MR angiography of the abdominal aorta and peripheral vessels

Noninvasive Testing in Peripheral Arterial Disease

Most patients suspected of having peripheral arterial disease should undergo noninvasive vascular testing to confirm the diagnosis, and to determine the severity and extent of the disease. This article reviews practical aspects of commonly used noninvasive tests for lower extremity peripheral arterial disease, including the ankle-brachial index, segmental limb pressures, pulse volume recordings, duplex ultrasonography, computed tomography angiography, and magnetic resonance angiography.

Dealing with vascular conundrums with MR imaging

Magnetic resonance (MR) imaging is a robust imaging modality for evaluation of vascular diseases. Technological advances have made MR imaging widely available for accurate and time-efficient vascular assessment. In this article the clinical usefulness of MR imaging techniques and their application are reviewed, using examples of vascular abnormalities commonly encountered in clinical practice, including abdominal, pelvic, and thoracic vessels. Common pitfalls and problem solving in interpretation of vascular findings in body MR imaging are also discussed.

Comparison of ventilation-perfusion scintigraphy with MR angiography in patients with Swyer-James syndrome

PURPOSE

The aim of this study was to establish the value of magnetic resonance angiography (MRA) in diagnosing) Swyer-James syndrome (SJS) and to compare MRA and ventilation-perfusion (V/Q) scan results in patients with established SJS.

METHODS

The V/Q scans and the MRA findings of 22 lungs of 11 patients with SJS (6 males, 5 females; age range: 17-69 years, mean: 38.4 years) were retrospectively studied. The perfusion scan was performed after the injection of Tc macroaggregated albumin. After 2 days, the ventilation scan was performed by using Tc diethylene triamine penta-acetic acid aerosol. The MRA was performed with a 1.5 T magnetic resonance unit. We compared the MRA and V/Q scan findings of the lungs of the patients.

RESULTS

The V/Q scans showed the characteristic pattern of a matched V/Q defect on the affected lungs. The MRA displayed a smaller pulmonary artery and markedly poor peripheral vasculature on the affected side in all patients. The MRA had a sensitivity of 84.6%, a specificity of 100% for the detection SJS. Interobserver variability was minimum as indicated by a weighted kappa statistic of 0.818.

CONCLUSION

This study indicates that the MRA is a fast, accurate, without radiation, and noninvasive technique for supporting the diagnosis of SJS. But, V/Q scans showed additional segmental perfusion/ventilation abnormalities on contralateral lung to reveal the segmental involvement of SJS. As a result, the MRA has no more any extra advantages for patient management.

Pulmonary arterial hypertension: an imaging review comparing MR pulmonary angiography and perfusion with multidetector CT angiography

Pulmonary hypertension (PH) is a progressive disease that leads to substantial morbidity and eventual death. Pulmonary multidetector CT angiography (MDCTA), pulmonary MR angiography (MRA) and MR-derived pulmonary perfusion (MRPP) imaging are non-invasive imaging techniques for the differential diagnosis of PH. MDCTA is considered the gold standard for the diagnosis of pulmonary embolism, one of the most common causes of PH. MRA and MRPP are promising techniques that do not require the use of ionising radiation or iodinated contrast material, and can be useful for patients for whom such material cannot be used. This review compares the imaging aspects of pulmonary MRA and 64-row MDCTA in patients with chronic thromboembolic or idiopathic PH.

Diabetes revealed: multisystem danger

OBJECTIVE

The purpose of this article is to review the role of diagnostic imaging in the evaluation of women with diabetes.

CONCLUSION

Diabetic patients present a challenging population for the performance of various imaging studies and special considerations need to be made to obtain adequate studies. Imaging plays a significant role in assessing the multisystem morbidity of diabetes. Furthermore, diabetes in women may have some unique features and consequences and imaging studies can aid in the correct management of these patients.

High-resolution 3D contrast-enhanced MRA with parallel imaging techniques before endovascular interventional treatment of arterial stenosis

This study aimed to evaluate the efficacy of high-resolution 3D contrast-enhanced magnetic resonance angiography (3D CE MRA) with parallel imaging techniques for the diagnosis of various arterial stenoses and its value for planning endovascular interventional treatment. Thirty-five patients underwent 3D CE MRA before endovascular interventional treatment. Numbers of patients were as follows: clinically documented renal artery stenosis (n = 10), renal transplant artery stenosis (n = 1), carotid artery stenosis (n = 12), iliac artery stenosis (n = 11) and femoro-popliteal artery stenosis (n = 1). A total of 39 arterial segments were treated. The depiction of various arterial stenoses was evaluated. The degree and length of the stenoses were compared and analyzed between 3D CE MRA and digital subtraction angiography (DSA). The accuracy of MRA in depicting lesion characteristics (ulceration, eccentricity, post-stenotic dilatation) was reviewed. The overall value of 3D CE MRA in planning interventional treatment was determined. The quality of 3D CE MRA in the demonstration of various arterial stenoses was judged excellent or good. A strong correlation was noted between 3D CE MRA and DSA regarding severity and length of stenosis. The accuracy of 3D CE MRA in depicting lesion characteristics was good. 3D CE MRA overestimated three severe iliac artery stenoses. Except in these three segments, the value of 3D CE MRA analysis was judged high. 3D CE MRA was found to be better than DSA in revealing the distal reconstitution and occluded segment in cases of iliac artery stenosis. 3D CE MRA is accurate in demonstrating the relevant anatomy necessary to plan endovascular interventional treatment for patients with arterial stenosis.

Ghost magnetic resonance angiography

Traditional methods for magnetic resonance angiography (MRA) involve the radiofrequency excitation of vascular spins within a selected region of tissue, followed by gradient localization and imaging of those spins within that same region. Signals that unfaithfully localize within the imaging volume, so-called "ghost artifacts", have historically been considered undesirable since they degrade image quality and every effort is made to suppress them. To the contrary, we hypothesized that these ghost artifacts could be manipulated to create detailed angiograms of the human body. In this initial demonstration of the method, which we call "Ghost MRA," we show that the human arterial system can be depicted with exquisite anatomic detail and near total suppression of background signal. Moreover, unlike alternative unenhanced methods, Ghost MRA can be acquired without the need for cardiac synchronization.

Contrast-enhanced MRA of the renal and aorto-iliac-femoral arteries: comparison of gadobenate dimeglumine and gadofosveset trisodium

RATIONALE AND OBJECTIVES

Dedicated contrast agents are now available for contrast-enhanced magnetic resonance angiography (CE-MRA). This study retrospectively compares the safety and diagnostic performance data from Phase III regulatory trials performed to evaluate gadobenate dimeglumine (MultiHance(®)) and gadofosveset trisodium (Vasovist®)) for renal and peripheral CE-MRA.

MATERIALS AND METHODS

Similar examination and blinded assessment methodology was utilized in all studies to determine the safety and diagnostic performance of the agents for detection of significant (>50%) steno-occlusive disease. Digital Subtraction Angiography (DSA) was used as the standard of truth. Diagnostic performance data (sensitivity, specificity, predictive values [PVs], and likelihood ratios [LRs]) were compared (Chi-square test).

RESULTS

CE-MRA with gadobenate dimeglumine was more specific (92.4% vs. 80.5%, p < 0.0001) and accurate (83.6% vs. 77.1%, p = 0.022) than CE-MRA with gadofosveset in the detection of significant renal artery stenosis. The average sensitivity was higher for gadofosveset (74.4% vs. 67.3%, p = 0.011) in peripheral vessels although gadobenate dimeglumine was more specific (93.0% vs. 88.2%, p < 0.0001) with no difference in accuracy (86.6% vs. 86.3%, p = 0.66). PPVs were higher (p < 0.0001) for gadobenate dimeglumine in both vascular territories. Pre- to post-test shifts in the probability of detecting significant disease were greater after gadobenate dimeglumine. Adverse events in the renal and peripheral studies were reported by 9.2% and 7.7% of patients after gadobenate dimeglumine compared with 30.3% and 22.1% of patients after gadofosveset.

CONCLUSION

The diagnostic performance of CE-MRA for the detection of significant steno-occlusive disease is similar with gadofosveset and gadobenate dimeglumine although the rate of adverse events appears higher with gadofosveset.

Gadolinium-enhanced off-resonance contrast angiography

We describe a novel physical basis and methodology for gadolinium (Gd)-enhanced MRA, which we call "off-resonance contrast angiography" (ORCA). Unlike standard contrast-enhanced (CE) MR angiography (MRA), ORCA contrast depends not on T(1) but on Gd-induced shifts in intravascular resonance frequency due to the bulk magnetic susceptibility (BMS) effects of Gd. The method was tested at 3 Tesla in phantoms with a range of dilutions of Gd-DTPA and ultrasmall iron oxide contrast agent (CA). With the use of ORCA, complete background suppression was obtained without image subtraction. As a result, catheters filled with various Gd dilutions proved to be highly conspicuous in ORCA projection images. This feature may make ORCA particularly attractive for passive catheter tracking during MR-guided endovascular procedures. Gd-induced intravascular frequency shifts were measured in human subjects and found to be in the expected range. ORCA was used to create angiograms of forearm veins that were comparable in quality to standard CE-MRA. In addition, ORCA images of the extracranial carotid bifurcation were successfully acquired during intravenous contrast administration. However, significant technical restrictions also exist, including a dependence on vessel orientation with respect to B(0), and sensitivity to static field inhomogeneities. Further study is needed to determine the practicality and potential clinical utility of this method.

Advances in vascular imaging

Advances in vascular surgery have mirrored advances in diagnostic imaging. Indeed, the endovascular revolution has been made possible largely by advances in computed tomography, magnetic resonance imaging, and vascular ultrasound. As technology allows better noninvasive vascular diagnosis, conventional angiography, once the gold standard for the diagnosis of vascular disease, is now reserved largely for intervention. This article discusses the current state of vascular imaging. Specific emphasis is placed on the comparative clinical utility of different imaging modalities in the detection and management of vascular disease.

3D contrast-enhanced MR angiography

Safe, fast, accurate contrast arteriography can be obtained utilizing gadolinium (Gd) and 3D MR data acquisition for diagnosing vascular diseases. Optimizing contrast enhanced MRA (CE MRA), however, requires understanding the complex interplay between Gd injection timing, the Fourier mapping of 3D MR data acquisition and a multitude of parameters determining resolution, anatomic coverage, and sensitivity to motion artifacts. It is critical to time the bolus peak to coincide with central k-space data acquisition, which dominates image contrast. Oversampling the center of k-space allows reconstruction of multiple 3D acquisitions in rapid succession to time-resolve the passage of the contrast bolus. Parallel imaging increases resolution, shortens scan time and compresses the center of k-space into a shorter period of time, thereby minimizing motion and timing artifacts. Absence of ionizing radiation allows MRA to be repeated and combined with additional sequences to more fully characterize anatomy, flow, and physiology. Utilizing stepping table technology and thigh compression, whole body MRA is possible with a single contrast injection. As MR technology continues to advance, CE MRA becomes better and simpler to perform, increasing its efficacy in the diagnosis and management of vascular diseases.

Whole-body three-dimensional contrast-enhanced magnetic resonance (MR) angiography with parallel imaging techniques on a multichannel MR system for the detection of various systemic arterial diseases

Using a 1.5-T magnetic resonance (MR) imager equipped with 32 receiving channels and integrated parallel acquisition techniques, 37 patients underwent whole-body three-dimensional (3D) contrast-enhanced MR angiography (WB 3D CE MRA). The patients included had clinically documented or suspected peripheral arterial occlusive disease (PAOD, n = 19), Takayasu arteritis (n = 8), polyarteritis nodosa (n = 1), type-B dissection (n = 4), thoracic and/or abdominal aneurysm (n = 5). Sixty-eight surface coils were employed to encompass the whole body. Four 3D CE MRA stations were acquired successively through automatic table moving. The spatial resolution was 1.6 x 1.0 mm and slice thickness was 1.5 mm for all stations. A total scan range of 188 cm was acquired. Overall image quality of each arterial segment and venous overlay were assessed. The depiction of various systemic arterial diseases was evaluated and compared, in 20 patients, with other imaging modalities. This WB 3D CE MRA yielded a detailed display of the arterial system with an average MR room time of 17.4 min. The image quality was considered diagnostic in 99.3% of the arterial segments. In 7 of 19 patients with PAOD, WB MRA showed additional vascular narrowing apart from peripheral arterial disease. In nine patients with vasculitis, WB MRA depicted luminal irregularity, narrowing or occlusion, aneurysm, and collateral circulation involving multiple vascular segments. WB MRA also clearly revealed the severity and extent of dissection and aortic aneurysm. In 20 cases where additional imaging investigations have been carried out, the vascular pathologies demonstrated by WB MRA agree with these additional imaging investigations.

Pulmonary Circulation: Contrast-enhanced 3.0-T MR Angiography—Initial Results

PURPOSE

To prospectively evaluate the technical feasibility of both high-spatial-resolution and time-resolved contrast material-enhanced magnetic resonance (MR) angiography of the pulmonary circulation at 3.0 T.

MATERIALS AND METHODS

All examinations were HIPAA compliant. After institutional review board approval and written informed consent, time-resolved and high-spatial-resolution three-dimensional contrast-enhanced MR angiography of the pulmonary circulation was performed with a 3.0-T MR system in 31 adults (13 men, 18 women; age range, 29-87 years old): 22 volunteers and nine patients (two with mediastinal masses, seven with pulmonary arterial hypertension [PAH]). The image quality of pulmonary arterial branches and parenchymal enhancement conspicuity were evaluated independently by two radiologists. The signal-to-noise ratio and quantitative analysis of perfusion parameters was performed. Statistical analysis of data was performed by using Wilcoxon rank sum test and two-sample Student t test, and interobserver variability was tested with kappa coefficient.

RESULTS

Visualization up to fourth-order pulmonary arterial branches was observed on time-resolved MR angiograms and that up to fifth-order branches was observed on high-spatial-resolution MR angiograms, with diagnostic-quality blood vessel definition and good interobserver agreement. Evaluation of parenchymal enhancement and semiquantitative analysis of perfusion parameters yielded dynamic information in all subjects. Comparative analysis of definition scores for fourth- and fifth-order pulmonary arterial branches, parenchymal enhancement, the time lag between the pulmonary arterial and parenchymal enhancement, and all of the calculated perfusion indices in patients with PAH showed statistically significant differences from volunteers (P < .05).

CONCLUSION

Three-dimensional contrast-enhanced MR angiography of the pulmonary circulation was feasible at 3.0 T and provided high vascular morphologic detail and dynamic functional information. Clearly detectable abnormalities were present in patients with PAH.

Scoutless stepping-table peripheral contrast-enhanced MR angiography

PURPOSE

To evaluate the feasibility of a scoutless method, termed EZ-STEP, for stepping-table peripheral contrast-enhanced magnetic resonance angiography (CE-MRA).

MATERIALS AND METHODS

This scoutless method involves the use of a stepping-table, fast 3D MRA acquisition that incorporates spatially nonselective radiofrequency (RF) pulses for excitation to reduce the repetition time (TR). The sequence was tested in a phantom. The EZ-STEP protocol was optimized in four healthy volunteers and used in 15 subjects. The image quality was scored in a blinded fashion and compared with conventional MRA in eight patients.

RESULTS

The acquisition speed of the EZ-STEP sequence was approximately 30% faster in the phantom study compared to the conventional MRA sequence. The total examination time for EZ-STEP was 6 minutes, compared to an average of 23 minutes for conventional MRA. The average image quality scores for EZ-STEP and conventional MRA for stations 1-3 were 3.50 vs. 3.06 (P = 0.087), 3.53 vs. 3.00 (P = 0.033), and 2.97 vs. 2.50 (P = 0.090), respectively.

CONCLUSION

EZ-STEP is a more efficient method than the conventional approach for stepping-table peripheral CE-MRA, and provides comparable or better image quality. This method shortens the examination time substantially and eliminates the risk of failing to image a vessel because of improper positioning of the scan volume.

Vascular imaging

Many rheumatic diseases affect the vasculature, either as a 'primary' manifestation of the disease process (as in vasculitis or scleroderma-spectrum disorders) or as a result of accelerated atherosclerosis. Recent years have seen very major developments in, and refinements of, vascular imaging methods. It is likely that this pace of development will continue, enhancing the rheumatologist's ability to diagnose different musculoskeletal conditions and follow their progression, using minimally invasive techniques. In this chapter, we describe these recent advances in vascular imaging techniques, concentrating on those most relevant to the practising clinician, but also discussing methods which are being used in clinical research. Three main groups of imaging modalities are described: large vessel imaging (X-ray, magnetic resonance (MR) and computed tomography (CT) angiography), nailfold microscopy and thermography. For each of these, the method(s) and then the clinical and research applications are discussed. Laser Doppler, a research technique, is also described.

Magnetic resonance angiography

MRA and MRI have become increasingly important diagnostic modalities in vascular surgery. The ability to obtain cross-sectional and angiographic images by these noninvasive and non-nephrotoxic modalities represents one of the most significant advances in vascular surgery over the past decade. We review the current status of MRI and MRA in vascular surgical practice.

Multidetector CT angiography of arterial inflow and runoff in the lower extremities: a challenge in data acquisition and evaluation

PURPOSE

To show the feasibility of acquiring homogenous 3-dimensional datasets with high temporal and spatial resolution from computed tomographic angiographic (CTA) scans of the lower extremities and to assess automated vessel-tracking techniques for vascular evaluation.

METHODS

Eighteen men (mean age 67.0 years, range 43-83) with aneurysmal or occlusive vascular diseases underwent contrast-enhanced CTA of the lower limb arteries utilizing a 16-row CT imager. Curved multiplanar reformations were generated by manual selection of vessel centerlines in the infrarenal aorta and the arterial vasculature in the pelvis, thigh, and calf based on volume-rendering techniques. For each vessel, opacification and depiction were quantitatively evaluated. The manually segmented images were compared to datasets processed with automated vessel-tracking strategies by 5 radiologists, who evaluated diagnostic reliability and image quality. A Differential Receiver Operating Characteristic (DROC) analysis was performed.

RESULTS

An increase in the temporal and spatial resolution led to acquisition of high quality CTA datasets. Significant homogeneity of the vascular contrast-to-noise ratios was achieved in the pelvic (coefficient of variance 1.5% to 10.1%), thigh (0.1% to 9.4%), and calf (3.3% to 19.2%) vessels. The assessment of vascular delineation revealed full-width-at-half-maximum contrast values of 96.4%, 95.5%, and 111.3% in the pelvis, thigh, and calf, respectively. Observers were not able to distinguish between manual and automated vascular segmentation, as represented by a 0.56 value for the area under the DROC curve.

CONCLUSIONS

High-resolution CTA lower extremity datasets were acquired successfully, presenting vascular signal intensities of high homogeneity suitable for automated vessel-tracking techniques. Automated 3D visualization tools produced reliable, reproducible, and time-efficient centerline extractions that were comparable to manually defined centerlines.