Imaging Peripheral Arterial Disease: A Randomized Controlled Trial Comparing Contrast-enhanced MR Angiography and Multi–Detector Row CT Angiography

Development of a Tetherless Bioimpedance Device That Uses Morphologic Changes to Predict Blood Flow Restrictions Mimicking Peripheral Artery Disease Progression

A tetherless multi-targeted bioimpedance device was designed, modeled, built, and tested for measuring arterial pulse and, using morphological analysis, its potential for monitoring blood flow restrictions that mimic Peripheral Artery Disease (PAD) was assessed across multiple peripheral arteries. Specifically, we first developed a small form factor, tetherless, bioimpedance device, based on high-frequency structure simulator (HFSS) simulations. After designing and building the device we then tested it in vivo on human subjects on multiple arteries and found that we did not need to modify the gain on the device compared to the bench top system. Further, it was found that changes in the morphology of the bioimpedance signal over time, depicted through the ratio of the first and second harmonic in the signal frequency, could be used to predict blood flow restrictions that mimic peripheral artery disease (PAD). The HFSS simulations helped guide the modulation frequency selection and the placement of the bioimpedance electrodes. We built the device and compared it to two commercially available bioimpedance devices and it was shown to demonstrate a distinct advantage in its multi-target capability, enabling more accurate pulse measurements from different arteries without the need for tuning the circuit for each artery. Comparing the ratio of the 1st and 2nd harmonics as a function of the blood flow restriction, the two commercial devices showed a maximum error across arteries of between 22% and 27% depending on the measurement location, whereas our system consistently displayed a stable value of just below 4%. With this system, there is the potential for comprehensive and personalized medical examinations for PAD at the point of care (POC).

Evaluation of Tissue Perfusion by Wound Blush and 2D Color-Coded Digital Subtraction Angiography During Endovascular Intervention and Its Impact on Limb Salvage in Critical Limb Ischemia

PURPOSE

Critical limb ischemia (CLI) is an entity with high mortality if not properly treated. The primary aim of CLI revascularization is to enhance wound healing, which greatly depends on microvascular circulation. The available tools for assessment of revascularization success are deficient in the evaluation of local microvascular tissue perfusion, that wound blush (WB) reflects. A reliable technique that assesses capillary flow to foot lesions is needed. This study aims to assess WB angiographically at sites of interest in the foot after revascularization and its impact on limb salvage in CLI.

MATERIALS AND METHODS

198 CLI patients (Rutherford category 5/6) with infrainguinal atherosclerotic lesions amenable for endovascular revascularization (EVR) were included. Limbs were directly or indirectly revascularized by EVR. Direct revascularization meant that successful revascularization of the area of interest according to the angiosome concept was achieved. A completion angiographic run was taken to assess WB. Patients were divided into 2 groups; positive and negative WB groups. In the event of a disagreement between the observational investigators, the digital subtraction angiography (DSA) series was analyzed for hemodynamic changes with a computerized 2D color-coded DSA (Syngo iFlow).

RESULTS

176 limbs had successful revascularization in 157 patients. The successful revascularization rate was 88.9% (176/198), with technical failure encountered in 22 limbs. 121 patients had positive WB and 55 patients had negative WB. Direct revascularization of target areas was obtained in 98 limbs (55.7%). There was a significant difference in the rate of achieving direct flow to the lesion between the positive WB and negative WB groups (36.4% vs 19.3%, p≤0.001). We noticed a nonsignificant difference between patients who had direct revascularization of the foot lesion(s) and those who had indirect revascularization as regards limb salvage. Patients were followed up for 25.2 ± 12.7 months. By the end of the first year, limb salvage rate was significantly higher in patients who had positive WB (98% vs 63%, p<0.001, after 2 years (97% vs 58%, p<0.001) and after 3 years (94% vs 51.5%, p<0.001).

CONCLUSIONS

WB is an important predictor and a prognostic factor for wound healing in CLI patients with soft tissue lesions.

Lower extremity CT angiography in peripheral arterial disease: from the established approach to evolving technical developments

With the advent of multidetector computed tomography (CT), CT angiography (CTA) has gained widespread popularity for noninvasive imaging of the arterial vasculature. Peripheral extremity CTA can nowadays be performed rapidly with high spatial resolution and a decreased amount of both intravenous contrast and radiation exposure. In patients with peripheral artery disease (PAD), this technique can be used to delineate the bilateral lower extremity arterial tree and to determine the amount of atherosclerotic disease while differentiating between acute and chronic changes. This article provides an overview of several imaging techniques for PAD, specifically discusses the use of peripheral extremity CTA in patients with PAD, clinical indications, established technical considerations and novel technical developments, and the effect of postprocessing imaging techniques and structured reporting.

Prevalence and Risk Factors of Peripheral Arterial Disease in Patients with Lumbar Spinal Stenosis and Intermittent Claudication: CT Angiography Study

BACKGROUND

It can be difficult to differentiate between vascular and neurogenic intermittent claudication. The exact diagnosis often cannot be made on clinical evidence and ultimately requires imaging. Perioperative screening for peripheral arterial disease (PAD) in lumbar spinal stenosis (LSS) patients is important because untreated PAD increases the risk of severe vascular events. The aims of this study were to study the prevalence of PAD in LSS patients with symptoms of intermittent claudication, and to study the independent risk factors for PAD. We specified the cases where it was necessary to perform computed tomography angiography (CTA) as a preoperative screening tool in surgery for spinal stenosis.

METHODS

This study involved a retrospective analysis of 186 consecutive subjects with radiographic evidence of LSS and symptoms of intermittent claudication, who underwent 3D CTA of the lower extremities at our institution during a three-year period. More than 50% luminal narrowing on CT angiograms was determined to be clinically significant and placed in the PAD group.

RESULTS

Thirty-two subjects were diagnosed with PAD and referred to the general vascular team in our hospital, where they received treatment for PAD. In the non-PAD group (154 subjects), 117 underwent definitive surgery for spinal stenosis such as posterior lumbar interbody fusion and a further 37 underwent conservative treatment. Only hypertension, diabetes, and men gender were found to be statistically significant predictors of PAD.

CONCLUSION

The current study showed that man gender, diabetes and hypertension were the greatest risk factors for PAD. We conclude that man patients with diabetes and/or hypertension should be put under serious consideration for routine CTA examination when under evaluation for LSS and intermittent claudication.

Changing National Medicare Utilization of Catheter, Computed Tomography, and Magnetic Resonance Extremity Angiography: A Specialty-focused 16-Year Analysis

To assess changing utilization of extremity angiography from 2001 to 2016, focusing on modalities and provider specialties. Medicare PSPS Master Files from 2001-2016 and POSPUF from 2016 were used to determine overall and specialty utilization of diagnostic catheter angiography (DCA), CT angiography (CTA), and MR angiography (MRA). From 2001 to 2016, extremity angiography increased from 1107 to 1590 extremities imaged per 100,000 beneficiaries, with rapid expansion of CTA (22 in 2001 to 619 in 2009; plateau of 645 in 2016), but declines in DCA (1039 to 914) and MRA (45 to 30). Over time, extremity angiography shifted from 94% DCA, 4% MRA, and 2% CTA to 58% DCA, 41% CTA, and 2% MRA. For radiologists, extremity angiography increased slightly (741 to 767) with increases in CTA (20 to 595) and large decreases in DCA (681 to 145), with MRA remaining low (40 to 27). Extremity angiography increased for cardiologists (197 to 349) and vascular surgeons (87 to 351), both overwhelmingly performing DCA. Radiologists' share of all extremity angiography shifted from 67% to 48%, with interventionalists (47%), generalists (43%), and abdominal radiologists (7.4%) providing most radiologist services in 2016. Throughout, radiologists were the dominant providers of CTA (89% to 92%) and MRA (89% to 90%). Extremity angiography utilization in Medicare beneficiaries increased nearly 50% from 2001 to 2016, largely related to CTA performed by radiologists. Of radiologists, interventionalists and generalists together render most services. Cardiologists and surgeons assumed a large share of DCA previously performed by radiologists.

Modified calcium subtraction in dual-energy CT angiography of the lower extremity runoff: impact on diagnostic accuracy for stenosis detection

OBJECTIVES

To investigate the diagnostic accuracy of a modified three-material decomposition calcium subtraction (CS) algorithm for the detection of arterial stenosis in dual-energy CT angiography (DE-CTA) of the lower extremity runoff compared to standard image reconstruction, using digital subtraction angiography (DSA) as the reference standard.

METHODS

Eighty-eight patients (53 males; mean age, 65.9 ± 11 years) with suspected peripheral arterial disease (PAD) who had undergone a DE-CTA examination of the lower extremity runoff between May 2014 and May 2015 were included in this IRB-approved, HIPAA-compliant retrospective study. Standard linearly blended and CS images were reconstructed and vascular contrast-to-noise ratios (CNR) were calculated. Two independent observers assessed subjective image quality using a 5-point Likert scale. Diagnostic accuracy for ≥ 50% stenosis detection was analyzed in a subgroup of 45 patients who had undergone additional DSA. Diagnostic accuracy parameters were estimated with a random-effects logistic regression analysis and compared using generalized estimating equations.

RESULTS

CS datasets showed higher CNR (15.3 ± 7.3) compared to standard reconstructions (13.5 ± 6.5, p < 0.001). Both reconstructions showed comparable qualitative image quality scores (CS, 4.64; standard, 4.57; p = 0.220). Diagnostic accuracy (sensitivity, specificity, positive and negative predictive values) for CS reconstructions was 96.5% (97.5%, 95.6%, 90.9%, 98.1) and 93.1% (98.8%, 90.4%, 82.3%, 99.1%) for standard images.

CONCLUSIONS

A modified three-material decomposition CS algorithm provides increased vascular CNR, equivalent qualitative image quality, and greater diagnostic accuracy for the detection of significant arterial stenosis of the lower extremity runoff on DE-CTA compared with standard image reconstruction.

KEY POINTS

• Calcified plaques may lead to overestimation of stenosis severity and false positive results, requiring additional invasive digital subtraction angiography (DSA). • A modified three-material decomposition algorithm for calcium subtraction provides greater diagnostic accuracy for the detection of significant arterial stenosis of the lower extremity runoff compared with standard image reconstruction. • The application of this algorithm in patients with heavily calcified vessels may be helpful to potentially reduce inconclusive CT angiography examinations and the need for subsequent invasive DSA.

CT Angiography of Peripheral Arterial Disease by 256-Slice Scanner: Accuracy, Advantages and Disadvantages Compared to Digital Subtraction Angiography

BACKGROUND

Peripheral arterial occlusive disease (PAOD) may cause disabling claudication or critical limb ischemia. Multidetector computed tomography (CT) technology has evolved to the level of 256-slice CT scanners which has significantly improved the spatial and temporal resolution of the images. This has provided the capability of chasing the contrast bolus at a fast speed enabling angiographic imaging of long segments of the body. These images can be reconstructed in various planes and various modes for detailed analysis of the peripheral vascular diseases which helps in making treatment decision.

PURPOSE

The aim of this retrospective study was to compare the CT angiograms (CTAs) of all cases of PAOD done by 256-slice CT scanner at a tertiary care vascular center and comparing these images with the digital subtraction angiograms (DSAs) of these patients.

MATERIALS AND METHODS

The retrospective study included 53 patients who underwent both CTA and DSA at our center over a period of 3 years from March 2013 to March 2016.

RESULTS

The CTA showed high sensitivity (93%) and specificity (92.7%) for overall assessment of degree of stenosis in a vascular segment in cases of aortic and lower limb occlusive disease. The assessment of lesions of infrapopliteal segment was comparatively inferior (sensitivity 91.6%, accuracy 73.3%, and positive predictive value 78.5%), more so in the presence of significant calcification. The advantages of CTA were its noninvasive nature, ability to image large area of body, almost no adverse effects to the patients, and better assessment of vessel wall disease. However, the CTA assessment of collaterals was inferior with a sensitivity of only 62.7% as compared to DSA. Overall, 256-slice CTA provides fast and accurate imaging of vascular tree which can restrict DSA only in few selected cases as a problem-solving tool where clinico-radiological mismatch is present.

Use of blood pool agents with steady-state MRI to assess the vascular system

Over the past two decades there have been significant advances in the use of magnetic resonance imaging (MRI) to assess the vascular system. New imaging sequences and improvements in magnet design have enabled the creation of higher spatial resolution images. MRI is now a viable alternative imaging modality when compared to both invasive angiography and computed tomographic angiography. The use of blood pool agents has further facilitated the use of MR angiography (MRA); their high molecular weight allows for lower doses of contrast medium administration while their prolonged presence in the blood stream allows for repeated high-quality volumetric imaging of both the arterial and venous circulation. As such, MRA is now no longer constrained by the tight windows for first-pass arterial and venous enhancement, which has resulted in the ability to assess and diagnose a large range of vascular pathologies in both arterial and venous systems. The intent of this review is to highlight MRI findings in common vascular pathologies including peripheral arterial disease (PAD), abnormalities of the abdominal aortic branches, postendovascular aortic aneurysm repair (EVAR) endoleak assessment, popliteal artery entrapment syndrome (PAES), deep venous thrombosis (DVT), vascular thoracic outlet syndrome (TOS), and vascular malformations. In addition, the latest MRI techniques currently used to optimally assess each of these pathologies will be discussed.

LEVEL OF EVIDENCE

5 Technical Efficacy: Stage 3 J. MAGN. RESON. IMAGING 2017;45:1559-1572.

Advances in axial imaging of peripheral vascular disease

Peripheral artery disease (PAD) has become increasingly common in the US patient population and can be a highly symptomatic and significant source of morbidity. When PAD is suspected, the first-line screening study that is obtained is typically a noninvasive evaluation that includes the ankle brachial index (ABI). Following a positive screening study, invasive catheter digital subtraction angiography (DSA) has been historically used to image the peripheral artery system and still remains the gold standard. However, newer developments in axial imaging including computed tomography angiography (CTA) and magnetic resonance angiography (MRA) have in large part supplanted DSA for imaging the peripheral artery system in clinical practice. Benefits of CTA include rapid noninvasive acquisition, wide availability, high spatial resolution, and the ability to generate isotropic datasets on 64-detector row and higher CT scanners, thereby allowing for multiplanar 3D reformatting. Drawbacks of CTA include the exposure to both iodinated contrast and ionizing radiation, although the radiation dose exposure is lower than for DSA, and newer techniques such as using low tube voltage and rapid acquisition times allow for lower contrast doses. The presence of vascular calcification also limits the evaluation of small distal arteries using CTA, although the development of dual-energy CT techniques has significantly addressed this issue. Benefits of MRA include the avoidance of exposure to ionizing radiation and high diagnostic accuracy, while drawbacks include limited availability and increased cost along with the risk of nephrogenic systemic fibrosis that is associated with gadolinium-based contrast agents, although the latter can be mitigated by using newer non-contrast MR angiography techniques. Future technical advances in CT and MR hardware and software and MR pulse sequences will likely lead to the broader applicability and increased accuracy of noninvasive axial imaging in the evaluation of patients with peripheral artery disease.

Comparison of CT and MR angiography in evaluation of peripheral arterial disease before endovascular intervention

BACKGROUND

Multidetector computed tomography angiography (MDCTA) and magnetic resonance angiography (MRA) are accurate techniques for selecting patients with peripheral arterial disease for surgical and endovascular treatment. No studies in the literature have directly compared MDCTA and MRA to establish which one should be employed, in patients suitable for both techniques, before endovascular treatment.

PURPOSE

To compare diagnostic performance of MDCTA vs MRA before endovascular intervention.

MATERIAL AND METHODS

We prospectively compared MDCTA (64 slices scanner) and MRA (1.5 T scanner; 3D gadolinium-enhanced bolus-chase acquisition plus time resolved acquisition on calves) to stratify 35 patients according to the TASC II score and a runoff severity score. We also evaluated the accuracy of both techniques in each arterial segment. Selective angiography performed during the treatment was the standard of reference.

RESULTS

MDCTA and MRA accurately classify disease in the aorto-iliac (accuracy 0.92 for MDCTA and MRA) and femoro-popliteal (MDCTA 0.94, MRA 0.90) segments. MDCTA was more accurate in stratifying disease in the infrapopliteal segments (0.96 vs. 0.9) and in assessing the impairment of runoff arteries (0.92 vs. 0.85) at per-segment analysis. MDCTA showed a higher confidence and a shorter examination time.

CONCLUSION

Our results suggest that MDCTA can be considered as a first-line investigation in patients being candidates for endovascular procedures when clinical history or duplex sonographic evaluation are indicative of severe impairment of the infrapopliteal segment.

Run-Off Computed Tomography Angiography (CTA) for Discriminating the Underlying Causes of Intermittent Claudication

Aim

To evaluate run-off computed tomography angiography (CTA) of abdominal aorta and lower extremities for detecting musculoskeletal pathologies and clinically relevant extravascular incidental findings in patients with intermittent claudication (IC) and suspected peripheral arterial disease (PAD). Does run-off CTA allow image-based therapeutic decision making by discriminating the causes of intermittent claudication in patients with suspected peripheral arterial disease PAD?

Material and Methods

Retrospective re-evaluation of CTAs performed in patients with acute or chronic intermittent claudication (i.e., Fontaine stages I to IIB) between January 2005 and October 2013. Allocation to one of three categories of underlying causes of IC symptoms: vascular, musculoskeletal (MSK) or both. Clinically relevant extravascular incidental findings were evaluated. Medical records were reviewed to verify specific therapies as well as main and incidental findings.

Results

While focused on vascular imaging, CTA image quality was sufficient for evaluation of the MSK system in all cases. The underlying cause of IC was diagnosed in run-off CTA as vascular, MSK and a combination in n = 138 (65%), n = 10 (4%), and n = 66 (31%) cases, respectively. Specific vascular or MSK therapy was recorded in n = 123 and n = 9 cases. In n = 82, no follow-up was possible. Clinically relevant extravascular incidental findings were detected in n = 65 patients (30%) with neoplasia, ascites and pleural effusion being the most common findings.

Discussion

Run-off CTA allows identification of vascular, MSK, and combined causes of IC in patients with suspected PAD and can guide specific therapy. CTA also allowed confident detection of crEVIF although detection did not necessarily trigger workup or treatment.

[Diagnostic accuracy of dual energy CT angiography in patients with diabetes mellitus]

OBJECTIVES

Peripheral arterial disease (PAD) represents a major and highly prevalent complication in patients with diabetes mellitus. The diagnostic, non-invasive work-up by computed tomography angiography (CTA) is limited in the presence of extensive calcification. The aim of the study was to determine the diagnostic accuracy of dual energy CTA (DE-CTA) for the detection and characterization of PAD in patients with diabetes mellitus.

MATERIAL AND METHODS

In this study 30 diabetic patients with suspected or known PAD were retrospectively included in the analysis. All subjects underwent DE-CTA (Somatom Definition Flash, Siemens Healthcare, Erlangen, Germany) prior to invasive angiography, which served as the reference standard. Blinded analysis included assessment of the presence and degree of peripheral stenosis on curved multiplanar reformatting (MPR) and maximum intensity projections (MIP). Conventional measures of diagnostic accuracy were derived.

RESULTS

Among the 30 subjects included in the analysis (83% male, mean age 70.0 ± 10.5 years, 83% diabetes type 2), the prevalence of critical stenosis in 331 evaluated vessel segments was high (30%). Dual energy CT identified critical stenoses with a high sensitivity and good specificity using curved MPR (100% and 93.1%, respectively) and MIP images (99% and 91.8%, respectively). In stratified analysis, the diagnostic accuracy was higher for stenosis pertaining to the pelvic and thigh vessels as compared with the lower extremities (curved MPR accuracy 97.1% vs. 99.2 vs. 90.9%; respectively, p < 0.001).

CONCLUSION

The use of DE-CTA allows reliable detection and characterization of peripheral arterial stenosis in patients with diabetes mellitus with higher accuracy in vessels in the pelvic and thigh regions compared with the vessels in the lower legs.

Gadolinium Enhanced MR-angiography Results in Patients With Peripheral Arterial Disease: Positive Predictive Value Compared to Surgery

Background:

Peripheral arterial disease (PAD) represents systematic atherosclerosis of great vessels. PAD affects approximately 10-20 % of patients older than 60 years and is associated with high mortality and morbidity rate debilitating individuals’ life.

Objectives:

To compare the results of Gadolinium enhanced MR-Angiography and surgery in patients suspected to have peripheral arterial disease.

Materials and Methods:

In this prospective cohort study, 30 consecutive patients matching the inclusion criteria were enrolled and MR-Angiography was performed prior to surgery for each one.

Results:

22 patients were male (73.3%) and the mean age was 60.3 ± 10.6 years in our study group. The most common artery for cut off and run off was superior femoral artery in both assessments. Proximal section of each artery was the most common anatomical section for cut off and run off. There was a same report of cut off artery by MR-Angiography and surgery (kappa coefficient of agreement was 0.96, P value < 0.001) and positive predictive value was 0.97 (95% CI: 0.83-0.99).

Conclusions:

According to our findings MR-angiography is an appropriate alternative imaging modality for patients suspected to have peripheral arterial disease and it facilitates the early diagnosis proposed by the clinical findings. Also beneficial characteristics of this method such as low exposure to ionizing radiation, repeatability, and low risk of contrast agent-induced nephropathy make it a modality of choice in patients with renal impairment.

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.

CT angiography after 20 years: a transformation in cardiovascular disease characterization continues to advance

Through a marriage of spiral computed tomography (CT) and graphical volumetric image processing, CT angiography was born 20 years ago. Fueled by a series of technical innovations in CT and image processing, over the next 5-15 years, CT angiography toppled conventional angiography, the undisputed diagnostic reference standard for vascular disease for the prior 70 years, as the preferred modality for the diagnosis and characterization of most cardiovascular abnormalities. This review recounts the evolution of CT angiography from its development and early challenges to a maturing modality that has provided unique insights into cardiovascular disease characterization and management. Selected clinical challenges, which include acute aortic syndromes, peripheral vascular disease, aortic stent-graft and transcatheter aortic valve assessment, and coronary artery disease, are presented as contrasting examples of how CT angiography is changing our approach to cardiovascular disease diagnosis and management. Finally, the recently introduced capabilities for multispectral imaging, tissue perfusion imaging, and radiation dose reduction through iterative reconstruction are explored with consideration toward the continued refinement and advancement of CT angiography.

Detailed cross-sectional study of 60 superficial femoral artery occlusions: morphological quantitative analysis can lead to a new classification

OBJECTIVE

Current clinical classification of superficial femoral artery (SFA) occlusions as defined by TASC II guidelines is limited to length and calcifications analysis on 2D angiograms, while state-of-the-art cross-sectional imaging like computed tomography angiography (CTA) and magnetic resonance angiography (MRA) provides much more detailed anatomical information than traditional invasive angiography: quantitative morphological analysis of these advanced imaging techniques could therefore be the basis of a refined classification.

METHODS AND RESULTS

Forty-six patients (65% men, 68±11.6 years) that underwent lower limb CTA were retrospectively included, totalizing 60 SFA occlusions. Lesions were classified as TASC II stage A in 3% of cases, stage B in 20%, stage C in 2% and stage D in 75%. For each pathological artery, curved multiplanar reconstructions following the occluded SFA course were used to measure the total length and the mean diameter of the occluded segment. Color-coded map provided an accurate estimation of calcifications' volume. Thirty-nine percent of the occlusions were total. Mean occluded segment length was 219±107 mm (range, 14-530 mm); mean occluded segment diameter was 6.1±1.6 mm (range, 3.4-10 mm); mean calcifications' volume in the occluded segment was 1,265±1,893 mm(3) (range, 0-8,815 mm(3)), corresponding to a percentage of 17.4%±20% (range, 0-88.7%). Shrinked occluded occlusions were defined by a mean diameter under 5 mm and heavily calcified occlusions by a mean percentage of calcifications above 4%. Use of these thresholds allowed the distinction of four groups of patients: heavily calcified occlusions with preserved caliber (56%), non-calcified occlusions with preserved caliber (19%), non-calcified occlusions with small caliber (15%) and heavily calcified occlusions with small caliber (10%).

CONCLUSIONS

SFA OCCLUSIONS ARE DISPARATE: this simple morphological study points out TASC II classification weaknesses for SFA occlusions, as quantitative cross-sectional imaging analysis with measurement of mean occluded diameter and percentage of calcifications can refine it. This could be particularly useful in the management of TASC II type D lesions, for which new endovascular revascularization techniques are arising, and where a CTA or MRA-based morphological classification could provide support in choosing between them.

KEYWORDS

Computer-assisted image processing; femoral artery; multidetector computed tomography; magnetic resonance angiography (MRA); peripheral arterial disease.

Three-station three-dimensional bolus-chase MR angiography with real-time fluoroscopic tracking

PURPOSE

To determine the feasibility of using real-time fluoroscopic tracking for bolus-chase magnetic resonance (MR) angiography of peripheral vasculature to image three stations from the aortoiliac bifurcation to the pedal arteries.

MATERIALS AND METHODS

This prospective study was institutional review board approved and HIPAA compliant. Eight healthy volunteers (three men; mean age, 48 years; age range, 30-81 years) and 13 patients suspected of having peripheral arterial disease (five men; mean age, 67 years; age range, 47-81 years) were enrolled and provided informed consent. All subjects were imaged with the fluoroscopic tracking MR angiographic protocol. Ten patients also underwent a clinical computed tomographic (CT) angiographic runoff examination. Two readers scored the MR angiographic studies for vessel signal intensity and sharpness and presence of confounding artifacts and venous contamination at 35 arterial segments. Mean aggregate scores were assessed. The paired MR angiographic and CT angiographic studies also were scored for visualization of disease, reader confidence, and overall diagnostic quality and were compared by using a Wilcoxon signed rank test.

RESULTS

Real-time fluoroscopic tracking performed well technically in all studies. Vessel segments were scored good to excellent in all but the following categories: For vessel signal intensity and sharpness, the abdominal aorta, iliac arteries, distal plantar arteries, and plantar arch were scored as fair to good; and for presence of confounding artifacts, the abdominal aorta and iliac arteries were scored as fair. The MR angiograms and CT angiograms did not differ significantly in any scoring category (reader 1: P = .50, .39, and .39; reader 2: P = .41, .61, and .33, respectively). CT scores were substantially better in 20% (four of 20) and 25% (five of 20) of the pooled evaluations for the visualization of disease and overall image quality categories, respectively, versus 5% (one of 20) for MR scores in both categories.

CONCLUSION

Three-station bolus-chase MR angiography with real-time fluoroscopic tracking provided high-spatial-resolution arteriograms of the peripheral vasculature, enabled precise triggering of table motion, and compared well with CT angiograms.

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.

Percutaneous intervention in peripheral artery disease improves calf muscle phosphocreatine recovery kinetics: a pilot study

We hypothesized that percutaneous intervention in the affected lower extremity artery would improve calf muscle perfusion and cellular metabolism in patients with claudication and peripheral artery disease (PAD) as measured by magnetic resonance imaging (MRI) and spectroscopy (MRS). Ten patients with symptomatic PAD (mean ± SD: age 57 ± 9 years; ankle-brachial index (ABI) 0.62 ± 0.17; seven males) were studied 2 months before and 10 months after lower extremity percutaneous intervention. Calf muscle phosphocreatine recovery time constant (PCr) in the revascularized leg was measured by (31)P MRS immediately after symptom-limited exercise on a 1.5-T scanner. Calf muscle perfusion was measured using first-pass gadolinium-enhanced MRI at peak exercise. A 6-minute walk and treadmill test were performed. The PCr recovery time constant improved significantly following intervention (91 ± 33 s to 52 ± 34 s, p < 0.003). Rest ABI also improved (0.62 ± 0.17 to 0.93 ± 0.25, p < 0.003). There was no difference in MRI-measured tissue perfusion or exercise parameters, although the study was underpowered for these endpoints. In conclusion, in this pilot study, successful large vessel percutaneous intervention in patients with symptomatic claudication, results in improved ABI and calf muscle phosphocreatine recovery kinetics.

Peripheral arterial disease: a literature review

INTRODUCTION

Peripheral arterial disease (PAD) is a common vascular condition that affects both quality of life and life expectancy with an increased risk of cardiovascular events.

SOURCES OF DATA

A literature search was carried out of Pub-Med, MEDLINE, the Cochrane Library and Google Scholar from the establishment of these databases up to February 2012. The search was performed by using the keywords 'peripheral arterial disease' and one of the following words: 'management', 'investigations', 'risk factors', 'epidemiology', 'revascularization', 'cryoplasty', 'atherectomy' and 'gene therapy'. Studies were limited to those published in English language.

AREAS OF AGREEMENT

Aggressive risk factors modification is needed to reduce cardiovascular-related mortality in PAD patients.

AREAS OF CONTROVERSY

Choice of endovascular or surgical intervention remains controversial in an ever-evolving field.

GROWING POINTS

There is a rapid expansion of endovascular technologies aiming to improve the effectiveness of this modality.

AREAS TIMELY FOR DEVELOPING RESEARCH

The advances in the fields of gene therapy and therapeutic angiogenesis mean these are potential future treatments. Tissue engineering is a developing area and aims to produce grafts with similar patency and infection profiles to those of autologous material. Further elucidation of the pathophysiology of atherosclerosis is required to provide new targets for pharmacotherapy.

Current approach to the diagnosis and treatment of femoral-popliteal arterial disease. A systematic review

Peripheral arterial disease (PAD) is a common manifestation of atherosclerosis affecting 5 million adults in the United States, with an age-adjusted prevalence of 4% to 15% and increasing up to 30% with age and the presence of cardiovascular risk factors. In this article we focus on lower extremity PAD and specifically on the superficial femoral and proximal popliteal artery (SFPA), which are the most common anatomic locations of lower extremity atherosclerosis. We summarize current evidence and perform a systematic review on the diagnostic evaluation as well as the medical, endovascular and surgical management of SFPA disease.

Graph-matching-based computed tomography angiography in peripheral arterial occlusive disease

The objective of this study is to compare a graph-matching-based software and a conventional tool for postprocessing of computed tomography angiography (CTA) in correlation with the gold standard digital subtraction angiography. Sensitivity, specificity, accuracy, and interobserver agreement increased from 80.3% to 92.9%, from 69.1% to 92.4%, from 73.5% to 92.8%, and from 0.45 to 0.96, respectively, using the graph-matching-based technique. Graph-matching-based CTA increases sensitivity, specificity, accuracy, and interobserver agreement in comparison to a conventional bone elimination tool in the assessment of peripheral arterial occlusive disease.

Current concepts in the pathophysiology and management of arteriovenous access-induced hand ischemia

The manifestations of hand ischemia because of an arteriovenous access can range from hand pain, tissue necrosis, and loss of the entire hand. Recent data have emphasized that multiple mechanisms (arterial steal, ie, retrograde flow, arterial stenosis, and arterial calcification) are responsible for inducing hand ischemia. Because any or a combination of the 3 mechanisms can lead to peripheral ischemia, distal hypoperfusion ischemic syndrome is a more appropriate term to denote hand ischemia. A detailed history, physical examination, and differential diagnosis form the initial step in the management of distal hypoperfusion ischemic syndrome. A complete arteriogram to evaluate the circulation of the extremity from the aortic arch to the palmar arch is essential. The choice of treatment modality should be based on this evaluation. In this article, we review the pathophysiology and present current strategies to ameliorate distal hypoperfusion ischemic syndrome.

Multifactorial determinants of functional capacity in peripheral arterial disease: uncoupling of calf muscle perfusion and metabolism

OBJECTIVES

We aimed to investigate the pathophysiology of peripheral arterial disease (PAD) by examining magnetic resonance imaging (MRI) and spectroscopic (MRS) correlates of functional capacity.

BACKGROUND

Despite the high prevalence, morbidity, and cost of PAD, its pathophysiology is incompletely understood.

METHODS

Eighty-five patients (age 68 +/- 10 years) with mild-to-moderate PAD (ankle-brachial index 0.69 +/- 0.14) had their most symptomatic leg studied by MRI/MRS. Percent wall volume in the superficial femoral artery was measured with black blood MRI. First-pass contrast-enhanced MRI calf muscle perfusion and (31)P MRS phosphocreatine recovery time constant (PCr) were measured at peak exercise in calf muscle. All patients underwent magnetic resonance angiography (MRA), treadmill testing with maximal oxygen consumption measurement, and a 6-min walk test.

RESULTS

Mean MRA index of number and severity of stenoses was 0.84 +/- 0.68 (normal 0), % wall volume 74 +/- 11% (normal 46 +/- 7%), tissue perfusion 0.039 +/- 0.015 s(-1) (normal 0.065 +/- 0.013 s(-1)), and PCr 87 +/- 54 s (normal 34 +/- 16 s). MRA index, % wall volume, and ankle-brachial index correlated with most functional measures. PCr was the best correlate of treadmill exercise time, whereas calf muscle perfusion was the best correlate of 6-min walk distance. No correlation was noted between PCr and tissue perfusion.

CONCLUSIONS

Functional limitations in PAD are multifactorial. As measured by MRI and spectroscopy, atherosclerotic plaque burden, stenosis severity, tissue perfusion, and energetics all play a role. However, cellular metabolism is uncoupled from tissue perfusion. These findings suggest a potential role for therapies that regress plaque, increase tissue perfusion, and/or improve cellular metabolism. (Comprehensive Magnetic Resonance of Peripheral Arterial Disease; NCT00587678).

Value of MDCT angiography in developing treatment strategies for critical limb ischemia

OBJECTIVE

The purpose of this study was to assess the value of MDCT angiography in the development of strategies for the treatment of patients with critical limb ischemia.

MATERIALS AND METHODS

During a 12-month period, 150 patients were referred to our department for CT angiography of the peripheral arteries. All patients (n = 28) with clinical stage IV peripheral arterial occlusive disease were included in this retrospective study. The treatment reports, discharge summaries, and follow-up examinations were reviewed to ascertain the number of patients correctly treated on the basis of the CT angiographic findings.

RESULTS

After CT angiography, endovascular treatment was indicated for eight patients, surgical revascularization for four patients, and a combined endovascular and surgical approach for two patients. That the correct treatment decision had been made in all 14 cases was confirmed on the basis of successful endovascular or surgical revascularization. In eight patients, medical treatment was indicated, and one patient underwent amputation at the level of the thigh. Five patients were referred for complementary digital subtraction angiography, but no additional findings were made. During follow-up, three of the original 28 patients were in grave general condition and died within 7 weeks after CT angiography. Thirteen patients needed no additional treatment during the follow-up period through January 2008. After a median treatment-free interval of 381 days, 12 patients underwent additional revascularization because of clinical progression of disease.

CONCLUSION

MDCT angiographic findings lead to accurate recommendations for the management of critical limb ischemia. Thus CT angiography seems to be an important technique for the management of stage IV peripheral arterial occlusive disease in patients without absolute contraindications to CT angiography.

Dual-energy CT discrimination of iodine and calcium: experimental results and implications for lower extremity CT angiography

RATIONALE AND OBJECTIVES

The purpose of this work was to measure the accuracy of dual-energy computed tomography for identifying iodine and calcium and to determine the effects of calcium suppression in phantoms and lower-extremity computed tomographic (CT) angiographic data sets.

MATERIALS AND METHODS

Using a three-material basis decomposition method for 80- and 140-kVp data, the accuracy of correctly identified contrast medium and calcium voxels and the mean attenuation before and after calcium suppression were computed. Experiments were first performed on a phantom of homogenous contrast medium and hydroxyapatite samples with mean attenuation of 57.2, 126, and 274 Hounsfield units (HU) and 50.0, 122, and 265 HU, respectively. Experiments were repeated in corresponding attenuation groups of voxels from manually segmented bones and contrast medium-enhanced arteries in a lower-extremity CT angiographic data set with mean attenuation of 293 and 434 HU, respectively. Calcium suppression in atherosclerotic plaques of a cadaveric specimen was also studied, using micro-computed tomography as a reference, and in a lower-extremity CT angiographic data set with substantial below-knee calcified plaques.

RESULTS

Higher concentrations showed increased accuracy of iodine and hydroxyapatite identification of 87.4%, 99.7%, and 99.9% and 88.0%, 95.0%, and 99.9%, respectively. Calcium suppression was also more accurate with higher concentrations of iodine and hydroxyapatite, with mean attenuation after suppression of 47.1, 122, and 263 HU and 7.14, 11.6, and 12.6 HU, respectively. Similar patterns were seen in the corresponding attenuation groups of the contrast medium-enhanced arteries and bone in the clinical data set, which had overall accuracy of 81.3% and 78.9%, respectively, and mean attenuation after calcium suppression of 254 and 73.7 HU, respectively. The suppression of calcified atherosclerotic plaque was accurate compared with the micro-CT reference; however, the suppression in the clinical data set showed probable inappropriate suppression of the small vessels.

CONCLUSION

Dual-energy computed tomography can detect and differentiate between contrast medium and calcified tissues, but its accuracy is dependent on the CT density of tissues and limited when CT attenuation is low.