PURPOSE: To develop a fast volumetric T mapping technique.
MATERIALS AND METHODS: A stack-of-stars (SOS) Look Locker technique based on the acquisition of undersampled radial data (>30× relative to Nyquist) and an efficient multi-slab excitation scheme is presented. A principal-component based reconstruction is used to reconstruct T maps. Computer simulations were performed to determine the best choice of partitions per slab and degree of undersampling. The technique was validated in phantoms against reference T values measured with a 2D Cartesian inversion-recovery spin-echo technique. The SOS Look Locker technique was tested in brain (n = 4) and prostate (n = 5). Brain T mapping was carried out with and without k acceleration and results between the two approaches were compared. Prostate T mapping was compared to standard techniques. A reproducibility study was conducted in brain and prostate. Statistical analyses were performed using linear regression and Bland Altman analysis.
RESULTS: Phantom T values showed excellent correlations between SOS Look Locker and the inversion-recovery spin-echo reference (r = 0.9965; p < 0.0001) and between SOS Look Locker with slab-selective and non-slab selective inversion pulses (r = 0.9999; p < 0.0001). In vivo results showed that full brain T mapping (1 mm) with k acceleration is achieved in 4 min 21 s. Full prostate T mapping (0.9 × 0.9 × 4 mm) is achieved in 2 min 43 s. T values for brain and prostate were in agreement with literature values. A reproducibility study showed coefficients of variation in the range of 0.18-0.2% (brain) and 0.15-0.18% (prostate).
CONCLUSION: A rapid volumetric T mapping technique was developed. The technique enables high-resolution T mapping with adequate anatomical coverage in a clinically acceptable time.