Method and apparatus for anatomically tailored k-space sampling and recessed elliptical view ordering for bolus-enhanced 3D MR angiography

Abstract

Current bolus chase magnetic resonance angiography is limited by the imaging time for each station. Tailoring the density of k-space sampling along the anterior-posterior direction of the coronal station allows a substantial decrease in scan time that leads to greater contrast bolus sharing among stations and consequently a significant improvement in image quality. Fast arterial-venous transit in the carotid arteries requires accurate, reliable timing of the acquisition to the bolus transit to maximize arterial signal and minimize venous artifacts. The rising edge of the bolus is not utilized in conventional elliptical-centric view ordering because the critical k-space center must be acquired with full arterial enhancement. The invention provides a recessed elliptical-centric view ordering scheme is introduced in which the k-space center is acquired a few seconds following scan initiation. The recessed view ordering is shown to be more robust to timing errors in a patient studies.

Description

[0001] The invention was made with government support under R01HL60879 by the National Institutes of Health. The government has certain rights in the invention.FIELD OF INVENTION [0002] The present invention relates to MR angiography using a reduced sample set to decrease the time needed to acquire image data for arterial features. As a result of the time reduction, the MR data acquisition can be performed in conjunction with the arrival and flow of a contrast agent through the arteries, thereby reducing the amount of contrast agent introduced in a patient. The invention further relates to method for acquiring MR to better delineate arterial features from a background and venous artifacts. In particular, modification of k-space view ordering more accurately times data acquisition to contrast arrival and peak contrast enhancement in a region of interest. DESCRIPTION OF THE RELATED ART [0003] Generally, contrast-enhanced MRA offers many advantages in imaging, including reduced flow ar...

AI Technical Summary

Benefits of technology

[0009] The present invention uses a variable k-space sampling method that minimizes scan time by tailoring the acquisition according to the vascular anatomy of the station, hence increasing dose sharing between stations. In particular, in a three station scan of the lower extremities (abdomen, thigh, and calf), at least the central station is sampled such that the number of samples taken is less than would be taken at the Nyquist rate. The spacing is more sparse than that required by the Nyquist sampling theorem, to prevent the well-known imaging artifact of wrap-around (aliasing). The MR images of the region of interest are duplicated. Subtraction of a pre-contrast mask removes non-enhancing tissue (ref. Wang), while the limited extent of vessels allows duplicated vessels to be removed using volume of interest imaging.

Problems solved by technology

However, there is little sharing of contrast dose between stations, and venous enhancement can still occur.

However, sampling at the Nyquist rate and at the spacing interval required by the Nyquist theorem increases the acquisition time at a particular station, making it difficult to image multiple stations using a single administration of a contrast agent.

The rapid transit time of a contrast agent through the peripheral vascular anatomy also poses timing problems in other regions, such as the carotid artery.

Although 2D and 3D time-of-flight MRA have revolutionized the evaluation of the carotid arteries, these MRA techniques have important limitations related to motion and flow artifacts, long acquisition times, and the difficulty in imaging the entire vessel down to the aortic arch.

However, a major challenge in contrast enhanced imaging of the carotid arteries is due to rapid arterial-venous transit.

However, if the k-space center is acquired during the rising edge of arterial enhancement, reduced arterial signal intensity and arterial ringing artifacts may result.

Delaying the acquisition of the k-space center (while using the conventional centric-order view) too far into the scan produces a significant venous artifact due to rapid contrast transit.

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