Peripheral MRA with k-space Segmentation and Blood-Pool Contrast Agent

Rationale and Objectives

The purpose of this study was to perform high-resolution contrast-enhanced peripheral multistation magnetic resonance angiography using a new blood-pool contrast agent (gadofosveset trisodium; Vasovist) while suppressing venous signal by using an acquisition scheme with k-space segmentation.

Materials and Methods

Multistation peripheral magnetic resonance angiography with Vasovist was performed in 20 patients with known peripheral arterial occlusive disease. The k-space of the three-dimensional data sets was segmented such that the central parts were acquired during the first pass of the blood-pool agent, while the peripheral parts were acquired in the steady state. A third magnetic resonance angiographic data set acquired using the conventional technique served as comparison for venous overlay. Two radiologists blindly compared vessel sharpness, conspicuity, and venous contamination. Furthermore, a semiautomatic program to compare edge sharpness was used. Results were compared by means of Wilcoxon’s signed rank sum test.

Results

Comparison of vessel sharpness revealed statistically significant differences in favor of the fused data sets in all three stations. Arteries were depicted more sharply in the fused images and over longer parts, while veins were almost completely suppressed.

Conclusions

Peripheral contrast-enhanced magnetic resonance angiography with first-pass and steady-state k-space segmentation using a blood-pool contrast agent proved feasible and provided high-resolution data with sharp delineation of the arteries while reducing venous contamination.

Peripheral arterial occlusive disease (PAOD) is a significant cause of morbidity in the Western world and can lead to lower-extremity ischemia. Until recently, contrast-enhanced (CE) digital subtraction angiography had to be performed as reference standard. By now, three-dimensional (3D) CE magnetic resonance angiography (MRA) has been successfully applied to the peripheral vessels, leading to diagnostic images , and has been established as standard of reference for diagnostic evaluation of PAOD because of its noninvasiveness, its 3D nature encompassing multistation large fields of view, and its relatively good spatial resolution.

The timing and synchronization of the contrast agent with magnetic resonance data acquisition for peripheral CE MRA play a major role in acquiring high-signal arterial angiograms while simultaneously avoiding venous signal overlay.

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Materials and methods

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Technique

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Table 1

Imaging Parameters

Sequence Acquisition Time (seconds) Field of View, Head to Feet × Left to Right (mm 2 ) Acquired Voxel Size (mm 3 ) First pass Abdomen 20 500 × 344 0.8 × 2.0 × 2.0 Thighs 20 500 × 344 0.8 × 2.0 × 2.0 Calves 23 500 × 344 0.7 × 1.8 × 1.8 Fused data set Abdomen 93 500 × 344 0.8 × 0.8 × 0.8 Thighs 89 500 × 344 0.8 × 0.8 × 0.8 Calves 104 500 × 344 0.7 × 0.7 × 0.7 Steady state Abdomen 78 500 × 344 0.8 × 0.8 × 0.8 Thighs 78 500 × 344 0.8 × 0.8 × 0.8 Calves 107 500 × 344 0.7 × 0.7 × 0.7

Sequence parameters for all three stations and their first-pass and steady-state acquisitions. Sequence parameters that were identical for all acquisitions were flip angle (25°), bandwidth (490 Hz/pixel), repetition time (3.4 ms), echo time (1.3 ms), number of slices per slab (160), and generalized auto-calibrating partially parallel acquisition acceleration factor .

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Patients

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Image Evaluation

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Statistical Analysis

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Results

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Image Quality

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Table 2

Results for Image Quality

Sequence Data Set I (First Pass) Data Set II (Fused Data Set)P Abdomen 2.5 2.9 <.01 Thighs 2.4 3.0 <.01 Calves 2.3 2.9 <.01

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Venous Overlay and Evaluation of Trace of Vessels and Minimal Vessel Size

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Sharpness of Edges

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Discussion

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Conclusions

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References

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Peripheral MRA with k-space Segmentation and Blood-Pool Contrast Agent

Rationale and Objectives

Materials and Methods

Results

Conclusions

Materials and methods

Technique

Patients

Image Evaluation

Statistical Analysis

Results

Image Quality

Venous Overlay and Evaluation of Trace of Vessels and Minimal Vessel Size

Sharpness of Edges

Discussion

Conclusions

References

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