C-DIR: Double Inversion Recovery with Controlled Artifact Suppression in Brain MRI

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Abstract
BACKGROUND AND PURPOSE: Double inversion recovery (DIR) is an MRI technique in which two types of tissue are suppressed, usually cerebrospinal fluid (CSF) and white matter (WM). The suppression is achieved with two inversion pulses prior to the acquisition of the imaging data. In the presence of strong inhomogeneities in the static magnetic field B0 and/or the radiofrequency (RF) field, inversion may be inadequate, resulting in bright signal in tissues that should have been suppressed. The purpose of this work was to develop a DIR scan with inversion pulses that are robust against inhomogeneities in the B0 and RF field. MATERIALS AND METHODS: In this prospective study, the DIR sequence was equipped with inversion pulses designed with optimal control. Robustness against field inhomogeneities was incorporated into the cost functional for pulse optimization. DIR and controlled DIR (C-DIR) MRI images were acquired at 3T in 14 participants (9 male, age=36.1±11.5 years) enrolled between October 2024 to August 2025 from a single academic medical center: nine healthy; two with relapsing-remitting multiple sclerosis; one with persistent concussion symptoms; two with asymptomatic white matter hyperintensities. Suppression of CSF, presence of artifacts, and visibility of multiple sclerosis lesions and white matter hyperintensities were independently assessed visually by a radiologist. In eight healthy volunteers, means and SDs were computed for signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), with significance evaluated using a Student’s t-test. RESULTS: C-DIR exhibits improved inversion in the presence of inhomogeneities in the B0 and the radiofrequency field, resulting in the removal of artifactual signal. CNR increases ranged from 27% between gray matter and CSF (p<.001) to 102% between the brainstem and adjacent CSF (p<0.001). SNR in the cortical gray matter was 10.74±1.48 in DIR and 11.68±2.21 in C-DIR (p=.07). CONCLUSIONS: Inversion with a robust RF pulse improves the quality of DIR, demonstrating artifact reduction and improved CNR.
Funding Information
  • Natural Sciences and Engineering Research Council of Canada (016-05371)
  • Canada Research Chairs (950-230363)

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