In vivo T1 mapping of neonatal brain tissue at 64 mT

Purpose Ultralow-field (ULF) point-of-care MRI systems allow image acquisition without interrupting medical provision, with neonatal clinical care being an important potential application. The ability to measure neonatal brain tissue T-1 is a key enabling technology for subsequent structural image contrast optimization, as well as being a potential biomarker for brain development. Here we describe an optimized strategy for neonatal T-1 mapping at ULF. Methods Examinations were performed on a 64-mT portable MRI system. A phantom validation experiment was performed, and a total of 33 in vivo exams were acquired from 28 neonates with postmenstrual age ranging from 31(+4) to 49(+0) weeks. Multiple inversion-recovery turbo spin-echo sequences were acquired with differing inversion and repetition times. An analysis pipeline incorporating inter-sequence motion correction generated proton density and T-1 maps. Regions of interest were placed in the cerebral deep gray matter, frontal white matter, and cerebellum. Weighted linear regression was used to predict T-1 as a function of postmenstrual age. Results Reduction of T-1 with postmenstrual age is observed in all measured brain tissue; the change in T-1 per week and 95% confidence intervals is given by dT(1) = -21 ms/week [-25, -16] (cerebellum), dT(1) = -14 ms/week [-18, -10] (deep gray matter), and dT(1) = -35 ms/week [-45, -25] (white matter). Conclusion Neonatal T-1 values at ULF are shorter than those previously described at standard clinical field strengths, but longer than those of adults at ULF. T-1 reduces with postmenstrual age and is therefore a candidate biomarker for perinatal brain development.

Automated summary

This study utilizes ultralow-field MRI systems to measure T-1 values in neonates and finds that these values are shorter than those previously measured at standard clinical field strengths, but longer than those of adults at ultralow-field. T-1 values decrease with postmenstrual age, making them a potential biomarker for perinatal brain development.