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C-DIR: Double Inversion Recovery with Controlled Artifact Suppression in Brain MRI
Alexander Jaffray1,2, Christina Graf1,2,3, Armin Rund2
1From the Department of Physics and Astronomy (A.J., C.G., A. Rauscher), University of British Columbia, Vancouver British Columbia, Canada.
Background And Purpose:
Double inversion recovery (DIR) is an MRI technique in which 2 types of tissue are suppressed, usually CSF and WM. The suppression is achieved with 2 inversion pulses before 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 double inversion recovery (C-DIR) MR images were acquired at 3T in 14 participants (8 men, age = 36.1 ± 11.5 years) enrolled between October 2024 and August 2025 from a single academic medical center: 9 healthy; 2 with relapsing-remitting MS; 1 with persistent concussion symptoms; and 2 with asymptomatic WM hyperintensities. Suppression of CSF, presence of artifacts, and visibility of MS lesions and WM hyperintensities were independently assessed visually by a radiologist. In 8 healthy volunteers, means and SDs were computed for SNR and contrast-to-noise ratio (CNR), with significance evaluated using a Student t test.
Results:
C-DIR exhibits improved inversion in the presence of inhomogeneities in the B0 and the RF 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 < .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. Controlled inversion in double inversion recovery reduces artifacts and increases contrast to noise ratio in brain MRI.
Insights
Controlled Double Inversion Recovery (C-DIR) MRI uses robust inversion pulses to reduce artifacts caused by magnetic field inhomogeneities. This technique improves image quality and contrast-to-noise ratio (CNR) for better visualization of tissues like cerebrospinal fluid (CSF).
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Medical Physics
- Neuroimaging
Background:
- Double Inversion Recovery (DIR) MRI suppresses cerebrospinal fluid (CSF) and white matter (WM) using two inversion pulses.
- Field inhomogeneities (B0 and RF) can cause inadequate inversion, leading to artifacts and reduced image quality.
- Existing DIR techniques are susceptible to these artifacts, limiting diagnostic accuracy.
Purpose of the Study:
- To develop a DIR MRI sequence with inversion pulses robust against B0 and RF field inhomogeneities.
- To improve the reliability and quality of DIR imaging in the presence of magnetic field variations.
Main Methods:
- Developed Controlled DIR (C-DIR) using optimal control theory for inversion pulse design.
- Incorporated robustness against field inhomogeneities into the pulse optimization cost functional.
- Acquired 3T MRI images in 14 participants (healthy, MS, concussion, WMH) and assessed artifacts and lesion visibility.
Main Results:
- C-DIR demonstrated improved inversion and artifact removal in the presence of field inhomogeneities.
- Significant increases in Contrast-to-Noise Ratio (CNR) were observed (e.g., 102% between brainstem and CSF, p<0.001).
- Signal-to-Noise Ratio (SNR) in cortical gray matter showed a trend towards improvement with C-DIR (p=0.07).
Conclusions:
- Robust RF pulse design in C-DIR significantly enhances DIR MRI quality.
- The technique effectively reduces artifacts and improves CNR, leading to better tissue contrast.
- C-DIR offers a more reliable method for DIR imaging, especially in challenging magnetic field conditions.
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