than in the left side of the arm (P < 0.05). Reflux of contrast material into the azygos arch was common in the high-injection-rate group and residual contrast material in the azygos arch valves was far more frequently seen in the high-injection-rate group than in the low-injection-rate group on MDCT.
To evaluate the feasibility of three-dimensional (3D) steady state free precession (SSFP) magnetic resonance angiography (MRA) using nonselective radiofrequency excitation for the assessment of thoracic central veins.
Thirty consecutive patients (17 males, 13 females, age range 22-76) with various cardiac and thoracic vascular diseases underwent free-breathing electrocardiogram-gated noncontrast SSFP MRA and conventional high-resolution 3D contrast-enhanced (CE) MRA of the thorax at 1.5 T. Two readers evaluated both datasets for findings: venous visibility and sharpness (from 0, not visualized to 3, excellent definition); artifacts; signal-to-noise ratio (SNR); and contrast-to-noise ratio (CNR) in 8 venous segments including superior vena cava (SVC), supra-diaphragmatic inferior vena cava, bilateral brachiocephalic, proximal subclavian, and lower internal jugular veins. Statistical analysis was performed using Wilcoxon test for overall image quality and vessel visibility, t test for SNR and CNR analysis, and kappa coefficient for inter-observer variability.
3D SSFP and CE-MRA were successfully performed in all patients. Scan time for SSFP MRA ranged from 5 to 10 minutes (mean +/- standard deviation, 7 +/- 2 minutes). Reader 1 (2) graded the overall image quality as excellent and good on SSFP MRA in 23 (25) and 7 (5) patients, and on CE-MRA in 22 (23) and 8 (9) patients, respectively. On SSFP MRA, readers 1 and 2 graded 234 (97.5%) and 233 (97.1%) venous segments with diagnostic definition (grades 2 and 3) (kappa = 0.69), respectively. On conventional CE-MRA, readers 1 and 2 graded 231 (96.3%) and 232 (96.7%) venous segments with diagnostic definition (grades 2 and 3) (kappa = 0.68), respectively. Segmental visibility and sharpness were higher for lower internal jugular veins on CE-MRA for each reader (P < 0.001). No significant difference existed for venous visibility and sharpness scores for other venous segments between the 2 techniques for both readers (P > 0.05). SNR and CNR values were lower for internal jugular veins on SSFP MRA (P < 0.001). No significant difference existed between SNR and CNR values for the other venous segments on SSFP and CE-MRA (P > 0.05 for all). The 2 readers demonstrated patent SVC Glenn shunt to main pulmonary artery (n = 3), patent extra cardiac Fontan shunt from inferior vena cava to pulmonary artery confluence (n = 2), and dilatation and thrombosis of SVC (n = 1) and right brachiocephalic vein (n = 1) on both datasets.
Free breathing navigator-gated noncontrast 3D SSFP MRA with nonselective radiofrequency excitation provides high image quality and sufficient SNR and CNR for confident evaluation of thoracic central veins.
In 44 patients with suspected dissecting aneurysm of the aorta, an aortographic diagnosis of dissection, based on the demonstration of a narrowed true lumen and of a false channel, was made in 23. Aortographic findings were negative for dissection in 11. In the remaining 10 diagnostic difficulties were encountered. In four, eventually shown to have dissection, problems resulted from faint false-channel opacification, unusual tearing of the intima and equal simultaneous opacification of both channels. In one with aortic insufficiency, findings suggestive of false-channel injection were caused by layering of contrast material in the descending aorta. In another, mediastinal rupture of a thoracoabdominal aneurysm simulated thickening of the aortic wall. In the remaining four, a definite diagnosis could not be made. Three of these had thickening of the aortic wall as the only abnormality, and one had a hemothorax obscuring the descending aortic wall.