Magnetic resonance angiography of lower-extremity arterial disease

Improvements in vascular technique have expanded the treatment options for patients with severe occlusive peripheral vascular disease. The decision to perform a major revascularization procedure in patients who are often at high risk for cardiovascular morbidity and mortality depends on the risk-benefit ratio. Detailed and accurate vascular imaging is essential and evaluating the likelihood of a successful revascularization with subsequent limb salvage. Although contrast angiography has been the time-honored reference standard imaging technique, the method is an invasive procedure with limitations and risks. MRA is a new, noninvasive vascular imaging technique that may now be added to the imaging options with the potential for improved sensitivity for finding patent runoff vessels, avoidance of morbidity, and cost equivalent to that of conventional contrast angiography. Magnetic resonance angiography is a rapidly developing and exciting new vascular imaging technique. As with any new technique, it is imperative that individual centers validate their MRA results and interpretations against the time-honored standard, which continues to be contrast arteriography. Several studies now indicate that MRA can be a cost-effective outpatient imaging technique sufficient for planning and successfully performing peripheral bypass procedures. As developments in hardware, software, and non-nephrotoxic contrast agents continue to increase, applicability of MRA in vascular surgery will continue to expand. Predictably, MRA will have a major role in the future of vascular imaging, and it is likely to supplant the need for conventional contrast angiography in the majority of patients.     

Three-dimensional respiratory-gated MR angiography of coronary arteries: comparison with conventional coronary angiography

OBJECTIVE: MR coronary angiography is most often performed using two-dimensional techniques. Although three-dimensional (3D) acquisitions do have important advantages, they take too long for a single breath-hold and are thus susceptible to respiratory motion artifacts. The purpose of this study was to investigate the accuracy of a unique respiratory-gated 3D MR angiographic technique in identifying the proximal coronary arteries in patients suspected of having coronary artery disease. In addition, we investigated the capability of this technique to detect proximal stenoses. SUBJECTS AND METHODS: We performed a prospective blinded study in 20 patients who were referred for conventional coronary angiography. A cardiac-gated 3D gradient-echo sequence with fat suppression was used. Retrospective respiratory gating was performed using navigator echoes of the diaphragm position. Using multiplanar reformatting, two independent readers blindly analyzed the data sets for visualization of major coronary arteries, lengths of imaged segments, and detection of significant stenoses (> 50% occlusion of the luminal diameter by conventional angiography). RESULTS: Seventy-seven of 80 (96%) coronary arteries were positively identified. In one patient, an anomalous coronary anatomy was readily identified and confirmed by conventional angiography. The average lengths of the imaged segments of the right, left main, left anterior descending, and left circumflex coronary arteries were 58 +/- 13 mm, 9 +/- 5 mm, 59 +/- 16 mm, and 24 +/- 10 mm, respectively. Overall sensitivity for the detection of stenoses was low (38%), with a specificity of 95%. Interobserver agreement was 0.92, with a kappa value of 0.65. CONCLUSION: Respiratory-gated 3D MR angiography allows accurate identification of proximal coronary arteries and may be valuable for 3D imaging of coronary anomalies. Further technical improvements are required to enhance the value of the technique in detecting stenoses.     

MR angiography of patients with peripheral arterial disease before and after transluminal angioplasty

The strength of the cytotoxic T lymphocyte (CTL) response is believed to influence the final outcome of hepatitis B virus (HBV) infection. Among the different CTL epitopes so far identified, the sequence 18-27 of the HBV nucleocapsid antigen is widely recognized by CTL of HLA-A2-positive patients with acute self-limited HBV infection, and represents the main component of a peptide-based therapeutic vaccine aimed at stimulating the antiviral CTL response in patients with chronic hepatitis B. In the present study, we further analyzed the features of this important HBV region by the following: 1) defining the contribution of individual residues of the epitope to the interaction with the T-cell receptor (TCR) and with the HLA-A0201 molecule; 2) assessing the antigenicity of this viral region in the context of the different HLA-A2 subtypes; and 3) testing whether this sequence can stimulate not only HLA-class I but also HLA class II restricted T-cell responses. A clear hierarchy was observed in the ability of individual residues to act as TCR or HLA binding sites. Furthermore, the sequence HBc18-27 was able to be recognized by specific CTL when presented in the context of different HLA-A2 subtypes. Finally, this HBV region was also found to stimulate HLA class II restricted T-cell responses. These data further increase the potential coverage and efficacy of therapeutic vaccines based on the HBc18-27 sequence.     

Symptomatic peripheral vascular disease: selection of imaging parameters and clinical evaluation with MR angiography

In the first phase of this study, seven healthy subjects underwent examination with two-dimensional time-of-flight (TOF) magnetic resonance (MR) angiography to develop a protocol for evaluation of peripheral arterial vasculature from the infrarenal aorta to the foot. In the second phase, 73 patients with symptomatic peripheral vascular disease underwent examination with both conventional contrast material-enhanced arteriography and two-dimensional TOF MR angiography to evaluate the clinical usefulness of MR angiography. Postinterventional and intraoperative angiography or direct surgical exploration was the standard of reference. In 32 patients, discrepancies occurred between findings on arteriograms and those on MR angiograms; most of these discrepancies were caused by improved depiction of runoff vessels on MR angiograms. The demonstration with MR angiography of blood vessels not seen on conventional arteriograms, unidentified stenoses, or misidentified blood vessels altered surgical management in 12 patients (16%). Metal-clip artifacts obscured clinically important disease on MR angiograms in two patients. It is concluded that two-dimensional TOF MR angiography is very useful in preoperative assessment of patients with severe peripheral vascular disease.     

Renal cancer: preoperative evaluation with dual-phase three-dimensional MR angiography

Using a highly sensitive allele-specific PCR amplification method, we have previously shown that maternal cells could be detected in all 10 cord bloods tested. This raised the question of whether maternal cells are released into cord blood during the process of delivery or whether they are already present during pregnancy. We have now used the same PCR method to detect the presence of maternal cells in nine fetal blood samples collected at different gestational ages. Maternal cells were detected in eight samples obtained between 24 and 35 weeks of gestation. They were estimated to amount between 10(-4) and 10(-5) of nucleated fetal blood cells. In two cases mononuclear and polymorphonuclear cell fractions were separated by Ficoll gradient centrifugation and maternal cells were detected as comparable levels in both fractions. Maternal cells could not be detected in the one fetal blood sample obtained at 20 weeks of gestation, suggesting that maternal cells could appear at detectable levels in fetal blood during the third trimester of pregnancy. These results are discussed in terms of materno-fetal immune tolerance and of transmission of viruses (and more specifically of the human immunodeficiency virus) from mother to child.     

Bithalamic hyperintensity on T2-weighted MR: vascular causes and evaluation with MR angiography

PURPOSE: To determine whether MR angiography can be used to differentiate between the two vascular causes of bithalamic hyperintensity on T2-weighted MR images: "top of the basilar" artery occlusion and deep cerebral vein thrombosis. METHODS: A retrospective review identified six patients with bithalamic T2 hyperintensity of vascular causes. MR angiography was performed in four patients, MR angiography and conventional angiography in one patient, and conventional angiography in one patient. Data pertaining to clinical presentation and hospital course were collected. MR angiographic techniques were multislab overlapping three-dimensional time-of-flight, 2-D time-of-flight, and 2-D phase-contrast. RESULTS: Three cases of top of the basilar artery occlusion and three cases of deep cerebral vein thrombosis were recognized. In all cases, T2 hyperintensity in a vascular distribution suggested cerebral occlusive disease. Infarction involving the thalami and basal ganglia was present in two cases of deep cerebral vein thrombosis. Infarction of the thalami, mesodiencephalic region, and cerebellar hemispheres was present in two cases of basilar artery occlusion. Bithalamic infarction alone was seen in one case of deep cerebral vein thrombosis and one case of basilar artery occlusion. In the five cases in which MR angiography was used, this technique accurately distinguished the vessels involved (arterial or venous). CONCLUSION: MR angiography is a useful adjunct to MR imaging in the evaluation of bithalamic T2 hyperintensity. It does help distinguish between the two vascular causes: top of basilar artery occlusion and deep cerebral vein thrombosis.     

MR angiography with three-dimensional MR digital subtraction angiography

We have developed a time-resolved, contrast-enhanced, volume-imaging technique for magnetic resonance (MR) angiography, known as three-dimensional (3D) MR digital subtraction angiography (DSA). This technique greatly improves MR angiogram quality because it combines the injection of a contrast agent with the ability to image the temporal passage of this agent and, thereby, obviates the need for timing scans or other complicated synchronization schemes. Three-dimensional MR DSA also represents a potential improvement in the sense that, relative to DSA and computed tomography (CT) angiography, the contrast agent is less toxic. Additionally, unlike CT angiography, images may be acquired during the passage of the contrast agent. Therefore, 3D MR DSA shows the sequential passage of contrast through the arterial and venous system, followed by uptake in various organs. Unlike conventional DSA, 3D MR DSA imaging acquires full volume datasets, which allows subsequent reprojection and reformatting. Because images are obtained at approximately 2-6 s time intervals using a temporal aperture on the order of several seconds, motion (such as respiration) causes only a temporary disruption of image quality, similar to that observed in MR fluoroscopy. These temporal characteristics also make the proposed sequence insensitive to variations in the shape and timing of the contrast-pass curve. Although the individual time-resolved images will have somewhat decreased signal-to-noise ratio (SNR) relative to nontime-resolved scans collected in the same acquisition time, the SNR improvement due to the gadolinium appears to accommodate this trade-off. Additionally, if motion between successive images is small, then the full suite of temporal processing schemes, previously investigated in connection with DSA and time-resolved two-dimensional (2D) MR, such as mask mode subtraction, simple matched filtering and Eigen filtering, can be used to obtain composite images. These derived images generally have an increased SNR or negligible venous signal if an arterial-phase image is not obtained in the early time-resolved images. In summary, 3D MR DSA will significantly advance MR angiography because of the following intrinsic advantages: (1) improved signal-to-noise, (2) scan orientation may be chosen independently of the direction of blood flow, (3) uniform vascular signal, even from regions of complex flow, (4) minimization of motion artifacts, (5) greatly reduced sensitivity to variation in the shape and timing of the contrast bolus, (6) ability to be reformatted or reprojected, and (7) ability to apply a variety of temporal postprocessing techniques.     

Peripheral vascular disease evaluated with reduced-dose gadolinium-enhanced MR angiography

OBJECTIVE: To examine the effect of oxygen on apneas and sleep quality in patients with frequent central apneas during sleep. DESIGN/SUBJECTS: Prospective intervention study of 20 consecutive patients with predominant central apnea identified from 570 patients referred for suspected sleep apnea syndrome. Sixteen patients had congestive heart failure and seven of them had a previous stroke. Three of the remaining four patients without heart failure had experienced a previous stroke, and one was being treated with morphine. SETTING: The Department of Pulmonary Medicine at Ume? (Sweden) University Hospital. INTERVENTIONS: The patients were investigated for one night receiving nasal oxygen and one night without it. MEASUREMENTS: Overnight polysomnography with transcutaneous PCO2 and arterial blood gases. RESULTS: Central apneas occurred during Cheyne-Stokes respiration in 18 of 20 patients and two patients had idiopathic central apneas. Without oxygen, the median number of all central apneas and hypopneas was 33.5 (range, 8.0 to 52.0) per hour of sleep. These episodes decreased to 5.0 (range, 0.0 to 31.0)(p < 0.01) during oxygen therapy. In 17 of 20 patients, the frequency of central apneas was reduced by more than 50%. Central apneas were reduced by oxygen irrespective of the presence or absence of heart failure or Cheyne-Stokes respiration. The arousal frequency was reduced during oxygen treatment. Daytime sleepiness, difficulty falling asleep, snoring, and self-scored awakenings were reduced in seven patients who were given nocturnal oxygen at home. Obstructive and mixed apneas were unaffected by oxygen. CONCLUSIONS: Oxygen effectively reduces central sleep apnea in eucapnic patients.     

Clinical application of magnetic resonance angiography for coronary arteries: correlation with conventional angiography and evaluation of imaging time

Magnetic resonance angiography (MRA) of the coronary arteries is a particularly difficult task because of the small size of the vessels and cardio-respiratory motion. The authors describe a method of performing of ultrafast MRA of the coronary arteries with a standard MR system and body coil. Each image was obtained within a single breath hold by "segmented Turbo FLASH" sequences using an electrocardiography gate. Clinical application was performed in 20 patients with ischemic heart disease, and a comparison was made with conventional coronary angiography. The imaging time was shortened significantly by our methods. The diagnosis was made by at least two different images to avoid false positives. The results indicated a good correlation between MRA and conventional angiography.     

Aortocaval fistula: diagnosis with MR angiography

A case of intramuscular hemangioma (large vessel type) occurring in an eighteen year old woman is described. Medical history reported a pulled muscle in the same region 5 years earlier. By needle biopsy was performed the diagnosis of hematoma evolved to sclerosis. Since pain persisted the neoplasia was removed. Intramuscular hemangioma is a benign neoplasia. Recurrences are always due to incomplete excision. Angiosarcomas and liposarcomas are the two tumors to be differentiated from hemangiomas of skeletal muscle. The relative paucity of cases combined with widespread histological pictures make the diagnosis very difficult.     

Spontaneous dural carotid cavernous sinus fistula presenting isolated ophthalmoplegia: evaluation with MR angiography

We describe three patients with spontaneous dural carotid cavernous sinus fistula presenting an isolated ophthalmoplegia where magnetic resonance angiography demonstrated abnormal flow-related enhancements in the cavernous sinus with extension into the inferior petrosal sinus. Magnetic resonance angiography is of value in evaluation of patients with isolated ophthalmoplegia.     

Biphasic spiral computed tomography versus digital subtraction angiography for evaluation of arterial thrombosis after orthotopic liver transplantation

Aseptic loosening of implant components is a common and important complication of both cemented and uncemented prosthetic joint replacements. Wear particles derived from organic polymer and metal implant biomaterials are commonly found within macrophages and macrophage polykaryons in the fibrous membrane between loose implant components and the host bone undergoing resorption. In order to determine whether biomaterial particle-containing, foreign-body macrophages may contribute to periprosthetic bone resorption, we cultured murine monocytes that had phagocytosed particles of biomaterials commonly employed in bone implant surgery [polymethylmethacrylate (PMMA), ultra-high molecular weight polyethylene (PE), titanium and chromium-cobalt] on bone slices and glass coverslips with UMR 106 osteoblast-like stromal cells in the presence of 1,25-dihydroxy-vitamin D3. Under these conditions, all biomaterial particle-containing, foreign-body macrophages differentiated into osteoclastic cells, i.e. tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells capable of extensive lacunar bone resorption. This study shows that particle phagocytosis by macrophages does not abrogate the ability of these cells to undergo osteoclast differentiation. These findings emphasise the importance of the foreign-body macrophage response to biomaterial wear particles in the pathogenesis of aseptic loosening.     

MR angiography: basic principles and theory

The most commonly used MR angiography techniques are categorized as time-of-flight, phase-contrast, or contrast-enhanced methods. When the basic principles of the various MR angiographic methods are understood, the techniques can be used to achieve high-quality angiograms. This article describes the physical principles and theory of some of the most widely used MR angiographic methods.     

Coronary artery disease in diabetic patients with lower-extremity arterial disease: disease characteristics and survival. A report from the Coronary Artery Surgery Study (CASS) registry

OBJECTIVE: Patients who have diabetes and lower-extremity arterial disease (LEAD) are at an increased risk of dying from coronary artery disease (CAD). This study was undertaken to: 1) define the clinical and arteriographic factors associated with LEAD among diabetic patients; 2) determine the long-term survival and predictors of mortality of diabetic patients with LEAD, compared to those without LEAD; and 3) determine if the presence of LEAD is an independent risk factor for mortality among diabetic patients with CAD. RESEARCH DESIGN AND METHODS: A total of 263 diabetic patients from the Coronary Artery Surgery Study (CASS) registry with LEAD, who were > or = 50 years of age, and who had arteriographically proven CAD, were identified and followed for a mean of 12.8 years. A total of 1,349 comparably aged diabetic patients from the CASS registry with CAD and no evidence of LEAD were followed for an equivalent period of time. RESULTS: Compared with diabetic patients without LEAD, diabetic patients with LEAD were characterized by the presence of cerebrovascular disease, a high rate of current smoking, elevated systolic blood pressure, high grades of angina pectoris, and digitalis use. Severity of epicardial CAD and extent of CAD were not independent predictors of the presence of LEAD. On follow-up, diabetic patients with LEAD had significantly higher mortality (mostly cardiovascular) than diabetic patients without LEAD, with a median survival of 8.1 and 10.9 years, respectively. On multivariate analysis, age, the number of significantly narrowed coronary arteries, and the presence of left ventricular dysfunction predicted mortality in both subsets of diabetic patients. Among all the diabetic patients with CAD, the presence of LEAD was an independent risk factor for mortality. CONCLUSIONS: Diabetic patients with LEAD have a higher mortality rate (mostly cardiovascular) than diabetic patients without LEAD, despite no apparent anatomic differences in the severity and extent of CAD. This suggests that factors associated with the presence of LEAD, other than the anatomy of the coronary circulation, may play a role in determining survival among diabetic patients with LEAD and CAD.     

MR angiography in the preoperative evaluation of abdominal aortic aneurysms: a preliminary study

PURPOSE: The ability of magnetic resonance (MR) angiography to depict visceral and renal vessels was evaluated in patients with abdominal aortic aneurysms (AAAs). PATIENTS AND METHODS: MR sequences (sagittal T1-weighted, two-dimensional coronal, and three-dimensional axial time-of-flight) were compared in a prospective blinded fashion with conventional angiograms obtained preoperatively in 23 patients with AAAs. Results were correlated with surgical findings when available. RESULTS: Operative aortic clamp site was correctly predicted with conventional angiography in 95% of patients and with MR angiography in 86% (P > .1). Aneurysm neck measurements obtained with the two modalities were within 1 cm in 91% of cases. With conventional angiography as the standard of reference, 96% of all renal arteries were identified on MR angiograms but 36% of accessory arteries were missed. MR angiography enabled identification of patients who had at least one renal artery stenosis greater than 50% with a sensitivity of 100% and specificity of 89%. For identifying individual renal artery, celiac artery, and superior mesenteric artery stenoses of similar severity, the sensitivity and specificity were 67% and in excess of 96%, respectively. The celiac artery could not be evaluated in one case. CONCLUSION: The results of this small study suggest that the role of MR angiography in the preoperative evaluation of AAA warrants further investigation.     

CT angiography versus intraarterial digital subtraction angiography for assessment of aortoiliac occlusive disease

OBJECTIVE: The purpose of this study was to evaluate the accuracy of CT angiography (CTA) with a single helical acquisition for assessment of stenoses and occlusions of the iliac arteries. SUBJECTS AND METHODS: In our prospective study, intraarterial digital subtraction angiography and IV CTA were performed from the suprarenal aorta to below the femoral bifurcation in 30 patients with vascular occlusive disease. Maximum-intensity-projection images in multiple views were also obtained. The accuracy of CTA with and without analysis of axial images was determined. RESULTS: Sensitivity and specificity of CTA were 100% for iliac artery occlusions with a confidence interval 85-100% and 97-100%, respectively. When axial scans were interpreted, 14 of 15 high-grade (> 75%) stenoses were recognized. Sensitivity and specificity of CTA were 93% (range, 68-100%) and 99% (range, 97-100%), respectively. When maximum intensity projections alone were analyzed, sensitivity for the diagnosis of 15 high-grade stenoses was only 53% (range, 27-79%) because calcified plaques obscured six stenoses. CONCLUSIONS: CTA accurately reveals iliac artery occlusions. Observers of CT angiograms may overlook short stenoses in rare instances. Calcified plaques limit the use of maximum-intensity-projection images.     

Anomalous systemic arterial supply to the basal segment of the left lung: demonstration using MR angiography

Open reduction with internal stabilization is considered to be the standard therapy for the treatment of displaced acetabular fractures. The internal fixation is routinely achieved by the use of plates and screws. The use of cerclage wires and cables as a reduction aid and definitive implant for stabilization has only occasionally been reported in the literature. The indication was mostly limited to use in elderly patients with insufficient bone stock. A newly instrument developed on the basis of a standard bone elevator is presented. It allows a safe, semiclosed application of a cerclage wire around the greater ischiatic notch through use of the second window of the ilioinguinal approach. A wide dissection at the "outside" of the pelvis is not necessary.     

Case report. Aortic pseudoaneurysm with aortobronchial fistula: diagnosis with CT angiography

We report the case of an 82-year-old man with a 12-month history of recurrent hemoptysis caused by an aortobronchial fistula. Twenty-five years earlier, the patient underwent placement of an aortic graft for aortic transection sustained in a motor vehicle accident. Chest radiography and bronchoscopy showed nonspecific abnormalities. We emphasize the role of CT angiography with 2D and 3D reconstructions for the diagnosis of and surgical planning for this rare but potentially lethal aortic postoperative complication.