Anatomically Tailored K-Space Sampling for Bolus Chase 3D MR Digital Subtraction

MRA is used to generate images for diagnosing vascular diseases. Conventional MRA employs elliptical-centric view ordering of the k-space. This standard view order concentrates the high signal k-space center at the beginning of a scan. 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. On the other hand, delaying the acquisition of the k-space center too far into the scan produces a significant venous artifact.

Conventional MRA also uses sampling according to the Nyquist sampling theorem, which increases the acquisition time and make it difficult to image multiple stations using a single administration of a contrast agent.

Cornell inventors have developed a recessed elliptical-centric view ordering scheme to time data acquisition more accurately with peak contrast enhancement: data acquisition in the ky-kz space starts in the central sector outside the exact center of k-space; the exact central sector is acquired a few seconds following scan initiation. This recessed view ordering scheme better matches the acquisition of the k-space center to the peak arterial concentration and prevents the well-known imaging artifact of aliasing. A dynamic view ordering is also introduced for three-station studies, which reduces the minimal separation of the k-space centers of the three stations and optimizes the acquisition of the k-space centers.

The inventors have also developed and tested a variable k-space sampling method that minimizes imaging time by tailoring the acquisition according to the vascular anatomy of the station. The k-space sampling rate is reduced, which allows a substantial decrease in scan time and increases dose sharing between stations. With post-processing subtraction techniques, this method retains image resolution without causing artifacts.

Potential Applications

Improve imaging quality in contrast-enhanced MRA

Advantages

• Better match the acquisition of k-space center to peak arterial enhancement
• Allow triggering the scan at the start of contrast arrival, resulting in less venous signal
• Significantly reduce scan time and increase dose sharing among between stations
• Significantly higher quality images than conventionally used protocols