Designing of RF Pulse Sequences for Magnetic Resonance Imaging System

Magnetic Resonance Imaging (MRI) is a non invasive medical test which is used by radiologists to diagnose and treat medical conditions. Comprehensive images of the body part/tissue are produced using 1.5 Tesla strong magnetic field and radio frequency pulses. Magnetic Resonance Imaging is based on the principle of changing the magnetization property of the hydrogen atoms in human body by using RF fields. These RF fields are generated using a set of pulses called as pulse sequence. Design of these pulse sequences depend on the imaging application required. In this paper the design method of producing these pulse sequences is explained in detail. Pulse sequence is a sequence of temporal waveforms consisting of RF pulses, gradient (magnetic fields) waveforms and data acquisition intervals. Some of the commonly used pulse sequences are: Spin Echo (SE) sequence, Inversion Recovery (IR) sequence, Gradient Echo (GRE) sequence etc. Using these SE, IR, GRE pulse sequences we get different images like T1 weighted, T2 weighted, proton density (PD) weighted image. These images depend on Repetition Time (TR), Echo Time (TE) and Proton Density (PD) (1). The signal received from hydrogen proton is recorded and then K space is filled. By taking the Inverse Fourier Transform of K space data the image is reconstructed.