Combined quantification of fatty infiltration, T1-relaxation times and T2*-relaxation times in normal-appearing skeletal muscle of controls and dystrophic patients.
OBJECTIVE
To evaluate the combination of a fat-water separation method with an automated segmentation algorithm to quantify the intermuscular fatty-infiltrated fraction, the relaxation times, and the microscopic fatty infiltration in the normal-appearing muscle.


METHODS
MR acquisitions were performed at 1.5T in seven patients with facio-scapulo-humeral dystrophy and eight controls. Disease severity was assessed using commonly used scales for the upper and lower limbs. The fat-water separation method provided proton density fat fraction (PDFF) and relaxation times maps (T2* and T1). The segmentation algorithm distinguished adipose tissue and normal-appearing muscle from the T2* map and combined active contours, a clustering analysis, and a morphological closing process to calculate the index of fatty infiltration (IFI) in the muscle compartment defined as the relative amount of pixels with the ratio between the number of pixels within IMAT and the total number of pixels (IMAT + normal appearing muscle).


RESULTS
In patients, relaxation times were longer and a larger fatty infiltration has been quantified in the normal-appearing muscle. T2* and PDFF distributions were broader. The relaxation times were correlated to the Vignos scale whereas the microscopic fatty infiltration was linked to the Medwin-Gardner-Walton scale. The IFI was linked to a composite clinical severity scale gathering the whole set of scales.


CONCLUSIONS
The MRI indices quantified within the normal-appearing muscle could be considered as potential biomarkers of dystrophies and quantitatively illustrate tissue alterations such as inflammation and fatty infiltration.
Laboratoire CREATIS CNRS UMR 5220; Inserm U1206; INSA-Lyon; UCBL Lyon 1, 7, Avenue Jean Capelle, 69621, Villeurbanne Cedex, France. benjamin.leporq2@gmail.com.
Benjamin
B
Leporq
Aix-Marseille University, CRMBM, CNRS UMR, 6612, Marseille, France.
Arnaud
A
Le Troter
Aix-Marseille University, CRMBM, CNRS UMR, 6612, Marseille, France.
Yann
Y
Le Fur
Reference Center for Neuromuscular Disorders, Timone Hospital, Marseille, France.
Emmanuelle
E
Salort-Campana
Aix-Marseille University, CRMBM, CNRS UMR, 6612, Marseille, France.
Maxime
M
Guye
Laboratoire CREATIS CNRS UMR 5220; Inserm U1206; INSA-Lyon; UCBL Lyon 1, 7, Avenue Jean Capelle, 69621, Villeurbanne Cedex, France.
Olivier
O
Beuf
Reference Center for Neuromuscular Disorders, Timone Hospital, Marseille, France.
Shahram
S
Attarian
Aix-Marseille University, CRMBM, CNRS UMR, 6612, Marseille, France.
David
D
Bendahan
D000273:Adipose Tissue / Q000000981:diagnostic imaging*; D000328:Adult; D000465:Algorithms; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging*; D020391:Muscular Dystrophy, Facioscapulohumeral / Q000000981:diagnostic imaging*
Magnetic resonance imaging; Muscle dystrophies; Segmentation