Work

B 1 ‐corrected breast T 1 mapping at ultralow field

Year: 2025

Type: article

Abstract: Purpose This study aims to develop an efficient T 1 mapping approach that is free from systematic bias caused by B 1 inhomogeneity in ultralow‐field (ULF) MRI and to determine the T 1 values (without fat suppression) of breast tissues at 6.5 mT. Methods We describe here a method for ULF T 1 mapping using a variable flip angle approach for both mapping T 1 and B 1 . The B 1 mapping is used to correct the T 1 maps—and, unique to operation in the ULF regime, a B 1 map acquired in a phantom can be applied to the in vivo T 1 mapping data, reducing in vivo scan time. The T 1 mapping method was validated in vitro with copper sulphate phantoms at seven different concentrations. A breast phantom was scanned to test the T 1 mapping protocol. Four healthy volunteers were recruited for T 1 mapping to obtain in vivo T 1 values of breast tissues. No fat suppression was implemented in this preliminary study. Results The copper sulphate phantom T 1 map measurements have less than 13% deviation from the reference T 1 values, and less than 6% deviation when the reference T 1 was greater than 50 ms. Four healthy volunteers were scanned for T 1 mapping. In these in vivo breast T 1 maps, the 25th to 75th percentiles ranged from 79 to 243 ms at 6.5 mT. Conclusion Variable flip angle method can be used for both B 1 and T 1 mapping at ULFs, which enables efficient in vivo T 1 mapping for ULF MRI.

Source: Magnetic Resonance in Medicine

DOI: 10.1002/mrm.30602