Changes

For '''on-resonance''' models, f.ex [[M61]],  See (see also [[Relax_disp.spin_lock_offset%2Bfield | relaxx disp.spin lock offset+field]])), if<math>\bar{\Omega}_{S,i} = 0.0</math>then<math>\theta = frac{\pi}{2}</math>and as such<math>cos^2\theta = cos^2(rac{\pi}{2})</math>