A fast Look-Locker method for T ₁ mapping of the head and neck region

Objective: A sequence for T₁ relaxation time measurements that allows a high-resolution image to be obtained within a short acquisition time is described. Its application to the orofacial region is investigated. Methods: The sequence is based on the Look-Locker (LL) method and employs a magnetization-preparation pulse prior to data acquisition, with either a turbo-field echo (TFE) or turbo-field echo echo-planar imaging (TFEPI) sequence. We applied the multiple LL sequence by synchronizing the data acquisition with the virtual electrocardiogram. T₁ results from the LL sequence were compared with those from the inversion recovery (IR) sequence. In an in vitro study, we evaluated the T₁ maps of contrast medium at different concentrations. In an in vivo study, we evaluated the T₁ maps in seven volunteers. Results: In the in vitro study, the correlation between the T₁ values obtained from the LL sequence and those from the IR sequence was high, with an R ² of more than 0.99. For T₁ values between 200 and 1,500 ms, the difference between the two methods was less than 7%. In the in vivo study, a high correlation was observed between the T₁ values from the IR sequence and those from the LL sequence. The scan duration for the LL sequence was less than 3 min. Conclusion: Our method, based on the LL sequence, was found to be clinically useful for producing a T₁ map.