Multi-parametric MRI characterization of healthy human thigh muscles at 3.0 T - relaxation, magnetization transfer, fat/water, and diffusion tensor imaging

Abstract

Muscle diseases commonly have clinical presentations of inflammation, fat infiltration, fibrosis, and atrophy. However, the results of existing laboratory tests and clinical presentations are not well correlated. Advanced quantitative MRI techniques may allow the assessment of myo-pathological changes in a sensitive and objective manner. To progress towards this goal, an array of quantitative MRI protocols was implemented for human thigh muscles, their reproducibility was assessed, and the statistical relationships among parameters were determined. These quantitative methods included fat/water imaging, multiple spin-echo T2 imaging (with and without fat signal suppression, FS), selective inversion recovery for T1 and quantitative magnetization transfer (qMT) imaging (with and without FS), and diffusion tensor imaging. Data were acquired at 3.0 T from nine healthy subjects. To assess the repeatability of each method, the subjects were re-imaged on an average of 35 days later. Pre-testing lifestyle restrictions were applied to standardize physiological conditions across scans. Strong between-day intra-class correlations were observed in all quantitative indices except for the macromolecular-to-free water pool size ratio (PSR) with FS, a metric derived from qMT data. Two-way analysis of variance revealed no significant between-day differences in the mean values for any parameter estimate. The repeatability was further assessed with Bland-Altman plots, and low repeatability coefficients were obtained for all parameters. Among-muscle differences in the quantitative MRI indices and inter-class correlations among the parameters were identified. There were inverse relationships between fractional anisotropy (FA) and the 2nd eigenvalue, the 3rd eigenvalue, and the standard deviation of first eigenvector. The FA was positively related to the PSR, while the other diffusion indices were inversely related to the PSR. These findings support the use of these T1, T2, fat/water, and DTI protocols for characterizing skeletal muscle using MRI. Moreover, the data support the existence of a common biophysical mechanism, water content, as a source of variation in these parameters.

A rapid approach for quantitative magnetization transfer imaging in thigh muscles using the pulsed saturation method

“…As noted previously (15), voluntary and involuntary motion artifacts can occur during data collection (~10 min for a full dataset). These movements can result from gross subject movements, prolonged muscle contraction, and/or brief twitches.…”

“…For example, the PSR is correlated with myelin content in white matter (9,12). QMT studies have also been performed in healthy skeletal muscles (13-15) and in a murine model of inflammation (16). It was demonstrated that PSR may also serve as a biomarker of inflammation (16).…”

“…It was demonstrated that PSR may also serve as a biomarker of inflammation (16). However, quantitative MRI studies in skeletal muscle are challenged by low signal-to-noise ratio (SNR), caused by the short T 2 values of water protons (~30 ms at 3.0T), as well as static (B 0 ) and radiofrequency transmit (B 1 + ) field inhomogeneities (15). In a number of muscle diseases, fat infiltration is a major pathological component.…”

Skeletal muscle quantitative nuclear magnetic resonance imaging and spectroscopy as an outcome measure for clinical trials (part II)

“…Недавно при применении уско-ренных последовательностей с оптимизированными схемами насыщения были получены обнадеживающие результаты с высокой корреляцией различий магнити-зации с фиброзом в печени [102]. Перенос магнитиза-ции имеет высокий уровень в скелетных мышцах, его происхождение и механизмы развития были изучены несколькими группами ученых у здоровых людей, а также при старении и заболеваниях мышц, однако связь изменений с фиброзом по-прежнему остается до конца не ясной [103][104][105][106][107][108]. Много вопросов вызвало обнаружение обратной корреляции различий магни-тизации с возрастными изменениями у здоровых лю-дей.…”

Imagerie et spectroscopie par résonance magnétique nucléaire du muscle strié squelettique

“…Cette méthode a été transférée chez l'homme sous le nom d'ISIS-CPMG. Elle a permis d'identifier des composantes T2 intra-et extracellulaires mais n'a jusqu'à présent pas mis en évidence cette composante de spins à T2 très court (Schwenzer et al 2009a ;Sinclair et al 2010 ;Sinclair et al 2012 ;Morrow et al 2014 ;Li et al 2014 ;Li et al 2015). La corrélation négative entre le contraste de transfert d'aimantation et l'âge dans une cohorte d'individus sains est par exemple, relativement déroutante .…”