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Increasing T1 Contrast in MRI with Quasi-continuous Low-level Radio Frequency Energy

IP.com Disclosure Number: IPCOM000012471D
Publication Date: 2003-May-08
Document File: 2 page(s) / 91K

Publishing Venue

The IP.com Prior Art Database

Abstract

This invention increases the T1 contrast in spin-echo imaging, with very little reduction in the total number of slices that can be acquired. Throughout the multiple-slice imaging experiment, the whole object is quasi-continuously irradiated with low-level RF energy at or near the spin resonance frequency. The effect of the saturation is to change the steady state magnetization of the different T1 components, such that the steady state longitudinal magnetization of the long T1 components is reduced with respect to that of the short T1 components. Simulations suggest that a saturation pulse with a flip angle of between 5 and 15 degrees, applied every 25ms, in a 20 slice T1 weighted spin-echo imaging acquisition, should increase the contrast between white and gray matter in the brain by at least 50%. The signal difference to noise ratio should increase about 15%. The technique could also be applied for other T1 weighted imaging sequences such as gradient-echo.

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FIELD OF TECHNOLOGY: 

Magnetic Resonance (MR)

INVENTION TITLE:

Increasing T1 contrast in MRI with quasi-continuous low-level Radio Frequency Energy

PROBLEM/BACKGROUND: 

This invention increases the T1 contrast in spin-echo imaging, with very little reduction in the total number of slices that can be acquired.

The idea was discovered in the course of an investigation into T1 contrast differences between old and new scanner generations. One suspicion as to the cause of this difference was the increased radio frequency (RF) noise on one system. Upon analyzing the effect of this extraneous noise, it was discovered that the noise could actually improve T1 contrast.

The invention takes this basic phenomenon and tailors it more specifically for MR imaging.

Applying this invention should result in improved T1 weighted brain and spine images.

INVENTION DESCRIPTION:

The invention is intended for use in conjunction with multiple-slice spin-echo imaging.

Throughout the multiple-slice imaging experiment, the whole object is quasi-continuously irradiated with low-level RF energy at or near the spin resonance frequency. This RF energy partially saturates the spins in a fairly continuous manor, such that the saturation is the same for each individual slice.

The effect of the saturation is to change the steady state magnetization of the different T1 components, such that the steady state longitudinal magnetization of the long T1 components is reduced with respect to that of the short T1 components.

The quasi-continuous RF irradiation should be applied in an incoherent fashion, such that saturated spins are not refocused. This can be achieved by (a) continuously applying a noise-like signal (except during actual signal reception); or (b) applying a non-spatially selective low flip angle saturation pulse, with dephasing gradient, between each of the spin echo acquisitions. Other variations are also possible.

The second approach appears to be the easier to implement, as it requires only minor software changes. Simulations suggest that a saturation pulse with a flip angle of between 5 and 15 degrees, applied every 25ms, in a 20 slice T1 weighted spin-echo imaging acquisition, should increase the contrast between white and gray matter in the brain by at least 50%. The signal difference to noise ratio should increase about 15%.

The technique could al...