Peripheral arteries in diabetic patients: standard bolus-chase and time-resolved MR angiography

Multi-Modality Imaging of Atheromatous Plaques in Peripheral Arterial Disease: Integrating Molecular and Imaging Markers

Peripheral artery disease (PAD) is a common and debilitating condition characterized by the narrowing of the limb arteries, primarily due to atherosclerosis. Non-invasive multi-modality imaging approaches using computed tomography (CT), magnetic resonance imaging (MRI), and nuclear imaging have emerged as valuable tools for assessing PAD atheromatous plaques and vessel walls. This review provides an overview of these different imaging techniques, their advantages, limitations, and recent advancements. In addition, this review highlights the importance of molecular markers, including those related to inflammation, endothelial dysfunction, and oxidative stress, in PAD pathophysiology. The potential of integrating molecular and imaging markers for an improved understanding of PAD is also discussed. Despite the promise of this integrative approach, there remain several challenges, including technical limitations in imaging modalities and the need for novel molecular marker discovery and validation. Addressing these challenges and embracing future directions in the field will be essential for maximizing the potential of molecular and imaging markers for improving PAD patient outcomes.

Postintervention monitoring of peripheral arterial disease wound healing using dynamic vascular optical spectroscopy

SIGNIFICANCE

Due to the persistence of chronic wounds, a second surgical intervention is often necessary for patients with peripheral arterial disease (PAD) within a year of the first intervention. The dynamic vascular optical spectroscopy system (DVOS) may assist physicians in determining patient prognosis only a month after the first surgical intervention.

AIM

We aim to assess the DVOS utility in characterizing wound healing in PAD patients after endovascular intervention.

APPROACH

The DVOS used near-infrared light ( 670 < λ < 850    nm ) to record hemodynamic response to a cuff inflation in 14 PAD patients with lower limb ulcers immediately before, immediately after, and at a first follow-up 3 to 4 weeks after intervention. Ankle-brachial index (ABI) and arterial duplex ultrasound (A-DUS) measurements were obtained when possible.

RESULTS

The total hemoglobin plateau time differed significantly between patients with ulcers that reduced in size ( N = 9 ) and patients with ulcers that did not ( N = 5 ) 3 to 4 weeks after intervention ( p  value < 0.001 ). Data correlated strongly (89% sensitivity, 100% specificity, and AUC = 0.96 ) with long-term wound healing. ABI and A-DUS measurements were not statistically associated with wound healing.

CONCLUSIONS

This pilot study demonstrates the potential of the DVOS to aid physicians in giving accurate long-term wound healing prognoses 1 month after intervention.

Pseudoaneurysm after total knee arthroplasty: imaging findings in 7 patients

OBJECTIVE

To describe the clinical presentation of arterial pseudoaneurysms following total knee arthroplasty (TKA) and their diagnostic imaging features on ultrasound and magnetic resonance angiography (MRA) in 7 patients.

MATERIALS AND METHODS

A search of our radiology report database from 2007 to 2017 yielded 7 patients with a pseudoaneurysm diagnosed by imaging after TKA. Clinical notes and imaging were reviewed.

RESULTS

All 7 patients were male and ranged in age from 53 to 68 (mean 61) years. All patients presented with a painful swollen knee and hemarthrosis within the first month following surgery. Five patients presented after primary TKA. One patient presented after explantation for septic arthritis and another after partial synovectomy for septic arthritis without explantation. Ultrasound identified the pseudoaneurysm as a hypoechoic or hyperechoic mass with a "yin-yang" appearance of turbulent arterial flow and associated complex joint effusion. On MRA, the pseudoaneurysm was a mass next to a parent artery showing avid contrast enhancement in the arterial phase that persisted into the venous phase and washed out in the late venous phase. Six pseudoaneurysms arose from lateral geniculate arteries and 1 from a medial geniculate artery. There were no popliteal artery pseudoaneurysms. Five patients were treated endovascularly, 1 patient thrombosed without intervention, and 1 patient was treated with open surgery.

CONCLUSION

Pseudoaneurysm is a potential source of a painful swollen knee with hemarthrosis or a drop in hematocrit after TKA and can be identified with either ultrasound or MRA.

Modeling of the hemodynamics in the feet of patients with peripheral artery disease

To simulate the hemodynamic effects in the feet in response to a thigh cuff occlusion, we have developed a multi-compartmental model in which the circulatory system for the leg is represented by its electrical equivalents. Dynamic vascular optical tomographic imaging data previously obtained from 20 patients with peripheral artery disease (PAD) and 20 healthy subjects is used to test the model. Analyzing the clinical data with the support of the model yields diagnostic specificity and sensitivity in the 90-95% range, significantly higher than previously reported.

Evaluation of Quiescent-Interval Single-Shot Magnetic Resonance Angiography in Diabetic Patients With Critical Limb Ischemia Undergoing Digital Subtraction Angiography: Comparison With Contrast-Enhanced Magnetic Resonance Angiography With Calf Compression at 3.0 Tesla

PURPOSE

To assess the diagnostic performance of quiescent-interval single-shot magnetic resonance angiography (QISS-MRA) at 3 tesla in diabetic patients with critical limb ischemia (CLI) vs contrast-enhanced MR angiography (CE-MRA) using digital subtraction angiography (DSA) as the standard of reference.

METHOD

Thirty-seven consecutive diabetic patients (mean age 71.8±7.2 years; 30 men) with CLI (Fontaine stage III-IV) underwent QISS-MRA and CE-MRA with calf compression; DSA was the standard. Image quality (5-point Likert-type scale) and stenosis severity (5-point grading) for QISS-MRA and CE-MRA were evaluated by 2 blinded readers in 1147 and 654 vessel segments, respectively. Per-segment and per-region (pelvis, thigh, calf) sensitivity, specificity, positive predictive value, and negative predictive value were calculated.

RESULTS

Image quality of QISS-MRA was lower compared with CE-MRA in the pelvic region (p<0.001 in both readers) and thigh region (p=0.033 in reader 1 and p=0.018 in reader 2), whereas in the calf region, the image quality of QISS-MRA was better than CE-MRA (p=0.009 in reader 1 and p=0.001 in reader 2). In segment-based analyses, there was no difference between QISS-MRA and CE-MRA in sensitivity [89.5% vs 90.3% in reader 1 (p=0.774) and 87.6% vs 90.6% in reader 2 (p=0.266)] or specificity [94.2% vs 92.9% in reader 1 (p=0.513) and 92.9% vs 92.9% in reader 2 (p>0.999)]. In region-based analyses, QISS-MRA and CE-MRA yielded similar sensitivity and specificity in all areas but the pelvic region for reader 2 (specificity 95.5% vs 84.8%, p=0.041).

CONCLUSION

QISS-MRA performed very well in diabetic patients with CLI and was a good alternative for patients with contraindications to CE-MRA.

Vascular CT and MRI: a practical guide to imaging protocols

Non-invasive cross-sectional imaging techniques play a crucial role in the assessment of the varied manifestations of vascular disease. Vascular imaging encompasses a wide variety of pathology. Designing vascular imaging protocols can be challenging owing to the non-uniform velocity of blood in the aorta, differences in cardiac output between patients, and the effect of different disease states on blood flow. In this review, we provide the rationale behind—and a practical guide to—designing and implementing straightforward vascular computed tomography (CT) and magnetic resonance imaging (MRI) protocols.

Teaching Points

• There is a wide range of vascular pathologies requiring bespoke imaging protocols.

• Variations in cardiac output and non-uniform blood velocity complicate vascular imaging.

• Contrast media dose, injection rate and duration affect arterial enhancement in CTA.

• Iterative CT reconstruction can improve image quality and reduce radiation dose.

• MRA is of particular value when imaging small arteries and venous studies.

Combined Static and Dynamic Computed Tomography Angiography of Peripheral Artery Occlusive Disease: Comparison with Magnetic Resonance Angiography

PURPOSE

To compare in patients with known peripheral artery occlusive disease (PAOD), image quality of a combined CTA to a combined MRA protocol, including both static and dynamic acquisitions.

MATERIALS AND METHODS

Twenty-two patients with PAOD were examined with a combined CTA and MRA protocol consisting of static acquisitions (s-CTA, s-MRA) of the entire runoff and dynamic acquisitions (d-CTA, d-MRA) of the calves. Two radiologists compared image quality of the s-MRA versus s-CTA as well as d-MRA versus d-CTA. Image quality was assessed on a segmental basis using a 4-point Likert scale.

RESULTS

For s-CTA, 76% of segments were rated as excellent or good. For s-MRA, 50% of segments were rated as excellent or good (p < 0.0001). For d-CTA, median image quality score for all segments was rated as excellent for both readers. For d-MRA, median image quality for the different segments ranged from moderate to good. For both d-CTA and d-MRA, the median image quality scores were significantly higher for all segments of the lower limb compared with the static examinations of the lower limb segments (all p values < 0.0001). In patients with PAOD category 4-6, 80% of segments were rated as excellent or good for d-CTA, while 45% of segments were rated as poor or non-diagnostic for d-MRA.

CONCLUSION

In patients with known PAOD, a combined static and dynamic CTA examination improves image quality relative to static and dynamic MRA and should be considered as an alternative to MRA, particularly in patients with advanced stage PAOD.

The diabetic foot in 2015: an overview

In 2015, it can be said that the diabetic foot is no longer the Cinderella of diabetic complications. Thirty years ago there was little evidence-based research taking place on the diabetic foot, and there were no international meetings addressing this topic. Since then, the biennial Malvern Diabetic Foot meetings started in 1986, the American Diabetes Association founded their Foot Council in 1987, and the European Association for the Study of Diabetes established a Foot Study Group in 1998. The first International Symposium on the Diabetic Foot in The Netherlands was convened in 1991, and this was soon followed by the establishment of the International Working Group on the Diabetic Foot that has produced useful guidelines in several areas of investigation and the management of diabetic foot problems. There has been an exponential rise in publications on diabetic foot problems in high impact factor journals, and a comprehensive evidence-base now exists for many areas of treatment. Despite the extensive evidence available, it, unfortunately, remains difficult to demonstrate that most types of education are efficient in reducing the incidence of foot ulcers. However, there is evidence that education as part of a multi-disciplinary approach to diabetic foot ulceration plays a pivotal role in incidence reduction. With respect to treatment, strong evidence exists that offloading is the best modality for healing plantar neuropathic foot ulcers, and there is also evidence from two randomized controlled trials to support the use of negative-pressure wound therapy in complex post-surgical diabetic foot wounds. Hyperbaric oxygen therapy exhibits the same evidence level and strength of recommendation. International guidelines exist on the management of infection in the diabetic foot. Many randomized trials have been performed, and these have shown that the agents studied generally produced comparable results, with the exception of one study in which tigecycline was shown to be clinically inferior to ertapenem ± vancomycin. Similarly, there are numerous types of wound dressings that might be used in treatment and which have shown efficacy, but no single type (or brand) has shown superiority over others. Peripheral artery disease is another major contributory factor in the development of ulceration, and its presence is a strong predictor of non-healing and amputation. Despite the proliferation of endovascular procedures in addition to open revascularization, many patients continue to suffer from severely impaired perfusion and exhaust all treatment options. Finally, the question of the true aetiopathogenesis of Charcot neuroarthropathy remains enigmatic, although much work is currently being undertaken in this area. In this area, it is most important to remember that a clinically uninfected, warm, insensate foot in a diabetic patient should be considered as a Charcot foot until proven otherwise, and, as such, treated with offloading, preferably in a cast.

Lower limb complications of diabetes mellitus: a comprehensive review with clinicopathological insights from a dedicated high-risk diabetic foot multidisciplinary team

Diabetic complications in the lower extremity are associated with significant morbidity and mortality, and impact heavily upon the public health system. Early and accurate recognition of these abnormalities is crucial, enabling the early initiation of treatments and thus avoiding or minimizing deformity, dysfunction and amputation. Following careful clinical assessment, radiological imaging is central to the diagnostic and follow-up process. We aim to provide a comprehensive review of diabetic lower limb complications designed to assist radiologists and to contribute to better outcomes for these patients.

Recent advances in 3D time-resolved contrast-enhanced MR angiography

Contrast-enhanced magnetic resonance angiography (CE-MRA) was first introduced for clinical studies approximately 20 years ago. Early work provided 3-4 mm spatial resolution with acquisition times in the 30-second range. Since that time there has been continuing effort to provide improved spatial resolution with reduced acquisition time, allowing high resolution 3D time-resolved studies. The purpose of this work is to describe how this has been accomplished. Specific technical enablers have been: improved gradients allowing reduced repetition times, improved k-space sampling and reconstruction methods, parallel acquisition, particularly in two directions, and improved and higher count receiver coil arrays. These have collectively made high-resolution time-resolved studies readily available for many anatomic regions. Depending on the application, ∼1 mm isotropic resolution is now possible with frame times of several seconds. Clinical applications of time-resolved CE-MRA are briefly reviewed.

Runoff Detected by Magnetic Resonance Angiography as an Indicator for Better Recanalization Outcomes in Below-the-Knee Chronic Total Occlusions in Diabetic Patients

Purpose: To compare the feasibility and efficacy of recanalizing below-the-knee (BTK) chronic total occlusions (CTOs) between patients with good or poor distal runoff based on magnetic resonance angiography (MRA) scans. Methods: Two hundred long-segment BTK CTOs in 171 limbs of 113 diabetic patients (58 men; mean age 69.8±1.9 years) were divided into good distal runoff (GDR: 119 lesions, 98 limbs) or poor distal runoff groups (PDR: 81 lesions, 73 limbs) based on baseline MRA findings. After angioplasty, modified thrombolysis in myocardial ischemia (mTIMI) grades and ankle-brachial index (ABI) were used to assess immediate outcomes. Regularly scheduled duplex or MRA imaging was performed in follow-up. The restenosis and limb salvage rates were compared. Results: The success rates were 93.3% and 87.7% in the GDR and PDR groups, respectively (p=0.21); subintimal angioplasty was more common in the PDR group (93.0% vs. 63.1%, p<0.01). Completion angiography indicated an mTIMI grade 3 blood flow in 71.2% lesions in the GDR patients and in 52.1% in the PDR (p=0.01) group. Improvement in the ABI was greater in the GDR limbs (p<0.001 vs. PDR). Mean imaging follow-up was 10.8±6.9 months in the GDR group and 11.1±6.6 months in the PDR group. Kaplan-Meier analysis showed a better restenosis-free rate in the GDR group (80.6% vs. 61.7%; p=0.02) at 12 months and for lesions with mTIMI grade 3 flow (p<0.01). At 24 months, Kaplan-Meier analysis revealed a better limb salvage rate in the GDR group (84.2% vs. 54.6%; p=0.02). Conclusion: Distal runoff detected using MRA could be a predictor for successful intraluminal recanalization, better distal tissue perfusion, improved long-term patency, and better limb salvage for patients with BTK CTOs.

Time-resolved contrast-enhanced MR angiography of spinal vascular malformations

BACKGROUND AND PURPOSE

The diagnosis of spinal vascular malformations may be challenging on conventional MR imaging because neither the location of the signal abnormality in the spinal cord nor the level of the abnormal flow voids correlates with the level of the fistula. We conducted a retrospective evaluation of the utility of using a time-resolved imaging of contrast kinetics sequence in the diagnosis, characterization, and localization of spinal vascular malformations, comparing it with the criterion standard of spinal DSA.

MATERIALS AND METHODS

Fifty-five consecutive patients with a suspected diagnosis of spinal vascular malformation underwent time-resolved imaging of contrast kinetics followed by spinal DSA. All scans were performed on a 1.5T scanner by using a standard 8-channel spine coil and were reported by a neuroradiologist before the DSA was performed.

RESULTS

Forty-seven lesions were confirmed on time-resolved imaging of contrast kinetics and classified as spinal dural arteriovenous fistulas (n = 33, with 1 patient having a type Ib fistula), perimedullary spinal cord arteriovenous fistulas (n = 10), and intramedullary arteriovenous malformations (n = 3). One patient had an extradural spinal vascular malformation. Time-resolved imaging of contrast kinetics identified the location of the arterial feeder to within 1 vertebral level in 27/33 patients (81.8%) with spinal dural arteriovenous fistulas and correctly predicted the side in 22/33 (66.6%) patients. Perimedullary spinal cord arteriovenous fistulas were erroneously considered to represent spinal dural arteriovenous fistulas before spinal DSA. The anatomy of the arterial supply to intramedullary arteriovenous malformations was also poorly characterized on time-resolved contrast-enhanced MR angiography.

CONCLUSIONS

It has been our experience that time-resolved imaging of contrast kinetics is a useful confirmatory tool when a spinal vascular malformation is suspected on the basis of clinical and conventional MR imaging findings. As experience with the technique grows and sequences are refined, it may be possible to rely on time-resolved imaging of contrast kinetics as a screening tool for the diagnosis of spinal vascular malformations.

Computed tomography angiography and magnetic resonance angiography imaging in critical limb ischemia: an overview

Critical limb ischemia (CLI) is exhibited in patients with symptoms of severe claudication (rest pain) and ischemic tissue loss and gangrene. Magnetic resonance angiography and computed tomography angiography have risen to the forefront of vascular imaging over the last 2 decades. Both modalities have been shown to compare favorably with digital subtraction angiography in guiding the clinical management of patients with CLI. Understanding the advantages and limitations of both modalities allows for the proper selection of the best examination for a particular patient with CLI. Ultimately, the enhanced understanding of the vascular anatomy by obtaining noninvasive imaging should make subsequent revascularization safer and more effective.

Enhancement characteristics and impact on image quality of two gadolinium chelates at equimolar doses for time-resolved 3-Tesla MR-angiography of the calf station

PURPOSE

To compare enhancement characteristics and image quality of two macrocyclic gadolinium chelates, gadoterate meglumine and gadobutrol, in low-dose, time-resolved MRA of the calf station.

MATERIALS AND METHODS

100 consecutive patients with peripheral arterial disease (stages II-IV) were retrospectively analysed. Fifty patients were included in each group - 32 men and 18 women for gadobutrol (mean age 67 years) and 34 men, 16 women for gadoterate meglumine (mean age 64 years). 0.03 mmol/kg bw of either gadobutrol or gadoterate meglumine was injected. Gadobutrol was diluted 1 ∶ 1 with normal saline (0.9% NaCl) to provide similar injection volume and bolus geometry compared to the undiluted 0.5 M dose of gadoterate meglumine. Signal-to-noise-ratio (SNR), contrast-to-noise-ratio (CNR) and image quality were analysed and compared between the two groups.

RESULTS

Mean SNR ranged from 83.0 ± 46.7 (peroneal artery) to 96.4 ± 64.5 (anterior tibial artery) for gadobutrol, and from 37.6 ± 13.8 (peroneal artery) to 45.3 ± 16.4 (anterior tibial artery) for the gadoterate meglumine group (p<0.0001). CNR values ranged from 30.1 ± 20.1 (peroneal artery) to 37.6 ± 26.0 (anterior tibial artery) for gadobutrol and from 14.9 ± 8.0 (peroneal artery) to 18.6 ± 16.4 (anterior tibial artery) for gadoterate meglumine (p<0.0001). No significant difference in image quality was found except for the peroneal arteries (p = 0.006 and p = 0.04). Interreader agreement was excellent (kappa 0.87-0.93).

CONCLUSION

The significantly better enhancement as assessed by SNR and CNR provided by gadobutrol compared to gadoterate meglumine does not translate into substantial differences in image quality in an equimolar, low-dose, time-resolved MRA protocol of the calves.

Unenhanced MR angiography of the foot: initial experience of using flow-sensitive dephasing-prepared steady-state free precession in patients with diabetes

PURPOSE

To assess image quality and diagnostic performance of unenhanced magnetic resonance (MR) angiography with use of flow-sensitive dephasing (FSD)-prepared steady-state free precession (SSFP) of the foot arteries in patients with diabetes.

MATERIALS AND METHODS

This prospective study was approved by institutional review board. Informed consent was obtained from all subjects. Thirty-two healthy volunteers and 38 diabetic patients who had been scheduled for lower-extremity contrast material-enhanced MR angiography were recruited to undergo unenhanced MR angiography with a 1.5-T MR unit. Image quality and diagnostic accuracy of unenhanced MR angiography in the detection of significant arterial stenosis (≥50%) were assessed by two independent reviewers. Contrast-enhanced MR angiography was used as the reference standard. The difference in the percentage of diagnostic arterial segments at unenhanced MR angiography between healthy volunteers and diabetic patients was evaluated with the McNemar test and generalized estimating equation for correlated data. Signal-to-noise ratio (SNR) and artery-to-muscle contrast-to-noise ratio (CNR) of pedal arteries were measured and compared between the two MR angiography techniques by using the paired t test.

RESULTS

All subjects successfully underwent unenhanced MR angiography of the foot. Unenhanced MR angiography yielded a high percentage of diagnostic arterial segments in both healthy volunteers (303 of 320 segments, 95%) and patients (341 of 370 segments, 92%), and there was no difference in the percentage between the two populations (P = .195). In patients, the average SNR and CNR at unenhanced MR angiography were higher than those at contrast-enhanced MR angiography (SNR: 90.7 ± 38.1 vs 81.7 ± 34.7, respectively, P = .023; CNR: 85.2 ± 33.2 vs 76.6 ± 33.5, respectively, P = .013). The average sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of unenhanced MR angiography were 88% (35 of 40 segments), 93% (107 of 115 segments), 81% (35 of 43 segments), 96% (107 of 112 segments), and 92% (142 of 155 segments), respectively. Interobserver agreement between the two readers for diagnostic accuracy was good (κ = 0.83).

CONCLUSION

Unenhanced MR angiography with use of FSD-prepared SSFP allows clear depiction of the foot arterial tree and accurate detection of significant arterial stenosis. The technique has the potential to be a safe and reliable screening tool for the assessment of foot arteries in diabetic patients without the use of gadolinium-based contrast material.

Detection of infragenual arterial disease using non-contrast-enhanced MR angiography in patients with diabetes

PURPOSE

To evaluate the diagnostic performance of a newly developed non-contrast-enhanced MR angiography (NCE-MRA) technique using flow-sensitive dephasing (FSD) prepared steady-state free precession (SSFP) for detecting calf arterial disease in patients with diabetes.

MATERIALS AND METHODS

Forty-five patients with diabetes who underwent routine contrast-enhanced MR angiography (CE-MRA) of lower extremities were recruited for NCE-MRA at the calf on a 1.5 Tesla MR system. Image quality evaluated on a 4-point scale and diagnostic performance for detecting more than 50% arterial stenosis were statistically analyzed, using CE-MRA as the standard of reference.

RESULTS

A total of 264 calf arterial segments were obtained in the 45 patients with 88 legs. The percentage of diagnostic arterial segments was all 98% for NCE- and CE-MRA. The image quality, SNR, CNR was 3.3, 177, 138, and 3.5, 103, 99, for NCE-MRA and CE-MRA, respectively. The average sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of NCE-MRA were 97%, 96%, 90%, 99%, and 96%, respectively on a per-segment basis and 90%, 84%, 82%, 91%, and 87%, respectively, on a per-patients basis.

CONCLUSION

The NCE-MRA technique demonstrates adequate image quality in the delineation of calf arteries and consistent diagnostic performance for detecting significant stenosis with CE-MRA in patients with diabetes.

Contrast-enhanced magnetic resonance angiography of the peripheral arteries: technique, tips, pitfalls and problems

Contrast-enhanced magnetic resonance angiography is a reliable way to assess peripheral vascular disease. This article reviews the basic physics behind this technique and discusses our institution's experience with regard to the clinical role, recent advances in image acquisition and use of contrast agents. Problems that can affect image quality and interpretation are also highlighted.

Evidence-based management of PAD & the diabetic foot

Diabetic foot ulceration (DFU) is associated with high morbidity and mortality, and represents the leading cause of hospitalization in patients with diabetes. Peripheral arterial disease (PAD), present in half of patients with DFU, is an independent predictor of limb loss and can be difficult to diagnose in a diabetic population. This review focuses on the evidence for therapeutic strategies in the management of patients with DFU. We highlight the importance of timely referral of patients presenting with a new foot ulcer to a multidisciplinary team, which includes vascular surgeons and interventional radiologists.

Comparison of nonenhanced MR angiographic subtraction techniques for infragenual arteries at 1.5 T: a preliminary study

PURPOSE

To evaluate diagnostic performance of three nonenhanced methods: variable-refocusing-flip angle (FA) fast spin-echo (SE)-based magnetic resonance (MR) angiography (variable FA MR) and constant-refocusing-FA fast SE-based MR angiography (constant-FA MR) and flow-sensitive dephasing (FSD)-prepared steady-state free precession MR angiography (FSD MR) for calf arteries, with dual-injection three-station contrast material-enhanced MR angiography (gadolinium-enhanced MR) as reference.

MATERIALS AND METHODS

This prospective study was institutional review board approved and HIPAA compliant, with informed consent. Twenty-one patients (13 men, eight women; mean age, 62.6 years) underwent calf-station variable-FA MR, constant-FA MR, and FSD MR at 1.5 T, with gadolinium-enhanced MR as reference. Image quality and stenosis severity were assessed in 13 segments per leg by two radiologists blinded to clinical data. Combined constant-FA MR and FSD MR reading was also performed. Methods were compared (logistic regression for correlated data) for diagnostic accuracy.

RESULTS

Of 546 arterial segments, 148 (27.1%) had a hemodynamically significant (≥ 50%) stenosis. Image quality was satisfactory for all nonenhanced MR sequences. FSD MR was significantly superior to both other sequences (P < .0001), with 5-cm smaller field of view; 9.6% variable-FA MR, 9.6% constant-FA MR, and 0% FSD MR segmental evaluations had nondiagnostic image quality scores, mainly from high diastolic flow (variable-FA MR) and motion artifact (constant-FA MR). Stenosis sensitivity and specificity were highest for FSD MR (80.3% and 81.7%, respectively), compared with those for constant-FA MR (72.3%, P = .086; and 81.8%, P = .96) and variable-FA MR (75.9%, P = .54; and 75.6%, P = .22). Combined constant-FA MR and FSD MR had superior sensitivity (81.8%) and specificity (88.3%) compared with constant-FA MR (P = .0076), variable-FA MR (P = .0044), and FSD MR (P = .0013). All sequences had an excellent negative predictive value (NPV): 93.2%, constant-FA MR; 94.7%, variable-FA MR; 91.7%, FSD MR; and 92.9%, combined constant-FA MR and FSD MR.

CONCLUSION

At 1.5 T, all evaluated nonenhanced MR angiographic methods demonstrated satisfactory image quality and excellent NPV for hemodynamically significant stenosis.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120859/-/DC1.

TRICKS magnetic resonance angiography at 3-tesla for assessing whole lower extremity vascular tree in patients with high-grade critical limb ischemia: DSA and TASC II guidelines correlations

The entire vascular tree of 58 lower extremities with high-grade critical limb ischemia (CLI) was assessed with three-station time resolved imaging of contrast kinetics (TRICKS) magnetic resonance angiography (T-MRA) and correlated with digital subtraction angiography (DSA) examinations and Trans-Atlantic Inter-Society Consensus II (TASC II) guidelines. Kappa (κ) statistics were utilized to evaluate the agreement of stenosis scores (5-point scale; 0 normal to 4 occlusion) based on T-MRA and DSA. With DSA as the standard, significant stenosis instances (stenosis score ≥2) among vascular segments were compared. The κ-statistics of image quality (4-point scale; 1 nondiagnostic to 4 excellent) of T-MRA and TASC II classification assessed by a radiologist and a vascular surgeon were also evaluated. Among 870 vascular segments, excellent agreement was observed between T-MRA and DSA (mean κ = 0.883) in revealing stenosis (mean stenosis score, 2.1  ±  1.3 versus 2.0  ±  1.3). T-MRA harbored overall high sensitivity (99.5%), specificity (93.6%), positive predictive value (95.4%), negative predictive value (99.6%), and accuracy (97.7%) in depicting significant stenosis. Excellent interobserver agreement (mean κ = 0.818) of superb image quality (mean score = 3.5–3.6) of T-MRA and outstanding agreement of TASC II classification of aortoiliac and femoral-popliteal lesions (κ = 0.912–0.917) between two raters further verified the clinical feasibility of T-MRA for treatment planning.

Diagnostic accuracy of dynamic computed tomographic angiographic of the lower leg in patients with critical limb ischemia

OBJECTIVE

The purpose of this study was to assess the diagnostic accuracy of dynamic computed tomographic angiography (dyn-CTA) in patients with critical lower leg ischemia.

MATERIALS AND METHODS

A population of 29 patients with known peripheral arterial occlusive disease (Fontaine stage III or IV) was examined with a combined CTA protocol consisting of a standard CTA (s-CTA) of the lower leg runoff from the diaphragm to the toes and dyn-CTA of the calves (scan range, 48 cm; 8 phases; 3.5 seconds per phase, 100 kV; 120 mAs; contrast volume, 50 mL; flow rate, 5.0 mL/s). Digital subtraction angiography was performed on all patients and served as a reference standard. For each of seven lower leg artery segments, arterial contrast and diagnostic confidence for stenosis assessment (3-point scale) were tested for s-CTA and dyn-CTA. Similarly, stenoses of calf-segments were classified on a 3-point scale separately for s-CTA and dyn-CTA and were compared with digital subtraction angiography to assess diagnostic accuracy.

RESULTS

Compared with s-CTA, dyn-CTA resulted in significantly higher arterial contrast enhancement (68% vs 46% optimal contrast; P < 0.01) and higher diagnostic confidence (64% vs 48% fully confident, respectively, P < 0.05). Dyn-CTA had a slightly higher sensitivity for the detection of significant stenosis (98.0% vs 96.6%), and for the detection of occlusion (95.4% vs 94.4%). Specificity for dyn-CTA was higher than for s-CTA, both for detection of stenosis (97.1% vs 92.2%) and especially for the detection of vessel occlusions (99.3% vs 94.4%; P < 0.05).

CONCLUSIONS

Compared with s-CTA, dyn-CTA provides improved arterial contrast enhancement, higher diagnostic confidence, and increased diagnostic accuracy for the detection of stenoses and occlusions in peripheral arterial occlusive disease 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 dual-station calf-foot three-dimensional bolus chase MR angiography with fluoroscopic tracking

PURPOSE

To refine, adapt, and evaluate the technical aspects of fluoroscopic tracking for generating dual-station high-spatial-resolution MR angiograms of the calves and feet using a single injection of contrast material.

MATERIALS AND METHODS

Nine subjects (seven healthy volunteers followed by two patients) were imaged using a two-station calf-foot three-dimensional time-resolved bolus chase MR angiography protocol which provided <1.0 mm(3) spatial resolution throughout and 2.5- and 6.6-s frame times at the calf and foot stations, respectively. Real-time reconstruction of calf station time frames allowed visually guided triggering of table advance to the foot station. The studies were independently read and scored by two radiologists in six image quality categories.

RESULTS

On average, overall diagnostic quality at the calf and foot stations was good-to-excellent, the calf arteries and all but the smallest foot arteries had good-to-excellent signal and sharpness, artifact and venous contamination were minor, and signal continuity across the inter-station interface was good.

CONCLUSION

The feasibility of fluoroscopic tracking has been demonstrated as an efficient approach for high spatiotemporal imaging of the arteries of the calves and feet with good-to-excellent diagnostic quality and low degrading venous contamination.

Diagnostics and treatment of the diabetic foot

Every 30 s, a lower limb is amputated due to diabetes. Of all amputations in diabetic patients 85% are preceded by a foot ulcer which subsequently deteriorates to a severe infection or gangrene. There is a complexity of factors related to healing of foot ulcers including strategies for treatment of decreased perfusion, oedema, pain, infection, metabolic disturbances, malnutrition, non-weight bearing, wound treatment, foot surgery, and management of intercurrent disease. Patients with diabetic foot ulcer and decreased perfusion do often not have rest pain or claudication and as a consequence non-invasive vascular testing is recommended for early recognition of ulcers in need of revascularisation to achieve healing. A diabetic foot infection is a potentially limb-threatening condition. Infection is diagnosed by the presence or increased rate of signs inflammation. Often these signs are less marked than expected. Imaging studies can diagnose or better define deep, soft tissue purulent collections and are frequently needed to detect pathological findings in bone. The initial antimicrobial treatment as well as duration of treatment is empiric. There is a substantial delay in wound healing in diabetic foot ulcer which has been related to various abnormalities. Several new treatments related to these abnormalities have been explored in wound healing with various successes. An essential part of the strategy to achieve healing is an effective offloading. Many interventions with advanced wound management have failed due to not recognizing the need for effective offloading. A multidisciplinary approach to wounds and foot ulcer has been successfully implemented in different centres with a substantial decrease in amputation rate.

Diagnosis and treatment of peripheral arterial disease in diabetic patients with a foot ulcer. A progress report of the International Working Group on the Diabetic Foot

The International Working Group on the Diabetic Foot (IWDGF) has produced in 2011 a guideline on the diagnosis and treatment of peripheral arterial disease in patients with diabetes and a foot ulcer. This document, together with a systematic review that provided the background information on management, was produced by a multidisciplinary working group of experts in the field and was endorsed by the IWDGF. This progress report is based on these two documents and earlier consensus texts of the IWDGF on the diagnosis and management of diabetic foot ulcers. Its aim is to give the clinician clear guidance on when and how to diagnose peripheral arterial disease in patients with diabetes and a foot ulcer and when and which treatment modalities should be considered, taking both risks and benefits into account.

Time-resolved MR angiography of the calf arteries using a phased array cardiac coil: comparison of visibility with standard three-step bolus chase MR angiography

BACKGROUND

Standard bolus chase MR angiography (MRA) is increasingly replacing digital subtraction angiography (DSA) in the diagnostic evaluation of peripheral vascular disease. However, a major limitation of bolus chase MRA is the relatively poor visibility of the calf arteries.

PURPOSE

To evaluate the feasibility of visualizing the calf arteries and the visibility quality of an 8-channel cardiac phased array coil using time-resolved imaging of contrast kinetics (TRICKS) MRA compared with standard bolus chase MRA on a 1.5 Tesla MRI scanner.

MATERIAL AND METHODS

MRA findings of 59 sequential patients (mean age 57.8 years, range 14-83 years; 41 men) were retrospectively evaluated. All examinations included preliminary TRICKS for the lower leg using a surface 8-channel cardiac coil, followed by a 3-step MRA of the abdominal aorta, thigh, and lower leg using a body coil. Images yielded by both methods were separately evaluated by consensus of two radiologists unaware of the patients' clinical data. Visibility of the calf arteries (popliteal, tibialis anterior, tibialis posterior, tibioperoneal trunk, and peroneal) for both sides was subjectively classified as 'diagnostic' or 'non-diagnostic'. Descriptive statistics for image diagnostic quality were assessed.

RESULTS

A total of 575 calf arterial segments were evaluated. Visibility of all calf arteries was significantly better with TRICKS than with the standard bolus chase MRA (P < 0.001). The improvement of calf artery visibility with TRICKS was more pronounced in patients with peripheral vascular disease compared to those with arteritis, vascular malformation and popliteal entrapment syndrome.

CONCLUSION

Using a cardiac coil for MRA of the lower extremities resulted in visibility comparable to that of a dedicated leg coil, with diagnostic superiority for the TRICKS method compared to the standard bolus chase method.

Characteristics of peripheral arterial disease and its relevance to the diabetic population

Peripheral arterial disease (PAD) is very frequent in diabetics, and it increases with age. Foot examination contributes poorly to diagnosis of PAD. The ankle-brachial index (ABI) measurement is considered the most accurate noninvasive diagnostic method when evaluating PAD: ABI evaluation is recommended in all diabetics aged >50 years. Many diabetic patients with PAD have a concomitant sensitive neuropathy: as a consequence, perception of ischemic pain is remarkably reduced or completely blocked. The result is that the prevalence of claudication in the diabetic population with PAD is lower than the prevalence of critical limb ischemia (CLI) in this population. CLI is a major risk factor for lower extremity amputation without revascularization. Ankle and toe pressures and oxygen tension at the foot are the noninvasive diagnostic parameters of CLI though the medial artery calcification inhibits accurate determination of the ankle and toe pressures, especially when a forefoot ulcer is present. In diabetics, the anatomical localization is mainly distal; arterial wall calcification is frequently observed and occlusion occurs more frequently than stenosis. Such anatomical features, along with the difficulties in the diagnostic approach, account for the fundamental role of CLI as the main prognostic indicator for major amputation. PAD is an expression of systemic atherosclerotic disease. Prognosis of patients with PAD is related to the presence and extent of underlying coronary artery disease (CAD) but also to the severity of PAD: in particular, patients in whom revascularization is not feasible have the highest mortality rate.

Lower limb vascular disease in diabetic patients: a study with calf compression contrast-enhanced magnetic resonance angiography at 3.0 Tesla

RATIONALE AND OBJECTIVES

To retrospectively analyze the significance of 3.0-T contrast-enhanced (CE) magnetic resonance angiography (MRA) with calf compression in the lower limbs of diabetic patients with peripheral vascular disease.

MATERIALS AND METHODS

Sixty-one type 2 diabetes patients underwent both MRA and digital subtraction angiography (DSA) within 1 week. The patients were divided into two groups: one with (pressure) and one without (conventional) calf compression during MRA. Two radiologists evaluated the quality of MRA images and compared the two groups. Cohen's kappa statistic was used to determine the concordance between MRA and DSA.

RESULTS

Image quality in the calf and foot was better in the group with calf pressure than the conventional group without applied pressure (P = .001 [calf], 0.008 [foot]). Significantly more runoff vessels in the calf were detected with MRA than with DSA (P = .0043 [conventional], 0.0031 [pressure]). The kappa values were 0.928 in the conventional group and 0.979 in the pressure group, but in the conventional group, the diagnostic accuracy of CE-MRA was lower than that of DSA (P = .002). Diagnostic accuracy in the pressure group was significantly higher than that in the conventional group (P = .009). The overall sensitivity and specificity for >50% stenosis or occlusion was 93.8% and 98.5%, respectively, in the conventional group and 98.7% and 99.6%, respectively, in the pressure group. With calf compression, venous overlap (P = .0396, .0425) and deep vein overlap (P = .022, .022) were significantly reduced in the leg and foot.

CONCLUSION

Calf compression with 3.0-T CE-MRA was convenient and practical and could improve image quality and diagnostic accuracy in diabetic patients with peripheral vascular disease by reducing venous overlap.

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 spatial and temporal resolution imaging of the arterial vasculature of the lower extremity with contrast enhanced MR angiography

Vascular imaging can be essential in the diagnosis, monitoring, and planning and assessment of treatment of patients with peripheral vascular disease. The purpose of this work is to describe a recently developed three-dimensional (3D) time-resolved contrast-enhanced MR angiography (CE-MRA) technique, Cartesian Acquisition with Projection Reconstruction-like sampling (CAPR), and its application to imaging of the vasculature of the lower legs and feet. CAPR implements accelerated imaging techniques and uses specialized multielement imaging coil arrays to achieve high temporal and high spatial resolution imaging. Volunteer and patient studies of the vasculature of the lower legs and feet have been performed. Temporal resolution of 4.9-6.5 sec and spatial resolution less than or equal to 1 mm in all directions allow for the depiction of progressive arterial filling and complex flow patterns as well as sharp visualization of vascular structure as small as the fine muscular branches. High-quality diagnostic imaging is made possible with CAPR's advanced acquisition and reconstruction techniques and the use of specialized coil arrays.

Magnetic resonance angiography of fetal vessels: feasibility study in the sheep fetus

PURPOSE

The aim of this study was to perform fetal magnetic resonance angiography (MRA) in utero in a sheep model.

MATERIAL AND METHODS

Images of the great vessels, the heart, and the tracheal tree were performed on four pregnant ewes with a 1.5-T scanner (Philips Medical Systems, Best, The Netherlands). MRA was achieved in utero using a nontriggered free-breathing three-dimensional balanced fast field echo (FFE) technique. All obtained MRA images were evaluated in consensus on a three-point scale by two radiologists with 9 and 4 years of experience in fetal MRI, respectively.

RESULTS

The fetal heart frequencies were between 130 and 160 bpm. The aorta from the aortic bulb to the bifurcation as well as some of the main aortic branches could be depicted. The pulmonary trunk and arteries, the superior and inferior caval veins, and the subsegmental branches of the trachea could also be visualized.

CONCLUSION

The nontriggered MRA of the fetal great vessels with images of the tracheal tree allowed an excellent evaluation of anatomical structures.

Traumatic Lateral Plantar Artery Pseudoaneurysm and the Use of Time-Resolved MR Angiography

Vascular injury resulting in pseudoaneurysm formation in the plantar aspect of the foot is an uncommon injury after trauma. Such injuries are more often reported in the lateral plantar artery rather than the medial plantar artery, most likely because of its more superficial location. Traditional modalities in diagnosis have included ultrasound and digital subtraction angiography. We present a case of traumatic pseudoaneurysm of the lateral plantar artery following a foot laceration. Diagnosis was made by the use of high-resolution, time-resolved contrast-enhanced 3D magnetic resonance angiography, also referred to as "TRICKS" (time-resolved imaging of contrast kinetics). This technique provided high spatial resolution for the arterial anatomy as well as temporal resolution which allowed better delineation of the hemodynamic characteristics of the pseudoaneurysm.

ELECTRONIC SUPPLEMENTARY MATERIAL

The online version of this article (doi:10.1007/s11420-010-9170-3) contains supplementary material, which is available to authorized users.

Time-resolved lower extremity MRA with temporal interpolation and stochastic spiral trajectories: preliminary clinical experience

PURPOSE

To assess added value of a new time-resolved technique with temporal interpolation and stochastic spiral trajectory through k-space and parallel imaging (TR-MRA) to conventional bolus chase MRA (BC-MRA) for infragenual peripheral artery evaluation.

MATERIALS AND METHODS

An institutional review board-approved retrospective review of peripheral arterial disease patients was performed. Infragenual TR-MRA and BC-MRA were performed in 26 patients over four months. Two readers individually assessed image quality, diagnostic confidence, and stenosis severity and length in 13 defined below knee segments, first with BC-MRA alone, and then with a combined BC-MRA and TR-MRA reading (BC+TR-MRA). Perceived contribution of TR-MRA was rated by each reader. The reference standard was a consensus reading of both sequences. Catheter angiographic (CA) correlation was available in 6 patients.

RESULTS

A total of 646 infragenual segments in 51 extremities were evaluated. Image quality and diagnostic confidence were superior for BC+TR-MRA compared with BC-MRA alone (P < 0.001). Adding TR-MRA improved sensitivity (85.7% versus 80.7%; P < 0.05) and diagnostic accuracy (88.1% versus 85.4%; P < 0.05) for hemodynamically significant stenosis. Venous contamination (0% versus 13.1% segments) and motion (0.9% versus 8.0%) were decreased for BC+TR-MRA versus BC-MRA alone, P < 0.01. For BC+TR-MRA, TR-MRA was rated more useful than BC-MRA in 30/51 legs (58.8%). TR-MRA identified retrograde flow in 5 segments. Where available, there was high concordance between CA and BC+TR-MRA (91.6%) for stenosis.

CONCLUSION

Adding TR-MRA with temporal interpolation and stochastic spiral trajectories to bolus chase MRA improves image quality, diagnostic confidence and accuracy. It provides hemodynamic information and minimizes venous contamination and patient motion.

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.