FAST SE MRI OF THE CHEST - PARAMETER OPTIMIZATION AND COMPARISON WITHCONVENTIONAL SE IMAGING

Objective: This study was performed to optimize scanning parameters fo r fast spin echo (FSE) T2-weighted scans of the chest and to compare F SE T2-weighted images with conventional spin echo (CSE) T2-weighted sc ans. Materials and Methods: Thirty-nine FSE T2-weighted scans of the c hest were obtained in 12 subjects to determine the effect of cardiac g ating (with gating n = 20; without gating n = 19) and combinations of number of excitations (NEX) (2,4,8,16) and echo train length (ETL) (2, 4,8,16) on scan quality and visibility of thoracic structures. An addi tional 15 chest MR examinations consisting of FSE T2- and CSE T1-, pro ton-density- (PD), and T2-weighted scans were obtained in 15 patients with a variety of thoracic abnormalities. The FSE T2-weighted scans we re compared with CSE T2-weighted scans, and the combination of CSE T1- and FSE T2-weighted scans was compared with the combination of CSE PD - and T2-weighted scans. Results: Little difference in image quality w as found between cardiac-gated and nongated FSE scans. Increasing the ETL resulted in increased motion artifact. Forty lesions were detected with FSE and 42 lesions with CSE T2-weighted scans. Fifty-three lesio ns were detected with the combination of CSE T1- and FSE T2-weighted s equences, whereas 44 lesions were detected with the combination of CSE PD- and T2-weighted scans. Conclusion: The combination of cardiac-gat ed CSF T1- and non-cardiac-gated FSE T2-weighted scans was 20% more se nsitive and twice as fast as the combination of cardiac-gated CSE PD- and T2-weighted scans.