Cerebral Gray and White Matter Involvement in Anorexia Nervosa Evaluated by T1, T2, and T2* Mapping

Abstract

BACKGROUND AND PURPOSE Changes in the brain composition of anorexics could potentially be expected, opening the door to new imaging approaches where quantitative and qualitative MRI have a role. Our purpose was to investigate anorexia‐related brain dehydration and myelin depletion by analyzing T1, T2, and T2* relaxation times of different brain structures in anorexics and controls. METHODS Thirty‐eight anorexic female patients (mean age, 26.2 years; age range, 16.2‐48.7 years; mean BMI, 14.5 kg/m2; BMI range, 10.0‐18.4 kg/m2) underwent brain MRI between August 2014 and August 2018. Controls were 16 healthy females (mean age, 28.0 years; age range, 22.3‐34.7 years; mean BMI, 20.9 kg/m2; BMI range, 18.4‐26.6 kg/m2). T1, T2, and T2* relaxation times were obtained for different brain structures in anorexics and controls as part of this retrospective case‐control study. RESULTS The T1 relaxation times of gray and white matter were significantly lower in anorexics (P = .009), whereas the T2 relaxation times of gray matter were higher (P < .001). There were no statistically significant differences in gray matter T2* relaxation times or in white matter T2 and T2* relaxation times between anorexics and controls. Occipital lobe gray matter showed the shortest T1, T2, and T2* relaxation times of all brain regions (P < .05). CONCLUSIONS T1 shortening in anorexics suggests both dehydration and myelin loss, whereas T2 prolongation points toward myelin loss (myelin water has lower T2), which seems to be less discernible in white matter. Shorter overall relaxation times in the most posterior regions of the brain suggest higher iron content.

Initial evidence of abnormal brain plasticity in anorexia nervosa: an ultra-high field study

“…The use of a high-resolution MRI scanner allowed for the first time to use T 1 values as a proxy to investigate depth-dependent intracortical myelin organization in-vivo. Our results are consistent with previous findings of reduced myelin concentration in AN 27,44 , and go beyond these, showing that such a deficit is widespread and mainly affects the outer depth-levels dependent intracortical myelin organization. Travis and colleagues 27 reported a relationship between decreased fractional anisotropy (FA, defined as a marker of WM integrity) and decreased relaxation time R1 (considered as an index of myelin content) in AN adolescents.…”

“…Whereas in our study higher T 1 values were found in patients with AN, in a recent study 44 performed with a 3 T MRI scanner an opposite pattern emerged, i.e., patients with AN showed lower T 1 relaxation times (i.e. time constant indicating how long the protons need to return to the equilibrium state 41 ) than controls in both gray matter and WM.…”

“…time constant indicating how long the protons need to return to the equilibrium state 41 ) than controls in both gray matter and WM. Nonetheless, the authors suggested that these differences could be related to starvation-driven myelin loss 44 . Although the two interpretations seem counterintuitive, it is worth highlighting that T 1 relaxation time is strictly dependent on the physical properties of the underlying tissue 41 , including free water content 48,49 and concentration and types of macromolecules 50 such as iron content 49 and myelin 51 .…”

Quantification of the Intrinsic T1 and T2 of Heschl’s Gyri with MR Fingerprinting

“…MRF has several advantages over other MRI approaches, [7][8][9][10] allowing for superior quantification. Since the quantification of T1 and T2 values is obtained simultaneously using MRF, the effects of motion between scans are mitigated.…”

“…Matching the fingerprints to a database of simulated signals (dictionary) allows for parameter mapping of relaxation parameters, including T1, T2, and T2*. 5,6 Compared with other T1 and T2 mapping methods using conventional MRI approaches, [7][8][9][10] MRF is reported to have superior performance with regard to both accuracy and efficiency. 11 Recently, MRF became commercially available for joint T1 and T2 mapping.…”