• Investigative Magnetic Resonance Imaging
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• v.4 no.1
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• pp.42-51
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• 2000

Purpose: Projection-type Fast Spin Echo (PFSE) imaging is robust to patient motion or flow related artifact compared to conventional Fast Spin Echo (FSE) imaging, however, it has difficulty in controlling $T_2$ contrast. In this paper, Tz contrast in the PFSE method is analyzed and compared with those of the FSE method with various effective echo times by computer simulation. The contrasts in the FSE and PFSE methods are also compared by experiments with volunteers. From the analysis and simulation, it is shown that ${T_2}-weighted$ images can well be obtained by the PFSE method proposed. Materials and methods: Pulse sequence for the PFSE method is implemented at a 1.0 Tesla whole body MRI system and $T_2$ contrasts in the PFSE and FSE methods are analyzed by computer simulation and experiment with volunteers. For the simulation, a mathematical phantom composed of various $T_2$ values is devised and $T_2$ contrast in the reconstructed image by the PFSE is compared to those by the FSE method with various effective echo times. Multi-slice ${T_2}-weighted$ head images of the volunteers obtained by the PFSE method are also shown in comparison with those by the FSE method at a 1.0 Tesla whole body MRI system. Results: From the analysis, $T_2$ contrast by the PFSE method appears similar to those by the FSE method with the effective echo time in a range of SO-lOOms. Using a mathematical phantom, contrast in the PFSE image appears close to that by the FSE method with the effective echo time of 96ms. From experiment with volunteers, multi-slice $T_2-weighted$ images are obtained by the PFSE method having contrast similar to that of the FSE method with the effective echo time of 96ms. Reconstructed images by the PFSE method show less motion related artifact compared to those by the FSE method. Conclusion: The projection-type FSE imaging acquires multiple radial lines with different angles in polar coordinate in k space using multiple spin echoes. The PFSE method is robust to patient motion or flow, however, it has difficulty in controlling $T_2$ contrast compared to the FSE method. In this paper, it is shown that the PFSE method provides good $T_2$ contrast (${T_2}-weighted$ images) similar to the FSE method by both computer simulation and experiments with volunteers.