Arterial spin-labeled (ASL) multiplexed echo planar imaging (m-epi)

Abstract

An MRI system and method for imaging perfusion in an arterial spin labeled (ASL) process in which multiplexed echo-planar imaging (M-EPI) is used rather than conventional EPI, to thereby speed up imaging and generate sets of images that show different phases of perfusion and provide additional benefits. A single multiband RF excitation pulse can be used to excite multiple slices for imaging, or a time sequence of multiband pulses can be used to further increase the number of slices.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS AND INCORPORATION BY REFERENCE[0001]This patent application is a continuation-in-part of (a) PCT International Application No. PCT / US11 / 57161, filed Oct. 20, 2011, which claims the benefit of U.S. Provisional Application No. 61 / 394,929, filed Oct. 20, 2010, and (b) U.S. patent application Ser. No. 13 / 632,941, filed Oct. 1, 2012, which is a continuation of U.S. patent application Ser. No. 13 / 397,634, filed Feb. 15, 2012, which claims the benefit of U.S. Provisional Application Nos. 61 / 443,215, filed Feb. 15, 2011, 61 / 444,031, filed Feb. 17, 2011, and 61 / 444,039, filed Feb. 17, 2011. This patent specification incorporates by reference the entire contents of each of these applications, including their drawings and the appendices attached thereto.FIELD[0002]This patent specification is in the field of magnetic resonance imaging (MRI). More specifically it pertains to imaging tissue perfusion with MRI.BACKGROUND AND SUMMARY OF THE DISCLOSURE[0003]A...

AI Technical Summary

Benefits of technology

The replacement of EPI with M-EPI in ASL imaging has several advantages. Firstly, it improves the accuracy of the measured blood flow in the brain or other organs by reducing the impact of multiple interventions and the complexity of the brain's vascular system. Secondly, it allows for faster scanning of the brain using multiple magnetic resonance signals, which can provide more reliable and accurate data. Thirdly, it can help to better understand the perfusion of blood in different parts of the brain or organs, which is important for disease diagnosis and treatment. Overall, the patent describes a new method for ASL imaging that is faster, more accurate, and can provide more information about brain perfusion.

Problems solved by technology

Another limitation is that tissue blood is moving through different vascular compartments including arterial, capillary and venous compartments, so the time window of imaging can be constrained to a few hundred milliseconds for the capillary compartment.

Echo planar imaging (EPI) has been used as a readout image for the ASL perfusion technique but is limited in the number of slices that can be imaged due to the normal physiological time course of labeled blood moving through the different vascular compartments.

ASL with conventional multi-slice 2D EPI has not been able to satisfactorily image perfusion in the entire brain because of timing limitations.

This has not been possible for the entire brain with ASL based on conventional EPI due to the limited time window for measuring the hemodynamic perfusion effects because it was not believed possible to acquire enough conventional EPI images to cover the entire brain.

Equally limiting to ASL using conventional EPI in this relationship to hemodynamics, is that the EPI images are time sequential and so even during a limited total scan time to make 10 images within an acceptable time window, each image is at a different temporal delay with respect to the initial blood labeling inversion pulse, so that each image actually has a different inflow time and this gives error in calculating their combined measurement of perfusion in the brain.

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