High-resolution gadolinium-enhanced 3D MRA of the infrapopliteal arteries. Lessons for improving bolus-chase peripheral MRA

ACR Appropriateness Criteria® Sudden Onset of Cold, Painful Leg: 2023 Update

Acute onset of a cold, painful leg, also known as acute limb ischemia, describes the sudden loss of perfusion to the lower extremity and carries significant risk of morbidity and mortality. Acute limb ischemia requires rapid identification and the management of suspected vascular compromise and is inherently driven by clinical considerations. The objectives of initial imaging include confirmation of diagnosis, identifying the location and extent of vascular occlusion, and preprocedural/presurgical planning. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Optimization of the contrast dose and injection rates in whole-body MR angiography at 3.0T

PURPOSE

To optimize the contrast agent dose and delivery rate used in a novel whole-body magnetic resonance angiography (MRA) protocol using a 3.0T MR scanner.

MATERIALS AND METHODS

Six groups of 20 consenting volunteers underwent whole-body MRA, with each group receiving a different contrast dose and contrast delivery rate. The arterial tree was divided into 16 segments and the image quality at each of the anatomical locations, covering the whole body, was assessed. Qualitative analysis was carried out using a scoring assessment of image quality, and quantitative assessments were performed by measuring contrast-to-noise (CNR) and a signal-to-noise (SNR) index.

RESULTS

Reducing the contrast dose from 40 mL to 25 mL was found to significantly increase the CNR in several vessels of interest in the arterial tree. There was also a significant increase in the qualitative image quality score (P < 0.001).

CONCLUSION

This study demonstrates that reducing the contrast dose at 3.0T can result in an increase in the CNR in the vessels of interest without significantly affecting the SNR.

Magnetic resonance angiography: current status in the planning and follow-up of endovascular treatment in lower-limb arterial disease

Magnetic resonance angiography (MRA) has become an established imaging modality in the management of lower-limb arterial disease, with emerging roles in treatment planning and follow-up. Contrast-enhanced MRA is now the most widely used technique with clinically acceptable results in the majority of patients. Difficulties in imaging and image interpretation are recognised in certain subgroups, including patients with critical limb ischaemia as well as patients with stents. Although newer contrast agents and refined imaging protocols may offer some solutions to these problems, this optimism is balanced by concerns about the toxicity of certain gadolinium chelates. Further development of interventional MRA remains one of the most significant challenges in the development of magnetic resonance imaging-guided peripheral vascular intervention. The status of MRA in managing patients with lower-limb arterial disease in current clinical practice is reviewed.

Accuracy of semiautomated analysis of 3D contrast-enhanced magnetic resonance angiography for detection and quantification of aortoiliac stenoses

OBJECTIVES

We sought to compare reproducibility and accuracy of semiautomated stenosis detection and quantification in 3D contrast-enhanced magnetic resonance angiography (CE-MRA) images with conventional evaluation of 3D CE-MRA in patients with peripheral arterial disease (PAD) by using intra-arterial digital subtraction angiography (IA-DSA) as standard of reference.

METHODS

Twenty-five patients with PAD underwent CE-MRA and IA-DSA. Three blinded observers independently evaluated CE-MRA datasets for stenoses in the aortoiliac region using semiautomated computer analysis. Semiautomated measurements were compared with conventional measurements of stenosis on CE-MRA datasets, as measured by 3 other independent observers blinded to all other measurements. Interobserver agreement was quantified using kappa (kappa) and intraclass correlation coefficients (ICCs). Sensitivity and specificity were determined for both semiautomated and conventional measurements.

RESULTS

Semiautomated measurements were successful in 124 of the 125 arterial segments. The sensitivity of semiautomated measurements was 89% for all observers; specificity varied between 87% and 89%. For conventional measurements of CE-MRA, sensitivity varied between 79% and 86%; specificity was between 86% and 96%. There was good interobserver agreement between all readers for semiautomated measurements (combined kappa for all 3 observers together = 0.78; ICC = 0.82), as well as for conventional measurements (combined kappa = 0.70; and ICC = 0.83). Differences between ICCs, combined kappa values, and accuracy of both measurements were not significant (all P > 0.05).

CONCLUSION

Semiautomated analysis of aortoiliac 3D CE-MRA has the same high accuracy for detection and quantification of stenoses as conventional readings of CE-MRA.

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.

Infragenual cuff-compression reduces venous contamination in contrast-enhanced MR angiography of the calf

PURPOSE

To reduce venous contamination at the calf level in three-dimensional contrast-enhanced MR angiography (CE-MRA) by applying continuous infragenual cuff-compression.

MATERIALS AND METHODS

Ten patients with clinically relevant peripheral arterial occlusive disease (PAOD) underwent dynamic three-dimensional CE-MRA of the calf. Six consecutive measurements were acquired with the first measurement serving as mask. Cuff-compression of 50 mmHg was attached below the knee. To allow intra-individual comparison, compression was applied unilaterally. The cuff was inflated three minutes before scanning and was continued throughout the MRA session. Venous contamination and arterial visualization scores were ranked using a five-point rating scale. Contrast-to-noise ratios (CNRs) of superficial enhancing calf-veins on the uncompressed and compressed calf sides were evaluated. An asymmetry index (AI) defined by CNR(mean) (uncompressed)/CNR(mean) (compressed) was introduced to describe the ratio in venous contrast agent supply between both sides quantitatively.

RESULTS

Three-dimensional CE-MRA of the calves demonstrated significantly lower superficial venous contamination scores (P < 0.004) and clearly improved arterial visualization (P < 0.009) on the compressed side. Additionally, AI values were larger than 1 (P < 0.02), indicating a higher contrast agent supply in the superficial veins on the uncompressed side.

CONCLUSION

Infragenual cuff-compression minimizes venous overlay in three-dimensional CE-MRA at calf level by reduction of contrast agent supply in the superficial veins.

Comparison of MR Angiography Versus Digital Subtraction Angiography as a Basis for Planning Treatment of Lower Limb Occlusive Disease

PURPOSE

To compare contrast-enhanced moving-bed magnetic resonance angiography (MRA) with digital subtraction angiography (DSA) for the ability to provide adequate information on which to construct a therapeutic strategy in patients suffering from peripheral arterial occlusive disease (PAOD).

METHODS

A prospective study was conducted involving 48 consecutive patients (25 men; mean age 65.7+/-10.2 years) with PAOD who underwent MRA and DSA of the peripheral arteries on 2 consecutive days. Every leg was divided into 3 anatomical regions (suprainguinal, femoropopliteal, calf), and the sensitivity and specificity for the detection of significant (>70%) lesions, as well as the interobserver variability, were calculated. The potential differences in the therapeutic strategy based on the results of both modalities were evaluated.

RESULTS

The MRA and DSA studies in the 48 study patients produced 864 arterial segments for interpretation. The sensitivity of MRA for the detection of significant lesions was 94.7% for the suprainguinal, 89.5% for the femoropopliteal, and 91.3% for the calf arteries. Corresponding specificity was 98.1%, 96.2% and 93.4%, respectively. The interobserver correlation for the detection of significant lesions by MRA and DSA was excellent (kappa>0.8) for all 3 segments, with slightly superior values for MRA. MRA and DSA agreed in the grading of 821 (95.0%) segments. In 8 (16.7%) patients, MRA suggested an additional intervention, and in 3 (6.3%) patients, additional DSA was necessary for the final diagnosis.

CONCLUSIONS

The accuracy of MRA for the detection of significant lesions is comparable to DSA. Basing the therapeutic strategy solely on the results of MRA can reduce the number of DSAs by three quarters, but at the risk of incurring lesion overestimation in approximately 17%.

Contrast-enhanced peripheral MR angiography using SENSE in multiple stations: Feasibility study

PURPOSE

To investigate if the use of parallel imaging is feasible and beneficial for peripheral contrast-enhanced magnetic resonance angiography (CE-MRA).

MATERIALS AND METHODS

A total of 19 consecutive patients underwent peripheral CE-MRA using SENSE with two-fold reduction in the upper and lower leg stations. Conventional nonaccelerated imaging using constant level appearance (CLEAR) was used in the aortoiliac station. The findings were compared with those in a similar patient group that underwent peripheral CE-MR angiography using our standard imaging protocol without SENSE. Intraarterial digital subtraction angiography (IA-DSA) was used as the standard of reference. Lower extremity vessels were divided into anatomic segments (aortoiliac, upper legs, lower legs) for review. In each anatomic segment signal- and contrast-to-noise ratios (SNR, CNR), venous contamination, subjective image quality, as well as sensitivity and specificity, were determined for both patient groups.

RESULTS

SNR and CNR improved significantly for the aortoiliac and upper leg segments (all P-values < or = 0.001). Small reductions were seen in the frequency of disturbing venous enhancement (P = not significant). There were no significant differences with regards to subjective image quality or diagnostic accuracy (all P > 0.3). Overall sensitivity and specificity in the SENSE group were 81% and 95%, respectively. For the non-SENSE group, these values were 79% and 96%, respectively.

CONCLUSION

Preliminary results show that three-station peripheral CE-MRA using a full length peripheral arterial coil in combination with SENSE in the upper and lower leg stations is feasible and useful for further optimization of peripheral MRA. Using SENSE allows for routine, high-quality depiction of the entire peripheral vascular tree including the pedal arch. Higher SENSE factors are needed for further optimization.

Peripheral MR angiography

Peripheral arterial occlusive disease is a chronic and progressive disease with a reported incidence rate from 4.5% to 8.8% in men over 55 years of age. The diagnosis is usually made clinically, but for treatment planning and control, imaging of the peripheral arteries is required. Since its introduction in 1994, contrast-enhanced MR angiography has demonstrated a high diagnostic confidence and has replaced the invasive intra-arterial DSA, which is still the current gold standard for many different indications. For the peripheral arteries, clinical use of MR angiography was hampered for some years by the unsolved problem of the large imaging volume and the small diameter of the distal arteries. However, since the availability of ultra-fast high-gradient sequences and the possibility of moving-bed imaging, contrast-enhanced MR angiography, over the last few years, has shown its enormous potential and high accuracy in the diagnosis and follow-up of patients suffering from peripheral arterial occlusive disease. Exciting innovations in hardware and software allows very fast, very accurate, and very robust noninvasive imaging of the peripheral arteries, and both treatment planning as well as follow-up can be performed using contrast-enhanced MR angiography. The following review introduces the basic concepts of peripheral MR angiography--focusing on contrast enhanced imaging--and presents the different techniques as well as some potential limitations and how they could be solved. Finally, this article provides a look into the already-begun future of peripheral contrast-enhanced MR angiography with hybrid and combination techniques.