Optimization of three-dimensional T2-weighted image sequences in female pelvic magnetic resonance imaging

This study aimed to characterize T2-weighted fast spin-echo three-dimensional (3D) magnetic resonance images (MRI) by using variable refocusing angle (VRFA) in female pelvic organs and to extract clinically relevant parameters. A 3T MRI system was used, and contrast-to-noise ratio (CNR) and full width at half maximum (FWHM) were calculated using a phantom mimicking the uterine three-layered structure to confirm the characteristics of low-constant VRFA (LC-VRFA) and tissue-specific VRFA (TS-VRFA) under changing parameters. Parameters that were relatively well-evaluated in the phantom study were combined and visually evaluated as an overall assessment by volunteer images, using common turbo spin-echo (TSE) coefficients and equivalent TE (TEequiv). In most combinations, CNR tended to be higher for longer TEequiv for each TSE factor for both LC- and TS-VRFA, but particularly higher with RFA of 60 degrees-90 degrees, TSE factor of 60-90, and TEequiv of 90-100 ms. TS-VRFA was high in the common TSE factor and TEequiv, with some exceptions. In all combinations, the FWHM of LC-VRFA was narrower than TS-VRFA (P < 0.01). For visual evaluation of volunteer images, LC-VRFA was higher than TS-VRFA (P < 0.05). In LC-VRFA, the upper combinations of RFA (degrees)-TSE factor-TEequiv (ms) were 90-80-100, 90-90-100, and 90-60-100, respectively. We characterized VRFA 3D T2-weighted MR images for female pelvic organs, extracted optimal parameters. The better VRFA was LC-VRFA, with RFA of 60 degrees-90 degrees, TSE factor of 60-90, and TEequiv of 90-100 ms.