Actual imaging slice profile of 2D MRI

Haiying Liu; Edward Michel; Sean O. Casey; Charles L. Truwit

doi:10.1117/12.465627

3 May 2002 Actual imaging slice profile of 2D MRI

Haiying Liu, Edward Michel, Sean O. Casey, Charles L. Truwit

Proceedings Volume 4682, Medical Imaging 2002: Physics of Medical Imaging; (2002) https://doi.org/10.1117/12.465627
Event: Medical Imaging 2002, 2002, San Diego, California, United States

Abstract

It has been known that the actual slice profile of 2D MRI is often far form that of a perfect rectangular shape especially when the flip angle is large. This can be the source of error and image artifact in many MRI experiments. To carefully study this imperfection in RF excitation for various numerically optimized RF pulses, we have implemented an efficient numerical algorithm for simulating the evolution of the magnetization during a MR experiment. The scheme solves the Bloch equation via a numerical procedure that involves only the successive matrix multiplications, which are initialized by the values of RF amplitude and the frequency offset due to the companioning magnetic gradient field. It permits the consideration of the magnetization relaxation processes. The actual slice profile was numerically simulated by solving the Bloch equation for a given RF pulse shape and slice selection field gradient. The simulation results shows that the slice profile is often far from perfect for many commonly used frequency selective RF pulses. As a result of this, the apparent image intensity is an integrated signal over the slice envelope for the transverse magnetization for each pixel, which is an averaged contribution over the entire slice thickness, and can be significantly different than that predicted by the ideal case. As expected, this discrepancy worsens when the flip angle exceeds the flip angle for which the RF pulse was optimized. Furthermore, in the routine diagnostic imaging, because of the non-uniform excitation angle along the slice profile, it generates non-uniform steady state profile and can even alter the resulting image contrast.

Citation Download Citation

Haiying Liu, Edward Michel, Sean O. Casey, and Charles L. Truwit "Actual imaging slice profile of 2D MRI", Proc. SPIE 4682, Medical Imaging 2002: Physics of Medical Imaging, (3 May 2002); https://doi.org/10.1117/12.465627

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available