Time domain simulation of Fourier imaging by summation of isochromats

• Published in: International journal of imaging systems and technology Vol. 8; no. 5; pp. 419 - 426
• Main Authors: Shkarin, Pavel, Spencer, Richard G. S.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 1997
• ISSN: 0899-9457; 1098-1098
• DOI: 10.1002/(SICI)1098-1098(1997)8:5<419::AID-IMA1>3.0.CO;2-D

We have developed a time‐domain simulation of two‐dimensional Fourier imaging in which the signal is represented by a finite Fourier series. Each term corresponds to a spin isochromat and has a coefficient that evolves in response to radiofrequency and gradient pulses, and periods of free precession. An explicit calculation is performed to derive the number of isochromats required to achieve a specified degree of precision, permitting accurate results to be obtained in an efficient fashion. With this, the time‐domain signal throughout the entire experiment is calculated. The resulting time domain data is combined into the standard k‐space matrix and yields an image after two‐dimensional Fourier transformation. Multiple‐shot sequences such as spin warp and single‐shot experiments such as Burst are simulated in the same fashion. Our procedure makes no assumptions about transverse dephasing between pulses, so that complicated sequences of direct and stimulated echoes are correctly modeled. The influence of spin‐spin and spin‐lattice relaxation is included in a natural way. A number of artifacts can be quantitatively reproduced. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 419–426, 1997