Several quantitative magnetic resonance (MR) measures are used to investigate multiple sclerosis (MS) in vivo. Precise quantitative investigation of the histopathological correlates of such measures has, to date, been limited. This study investigates the relationship of quantitative measures of myelin content, axonal density, and gliosis with quantitative MR measures in postmortem (PM) MS tissue. MR imaging (MRI) was performed on a 1.5T scanner and T1-relaxation time (T1-RT) and magnetization transfer ratio (MTR) maps were acquired in fresh PM brain of 20 MS subjects. Myelin content, axonal counts, and the extent of gliosis all were quantified using morphometric and digital imaging techniques. MRI and pathological data were in most cases coregistered using stereotactic navigation. Using multiple regression analysis, we detected significant correlations between myelin content (Tr(myelin)) and MTR (r = -0.84, p < 0.001) and myelin content and axonal count (-0.80, p < 0.001); MTR correlated with T1-RT (r = -0.79, p < 0.001). No association was detected between the extent of gliosis and either MR measure. MTR was significantly higher in remyelinated than demyelinated lesions (means: 30.0 [standard deviation, 2.9] vs 23.8 [standard deviation, 4.3], p = 0.008). In conclusion, MTR is affected by myelin content in MS white matter.

Magnetization transfer ratio and myelin in postmortem multiple sclerosis brain

Rapid T(1)-weighted 3D spoiled gradient-echo (GRE) data sets were acquired in the abdomen of 23 cancer patients during a total of 113 separate visits to allow dynamic contrast-enhanced MRI (DCE-MRI) analysis of tumor microvasculature. The arterial input function (AIF) was measured in each patient at each visit using an automated AIF extraction method following a standardized bolus administration of gadodiamide. The AIFs for each patient were combined to obtain a mean AIF that is representative for any individual. The functional form of this general AIF may be useful for studies in which AIF measurements are not possible. Improvements in the reproducibility of DCE-MRI model parameters (K(trans), v(e), and v(p)) were observed when this new, high-temporal-resolution population AIF was used, indicating the potential for increased sensitivity to therapy-induced change.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/mrm.21066

Experimentally-derived functional form for a population-averaged high-temporal-resolution arterial input function for dynamic contrast-enhanced MRI.

Multi-center studies using magnetic resonance imaging facilitate studying small effect sizes, global population variance and rare diseases. The reliability and sensitivity of these multi-center studies crucially depend on the comparability of the data generated at different sites and time points. The level of inter-site comparability is still controversial for conventional anatomical T1-weighted MRI data. Quantitative multi-parameter mapping (MPM) was designed to provide MR parameter measures that are comparable across sites and time points, i.e., 1mm high-resolution maps of the longitudinal relaxation rate (R1=1/T1), effective proton density (PD*), magnetization transfer saturation (MT) and effective transverse relaxation rate (R2*=1/T2*). MPM was validated at 3T for use in multi-center studies by scanning five volunteers at three different sites. We determined the inter-site bias, inter-site and intra-site coefficient of variation (CoV) for typical morphometric measures (i.e., gray matter probability maps used in voxel-based morphometry) and the four quantitative parameters. The inter-site bias and CoV were smaller than 3.1% and 8%, respectively, except for the inter-site CoV of R2* (< 20%). The gray matter probability maps based on the MT parameter maps had a 14% higher inter-site reproducibility than maps based on conventional T1-weighted images. The low inter-site bias and variance in the parameters and derived gray matter probability maps confirm the high comparability of the quantitative maps across sites and time points. The reliability, short acquisition time, high resolution and the detailed insights into the brain microstructure provided by MPM makes it an efficient tool for multi-center imaging studies.

/pdf/quantitative-multi-parameter-mapping-of-r1-pd-mt-and-r2-at-2id9vo7w1b.pdf

Quantitative multi-parameter mapping of R1, PD(*), MT, and R2(*) at 3T: a multi-center validation.

Diffusion tensor imaging of post mortem multiple sclerosis brain

Carnosine (β-alanyl-l-histidine) is present in high concentrations in human skeletal muscle. The ingestion of β-alanine, the rate-limiting precursor of carnosine, has been shown to elevate the musc...

https://www.physiology.org/doi/pdf/10.1152/japplphysiol.00397.2007

Beta-alanine supplementation augments muscle carnosine content and attenuates fatigue during repeated isokinetic contraction bouts in trained sprinters

P Tofts. Chichester: John Wiley & Sons, 2003, pp 617, £175.00. ISBN 0-470-84721-2

We have waited for a long time for a comprehensive book on magnetic resonance (MR) techniques that will appeal to the neurologist/neuroradiologist as well as the physicist and researcher. A book that is right up to date and is relevant across the board for all who are interested in the technique and that deals with quantification.

Paul Tofts has produced a book that is in the coffee table style, in the best sense of …

https://jnnp.bmj.com/content/jnnp/75/10/1511.1.full.pdf

M Maier

Papers

Quantitative MRI of the brain—measuring changes caused by disease