Purpose
To develop a fast MR fingerprinting (MRF) sequence for simultaneous estimation of water T1 (T1H2O) and fat fraction (FF) in fat infiltrated skeletal muscles.
Methods
The MRF sequence for ...T1H2O and FF quantification (MRF T1‐FF) comprises a 1400 radial spokes echo train, following nonselective inversion, with varying echo and repetition time, as well as prescribed flip angle. Undersampled frames were reconstructed at different acquisition time‐points by nonuniform Fourier transform, and a bi‐component model based on Bloch simulations applied to adjust the signal evolution and extract T1H2O and FF. The sequence was validated on a multi‐vial phantom, in three healthy volunteers and five patients with neuromuscular diseases. We evaluated the agreement between MRF T1‐FF parameters and reference values and confounding effects due to B0 and B1 inhomogeneities.
Results
In phantom, T1H2O and FF were highly correlated with references values measured with multi‐inversion time inversion recovery‐stimulated echo acquisition mode and Dixon, respectively (R2 > 0.99). In vivo, T1H2O and FF determined by the MRF T1‐FF sequence were also correlated with reference values (R2 = 0.98 and 0.97, respectively). The precision on T1H2O was better than 5% for muscles where FF was less than 0.4. Both T1H2O and FF values were not confounded by B0 nor B1 inhomogeneities.
Conclusion
The MRF T1‐FF sequence derived T1H2O and FF values in voxels containing a mixture of water and fat protons. This method can be used to comprehend and characterize the effects of tissue water compartmentation and distribution on muscle T1 values in patients affected by chronic fat infiltration.
Objectives
To develop a fast, high-resolution T1-mapping sequence dedicated to skeletal muscle imaging, and to evaluate the potential of T1 as a robust and sensitive biomarker for the monitoring of ...chronic fatty degenerations in a dystrophic disease.
Methods
The magnetic resonance imaging sequence consisted of the acquisition of a 1,000-radial-spokes FLASH echo-train following magnetisation inversion, resulting in 10s scan time per slice. Temporal image series were reconstructed using compressed sensing and T1 maps were computed using Bloch simulations. Ten healthy volunteers and 30 patients suffering from Becker muscular dystrophy (BMD) participated in this prospective study, in order to evaluate the repeatability, the precision and the sensitivity of the proposed approach. Intramuscular fat fraction (FF) was also measured using a standard three-point Dixon method. The protocol was approved by a local ethics committee.
Results
The mean T1 evaluated in the thighs muscles of healthy volunteers was 1,199 ± 45 ms, with a coefficient of reproducibility of 2.3%. Mean T1 values were statistically decreased in the thighs of BMD patients and were linearly correlated with intramuscular FF (
R
= -0.98).
Conclusions
T1-mapping is a good candidate for fast, sensitive and quantitative monitoring of fatty infiltrations in neuromuscular disorders.
Key Points
• A T1 mapping sequence dedicated to skeletal muscle imaging was implemented.
• The acquisition time was 10 s per slice.
• Muscle T1 values were significantly decreased in dystrophic muscles compared to healthy muscles.
• T1 values correlated with intramuscular fat fraction measured by three-point Dixon.
• T1 represents an alternative biomarker for monitoring fatty infiltrations in neuromuscular disorders.
Muscle imaging in myositis: MRI, US, and PET Albayda, Jemima; Demonceau, Georges; Carlier, Pierre G.
Best practice & research. Clinical rheumatology,
06/2022, Volume:
36, Issue:
2
Journal Article
Outcome measures for clinical trials in neuromuscular diseases are typically based on physical assessments which are dependent on patient effort, combine the effort of different muscle groups, and ...may not be sensitive to progression over short trial periods in slow-progressing diseases. We hypothesised that quantitative fat imaging by MRI (Dixon technique) could provide more discriminating quantitative, patient-independent measurements of the progress of muscle fat replacement within individual muscle groups.
To determine whether quantitative fat imaging could measure disease progression in a cohort of limb-girdle muscular dystrophy 2I (LGMD2I) patients over a 12 month period.
32 adult patients (17 male;15 female) from 4 European tertiary referral centres with the homozygous c.826C>A mutation in the fukutin-related protein gene (FKRP) completed baseline and follow up measurements 12 months later. Quantitative fat imaging was performed and muscle fat fraction change was compared with (i) muscle strength and function assessed using standardized physical tests and (ii) standard T1-weighted MRI graded on a 6 point scale.
There was a significant increase in muscle fat fraction in 9 of the 14 muscles analyzed using the quantitative MRI technique from baseline to 12 months follow up. Changes were not seen in the conventional longitudinal physical assessments or in qualitative scoring of the T₁w images.
Quantitative muscle MRI, using the Dixon technique, could be used as an important longitudinal outcome measure to assess muscle pathology and monitor therapeutic efficacy in patients with LGMD2I.
•A method for spatially regularized reconstruction of magnetic resonance fingerprinting.•Comprehensive evaluation using 164 patients with a large phenotypic variability.•The method generalizes to ...anatomical regions unseen during training.•Deep learning-based reconstruction extracts MR physically meaningful features.
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Magnetic resonance fingerprinting (MRF) provides a unique concept for simultaneous and fast acquisition of multiple quantitative MR parameters. Despite acquisition efficiency, adoption of MRF into the clinics is hindered by its dictionary matching-based reconstruction, which is computationally demanding and lacks scalability. Here, we propose a convolutional neural network-based reconstruction, which enables both accurate and fast reconstruction of parametric maps, and is adaptable based on the needs of spatial regularization and the capacity for the reconstruction. We evaluated the method using MRF T1-FF, an MRF sequence for T1 relaxation time of water (T1H2O) and fat fraction (FF) mapping. We demonstrate the method’s performance on a highly heterogeneous dataset consisting of 164 patients with various neuromuscular diseases imaged at thighs and legs. We empirically show the benefit of incorporating spatial regularization during the reconstruction and demonstrate that the method learns meaningful features from MR physics perspective. Further, we investigate the ability of the method to handle highly heterogeneous morphometric variations and its generalization to anatomical regions unseen during training. The obtained results outperform the state-of-the-art in deep learning-based MRF reconstruction. The method achieved normalized root mean squared errors of 0.048 ± 0.011 for T1H2O maps and 0.027 ± 0.004 for FF maps when compared to the dictionary matching in a test set of 50 patients. Coupled with fast MRF sequences, the proposed method has the potential of enabling multiparametric MR imaging in clinically feasible time.
Age-related sarcopenia is a major health issue. To improve elderly person quality of life, it is important to characterize age-associated structural changes within the skeletal muscle. NMR imaging ...offers quantitative tools to monitor these changes. We scanned 93 subjects: 33 young adults aged between 19 and 27years old and 60 older adults between 69 and 80years old. Their physical activity was assessed using a tri-axial accelerometer and they were classified either as active or sedentary. A standard multi-slice multi-echo (MSME) sequence was run and water T2 maps were extracted using a tri-exponential fit. Fat fraction was quantified using three-point Dixon technique. Each quadriceps muscle was characterized by: water T2 mean value, water T2 heterogeneity and the mean fat fraction.
Statistical analysis (ANOVA) showed that water T2 mean values and its heterogeneity indices as well as fat fraction were significantly higher in the elderly group (p<0.05). Only fat fraction was significantly lower in the active group compared to the sedentary one (p<0.05). Linear regression confirmed the significant impact of age on these NMR parameters whereas physical activity impact was not systematic.
NMR imaging provided a comprehensive assessment of the aging process impact on skeletal muscle composition. Water T2 increase might be related to changes in fiber typology while increased T2 heterogeneities might correlate with some degree of tissue disorganization, like the development of interstitial fibrosis. Fat fraction and water T2 heterogeneity increase was partly slowed down by physical activity. These changes were not gender dependent.
•Intramuscular mean fat ratio, is significantly higher in older healthy volunteers.•Water T2 mean value and water T2 heterogeneity increase with age.•Intramuscular mean fat ratio is lower in active older volunteer.•The process of muscle aging is not different between men and women.
ABSTRACT
Introduction
Patients with anoctamin‐5 (ANO5) mutations may present not only with limb‐girdle muscular dystrophy type 2L or adult‐onset Miyoshi‐type myopathy but also with asymptomatic ...hyperCKemia, exercise intolerance, or rhabdomyolysis.
Materials and Methods
Data from 38 patients in France with ANO5 mutations with and without muscle weakness on first examination were compared.
Results
Twenty patients presented without muscle weakness. Median age at symptom onset or discovery of hyperCKemia was 23 years. Creatine kinase levels ranged from 200 to 40,000 U/L. Electromyography showed a myopathic pattern in 5 patients, and muscle imaging showed involvement of posterior calf muscles in 10 patients. Mild cardiac involvement was observed in 2 patients. Sixteen patients remain free of weakness after a median follow‐up period of 5 years.
Discussion
Asymptomatic, sometimes mild hyperCKemia or exercise intolerance is a presentation of ANO5‐related myopathy and may remain isolated or precede muscle weakness by many years. Muscle Nerve 56: 1096–1100, 2017
Abstract To describe muscle involvement on whole-body MRI scans in adult patients at different stages of late-onset Pompe disease. Twenty patients aged 37 to 75 were examined. Five were bedridden and ...required ventilatory support. Axial and coronal T1 turbo-spin-echo sequences were performed on 1.5 T or 3 T systems. MRI was scored for 47 muscles using Mercuri’s classification. Whole-body scans were obtained with a mean in-room time of 29 min. Muscle changes consisted of internal bright signals of fatty replacement without severe retraction of the muscles’ corpus. Findings were consistent with previous descriptions of spine extensors and pelvic girdle, but also provided new information on recurrent muscle changes particularly in the tongue and subscapularis muscle. Moreover thigh involvement was more heterogeneous than previously described, in terms of distribution across muscles as well as with respect to the overall clinical presentation. Whole-body MRI provides a very evocative description of muscle involvement in Pompe disease in adults.
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