The Theory of magnetic resonance imaging

Thesis (B.S.)--University of Rochester. Dept. of Physics and Astronomy, 1991.The basic theory of nuclearmagnetic resonance is discussed in both the quantummechanical and semi-classical pictures. The basic principles of imaging are then outlined, including certain pulse sequences used to obtain magnetic resonance signals. One of these is the spin-echo sequence. The effect of imperfect ISO-degree pulses in this sequence is explored indepth using rotation matrices as models for the pulses and the dephasing of the precessing nuclei caused by in homogeneities in the primary magnetic field. Specifically,the effect on measurements of the transverse relaxation time(T2)is calculated. The calculations are made for in homogeneities ranging from 1 to 5 ppm,time between successive echoes ranging from 20 to40 milliseconds, and errors in the ISO-degree pulse ranging from 5% to 20%.The resulting errors in the calculation of T2 are 1.2% or lower for errors in the pulse up to 10%.The errors in the measurements reach as high as 5.7% for errors in the pulse up to 20%.There also seems to be a correlation between the error in measurement and the phase of the precessing net magnetization at the time of the application of the pulse