Relaxometry: Application to Brain Disorders
Akifumi Hagiwara1
1Juntendo University School of Medicine, Japan

Synopsis

Keywords: Contrast mechanisms: Relaxometry, Neuro: Brain, Image acquisition: Quantification

Traditional MRI interpretations rely on contrasting tissue signals, not on absolute signal intensities. Quantification of tissue parameters such as relaxation rates and proton density, which provide an absolute scale, has been limited to research. Advances in rapid quantification are making clinical application viable. This lecture introduces these methods and the synthesis of contrast-weighted (synthetic MRI) images based on absolute values. It further examines the application of these techniques to brain diseases, with promising results in conditions like multiple sclerosis, brain metastases, Sturge-Weber syndrome, and pediatric disorders.

Typically, MRI is interpreted by examining the contrast between different tissue signals rather than their exact signal intensities. To establish a standardized scale, measuring specific tissue properties like relaxation times and proton density is useful, but such practices are largely limited to research environments. Advances in fast measurement techniques have made these methods more viable for clinical application. This presentation will cover these advanced quantification techniques, such as SyMRI1 and MR fingerprinting,2 and the creation of contrast-enhanced images (also known as synthetic MRI) using the absolute measurements obtained. These methods are then applied to a range of brain conditions. The use of relaxometry and synthetic MRI has been particularly encouraging in earlier research for diagnosing conditions like multiple sclerosis,3 brain metastases,4 Sturge-Weber syndrome,5 and various childhood neurological disorders.6

Acknowledgements

No acknowledgement found.

References

1. Hagiwara A, Warntjes M, Hori M, et al. SyMRI of the Brain: Rapid Quantification of Relaxation Rates and Proton Density, With Synthetic MRI, Automatic Brain Segmentation, and Myelin Measurement. Invest Radiol. 2017;52(10):647-657.

2. Ma D, Gulani V, Seiberlich N, et al. Magnetic resonance fingerprinting. Nature. 2013;495(7440):187-192.

3. Hagiwara A, Hori M, Yokoyama K, et al. Utility of a Multiparametric Quantitative MRI Model That Assesses Myelin and Edema for Evaluating Plaques, Periplaque White Matter, and Normal-Appearing White Matter in Patients with Multiple Sclerosis: A Feasibility Study. AJNR Am J Neuroradiol. 2017 Feb;38(2):237-242

4. Hagiwara A, Hori M, Suzuki M, et al. Contrast-enhanced synthetic MRI for the detection of brain metastases. Acta Radiol Open. 2016;5(2):2058460115626757.

5. Andica C, Hagiwara A, Hori M, et al. Aberrant myelination in patients with Sturge-Weber syndrome analyzed using synthetic quantitative magnetic resonance imaging. Neuroradiology. 2019;61(9):1055-1066.6. Tian Z, Zhu Q, Wang R, et al. The advantages of the magnetic resonance image compilation (MAGiC) method for the prognosis of neonatal hypoglycemic encephalopathy. Front Neurosci. 2023:17:1179535.

Proc. Intl. Soc. Mag. Reson. Med. 32 (2024)