Potential applications of small tip angle proton density imaging

Theoretical considerations suggest that proton density (PD) images can be acquired at very small tip angles and short echo time values. Thus, the authors used small tip angle techniques to produce reliable fast photon density (FPD) images and studied their potential applications for detecting and characterizing abnormalities at a magnetic field strength of 1.5 T. A variant of the rapid field echo pulse sequence GRASS (gradient recalled acquisition in the steady state) was used in the experiments. The contrast of the FPD images is strongly dependent on the pulse angle. FPD image of patients with demyelinating disease, hemorrhage, metastases, etc. have been acquired and evaluated. The authors obtained high-quality FPD images that clearly visualize the pathology and are helpful in diagnostic specificity. As expected, the FPD images have fewer characteristic artifacts than fast T2-weighted images