Whole-body (201)Tl scintigraphy can detect exercise lower limb perfusion abnormalities in asymptomatic diabetic patients with normal Doppler pressure indices

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.

SPECT/CT imaging of lower extremity perfusion reserve: A non-invasive correlate to exercise tolerance and cardiovascular fitness in patients undergoing clinically indicated myocardial perfusion imaging

BACKGROUND

Although exercise is often prescribed for the management of cardiovascular diseases, a non-invasive imaging approach that quantifies skeletal muscle physiology and correlates with patients' functional capacity and cardiovascular fitness has been absent. Therefore, we evaluated the potential of lower extremity single photon emission computed tomography (SPECT)/CT perfusion imaging as a non-invasive correlate to exercise tolerance and cardiovascular fitness.

METHODS

Patients (n = 31) undergoing SPECT/CT myocardial perfusion imaging underwent additional stress/rest SPECT/CT imaging of the lower extremities. CT-based image segmentation was used for regional quantification of perfusion reserve within the tibialis anterior, soleus, and gastrocnemius muscles. Metabolic equivalents (METs) at peak exercise and heart rate recovery (HRR) after exercise were recorded.

RESULTS

Peak METs were significantly associated with perfusion reserve of tibialis anterior (p = 0.02), soleus (p = 0.01) and gastrocnemius (p = 0.01). HRR was significantly associated with perfusion reserve of the soleus (p = 0.02) and gastrocnemius (p = 0.04) muscles. Perfusion reserve of the tibialis anterior (40.6 ± 20.2%), soleus (35.4 ± 16.7%), and gastrocnemius (29.7 ± 19.1%) all significantly differed from each other.

CONCLUSIONS

SPECT/CT imaging provides regional quantification of skeletal muscle perfusion reserve which is significantly associated with exercise tolerance and cardiovascular fitness. Future application of SPECT/CT may elucidate the underlying skeletal muscle adapations to exercise therapy in patients with cardiovascular diseases.

Prognostic Value of Radiotracer-Based Perfusion Imaging in Critical Limb Ischemia Patients Undergoing Lower Extremity Revascularization

OBJECTIVES

The purpose of this study was to evaluate the prognostic value of single-photon emission computed tomography (SPECT)/computed tomography (CT) imaging of angiosome foot perfusion for predicting amputation outcomes in patients with critical limb ischemia (CLI) and diabetes mellitus (DM).

BACKGROUND

Radiotracer imaging can assess microvascular foot perfusion and identify regional perfusion abnormalities in patients with critical limb ischemia CLI and DM, but the relationship between perfusion response to revascularization and subsequent clinical outcomes has not been evaluated.

METHODS

Patients with CLI, DM, and nonhealing foot ulcers (n = 25) were prospectively enrolled for SPECT/CT perfusion imaging of the feet before and after revascularization. CT images were used to segment angiosomes (i.e., 3-dimensional vascular territories) of the foot. Relative changes in radiotracer uptake after revascularization were evaluated within the ulcerated angiosome. Incidence of amputation was assessed at 3 and 12 months after revascularization.

RESULTS

SPECT/CT detected a significantly lower microvascular perfusion response for patients who underwent amputation compared with those who remained amputation free at 3 (p = 0.01) and 12 (p = 0.01) months after revascularization. The cutoff percent change in perfusion for predicting amputation at 3 months was 7.55%, and 11.56% at 12 months. The area under the curve based on the amputation outcome was 0.799 at 3 months and 0.833 at 12 months. The probability of amputation-free survival was significantly higher at 3 (p = 0.002) and 12 months (p = 0.03) for high-perfusion responders than low-perfusion responders to revascularization.

CONCLUSIONS

SPECT/CT imaging detects regional perfusion responses to lower extremity revascularization and provides prognostic value in patients with CLI (Radiotracer-Based Perfusion Imaging of Patients With Peripheral Arterial Disease; NCT03622359).

Clinical Applications for Radiotracer Imaging of Lower Extremity Peripheral Arterial Disease and Critical Limb Ischemia

Peripheral arterial disease (PAD) is an atherosclerotic occlusive disease of the non-coronary vessels that is characterized by lower extremity tissue ischemia, claudication, increased prevalence of lower extremity wounds and amputations, and impaired quality of life. Critical limb ischemia (CLI) represents the severe stage of PAD and is associated with additional risk for wound formation, amputation, and premature death. Standard clinical tools utilized for assessing PAD and CLI primarily focus on anatomical evaluation of peripheral vascular lesions or hemodynamic assessment of the peripheral circulation. Evaluation of underlying pathophysiology has traditionally been achieved by radiotracer-based imaging, with many clinical investigations focusing on imaging of skeletal muscle perfusion and cases of foot infection/inflammation such as osteomyelitis and Charcot neuropathic osteoarthropathy. As advancements in hybrid imaging systems and radiotracers continue to evolve, opportunities for molecular imaging of PAD and CLI are also emerging that may offer novel insight into associated complications such as peripheral atherosclerosis, alterations in skeletal muscle metabolism, and peripheral neuropathy. This review summarizes the pros and cons of radiotracer-based techniques that have been utilized in the clinical environment for evaluating lower extremity ischemia and common pathologies associated with PAD and CLI.

Radiotracer Imaging Allows for Noninvasive Detection and Quantification of Abnormalities in Angiosome Foot Perfusion in Diabetic Patients With Critical Limb Ischemia and Nonhealing Wounds

Background:

Single photon emission computed tomography (SPECT)/computed tomography (CT) imaging allows for assessment of skeletal muscle microvascular perfusion but has not been quantitatively assessed in angiosomes, or 3-dimensional vascular territories, of the foot. This study assessed and compared resting angiosome foot perfusion between healthy subjects and diabetic patients with critical limb ischemia (CLI). Additionally, the relationship between SPECT/CT imaging and the ankle–brachial index—a standard tool for evaluating peripheral artery disease—was assessed.

Methods and Results:

Healthy subjects (n=9) and diabetic patients with CLI and nonhealing ulcers (n=42) underwent SPECT/CT perfusion imaging of the feet. CT images were segmented into angiosomes for quantification of relative radiotracer uptake, expressed as standardized uptake values. Standardized uptake values were assessed in ulcerated angiosomes of patients with CLI and compared with whole-foot standardized uptake values in healthy subjects. Serial SPECT/CT imaging was performed to assess uptake kinetics of technetium-99m-tetrofosmin. The relationship between angiosome perfusion and ankle–brachial index was assessed via correlational analysis. Resting perfusion was significantly lower in CLI versus healthy subjects (P=0.0007). Intraclass correlation coefficients of 0.95 (healthy) and 0.93 (CLI) demonstrated excellent agreement between serial perfusion measurements. Correlational analysis, including healthy and CLI subjects, demonstrated a significant relationship between ankle–brachial index and SPECT/CT (P=0.01); however, this relationship was not significant for diabetic CLI patients only (P=0.2).

Conclusions:

SPECT/CT imaging assesses regional foot perfusion and detects abnormalities in microvascular perfusion that may be undetectable by conventional ankle–brachial index in patients with diabetes mellitus. SPECT/CT may provide a novel approach for evaluating responses to targeted therapies.

Diagnostic methods for measurement of peripheral blood flow during exercise in patients with type 2 diabetes and peripheral artery disease: a systematic review

INTRODUCTION

Measurement of systolic ankle and to some extent toe pressure in patients suffering from combined type 2 diabetes mellitus (T2DM) and peripheral arterial disease (PAD) face several obstacles due to complex changes in the vascular bed. The aim of this review was to address the current literature on blood flow during exercise in patients with PAD and T2DM and assess the feasibility of these methods to diagnose and grade arterial insufficiency.

EVIDENCE ACQUISITION

A systematic review of the PubMed and EMBASE databases, supplemented by hand searching was performed according to PRISMA guidelines. Clinical studies evaluating methods to investigate peripheral blood flow in patients with PAD and T2DM during exercise were included.

EVIDENCE SYNTHESIS

In total nine eligible studies consisting of 1105 non-diabetic PAD patients, 336 diabetic PAD patients, 161 diabetic patients without PAD and 69 healthy controls were included in the review. Near-infrared spectroscopy (NIRS) was described in three studies, transcutaneous oxygen pressure measurement (TcpO2) in two and the following methods described in single studies: thermodilution, contrast enhanced ultrasound (CEUS), scintigraphy and TcpO2 in combination with ultrasound. These studies shows that patients with PAD and T2DM compared with patients with only PAD suffers different atherosclerotic lesions characterised by increased arterial stiffness and microcirculation abnormalities, not well differentiated by pressure measurement alone. Investigating patients with PAD and T2DM during exercise reveals that NIRS, TcpO2, CEUS, and scintigraphy have distinct advantages over ankle and toe-pressure.

CONCLUSIONS

Using methods like NIRS, TcpO2, CEUS and scintigraphy, peripheral blood flow during exercise can be measured at a detailed level and potentially improve future severity grading in patients with combined T2DM and PAD.

High prevalence of exercise-induced ischemia in the asymptomatic limb of patients with apparently strictly unilateral symptoms and unilateral peripheral artery disease

BACKGROUND:

The prevalence of exercise-induced ischemia in the asymptomatic limb of patients with unilateral claudication based on history and treadmill evaluation, and with unilateral ipsilateral peripheral artery disease (i.e ankle-to-brachial systolic pressure index <0.90) is unknown.

METHODS:

We detected exercise-induced ischemia in the asymptomatic limb of patients with apparently unilateral claudication. Among 6059 exercise-oximetry tests performed in 3407 nondiabetic and 961 diabetic patients. We estimated the intensity of ischemia in the both limb (buttocks and calves) using the lowest minimum value of the decrease from rest of oxygen pressure (DROP; limb changes minus chest changes from rest), with significant ischemia defined as DROP lower than -15 mmHg.

RESULTS:

We found 152 tests performed in 142 nondiabetic patients and 40 tests performed in 38 diabetic patients. The asymptomatic limb showed significant ischemia in 46.7% and 37.5% of the tests. Strictly unilateral exercise-induced claudication with apparently unilateral peripheral artery disease was rare (<4% of all tests). However, among these highly selected tests, significant ischemia was found in the asymptomatic limb in more than one-third of cases.

CONCLUSION:

The asymptomatic limb of patients with peripheral artery disease should not be considered a normal limb.

Spinal Cord Stimulation Improves the Microvascular Perfusion Insufficiency Caused by Critical Limb Ischemia

OBJECTIVE

This retrospective case-controlled study intended to identify the benefits and efficacy of spinal cord stimulation (SCS) as a therapeutic strategy for patients with perfusion problems caused by critical limb ischemia (CLI). The outcomes of patients who received SCS were compared with those of patients who did not receive SCS.

METHODS

This study recruited 78 patients who were diagnosed with perfusion problems over the period of 2003-2011. Lower-limb Thallium-201 (²⁰¹ Tl) scintigraphy revealed that the patients exhibited a perfusion difference of <0.95. Thirty-seven of the recruited patients received SCS treatment and 41 did not receive SCS treatment. All patients received the same medication: 100 mg aspirin once a day and 500 mg paracetamol thrice a day. The outcomes of walking distance, walking time, and sleeping quality were measured and recorded. Pain intensities were evaluated using the visual analog scale (VAS) scoring system.

RESULTS

Prior to SCS implantation, patients in the SCS treatment group had worse walking distance (64.86 ± 40.80 vs. 613.70 ± 535.00, p < 0.001), walking time (2.65 ± 1.64 vs. 13.90 ± 11.91, p < 0.001), and sleep quality (1.70 ± 0.78 vs. 3.32 ± 1.17, p < 0.001) than patients in the non-SCS treatment group. At the one-year follow-up, however, patients in the SCS treatment group had significantly better walking distance (1595.00 ± 483.60, p < 0.001), walking time (48.92 ± 14.10, p < 0.001), and sleep quality (4.65 ± 0.92, p < 0.001) than patients in the non-SCS treatment group. Moreover, the VAS score of patients in the SCS treatment group improved one week (8.63 ± 0.54 vs. 4.48 ± 0.59, p < 0.001) and one year after SCS implantation (2.35 ± 0.62, p < 0.001). By contrast, at the one-year follow-up, the walking distance (277.60 ± 374.80, p = 0.002), walking time (9.44 ± 10.73, p = 0.078), sleep quality (2.20 ± 1.10, p < 0.001), and VAS score (7.98 ± 0.43, p = 0.020) of patients in the non-SCS treatment group worsened. Furthermore, lower-limb ²⁰¹ Tl scintigraphy revealed that microcirculation intensity increased in the lower extremities of patients in the SCS treatment group after SCS implantation relative to that before SCS implantation. Most importantly, 10 of the 41 patients in the non-SCS treatment group required the use of wheelchairs, whereas none of the patients in the SCS treatment group required the use of wheelchairs.

CONCLUSION

Treatment of CLI patient with SCS improved patient's walking ability, pain severity, and sleep quality. SCS should be considered as an effective treatment toward limb salvage in CLI.

Novel Applications of Radionuclide Imaging in Peripheral Vascular Disease

Peripheral vascular disease (PVD) is a progressive atherosclerotic disease that leads to stenosis or occlusion of blood vessels supplying the lower extremities. Current diagnostic imaging techniques commonly focus on evaluation of anatomy or blood flow at the macrovascular level and do not permit assessment of the underlying pathophysiology associated with disease progression or treatment response. Molecular imaging with radionuclide-based approaches can offer novel insight into PVD by providing noninvasive assessment of biological processes such as angiogenesis and atherosclerosis. This article discusses emerging radionuclide-based imaging approaches that have potential clinical applications in the evaluation of PVD progression and treatment.

Insights Into Microcirculation Underlying Critical Limb Ischemia by Single-Photon Emission Computed Tomography

Perfusion difference is used as a parameter to evaluate microcirculation. This study aims to differentiate lower-limb perfusion insufficiency from neuropathy to prevent possible occurrence of failed back surgery syndrome (FBSS).Patients were retrospectively gathered from 134 FBSS cases diagnosed in the past 7 years. Up to 82 cases that were excluded from neuralgia by radiologic imaging, electrodiagnostic electromyography, and nerve conduction velocity were enrolled in this study. Perfusion difference was evaluated by single-photon emission computed tomography, and pain intensities were recorded via visual analog scale (VAS) score.Lower perfusion at the left leg comprises 51.2% (42 of 82) of the patients. The mean perfusion difference of the 82 patients was 0.86 ± 0.05 (range: 0.75-0.93). Patients with systemic vascular diseases exhibited significantly higher perfusion difference than that of patients without these related diseases (P < 0.05), except for renal insufficiency (P = 0.134). Significant correlation was observed between perfusion difference and VAS score (r = -0.78; P < 0.0001; n = 82).In this study, we presented perfusion difference as a parameter for evaluating microcirculation, which cannot be detected by ultrasonography or angiography.

Radiotracer imaging of peripheral vascular disease

Peripheral vascular disease (PVD) is an atherosclerotic disease affecting the lower extremities, resulting in skeletal muscle ischemia, intermittent claudication, and, in more severe stages of disease, limb amputation and death. The evaluation of therapy in this patient population can be challenging, as the standard clinical indices are insensitive to assessment of regional alterations in skeletal muscle physiology. Radiotracer imaging of the lower extremities with techniques such as PET and SPECT can provide a noninvasive quantitative technique for the evaluation of the pathophysiology associated with PVD and may complement clinical indices and other imaging approaches. This review discusses the progress in radiotracer-based evaluation of PVD and highlights recent advancements in molecular imaging with potential for clinical application.

Multimodality imaging approach for serial assessment of regional changes in lower extremity arteriogenesis and tissue perfusion in a porcine model of peripheral arterial disease

BACKGROUND

A standard quantitative imaging approach to evaluate peripheral arterial disease does not exist. Quantitative tools for evaluating arteriogenesis in vivo are not readily available, and the feasibility of monitoring serial regional changes in lower extremity perfusion has not been examined.

METHODS AND RESULTS

Serial changes in lower extremity arteriogenesis and muscle perfusion were evaluated after femoral artery occlusion in a porcine model using single photon emission tomography (SPECT)/CT imaging with postmortem validation of in vivo findings using gamma counting, postmortem imaging, and histological analysis. Hybrid 201Tl SPECT/CT imaging was performed in pigs (n=8) at baseline, immediately postocclusion, and at 1 and 4 weeks postocclusion. CT imaging was used to identify muscle regions of interest in the ischemic and nonischemic hindlimbs for quantification of regional changes in CT-defined arteriogenesis and quantification of 201Tl perfusion. Four weeks postocclusion, postmortem tissue 201Tl activity was measured by gamma counting, and immunohistochemistry was performed to assess capillary density. Relative 201Tl retention (ischemic/nonischemic) was reduced immediately postocclusion in distal and proximal muscles and remained lower in calf and gluteus muscles 4 weeks later. Analysis of CT angiography revealed collateralization at 4 weeks within proximal muscles (P<0.05). SPECT perfusion correlated with tissue gamma counting at 4 weeks (P=0.01). Increased capillary density was seen within the ischemic calf at 4 weeks (P=0.004).

CONCLUSIONS

201Tl SPECT/CT imaging permits serial, regional quantification of arteriogenesis and resting tissue perfusion after limb ischemia. This approach may be effective for detection of disease and monitoring therapy in peripheral arterial disease.

Magnetic resonance imaging in peripheral arterial disease: reproducibility of the assessment of morphological and functional vascular status

OBJECTIVES

The aim of the current study was to test the reproducibility of different quantitative magnetic resonance imaging (MRI) methods to assess the morphologic and functional peripheral vascular status and vascular adaptations over time in patients with peripheral arterial disease (PAD).

MATERIALS AND METHODS

Ten patients with proven PAD (intermittent claudication) and arterial collateral formation within the upper leg and 10 healthy volunteers were included. All subjects underwent 2 identical MR examinations of the lower extremities on a clinical 1.5-T MR system, with a time interval of at least 3 days. The MR protocol consisted of 3D contrast-enhanced MR angiography to quantify the number of arteries and artery diameters of the upper leg, 2D cine MR phase contrast angiography flow measurements in the popliteal artery, dynamic contrast-enhanced (DCE) perfusion imaging to determine the influx constant and area under the curve, and dynamic blood oxygen level-dependent (BOLD) imaging in calf muscle to measure maximal relative T2* changes and time-to-peak. Data were analyzed by 2 independent MRI readers. Interscan and inter-reader reproducibility were determined as outcome measures and expressed as the coefficient of variation (CV).

RESULTS

Quantification of the number of arteries, artery diameter, and blood flow proved highly reproducible in patients (CV = 2.6%, 4.5%, and 15.8% at interscan level and 9.0%, 8.2%, and 7.0% at interreader level, respectively). Reproducibility of DCE and BOLD MRI was poor in patients with a CV up to 50.9%.

CONCLUSIONS

Quantification of the morphologic vascular status by contrast-enhanced MR angiography, as well as phase contrast angiography MRI to assess macrovascular blood flow proved highly reproducible in both PAD patients and healthy volunteers and might therefore be helpful in studying the development of collateral arteries in PAD patients and in unraveling the mechanisms underlying this process. Functional assessment of the microvascular status using DCE and BOLD, MRI did not prove reproducible at 1.5 T and is therefore currently not suitable for (clinical) application in PAD.

Peripheral arterial disease assessment: wall, perfusion, and spectroscopy

INTRODUCTION

Peripheral arterial disease (PAD) is characterized by lower limb arterial obstruction due to atherosclerosis and is increasingly common. Presently used methods for diagnosis and follow-up as well as for assessment of novel therapies are limited.

MATERIALS AND METHODS

Three distinct magnetic resonance examinations were developed. The first was high-resolution black-blood atherosclerotic plaque imaging of the superficial femoral artery using a surface coil and flow saturation. Second, first-pass contrast-enhanced dual-contrast perfusion imaging of the calf muscle was performed at peak exercise using a magnetic resonance (MR)-compatible pedal ergometer. Lastly, (31)P MR spectroscopy was also performed at peak exercise to measure phosphocreatine (PCr) recovery kinetics.

RESULTS

Seventeen patients (age, 63 +/- 10 yrs) with mild to moderate PAD were studied with black-blood atherosclerotic plaque imaging. Mean atherosclerotic plaque volume measured was 7.27 +/- 3.73 cm(3). Eleven patients (age, 61 +/- 11 yrs) with mild to moderate symptomatic PAD and 22 normal control subjects were studied with first-pass contrast-enhanced perfusion imaging. Perfusion index was stepwise increased from patients to normal subjects with matched workload to normal subjects at maximal exercise. For PCr recovery kinetics, 20 patients with mild to moderate PAD and 14 controls were studied. The median recovery time constant of PCr was 34.7 seconds in the controls and 91.0 seconds in the PAD patients (P < 0.0001).

CONCLUSIONS

Three distinct MR examinations of different aspects of peripheral arterial disease have been developed and tested and shown to differentiate patients with mild to moderate PAD from normal controls. Taken together, these tests are potential quantitative end points for clinical trials of novel therapies in PAD.

Calf muscle perfusion at peak exercise in peripheral arterial disease: measurement by first-pass contrast-enhanced magnetic resonance imaging

PURPOSE

To develop a contrast-enhanced magnetic resonance (MR) technique to measure skeletal muscle perfusion in peripheral arterial disease (PAD).

MATERIALS AND METHODS

A total of 11 patients (age = 61 +/- 11 years) with mild to moderate symptomatic PAD (ankle-brachial index [ABI] = 0.75 +/- 0.08) and 22 normals were studied using an MR-compatible ergometer. PAD and normal(max) (Nl(max); N = 11) exercised to exhaustion. Nl(low) (N = 11) exercised to the same workload achieved by PAD. At peak exercise, 0.1 mm/kg of gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) was infused at 3-4 cm(3)/second followed by a saline flush at the same rate. A dual-contrast gradient echo (GRE) sequence enabled simultaneous acquisition of muscle perfusion and arterial input function (AIF). The perfusion index (PI) was defined as the slope of the time-intensity curve (TIC) in muscle divided by the arterial TIC slope.

RESULTS

Median workload was 120 Joules in PAD, 210 Joules in Nl(low), and 698 Joules in Nl(max) (P < 0.001 vs. Nl(low) and PAD). Median PI was 0.29 in PAD (25th and 75th percentiles [%] = 0.20, 0.40), 0.48 in Nl(low) (25th, 75th % = 0.36, 0.62; P < 0.02 vs. PAD), and 0.69 in Nl(max) (25th, 75th % = 0.5, 0.77; P < 0.001 vs. PAD). Area under the ROC-curve for PI differentiating patients from Nl(max) was 0.95 (95% confidence interval [CI] = 0.77-0.99).

CONCLUSION

Peak-exercise measurement of lower limb perfusion with dual-contrast, first-pass MR distinguishes PAD from normals. This method may be useful in the study of novel therapies for PAD.

Quantitative evaluation of muscle perfusion with CEUS and with MR

Functional imaging might increase the role of imaging in muscular diseases, since alterations of muscle morphology alone are not specific for a particular disease. Perfusion, i.e., the blood flow per tissue and time unit including capillary flow, is an important functional parameter. Pathological changes of skeletal muscle perfusion can be found in various clinical conditions, such as degenerative or inflammatory myopathies or peripheral arterial occlusive disease. This article reviews the theoretical basics of functional radiological techniques for assessing skeletal muscle perfusion and focuses on contrast-enhanced ultrasound (CEUS) and magnetic resonance imaging (MRI) techniques. Also, the applications of microvascular imaging, such as in detection of myositis and for discriminating myositis from other myopathies or evaluating peripheral arterial occlusive disease, are presented, and possible clinical indications are discussed. In conclusion, dedicated MR and CEUS methods are now available that visualize and quantify (patho-)physiologic information about microcirculation within skeletal muscles in vivo and hence establish a useful diagnostic tool for muscular diseases.

Assessment of skeletal muscle perfusion by contrast medium first-pass magnetic resonance imaging: technical feasibility and preliminary experience in healthy volunteers

PURPOSE

To probe the potential and pitfalls of contrast medium first-pass skeletal muscle perfusion imaging under reproducible stress conditions.

MATERIALS AND METHODS

Magnetic resonance (MR) signal dynamics in calf muscle and lower-leg arteries of 20 healthy volunteers were analyzed under postarterial occlusion reactive hyperemia and concurrent contrast medium first pass, using a saturation recovery spoiled gradient-echo type sequence without heartbeat synchronization. The signal vs. time curves were analyzed descriptively and by two-compartment deconvolution analysis.

RESULTS

Highly significant changes in calf muscle signal dynamics in the hyperemic leg vs. those in the contralateral leg at rest were found in phenomenological and deconvolution analysis. Although a distortion of the arterial signal derived input function by inflow effects was found to cause large variations of the deconvolution results, the magnitude of the observed effects suggested a potential for immediate visual detection of areas with reduced tissue perfusion.

CONCLUSION

The first-pass approach appeared promising for visual evaluation. However, a disentanglement of inflow and contrast medium-induced effects on arterial signal intensity was deemed a prerequisite for input function-based numerical assessment.