MRA of the abdominal aorta and lower extremities

A congenital renal anomaly concomitant with a vascular emergency: a case of an ectopic pelvic kidney accompanied by aortoiliac aneurysms

Introduction and importance

Ectopic pelvic kidneys are an extremely rare congenital renal system anomaly. This embryological occurrence transpires between the 4th and 8th gestational weeks, and is seen in 1 in every 2100-3000 births. Moreover, research articles indicate an incidence of ectopic pelvic kidneys ranging from 0.033 to 0.047%. The co-occurrence of this anomaly with an abdominal aortic aneurysm is an even rarer finding.

Case presentation

We report a rare case involving a 62-year-old Middle Eastern male with a right ectopic pelvic kidney. The condition initially manifested as vague abdominal discomfort in the periumbilical region. The pain evolved into a continuous, localized, and insidious sensation. This was escorted by the perception of a pulsatile abdominal mass. Preoperative radiology illustrated a right ectopic pelvic kidney with concomitant aortoiliac aneurysms.

Clinical discussion

Via a successful surgical intervention, the abdominal aortic aneurysms were repaired via synthetic Dacron grafts and the renal perfusion to the ectopic pelvic kidney was secured. Moreover, the aneurysmal wall underwent a full histopathological analysis, and the results of which indicated an atherosclerotic cause.

Conclusion

Ectopic pelvic kidneys are an exceptionally rare congenital anomaly, especially when coupled with life-threatening co-occurrences like an abdominal aortic aneurysm. The need for timely surgical interventions is critical, and this topic requires comprehensive documentation as a guide for surgical professionals. This unique case is the first documented instance in the country. It emphasizes the fundamental role of proper intraoperative techniques in repairing aneurysmal conditions while preserving the function of the ectopic kidney.

Comparison of Magnetic Resonance Angiography and Computed Tomography Angiography Stereoscopic Cerebral Vascular Models

In this paper, we will discuss and compare the stereoscopic models developed from two types of radiographic data, Magnetic Resonance Angiography (MRA) images and Computed Tomography Angiography (CTA) images. Stereoscopic models were created using surface or volume segmentation and semi-auto combined segmentation techniques. Although, the CTA data were found to improve the speed and quality of constructing virtual vascular models compared to conventional CT data, small blood vessels were difficult to capture during the imaging and reconstruction process thereby limiting the fidelity of the stereoscopic models. Thus, high contrast Magnetic Resonance Angiography (MRA) images offer better resolution to visualize and capture the smaller branches of the cerebral vasculature than CTA images.

Anatomy Visualizations Using Stereopsis: Current Methodologies in Developing Stereoscopic Virtual Models in Anatomical Education

Technology for developing three-dimensional (3D) virtual models in anatomical sciences education has seen a great improvement in recent years. Various data used for creating stereoscopic virtual models have also been constantly improving. This paper focuses specifically on the methodologies of creating stereoscopic virtual models and the techniques and materials used in developing stereoscopic virtual models from both our previous studies and other published literature. The presentation and visualization of stereoscopic models are highlighted, and the benefits and limitations of stereoscopic models are discussed. The practice of making 3D measurements on the lengths, angles, and volumes of models can potentially be used to help predict typical measurement parameters of anatomical structures and for the placement of surgical instruments. Once stereoscopic virtual models have been constructed, their visualization and presentation can be implemented in anatomy education and clinical surgical trainings.

Abdominal Aortic Aneurysm With Ectopic Renal Artery Origins: A Case Report

The coexistense of an abdominal aortic aneurysm with ectopic main renal vasculature complicates aortic surgery and mandates a focused imaging evaluation and a carefully planned operation to minimize renal ischemia. We present the case of a 75-year-old man with an abdominal aortic aneurysm and a right kidney with two ectopic main renal arteries, one originating from the aneurysmal distal aorta and the other from the right common iliac artery; the patient underwent a surgical repair and followed an uneventful course with no deterioration of renal function. The preoperative and intraoperative details are reported, along with a review of the literature.

Comparison of gadofosveset (Vasovist(®)) with gadobenate dimeglumine (Multihance(®))-enhanced MR angiography for high-grade carotid artery stenosis

OBJECTIVE

To prove superiority of blood pool contrast agent gadofosveset over conventional contrast agent gadobenate dimeglumine for assessment of stenotic internal carotid artery (ICA).

METHODS

Eleven patients with high-grade ICA stenosis (≥75%), confirmed by duplex sonography, underwent MR angiography (MRA) with gadofosveset and gadobenate dimeglumine.

RESULTS

Agreement in stenosis grade was reached in 7 of 10 stenotic ICAs. In two ICAs, gadobenate dimeglumine led to underestimation of stenosis grade. There was a significant difference in signal intensity (pre-/post-stenotic segments), showing higher values for gadofosveset (P<0.01; P<0.05). Impression of contrast intensity with gadofosveset was better in 8 ICAs and only in 1 ICA with gadobenate dimeglumine (P<0.05).

CONCLUSION

Gadofosveset-enhanced MR angiography may be superior for assessment of high-grade ICA stenosis compared with gadobenate dimeglumine MR angiography.

Diagnostic approach to peripheral arterial disease

This article discusses diagnostic imaging techniques used in the evaluation and management of patients with peripheral arterial disease (PAD). Along with a complete vascular examination, noninvasive physiologic testing is used for the initial evaluation of patients with suspected PAD. Duplex ultrasonography provides information on the degree of stenosis or occlusion within a vessel and allows assessment of the vessel wall and plaque morphology. Angiographic imaging techniques should be reserved for determining the optimal endovascular or surgical approach for patients requiring revascularization. Together, all available diagnostic modalities contribute to successful evaluation and management of patients with PAD.

Peripheral artery disease: current insight into the disease and its diagnosis and management

Peripheral artery disease (PAD), which comprises atherosclerosis of the abdominal aorta, iliac, and lower-extremity arteries, is underdiagnosed, undertreated, and poorly understood by the medical community. Patients with PAD may experience a multitude of problems, such as claudication, ischemic rest pain, ischemic ulcerations, repeated hospitalizations, revascularizations, and limb loss. This may lead to a poor quality of life and a high rate of depression. From the standpoint of the limb, the prognosis of patients with PAD is favorable in that the claudication remains stable in 70% to 80% of patients over a 10-year period. However, the rate of myocardial infarction, stroke, and cardiovascular death in patients with both symptomatic and asymptomatic PAD is markedly increased. The ankle brachial index is an excellent screening test for the presence of PAD. Imaging studies (duplex ultrasonography, computed tomographic angiography, magnetic resonance angiography, catheter-based angiography) may provide additional anatomic information if revascularization is planned. The goals of therapy are to improve symptoms and thus quality of life and to decrease the cardiovascular event rate (myocardial infarction, stroke, cardiovascular death). The former is accomplished by establishing a supervised exercise program and administering cilostazol or performing a revascularization procedure if medical therapy is ineffective. A comprehensive program of cardiovascular risk modification (discontinuation of tobacco use and control of lipids, blood pressure, and diabetes) will help to prevent the latter.

Contrast-enhanced magnetic resonance angiography following subintimal recanalization

PURPOSE

To describe the appearance of lower extremity runoff vessels following subintimal recanalization (SIR) on contrast-enhanced magnetic resonance angiography (ceMRA) and compare 2 different ceMRA techniques.

METHODS

A total of 6 patients underwent stepping table 3-dimensional (3D) ceMRA and time-resolved 2-dimensional (2D) MRA within 1 to 3 days (mean 1.83 days) following SIR. The 2 techniques were compared with intra-arterial digital subtraction angiography (DSA).

RESULTS

A total of 15 arteries were recanalized in 6 patients. Three-dimensional ceMRA allowed evaluation of patency in all segments above the knee. Postprocedural hyperemia impaired the assessment of the trifurcation vessels on 3D ceMRA. Due to its higher temporal resolution 2D MRA was not affected by venous contamination and allowed reliable confirmation of patency of the recanalized vessels.

CONCLUSIONS

Diagnostic MRA studies of the lower extremity runoff vessels following SIR is possible, but a hybrid technique using a stepping table MR DSA and a time-resolved sequence like 2D MRA of the calf station is necessary for runoff assessment.

Gadofosveset-enhanced magnetic resonance angiography

Gadofosveset (Vasovist^®, Bayer Schering Pharma AG, Berlin/Germany) is the first intravascular contrast agent approved for use with magnetic resonance angiography in the European Union, Switzerland, Turkey, Canada, and Australia. Gadofosveset reversibly binds to albumin providing extended intravascular enhancement compared wth existing extracellular magnetic resonance contrast agents. Prior to approval, gadofosveset underwent extensive testing to evaluate the safety and efficacy of the drug; the clinical trials show that gadofosveset-enhanced magnetic resonance angiography (MRA) is safe and well tolerated in patients with vascular disease and effective for the detection of vascular stenosis and aneurysms gadofosveset has the potential to open new horizons in diagnostic MRA by increasing the spatial resolution and the robustness of MRA examinations and facilitating the examination of multiple vascular beds.

Risk factors for the association of intracranial and aortic aneurysms

This study investigated the association of intracranial aneurysms and abdominal aortic aneurysms to elucidate the incidence and independent risk factors for this association. Ultrasonography of the abdominal aorta was performed in 181 patients with 224 intracranial aneurysms. Six patients had suffered subarachnoid haemorrhage and the others had chronic disease or no symptoms. Magnetic resonance angiography was performed for confirmation if abdominal aortic aneurysm was identified by ultrasonography. Thirteen patients (7.2%) with 23 intracranial aneurysms had abdominal aortic aneurysms. Univariate analysis demonstrated that age (p < 0.01), size of intracranial aneurysms (p < 0.001), male sex (p < 0.01), multiplicity of intracranial aneurysms (p < 0.001), history of cerebrovascular diseases (p < 0.05), and current smoking (p < 0.0001) were significantly different between patients with and without this association. Multiple logistic analysis indicated that age (odds ratio [OR] 1.27, 95% confidence interval 1.08-1.48, p < 0.01), multiplicity (OR 22.1, 95% confidence interval 1.83-266.3, p = 0.01), size of intracranial aneurysms (OR 1.30, 95% confidence interval 1.10-0.54, p < 0.01), and current smoking (OR 33.3, 95% confidence interval 2.43-456.7, p = 0.01) were independent risk factors for the association. Patients with intracranial aneurysms who are older males with multiple or large intracranial aneurysms, and current smokers should be examined for abdominal aortic aneurysms using ultrasonography.

Gadofosveset: the first intravascular contrast agent EU-approved for use with magnetic resonance angiography

Gadofosveset is the first intravascular contrast agent approved for use with magnetic resonance angiography in the European Union. Gadofosveset reversibly binds to albumin, providing extended intravascular enhancement beyond that of existing extracellular magnetic resonance contrast agents. Prior to approval, gadofosveset underwent extensive testing to evaluate the safety and efficacy of the drug; the clinical trials program included blinded, placebo-controlled, dose-ranging, efficacy in a variety of vascular beds (areas of turbulent blood flow, renal and pedal), examination of potential drug interaction with warfarin and comparison with x-ray angiography. The clinical trials demonstrate that gadofosveset-enhanced magentic resonance angiography is: safe and well tolerated in patients with vascular disease; effective for the detection of vascular stenosis and aneurysms; significantly more accurate (both more sensitive and specific) than noncontrast magnetic resonance angiography for the diagnosis of vascular stenoses; and similar to conventional angiography for the overall characterization of vascular disease, without the need for catheterization.

A Summary of Safety of Gadofosveset (MS-325) at 0.03 mmol/kg Body Weight Dose

OBJECTIVE

We sought to summarize the Phase II and Phase III clinical trials safety data for gadofosveset (Vasovist, MS-325), a new magnetic resonance angiography contrast agent.

MATERIALS AND METHODS

Subjects with known or suspected vascular disease were administered 0.03 mmol/kg gadofosveset (767 subjects) or placebo (49 subjects) in phase II and phase III studies. Overall safety data were pooled from 8 studies and included adverse event monitoring, clinical laboratory assays, vital signs, oxygen saturation, physical examination, and electrocardiography. The safety was monitored for 72 to 96 hours postinjection (PI), and safety comparison with x-ray angiography using iodinated contrast media also was performed in 318 subjects. In the phase II trial, 5 doses of gadofosveset and placebo were evaluated. In this study, 38 patients were administered placebo and 39 patients received 0.03 mmol/kg gadofosveset.

RESULTS

In pooled data, treatment related adverse events were reported by 176 (22.9%) patients receiving gadofosveset and by 16 (32.7%) patients receiving placebo. In phase II trial, treatment-related adverse events were reported by 13 of the 39 (33.3%) patients receiving gadofosveset and 9 of the 38 (23.7%) patients receiving placebo. No severe or serious adverse events were reported in either gadofosveset or placebo groups in this phase II trial. Pooled data revealed no clinically significant trends in adverse events, laboratory assays, vital signs, or oxygen saturation. A QTc prolongation of 2.8 milliseconds was observed at 45 minutes after MS-325 injection; however, this trend was similar to that of the placebo group at the same time point (3.2 milliseconds).

CONCLUSION

Gadofosveset has exhibited a good safety profile and can be safely administered as an intravenous bolus injection. The overall rate and experience of adverse events was similar to that of placebo. The safety profile of gadofosveset is comparable with that of other gadolinium contrast agents as reported in the literature.

Peripheral Arterial Disease: Sensitivity-encoded Multiposition MR Angiography Compared with Intraarterial Angiography and Conventional Multiposition MR Angiography

A sensitivity-encoded magnetic resonance (MR) angiography protocol was developed in which imaging times in the pelvic and upper-leg positions were reduced and isotropic submillimeter voxel volumes were acquired in the lower-leg position. To achieve this, sensitivity encoding and random central-k-space segmentation in a centric filling order were applied. Results with this technique were compared with those with midstream aortic digital subtraction angiography (DSA) (as the reference standard) and conventional MR angiography in 15 patients with peripheral vascular disease. The results show that sensitivity-encoded MR angiography demonstrates increased diagnostic accuracy in comparison to that with conventional MR angiography and depicts more open infragenual arterial segments compared with both midstream aortic DSA and conventional MR angiography.

MR angiography with gadofosveset trisodium for peripheral vascular disease: phase II trial

PURPOSE

To evaluate the dose response and safety of gadofosveset trisodium-enhanced magnetic resonance (MR) angiography compared with nonenhanced two-dimensional time-of-flight MR angiography and with x-ray angiography as the standard.

MATERIALS AND METHODS

In this randomized, 20-center, double-blind study, 238 men and women who had peripheral vascular disease or were suspected of having it received intravenous injection of placebo or gadofosveset (0.005, 0.01, 0.03, 0.05, or 0.07 mmol per kilogram of body weight). MR angiographic images were evaluated by three blinded readers, and x-ray angiographic images were evaluated by two readers. Hypothesis testing for the presence of a dose response was based on a linear test for trend for increase in area under the receiver operating characteristic curve as a function of dose for each reader of MR angiographic images independently.

RESULTS

Gadofosveset administration resulted in a dose-dependent increase in diagnostic accuracy for detection of aortoiliac occlusive disease as reflected in the area under the receiver operating characteristic curve for each reader (P <.001). The plateau in effectiveness improvement began at the 0.03 mmol/kg dose. At doses of 0.03 mmol/kg and higher, gadofosveset-enhanced MR angiography provided an approximate 20% increase in accuracy over nonenhanced MR angiography for diagnosis of clinically significant aortoiliac occlusive disease. Gadofosveset exhibited a good safety profile in all dose groups. Three serious adverse events were possibly or probably related to gadofosveset administration. There were no dose-related trends in severe or serious adverse events in patients receiving gadofosveset.

CONCLUSION

A dose of 0.03 mmol/kg of gadofosveset was safe and effective for evaluation of aortoiliac occlusive disease with MR angiography.

Lower extremity arterial disease. Diagnostic aspects

The prevalence of peripheral arterial disease (PAD) continues to increase, with recent data suggesting that almost 30% of patients in at-risk populations have PAD. Interest in the management of PAD has increased, partly secondary to the technologic advancement of devices and procedures capable of treating a wide array of vascular disorders via endoluminal techniques. A thorough clinical evaluation and accurate noninvasive testing remain the cornerstones of successful patient management and will promote improved outcomes through better patient selection. The utility of physiologic tests for determination of the presence and severity of PAD and more sophisticated imaging studies will allow the cardiovascular specialist to make appropriate decisions about management options. The currently accepted methods for determining the presence of PAD include a historic review of patient symptoms and atherosclerotic risk factors, physical examination, and the appropriate use of noninvasive modalities and X-ray digital subtraction angiography.

Contrast-enhanced 3D MRA of the aortoiliac and infrainguinal arteries when conventional transfemoral arteriography is not feasible

PURPOSE

To evaluate whether contrast-enhanced 3-dimensional (3D) magnetic resonance angiography (MRA) can substitute for transaxillary or transbrachial catheter access when angiography via the transfemoral route is not possible.

METHODS

Contrast-enhanced 3D MRA was performed in 14 patients (12 men; mean 66.1 +/- 12.4 years, range 48-98) with atherosclerotic disease of the aorta or lower extremities in whom conventional transfemoral arteriography was not feasible. The images were evaluated for their ability to identify and characterize lesions directly responsible for the patient's symptoms, adequately depict the vascular anatomy for therapy planning, and identify additional lesions not directly responsible for the patient's symptoms. The arterial system was divided into 15 segments, and image quality and the presence of occlusive disease were determined.

RESULTS

MRA adequately depicted 387 (95%) of 406 arterial segments in 14 patients. Nineteen (5%) arterial segments were inadequately delineated because of low signal intensity distal from severe stenoses (n = 11), venous overlap (n = 6), or metallic clip-induced signal voids (n = 2). The lesions directly responsible for the patients' symptoms were identified in all 14 patients (2 aortic occlusions [Leriche's syndrome] and 12 iliac occlusions or severe stenoses). Visualization of the vascular anatomy was adequate for therapy planning in 13 of 14 patients, and 3D MRA satisfactorily identified other lesions not directly responsible for the current symptoms.

CONCLUSIONS

When transfemoral catheter angiography of the aortoiliac and lower extremities is not feasible, contrast-enhanced 3D MRA is suitable for determining and planning therapy and can be used instead of angiography via the transaxillary or transbrachial routes.

Contrast enhanced MR angiography in the assessment of relevant stenoses in occlusive disease of the pelvic and lower limb arteries: diagnostic value of a two-step examination protocol in comparison to conventional DSA

INTRODUCTION/OBJECTIVES

Contrast-enhanced MRA (ce-MRA) has been claimed by many authors as a replacement of conventional angiography evaluating peripheral arterial occlusive disease. However, reliable detection of relevant stenoses (>70%) has to be provided for planning vascular interventions. Only few data in the literature focuses on this crucial problem. The purpose of this study was to evaluate this topic using a two-step body-coil-based MRA protocol.

METHODS AND PATIENTS

Forty three patients presenting with 82 stenoses >/=50% and 61 stenoses >70% on conventional catheter angiogram received fast Gadolinium-DTPA-enhanced high resolution 3D MR angiography at 1.5 T covering the pelvic and peripheral vascular tree in two examination steps using the body-coil. The data were evaluated double-blinded by three readers distinguishing moderate (50-70%) from severe stenoses (>70%).

RESULTS

Overall sensitivity/specificity/accuracy was 84/60/70% evaluating 143 segments. Specificity was rather poor in the iliac (58%) and crural (50%) region and moderate in the femoral and popliteal level (73%). The negative predictive value ranged between 78 and 91%. The grade of stenosis tend to be overestimated rather than underestimated in all levels with positive predictive values between 55 and 78%.

DISCUSSIONS AND CONCLUSIONS

Body-coil-based contrast-enhanced MRA has limited potential in distinguishing moderate from severe stenoses in peripheral occlusive disease. Overestimations are more common than underestimations. Both occur mainly in small-sized crural arteries but also in larger iliac arteries where vessel course in partition direction may cause inadequacy between voxel size and lumen diameter in severe stenosis.

Lower extremity MR angiography: universal retrofitting of high-field-strength systems with stepping kinematic imaging platforms initial experience

In 15 volunteers and 84 patients with clinically suspected peripheral vascular disease, a stepping kinematic imaging platform, a manual retrofit stepping magnetic resonance (MR) imaging table, was used with three high-field-strength MR imaging systems to perform multistation peripheral contrast material-enhanced MR angiography in the lower extremity with the existing system phased-array coil. Each examination was performed in less than 45 minutes. Mounting of the stepping kinematic imaging platform was quick and simple and allowed rapid repositioning of a patient relative to the phased-array coil and acquisition of high-spatial-resolution MR angiograms of the peripheral vasculature with use of one injection of MR imaging contrast agent.

Separation of arteries and veins using flow-induced phase effects in contrast-enhanced MRA of the lower extremities

In 3-D contrast-enhanced magnetic resonance (MR) angiography of the lower extremities the goal is most often to enhance arterial structures while keeping veins and surrounding tissue unenhanced. Imaging during steady-state concentration of a blood pool agent or during poor timing of an extra-cellular contrast medium may result in simultaneous venous enhancement, making interpretation of the angiogram difficult. The aim of this study was to develop a post-processing method to separate the arteries from the veins in standard contrast-enhanced MR angiograms. The method was based on the different accumulation of flow-induced phase in the arteries and veins of the lower extremities. The method was tested in both phantom experiments and volunteers undergoing 3-D contrast-enhanced MR angiography using both an extra-cellular contrast medium and a blood pool agent. In the phantom studies, opposite directional flow was successfully separated at mean flow velocities as low as 9 cm/s. In the volunteer studies, the larger veins were successfully extinguished while the larger arteries were left unaffected. In smaller vessels with low flow velocities the separation was less successful. This was most apparent in vessels not oriented superior-inferior. The method developed here is promising for separating arteries from veins in contrast-enhanced MR angiography although the results could be further improved by either a different pulse sequence design or combining this method with other segmentation methods.

Nonneurologic indications for MRI. Technological advances have broadened applications

Traditionally used for neurologic indications, magnetic resonance imaging (MRI) is now being used to diagnose the most common musculoskeletal, vascular, hepatic, biliary, adrenal, and renal disorders. Drs Schnitker and Light discuss the nonneurologic indications for MRI as both a primary and an adjunct study. The advantages and disadvantages of fast scanning and open MRI are also presented.

Anatomically tailored k-Space sampling for bolus-chase three-dimensional MR digital subtraction angiography

The purpose of this study was to evaluate a variable k-space sampling method for bolus-chase three-dimensional magnetic resonance digital subtraction angiography in the arterial system from the abdomen to the calf. Imaging time was minimized by tailoring the acquisition according to the vascular anatomy of the station. For images obtained in 30 patients, results with the modified protocol were compared to those with the previously published protocol. For all stations, significant improvement (P <.001) was found with the modified protocol.