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SIMULTANEOUS MULTI SLICE IMAGING FOR FOCUSED ULTRASOUND ABLATION

IP.com Disclosure Number: IPCOM000241301D
Publication Date: 2015-Apr-15
Document File: 6 page(s) / 155K

Publishing Venue

The IP.com Prior Art Database

Abstract

The disclosed invention proposes a technique to acquire multiple slices simultaneously in real time in conjunction with a fast sequence suitable for tissue tracking and temperature monitoring. The technique provides ultra fast scan for magnetic resonance imaging (MRI) guided focused ultrasound (FUS) tissue ablation of moving organs, such as, liver and kidneys. Pulse sequence is a restricted field of view (rFOV) echo-planar imaging (EPI) acquired at a rate of about 20 images per second. Fast imaging speed enables filtering each pixel in the images along a time axis without affecting depiction of motion, while improving signal-to-noise (SNR). The technique initiates with excitation of the three slices, followed by separation and interpolation of slices.

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SIMULTANEOUS MULTI SLICE IMAGING FOR FOCUSED ULTRASOUND ABLATION

BACKGROUND

The present invention relates generally to magnetic resonance imaging (MRI) guided focused ultrasound (FUS) and more particularly to a technique to provide simultaneous multi slice imaging for MRI guided focused ultrasound (FUS) ablation.

Generally, magnetic resonance imaging (MRI) guided focused ultrasound (FUS) ablation requires continuous tracking and temperature calculation. However, shape of temperature distribution changes during heating and extends beyond a center slice.

A conventional technique includes phase-offset multiplanar (POMP) imaging. POMP is a technique that excites several sections simultaneously for improved imaging efficiency. Centers of reconstructed images from each of the POMP sections are offset from each other in a phase-encoding direction by means of view-dependent phase modulation of radio-frequency (RF) excitation pulses. Further POMP sections are placed adjacent to each other in the reconstruction. Then with a suitable reconstruction matrix size, the images are made non-overlapping and stored separately.

Another conventional technique provides multi-slice magnetic resonance imaging in which image data is acquired simultaneously from multiple slice locations using a radio frequency coil array.

However, the above mentioned conventional techniques do not provide real time multi slice image acquisition.

It would be desirable to have an efficient technique to provide real time multi slice acquisition in order to calculate thermal dose and location of the maximum temperature.

BRIEF DESCRIPTION OF DRAWINGS

 Figure 1 depicts frequency response of a filter, where normalized frequency of 1 corresponds to a real frequency of 1/TR, where TR is the time between images.

Figure 2 depicts application of RF waveforms on three slices.

Figure 3 depicts the disclosed technique that includes slice excitation, separation and interpolation.

Figure 4 depicts a two dimensional (2D) simulation showing Mxy along spectral and spatial directions of three slices spectral spatial RF pulse.

Figure 5 depicts a 2D simulation showing separated second slice.

Figure 6 depicts overlapping slices, where excited region is a wide band of 2.8 kHz.

Figure 7 depicts overlapping slices, where separated slices are of 1.0 kHz.

DETAILED DESCRIPTION

The disclosed invention proposes a technique to acquire multiple slices simultaneously in real time in conjunction with a fast sequence suitable for tissue tracking and temperature monitoring. The technique provides ultra fast scan for magnetic resonance imaging (MRI) guided focused ultrasound (FUS) tissue ablation of moving organs, such as, liver and kidneys. Pulse sequence is a restricted field of view (rFOV) echo-planar imaging (EPI) acquired at a rate of about 20 images per second.  Fast imaging speed enables filtering each pixel in the images along a time axis without affecting depiction of motion, while improving signal-to-noise (SNR...