Cuff-compression of the proximal calf to reduce venous contamination in contrast-enhanced stepping-table magnetic Resonance angiography

The Effects of a 4-Layer Compression Bandaging System on Skin Perfusion Pressure in Healthy Adults

OBJECTIVE

Current practice precludes compression in patients with wounds and reduced arterial flow; however, this treatment may reduce edema and vascular resistance, thus improving distal circulation. The objective of this study was to determine the effects of compression on skin perfusion pressure (SPP), edema, and ankle range of motion.

DESIGN

This was a quasi-experimental time series.

SETTING

The study was conducted at The Center for Skin Integrity in Cheektowaga, New York.

PARTICIPANTS

The study participants were 20 healthy adults, 10 in a younger age bracket (22.10 [SD, 2.77] years, 23.14 [SD, 5.03] kg/m) and 10 in an older age bracket (55.90 [SD, 4.48] years, 28.84 [SD, 4.83] kg/m).

INTERVENTIONS

Sixty minutes of Profore Multi-layer Compression was performed.

MAIN OUTCOME MEASURES

Precompression and postcompression measurements: SPP, Ankle Brachial Index, calf circumference (15 cm proximal to lateral malleolus), and static and dynamic ankle dorsiflexion range of motion (DF ROM) compared between young and older adults.

MAIN RESULTS

There was a significant main effect for time for SPP (P = .049) and static (P = .02) and dynamic (P = .03) DF ROM. Skin perfusion pressure significantly increased at 40, 50, and 60 minutes of compression compared with precompression. Static and dynamic DF ROM significantly increased from precompression to postcompression. Although not statistically significant, calf circumference decreased by 6 cm in the older-adult group postcompression.

CONCLUSION

A 4-layer compression dressing system improved SPP; this may be secondary to the decongestion of a proximal confined space. The 4-layer compression dressing also improves DF ROM postcompression and may reduce lower-extremity edema. Seeing these results in healthy participants suggests the need for future research in a patient population to determine if compression can be used to offload arterial structures and thus promote wound healing in patients.

Contrast-enhanced peripheral MRA: technique and contrast agents

In the last decade contrast-enhanced magnetic resonance angiography (CE-MRA) has gained wide acceptance as a valuable tool in the diagnostic work-up of patients with peripheral arterial disease. This review presents current concepts in peripheral CE-MRA with emphasis on MRI technique and contrast agents. Peripheral CE-MRA is defined as an MR angiogram of the arteries from the aortic bifurcation to the feet. Advantages of CE-MRA include minimal invasiveness and lack of ionizing radiation. The basic technique employed for peripheral CE-MRA is the bolus-chase method. With this method a paramagnetic MRI contrast agent is injected intravenously and T1-weighted images are acquired in the subsequent arterial first-pass phase. In order to achieve high quality MR angiograms without interfering venous contamination or artifacts, a number of factors need to be taken into account. This includes magnetic field strength of the MRI system, receiver coil configuration, use of parallel imaging, contrast bolus timing technique, and k-space filling strategies. Furthermore, it is possible to optimize peripheral CE-MRA using venous compression techniques, hybrid scan protocols, time-resolved imaging, and steady-state MRA. Gadolinium(Gd)-based contrast agents are used for CE-MRA of the peripheral arteries. Extracellular Gd agents have a pharmacokinetic profile similar to iodinated contrast media. Accordingly, these agents are employed for first-pass MRA. Blood-pool Gd-based agents are characterized by prolonged intravascular stay, due to macromolecular structure or protein binding. These agents can be used for first-pass, as well as steady-state MRA. Some Gd-based contrast agents with low thermodynamic stability have been linked to development of nephrogenic systemic fibrosis in patients with severe renal insufficiency. Using optimized technique and a stable MRI contrast agent, peripheral CE-MRA is a safe procedure with diagnostic accuracy close to that of conventional catheter X-ray angiography.

Time-resolved bolus-chase MR angiography with real-time triggering of table motion

Time-resolved bolus-chase contrast-enhanced MR angiography with real-time station switching is demonstrated. The Cartesian acquisition with projection reconstruction-like sampling (CAPR) technique and high 2D sensitivity encoding (SENSE) (6x or 8x) and 2D homodyne (1.8x) accelerations were used to acquire 3D volumes with 1.0-mm isotropic spatial resolution and frame times as low as 2.5 sec in two imaging stations covering the thighs and calves. A custom real-time system was developed to reconstruct and display CAPR frames for visually guided triggering of table motion upon passage of contrast through the proximal station. The method was evaluated in seven volunteers. High-spatial-resolution arteriograms with minimal venous contamination were consistently acquired in both stations. Real-time stepping table contrast-enhanced MR angiography is a method for providing time-resolved images with high spatial resolution over an extended field-of-view.

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.

Clinical experience in timed arterial compression contrast-enhanced magnetic resonance angiography of the hand

PURPOSE

A retrospective analysis of the diagnostic performance of the timed arterial compression (TAC) technique, which allows freezing of the contrast bolus during first-pass contrast-enhanced (CE) magnetic resonance angiography (MRA) to diagnose vascular pathologies in the hand.

MATERIAL AND METHODS

A total of 14 consecutive CE-MRAs of the hand were acquired by using the TAC technique. By inflating a blood pressure cuff up to 200 mm Hg triggered to the arterial contrast filling of the hand, prolonged measurement times up to 144 seconds, with a spatial resolution of 0.59 × 0.59 × 0.8 mm(3), could be realized. Overall image qualities, arterial signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and vessel conspicuity besides the final diagnosis were evaluated.

RESULTS

All 14 TAC-CE-MRAs of the hand were successfully accomplished without any adverse events and yielded, in all cases, a final diagnosis with a high total number of vascular pathologies (57). High arterial SNR and CNR values exceeding the soil of 85 and 60, respectively, resulted. Thus, overall vessel visibility (>90%), vessel conspicuity (mean Δ signal intensity [SI]/mm = 1,193) and image quality on a per patient level (>60%) were rated as excellent or good.

CONCLUSIONS

TAC-CE-MRA of the hand offers high diagnostic performance because of its increased spatial resolution while preserving contrast, which allowed detection of tiny stenoses of the digital arteries.

Whole-body MR angiography with body coil acquisition at 3 T in patients with peripheral arterial disease using the contrast agent gadofosveset trisodium

RATIONALE AND OBJECTIVES

Whole-body magnetic resonance angiography (WB-MRA) at 3 T with body coil acquisition has not previously been investigated. In this study, WB-MRA was performed in this manner using the blood pool contrast agent gadofosveset trisodium.

MATERIALS AND METHODS

Eleven consecutive patients (five men, six women) with symptomatic peripheral arterial disease (two with critical limb ischemia, nine with claudication) were examined. Conventional digital subtraction angiography (DSA) of the aorta and the inflow and runoff arteries was used as the reference method. WB-MRA was performed using four slightly overlapping stations covering the arteries from the neck to the ankles. The arterial system was divided into 42 segments that were analyzed for the presence of significant arterial disease (> or =50% luminal narrowing or occlusion) by two blinded observers.

RESULTS

Sensitivities for detecting a significant arterial lesion with WB-MRA using gadofosveset as the contrast agent were 0.66 (95% confidence interval [CI], 0.49-0.79) and 0.68 (95% CI, 0.52-0.81) for the two observers. Specificities were 0.82 (95% CI, 0.74-0.88) and 0.93 (95% CI, 0.87-0.96), respectively. Intermodality agreement between WB-MRA and DSA was moderate to good, with overall kappa values of 0.44 (95% CI, 0.29-0.59) and 0.63 (95% CI, 0.5-0.77) for the two observers. Interobserver agreement for WB-MRA was good, at kappa = 0.60 (95% CI, 0.50-0.71).

CONCLUSION

WB-MRA at 3 T with body coil acquisition in patients with peripheral arterial disease showed good reproducibility but only moderate to good agreement with DSA. Further assessment of the method's clinical application is warranted.

Intra-arterial MR-angiography on an open-bore MR-scanner compared to digital-subtraction angiography of the infra-popliteal runoff in patients with peripheral arterial occlusive disease

PURPOSE

To evaluate the diagnostic value of contrast-enhanced intra-arterial 3D-MR-angiography (IA-MRA) of the infra-popliteal arteries in an open-bore magnet. Number, severity of arterial lesions, and artefacts were compared to routinely performed intra-arterial digital-subtraction angiography (IA-DSA) in patients suffering from symptomatic peripheral arterial occlusive disease (PAOD).

MATERIAL AND METHODS

Fifteen patients admitted for PAOD underwent percutaneous transluminal angioplasty (PTA) by IA-DSA. After PTA, IA-MRA of the infra-popliteal station was performed on an open-bore 1.5T MR-scanner applying a low dose intra-arterial contrast-enhanced 3D-gradient-echo-MRA with gadopentate dimeglumine. The reading was performed by three blinded readers distinguishing moderate (< or =50%), significant stenoses (51-99%) and vessel occlusions. Imaging artefacts were recorded and binary classified as not disturbing or compromising the observation of the arterial tree.

RESULTS

Overall IA-DSA revealed 36 moderate stenoses (< or =50%), 38 significant stenoses (51-99%), and 10 vessel occlusions. For the detection of significant stenoses and occlusions, the overall sensitivity, specificity, positive predictive value, negative predictive value and accuracy of IA-MRA were 96%, 83%, 88%, 94% and 90%. The only observed artefact was venous overlay in four stations. The readout was not hampered in any case.

CONCLUSION

Intra-arterial contrast-enhanced 3D-gradient-echo-MRA on an open-bore MR-scanner offers an acceptable diagnostic accuracy in diagnosing peripheral arterial occlusive disease in the infra-popliteal region and correlates well with DSA.

MR angiography with blood pool contrast agents

Contrast-enhanced magnetic resonance angiography (CE-MRA) with standard extracellular contrast material is well established for vascular imaging. Recently, the first blood pool contrast agent (BPA) has become clinically available. This paper reviews characteristics and classification of BPA as well as first clinical experience in various vascular territories. BPAs comprise gadolinium-based compounds, synthetic compounds, and ultrasmall superparamagnetic iron-oxide (USPIO) particles. Such BPAs are retained in blood with a prolonged time-window of enhancement as compared to extracellular gadolinium chelates. Promising results from USPIO at first-pass and steady-state angiography have been published, but no USPIO is approved yet. Gadofosveset is the first clinically approved BPA. After bolus injection, gadofosveset binds noncovalently to serum-albumine, thus enhancing relaxivity. First published results from carotid, coronary, renal, and peripheral angiography are encouraging; particularly helpful is prolonged enhancement during steady state. More BPAs have been clinically evaluated, but no approval has been granted. Bolus-injectable BPAs allow for first-pass CE-MRA similar to standard extracellular contrast media, but with higher relaxivity, allowing lower doses and reduced injection rates. An additional feature of BPA is the steady-state phase with a broad time window enabling high-resolution angiography or double-gated angiography of coronary arteries to compensate for the complex motion pattern.

Technical inadequacies of peripheral contrast-enhanced magnetic resonance angiography: incidence, causes and management strategies

AIM

To assess the incidence, causes and effects of technical inadequacies in peripheral contrast-enhanced magnetic resonance angiography (CE-MRA) and to discuss relevant management strategies.

MATERIALS AND METHODS

A retrospective analysis of 249 peripheral CE-MRA examinations was performed using the radiology department's RIS/PACS (radiology information system/picture archiving and communication system) database. All failed or technically inadequate MRAs were reviewed. In cases that underwent further imaging by conventional angiography (CA), we assessed if relevant arterial disease had been masked on the MRA.

RESULTS

Of the 249 examinations, 215 (86.3%) were technically satisfactory while 34 (13.7%) were a combination of technical inadequacies [29 cases (11.6%)] and examination failures [five cases (2%)]. The causes of technical inadequacies were: (1) venous contamination (13 cases; 5.2%), (2) motion-induced subtraction artefact (eight cases; 3.2%), (3) stent-induced artefact (four cases; 1.6%), (4) inadequate scan coverage (two cases; 0.8%), and (5) contrast timing error (two cases; 0.8%). The causes of failed examinations were: (1) inability to tolerate lying in the scanner (three cases; 1.2%) and (2) inability to fit into the scanner (two cases; 0.8%). Fifteen (44.1%) of the 34 cases underwent further imaging by CA, and in eight of these there was significant arterial disease that was missed on the MRA.

CONCLUSION

Technical inadequacies occur in a small but significant proportion of peripheral CE-MRAs and can mask significant arterial disease. Knowledge of the potential causes of technical problems and the relevant management options is important for quality assurance and for limiting the need for an alternative investigation.

MR angiography of the hand with subsystolic cuff-compression optimization of injection parameters

OBJECTIVE

The purpose of our study was to assess the impact of various injection rates on contrast-enhanced high-resolution 3D MR angiography of the hand.

MATERIALS AND METHODS

Ten healthy individuals (mean age, 24.4 years; range, 20-27 years) underwent 3D contrast-enhanced MR angiography of both hands. Starting 3 minutes before data acquisition, subsystolic upper arm cuff compression was applied unilaterally. A 1.5-T whole-body scanner with 3D gradient-echo sequence was used. Seven data sets (20 seconds) were obtained consecutively. I.v. contrast material of 0.1 mg/kg of body weight of gadobutrol was injected at rates of 0.5, 1.0, and 1.5 mL/s. For both hands, quantitative data evaluation was performed with contrast-to-noise ratio (CNR) in the radial, ulnar, palmar, and digital arteries and veins. Qualitative assessment of the arterial visualization score and venous contamination score was rated by two experienced radiologists using a 4-point scale.

RESULTS

The lowest venous contamination score (CNR and reviewers' assessment) was observed with an injection rate of 0.5 mL/s (p < 0.05). For the arterial signal, the reviewers' assessment was that an injection rate of 0.5 mL/s was best (p = 0.08). Compression yielded a significantly lower venous contamination score for the compressed side than for the noncompressed side for flow rates of 0.5 mL/s and 1.0 mL/s (p < 0.05).

CONCLUSION

Image quality of hand MR angiography was better with cuff compression. A flow rate of 0.5 mL/s yielded a good CNR and a significantly lower venous contamination score than the other flow rates.

High-spatial-resolution multistation MR angiography with parallel imaging and blood pool contrast agent: initial experience

The purpose of this study was to prospectively evaluate the diagnostic accuracy of reader detection of 75% or greater stenosis at high-spatial-resolution multistation magnetic resonance (MR) angiography performed with matrix coils and a blood pool contrast agent. Ten healthy volunteers and 10 patients were examined. All participants provided informed consent to participate in this institutional review board-approved study. For contrast agent-enhanced multistation MR angiography, an albumin-binding gadolinium chelate, gadofosveset trisodium, was used. Imaging was performed during the first-pass and steady-state phases of the contrast agent. Vessel conspicuity on the first-pass MR angiograms obtained in both volunteers and patients was rated as excellent for 93% of vessels. At steady-state imaging, vessel conspicuity was rated as excellent or good for 89% of vessels. Gadofosveset trisodium-enhanced MR angiography yielded sensitivities of 100% and 97% and specificities of 96% and 97% for detection of significant disease in the carotid and lower extremity arteries, respectively.

Magnetic resonance angiography of abdominal and lower extremity vasculature

Magnetic resonance angiography (MRA) has evolved over the past years from an experimental imaging modality to a technique that is now widely applied in clinical practice. This article reviews the fundamentals of the different magnetic resonance angiographic techniques and how they can be applied for abdominal and peripheral arterial imaging. Currently, contrast-enhanced magnetic resonance angiography (CE-MRA), whereby a luminogram is obtained during initial arterial passage of contrast material, is the most widely used technique. With current hardware and software, high-spatial resolution images of the abdominal aorta and proximal visceral branches can be obtained that are equivalent to intra-arterial digital subtraction angiography (IA-DSA). High-quality imaging of the renal arteries demands isotropic voxels and reformations orthogonal to the vessel axis for evaluation. Contrast-enhanced magnetic resonance angiography of the peripheral vascular tree is now a highly accurate technique and has replaced diagnostic intra-arterial digital subtraction angiography and duplex ultrasonography in many hospitals.