Ungated radial quiescent-inflow single-shot (UnQISS) magnetic resonance angiography using optimized azimuthal equidistant projections

Turbo spin-echo-based enhanced acceleration-selective arterial spin labeling without electrocardiography or peripheral pulse unit triggering and contrast enhancement for lower extremity MRA

PURPOSE

Lower extremity magnetic resonance angiography (MRA) without electrocardiography (ECG) or peripheral pulse unit (PPU) triggering and contrast enhancement is beneficial for diagnosing peripheral arterial disease (PAD) while avoiding synchronization failure and nephrogenic systemic fibrosis. This study aimed to compare the diagnostic performance of turbo spin-echo-based enhanced acceleration-selective arterial spin labeling (eAccASL) (TSE-Acc) of the lower extremities with that of turbo field-echo-based eAccASL (TFE-Acc) and triggered angiography non-contrast enhanced (TRANCE).

METHODS

Nine healthy volunteers and a patient with PAD were examined on a 3.0 Tesla magnetic resonance imaging (MRI) system. The artery-to-muscle signal intensity ratio (SIR) and contrast-to-noise ratio (CNR) were calculated. The arterial visibility (1: poor, 4: excellent) and artifact contamination (1: severe, 4: no) were independently assessed by two radiologists. Phase-contrast MRI and digital subtraction angiography were referenced in a patient with PAD. Friedman's test and a post-hoc test according to the Bonferroni-adjusted Wilcoxon signed-rank test were used for the SIR, CNR, and visual assessment. p < 0.05 was considered statistically significant.

RESULTS

No significant differences in nearly all the SIRs were observed among the three MRA methods. Higher CNRs were observed with TSE-Acc than those with TFE-Acc (anterior tibial artery, p = 0.014; peroneal artery, p = 0.029; and posterior tibial artery, p = 0.014) in distal arterial segments; however, no significant differences were observed upon comparison with TRANCE (all p > 0.05). The arterial visibility scores exhibited similar trends as the CNRs. The artifact contamination scores with TSE-Acc were significantly lower (but within an acceptable level) compared to those with TFE-Acc. In the patient with PAD, the sluggish peripheral arteries were better visualized using TSE-Acc than those using TFE-Acc, and the collateral and stenosis arteries were better visualized using TSE-Acc than those using TRANCE.

CONCLUSION

Peripheral arterial visualization was better with TSE-Acc than that with TFE-Acc in lower extremity MRA without ECG or PPU triggering and contrast enhancement, which was comparable with TRANCE as the reference standard. Furthermore, TSE-Acc may propose satisfactory diagnostic performance for diagnosing PAD in patients with arrhythmia and chronic kidney disease.

Magnetic Resonance Imaging Techniques in Peripheral Arterial Disease

Significance: Peripheral arterial disease (PAD) leads to a significant burden of morbidity and impaired quality of life globally. Diabetes is a significant risk factor accelerating the development of PAD with an associated increase in the risk of chronic wounds, tissue, and limb loss. Various magnetic resonance imaging (MRI) techniques are being increasingly acknowledged as useful methods of accurately assessing PAD. Recent Advances: Conventionally utilized MRI techniques for assessing macrovascular disease have included contrast enhanced magnetic resonance angiography (MRA), noncontrast time of flight MRA, and phase contrast MRI, but have significant limitations. In recent years, novel noncontrast MRI methods assessing skeletal muscle perfusion and metabolism such as arterial spin labeling (ASL), blood-oxygen-level dependent (BOLD) imaging, and chemical exchange saturation transfer (CEST) have emerged. Critical Issues: Conventional non-MRI (such as ankle-brachial index, arterial duplex ultrasonography, and computed tomographic angiography) and MRI based modalities image the macrovasculature. The underlying mechanisms of PAD that result in clinical manifestations are, however, complex, and imaging modalities that can assess the interaction between impaired blood flow, microvascular tissue perfusion, and muscular metabolism are necessary. Future Directions: Further development and clinical validation of noncontrast MRI methods assessing skeletal muscle perfusion and metabolism, such as ASL, BOLD, CEST, intravoxel incoherent motion microperfusion, and techniques that assess plaque composition, are advancing this field. These modalities can provide useful prognostic data and help in reliable surveillance of outcomes after interventions.

Non-Contrast Magnetic Resonance Angiography: Techniques, Principles, and Applications

Several non-contrast magnetic resonance angiography (MRA) techniques have been developed, providing an attractive alternative to contrast-enhanced MRA and a radiation-free alternative to computed tomography (CT) CT angiography. This review describes the physical principles, limitations, and clinical applications of bright-blood (BB) non-contrast MRA techniques. The principles of BB MRA techniques can be broadly divided into (a) flow-independent MRA, (b) blood-inflow-based MRA, (c) cardiac phase dependent, flow-based MRA, (d) velocity sensitive MRA, and (e) arterial spin-labeling MRA. The review also includes emerging multi-contrast MRA techniques that provide simultaneous BB and black-blood images for combined luminal and vessel wall evaluation.

Phase contrast coronary blood velocity mapping with both high temporal and spatial resolution using triggered Golden Angle rotated Spiral k-t Sparse Parallel imaging (GASSP) with shifted binning

PURPOSE

High temporal and spatial resolutions are required for coronary blood flow measures. Current spiral breath-hold phase contrast (PC) MRI at 3T focus on either high spatial or high temporal resolution. We propose a golden angle (GA) rotated Spiral k-t Sparse Parallel imaging (GASSP) sequence for both high spatial (0.8 mm) and high temporal (<21 ms) resolutions.

METHODS

GASSP PC data are acquired in left anterior descending and right coronary arteries of eight healthy subjects. Binning of GA rotated spiral data into cardiac frames may lead to large k-space gaps. To reduce those gaps, the binning window is shifted and a triggered GA scheme that resets the rotation angle every heartbeat is proposed. The gap reductions are evaluated in simulations and all subjects. Peak systolic velocity (PSV), peak diastolic velocity (PDV), coronary blood flow rate, and vessel area are validated against two reference scans, and repeatability/reproducibility are determined.

RESULTS

Shifted binning reduced the mean k-space gaps of the triggered GA scheme by 14°-22° in simulations and about 20° in vivo. The k-space gap across three cardiac frames was reduced with the triggered GA scheme compared to the standard GA scheme (35.3°± 3.6° vs. 43°± 13.7°, t-test P = .04). PSV, PDV, flow rate, and area had high intra-scan repeatability (0.92 ≤ intraclass correlation coefficient [ICC] ≤ 0.99), and inter-scan (0.78 ≤ ICC ≤ 0.91) and intra-observer (0.91 ≤ ICC ≤ 0.98) reproducibility.

CONCLUSION

GASSP enables single breath-hold coronary PC MRI with high temporal and spatial resolutions. Shifted binning and a triggered GA scheme reduce k-space gaps. Quantitative coronary flow metrics are highly reproducible, especially within the same scanning session.

"Push-button" noncontrast MR angiography using balanced T1 relaxation-enhanced steady-state (bT1RESS)

PURPOSE

We introduce a MR imaging technique, balanced T₁ relaxation-enhanced steady-state (bT1RESS), that provides the unique capability to efficiently impart a flexible amount of T₁ weighting to a balanced steady-state free precession acquisition using periodically applied contrast-modifying RF pulses. Leveraging this capability to suppress the signal intensity of background tissues, we implemented a 3D noncontrast MR angiography technique that continuously acquires thin overlapping 3D volumes and tested it for evaluation of the peripheral arteries.

METHODS

bT1RESS used a fast interrupted steady-state readout with a 45° cslab-selective ontrast-modifying RF pulse applied at 262 msec intervals. A series of 16.4-mm thick overlapping 3D volumes was acquired using a radial stack-of-stars k-space trajectory. The combination of slice oversampling, slab overlap, and averaging of edge slices was helpful to reduce venetian blind artifact. Spatial resolution was near isotropic with reconstructed slice thickness = 0.7 mm and in-plane resolution = 0.5 mm.

RESULTS

Pilot studies in the peripheral arteries demonstrated improved vessel sharpness compared with cardiac-gated quiescent interval slice-selective noncontrast MR angiography. bT1RESS noncontrast MR angiography reliably identified stenotic and occlusive arterial disease in a small cohort of patients with peripheral artery disease.

CONCLUSIONS

bT1RESS provides the basis for a simplified, completely "push button" approach for noncontrast MR angiography that obviates the need for contrast agents, electrocardiographic gating, scout imaging, breath holding, or tailoring of imaging parameters for the individual patient. Further work is needed for technical optimization and clinical validation.

Feasibility of a sub-3-minute imaging strategy for ungated quiescent interval slice-selective MRA of the extracranial carotid arteries using radial k-space sampling and deep learning-based image processing

PURPOSE

To develop and test the feasibility of a sub-3-minute imaging strategy for non-contrast evaluation of the extracranial carotid arteries using ungated quiescent interval slice-selective (QISS) MRA, combining single-shot radial sampling with deep neural network-based image processing to optimize image quality.

METHODS

The extracranial carotid arteries of 12 human subjects were imaged at 3 T using ungated QISS MRA. In 7 healthy volunteers, the effects of radial and Cartesian k-space sampling, single-shot and multishot image acquisition (1.1-3.3 seconds/slice, 141-423 seconds/volume), and deep learning-based image processing were evaluated using segmental image quality scoring, arterial temporal SNR, arterial-to-background contrast and apparent contrast-to-noise ratio, and structural similarity index. Comparison of deep learning-based image processing was made with block matching and 3D filtering denoising.

RESULTS

Compared with Cartesian sampling, radial k-space sampling increased arterial temporal SNR 107% (P < .001) and improved image quality during 1-shot imaging (P < .05). The carotid arteries were depicted with similar image quality on the rapid 1-shot and much lengthier 3-shot radial QISS protocols (P = not significant), which was corroborated in patient studies. Deep learning-based image processing outperformed block matching and 3D filtering denoising in terms of structural similarity index (P < .001). Compared with original QISS source images, deep learning image processing provided 24% and 195% increases in arterial-to-background contrast (P < .001) and apparent contrast-to-noise ratio (P < .001), and provided source images that were preferred by radiologists (P < .001).

CONCLUSION

Rapid, sub-3-minute evaluation of the extracranial carotid arteries is feasible with ungated single-shot radial QISS, and benefits from the use of deep learning-based image processing to enhance source image quality.

Quiescent-Interval Single-Shot Magnetic Resonance Angiography

Lower extremity peripheral arterial disease (PAD) is a chronic, debilitating disease with a significant global burden. A number of diagnostic imaging techniques exist, including computed tomography angiography (CTA) and contrast-enhanced magnetic resonance angiography (CEMRA), to aid in PAD diagnosis and subsequent treatment planning. Due to concerns of renal toxicity or nephrogenic systemic fibrosis (NSF) for iodinated and gadolinium-based contrasts, respectively, a number of non-enhanced MRA (NEMRA) protocols are being increasingly used in PAD diagnosis. These techniques, including time of flight and phase contrast MRA, have previously demonstrated poor image quality, long acquisition times, and/or susceptibility to artifacts when compared to existing contrast-enhanced techniques. In recent years, Quiescent-Interval Single-Shot (QISS) MRA has been developed to overcome these limitations in NEMRA methods, with promising results. Here, we review the various screening and diagnostic tests currently used for PAD. The various NEMRA protocols are discussed, followed by a comprehensive review of the literature on QISS MRA to date. A particular emphasis is placed on QISS MRA feasibility studies and studies comparing the diagnostic accuracy and image quality of QISS MRA versus other diagnostic imaging techniques in PAD.

Advances in non-contrast quiescent-interval slice-selective (QISS) magnetic resonance angiography

There is a pressing clinical need to develop accurate, efficient non-contrast magnetic resonance angiography (NC-MRA) techniques. Our efforts in the field have focused on a novel non-subtractive technique called quiescent-interval slice-selective (QISS) MRA. Compared with other NC-MRA techniques, QISS has the advantage of being more accurate while enabling a simpler and more efficient workflow. The original implementation, which uses electrocardiogram (ECG) gating and a Cartesian k-space trajectory, is a reliable technique for the evaluation of peripheral arterial disease (PAD). Recent advances in QISS technology include the use of a radial k-space trajectory, which facilitates rapid imaging of the coronary, renal, and pulmonary arteries as well as other vascular beds, and ungated ("UnQISS") acquisitions for PAD.

Radial fast interrupted steady-state (FISS) magnetic resonance imaging

PURPOSE

To report a highly interrupted radial variant of balanced steady-state free precession (bSSFP) imaging, termed fast interrupted steady-state (FISS), for decreasing flow artifact as well as fat signal conspicuity with respect to bSSFP, and saturation effects vis-à-vis fast low-angle shot (FLASH) imaging.

METHODS

Numerical simulations, phantom studies, and human studies were conducted to examine the imaging contrast, off-resonance behavior, and flow properties of FISS. Human studies applied FISS for cine cardiac imaging and ungated nonenhanced MR angiography (MRA) of the legs, neck, and brain. Comparisons were made with bSSFP and FLASH imaging.

RESULTS

Simulations revealed that FISS retains the high signal levels of bSSFP for stationary on-resonant spins, while reducing undesirable signal heterogeneity from flowing spins. Phantom studies agreed with the simulations, and showed that FISS reduces fat signal and flow artifact with respect to bSSFP imaging. FISS imaging in human subjects agreed with the simulations and phantom studies, and showed reduced saturation artifact compared with FLASH imaging.

CONCLUSION

FISS imaging reduces flow artifact and fat signal conspicuity with respect to bSSFP imaging, and ameliorates arterial signal saturation observed with FLASH imaging. Potential clinical applications include fat-suppressed cine imaging and ungated nonenhanced MRA. Magn Reson Med 79:2077-2086, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Super-resolution intracranial quiescent interval slice-selective magnetic resonance angiography

PURPOSE

To evaluate the combination of nonenhanced quiescent-interval slice-selective (QISS) magnetic resonance angiography (MRA) with super-resolution reconstruction for portraying the intracranial arteries.

METHODS

The intracranial arteries of seven volunteers were imaged at 3T using QISS MRA acquired with a flow-compensated fast low-angle shot (FLASH) readout and thin overlapping slices. The impacts of super-resolution reconstruction and various acquisition parameters on the delineation of intracranial arteries were quantified using four metrics: arterial-to-background contrast-to-noise ratio (CNR), arterial-to-background contrast, arterial sharpness, and arterial full-width-at-half-maximum (FWHM). Three-dimensional time-of-flight (TOF) MRA was also acquired.

RESULTS

For similar voxel sizes, QISS MRA displayed the intracranial arteries with an arterial-to-background contrast that exceeded 3D TOF MRA by 59-84%, depending on the k-space sampling trajectory (P < 0.001). Super-resolution reconstruction improved CNR, contrast, and sharpness, while reducing arterial FWHM (P < 0.001). Cardiac triggering provided minimal benefits, while Cartesian sampling provided higher CNR than radial sampling for multishot QISS (P < 0.05). Scan time for a complete intracranial MRA was <90 s using an ungated single-shot QISS acquisition.

CONCLUSION

Thin, overlapping-slice QISS leveraging super-resolution reconstruction is a flexible approach for intracranial MRA that provides competitive image quality to standard-of-care 3D TOF, with the potential for reduced sensitivity to in-plane flow saturation and motion artifacts. Magn Reson Med 79:683-691, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Image Quality and Stenosis Assessment of Non-Contrast-Enhanced 3-T Magnetic Resonance Angiography in Patients with Peripheral Artery Disease Compared with Contrast-Enhanced Magnetic Resonance Angiography and Digital Subtraction Angiography

PURPOSE

To evaluate the diagnostic performance of flow-sensitive dephasing (FSD)-prepared steady-state free precession (SSFP) magnetic resonance angiography (MRA) at 3 T for imaging infragenual arteries relative to contrast-enhanced MRA (CE-MRA) and digital subtraction angiography (DSA).

MATERIALS AND METHODS

A series of 16 consecutive patients with peripheral arterial disease (PAD) underwent a combined peripheral MRA protocol consisting of FSD-MRA for the calves and large field-of-view CE-MRA. DSA was performed on all patients within 1 week of the MR angiographies. Image quality and degree of stenosis was assessed by two readers with rich experience. Inter-observer agreement was determined using kappa statistics. Receiver operating characteristic (ROC) curve analysis determined the diagnostic value of FSD-MRA, CE-MRA, and CE-MRA combined with FSD-MRA (CE+FSD MRA) in predicting vascular stenosis.

RESULTS

At the calf station, no significantly difference of subjective image quality scores was found between FSD-MRA and CE-MRA. Inter-reader agreement was excellent for both FSD-MRA and CE-MRA. Both of FSD-MRA and CE-MRA carry a stenosis overestimation risk relative to DSA standard. With DSA as the reference standard, ROC curve analysis showed that the area under the curve was largest for CE+FSD MRA. The greatest sensitivity and specificity were obtained when a cut-off stenosis score of 2 was used.

CONCLUSION

In patients with severe PAD,3 T FSD-MRA provides good-quality diagnostic images without a contrast agent and is a good supplement for CE-MRA. CE+FSD MRA can improve the accuracy of vascular stenosis diagnosis.

Improved dark blood imaging of the heart using radial balanced steady-state free precession

BACKGROUND

Dark blood imaging of the heart is conventionally performed using a breath-hold, dual-inversion Cartesian fast spin-echo pulse sequence. Our aim was to develop a faster, more flexible approach that would be less motion-sensitive and provide better image quality. For this purpose, we implemented a prototype radial balanced steady-state free precession (bSSFP) pulse sequence.

METHODS

The study was approved by the institutional review board. Six healthy volunteers and 27 subjects undergoing clinically-indicated cardiovascular magnetic resonance (CMR) were imaged using dark blood Cartesian fast spin-echo and radial bSSFP. For patient studies, overall image quality, fat suppression and blood nulling were scored on a 5-point Likert scale. The quality of visualization of the right and left ventricular free walls and septum were individually scored. Streaking and ghosting artifacts were noted, as well as signal dropout in the free wall of the left ventricle.

RESULTS

In volunteer studies, radial bSSFP showed less degradation by cardiac or respiratory motion than fast spin-echo as indicated by visual analysis and calculation of the temporal signal-to-noise ratio. The least motion sensitivity and maximal imaging efficiency were achieved with a single-shot radial bSSFP acquisition using only 35 views (temporal resolution = 95 ms). In patient studies, radial bSSFP images showed fewer motion artifacts and were judged to provide better myocardial visibility, including depiction of the right ventricular free wall, than fast spin-echo.

CONCLUSIONS

Dual-inversion radial bSSFP provides the benefits of diminished sensitivity to image artifacts from respiratory or cardiac motion, better myocardial visibility, and improved imaging efficiency compared with standard-of-care Cartesian fast spin-echo for dark blood imaging of the heart.

USPIO-enhanced 3D-cine self-gated cardiac MRI based on a stack-of-stars golden angle short echo time sequence: Application on mice with acute myocardial infarction

PURPOSE

To develop and assess a 3D-cine self-gated method for cardiac imaging of murine models.

MATERIALS AND METHODS

A 3D stack-of-stars (SOS) short echo time (STE) sequence with a navigator echo was performed at 7T on healthy mice (n = 4) and mice with acute myocardial infarction (MI) (n = 4) injected with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles. In all, 402 spokes were acquired per stack with the incremental or the golden angle method using an angle increment of (360/402)° or 222.48°, respectively. A cylindrical k-space was filled and repeated with a maximum number of repetitions (NR) of 10. 3D cine cardiac images at 156 μm resolution were reconstructed retrospectively and compared for the two methods in terms of contrast-to-noise ratio (CNR). The golden angle images were also reconstructed with NR = 10, 6, and 3, to assess cardiac functional parameters (ejection fraction, EF) on both animal models.

RESULTS

The combination of 3D SOS-STE and USPIO injection allowed us to optimize the identification of cardiac peaks on navigator signal and generate high CNR between blood and myocardium (15.3 ± 1.0). The golden angle method resulted in a more homogeneous distribution of the spokes inside a stack (P < 0.05), enabling reducing the acquisition time to 15 minutes. EF was significantly different between healthy and MI mice (P < 0.05).

CONCLUSION

The method proposed here showed that 3D-cine images could be obtained without electrocardiogram or respiratory gating in mice. It allows precise measurement of cardiac functional parameters even on MI mice. J. Magn. Reson. Imaging 2016;44:355-365.

Breath-hold imaging of the coronary arteries using Quiescent-Interval Slice-Selective (QISS) magnetic resonance angiography: pilot study at 1.5 Tesla and 3 Tesla

BACKGROUND

Coronary magnetic resonance angiography (MRA) is usually obtained with a free-breathing navigator-gated 3D acquisition. Our aim was to develop an alternative breath-hold approach that would allow the coronary arteries to be evaluated in a much shorter time and without risk of degradation by respiratory motion artifacts. For this purpose, we implemented a breath-hold, non-contrast-enhanced, quiescent-interval slice-selective (QISS) 2D technique. Sequence performance was compared at 1.5 and 3 Tesla using both radial and Cartesian k-space trajectories.

METHODS

The left coronary circulation was imaged in six healthy subjects and two patients with coronary artery disease. Breath-hold QISS was compared with T2-prepared 2D balanced steady-state free-precession (bSSFP) and free-breathing, navigator-gated 3D bSSFP.

RESULTS

Approximately 10 2.1-mm thick slices were acquired in a single ~20-s breath-hold using two-shot QISS. QISS contrast-to-noise ratio (CNR) was 1.5-fold higher at 3 Tesla than at 1.5 Tesla. Cartesian QISS provided the best coronary-to-myocardium CNR, whereas radial QISS provided the sharpest coronary images. QISS image quality exceeded that of free-breathing 3D coronary MRA with few artifacts at either field strength. Compared with T2-prepared 2D bSSFP, multi-slice capability was not restricted by the specific absorption rate at 3 Tesla and pericardial fluid signal was better suppressed. In addition to depicting the coronary arteries, QISS could image intra-cardiac structures, pericardium, and the aortic root in arbitrary slice orientations.

CONCLUSIONS

Breath-hold QISS is a simple, versatile, and time-efficient method for coronary MRA that provides excellent image quality at both 1.5 and 3 Tesla. Image quality exceeded that of free-breathing, navigator-gated 3D MRA in a much shorter scan time. QISS also allowed rapid multi-slice bright-blood, diastolic phase imaging of the heart, which may have complementary value to multi-phase cine imaging. We conclude that, with further clinical validation, QISS might provide an efficient alternative to commonly used free-breathing coronary MRA techniques.

Segmented golden ratio radial reordering with variable temporal resolution for dynamic cardiac MRI

PURPOSE

Golden ratio (GR) radial reordering allows for retrospective choice of temporal resolution by providing a near-uniform k-space sampling within any reconstruction window. However, when applying GR to electrocardiogram (ECG)-gated cardiac imaging, the k-space coverage may not be as uniform because a single reconstruction window is broken into several temporally isolated ones. The goal of this study was to investigate the image artifacts caused by applying GR to ECG-gated cardiac imaging and to propose a segmented GR method to address this issue.

METHODS

Computer simulation and phantom experiments were used to evaluate the image artifacts resulting from three k-space sampling patterns (ie, uniform radial, conventional GR, and segmented GR). Two- and three-dimensional cardiac cine images were acquired in seven healthy subjects. Imaging artifacts due to k-space sampling nonuniformity were graded on a 5-point scale by an experienced cardiac imaging reader.

RESULTS

Segmented GR provides more uniform k-space sampling that is independent of heart-rate variation than conventional GR. Cardiac cine images using segmented GR have significantly higher and more reliable image quality than conventional GR.

CONCLUSION

Segmented GR successfully addresses the nonuniform sampling that occurs with combining conventional GR with ECG gating. This technique can potentially be applied to any ECG-gated cardiac imaging application to allow for retrospective selection of a reconstruction window. Magn Reson Med 76:94-103, 2016. © 2015 Wiley Periodicals, Inc.

Noncontrast MR angiography (MRA) of infragenual arteries using flow-sensitive dephasing (FSD)-prepared steady-state free precession (SSFP) at 3.0 Tesla: Comparison with contrast-enhanced MRA

BACKGROUND

To evaluate the feasibility and diagnostic performance of flow-sensitive dephasing (FSD)-prepared steady-state free precession (SSFP) MR angiography (MRA) for imaging infragenual arteries at 3.0T, with contrast enhanced MR angiography (CE MRA) as reference.

METHODS

Twenty consecutive patients with suspicion of lower extremity arterial disease undergoing routine CE MRA were recruited. FSD MRA was performed at calf before CE MRA. Image quality and stenosis degree of infragenual arteries from both techniques were independently evaluated and compared. Six patients in this study underwent DSA examination.

RESULTS

Three undiagnostic segments were excluded with severe venous contamination in CE MRA. A total of 197 calf arterial segments images were analyzed. No significant difference existed in the relative signal intensity (rSI) of arterial segments between FSD MRA and CE MRA techniques (0.92 ± 0.09 versus 0.93 ± 0.05; P = 0.207). However, the subjective image quality score was slightly higher in FSD MRA (3.66 ± 0.81 versus 3.49 ± 0.87; P = 0.050). With CE MRA images as reference standard, slight overestimation existed in FSD MRA (2.19 ± 1.24 versus 2.09 ± 1.18; P = 0.019), with total agreement of 84.3% on the basis of all arterial segments. The sensitivity, specificity, negative predictive value, and positive predictive value of FSD MRA was 96.4%, 93.0%, 98.5%, and 84.1%. No significant difference in the stenosis degree score was detected between MRA (FSD MRA and CE MRA) and DSA (P > 0.05).

CONCLUSION

FSD MRA performed on at 3.0T without the use of contrast medium provides diagnostic images allowing for arterial stenosis assessment of calf arteries that was highly comparable with CE MRA. Moreover, venous contamination was less problematic with FSD MRA.