Quantitative ultrashort TE imaging of the short-T2 components in skeletal muscle using an extended echo-subtraction method.

PURPOSE: To introduce an ultrashort echo time (UTE) based method for quantitative mapping of short-T2 signals in skeletal muscle (SKM) in the presence of fat, with the aim of monitoring SKM fibrosis. METHODS: From a set of at least five UTE images of the same slice, a long- T2* map, a fat-fraction map, and a map of short-T2 -signal fraction are extracted. The method was validated by numerical simulations and in vitro studies on collagen solutions. Finaly, the method was applied to image the short-T2 signals in the leg of eight healthy volunteers. RESULTS: The imaged short-T2 -signal fractions in the collagen solutions correlated with their respective collagen concentrations ( R=0.999,  P=0.009). Short-T2 tissues such as cortical bone and fasciae were highlighted in the resulting short-T2 fraction maps. A significant fraction of short-T2 signal was systematically observed in the skeletal muscle of all of the subjects (4.5±1.2%). CONCLUSION: The proposed method allows the quantitative imaging of short-T2 components in tissues containing fat. By also having the fat-fraction and T2* maps as outcomes, long-T2 suppression is accomplished without requiring modifications to the basic UTE sequence. Although the hypersignal observed in the fasciae suggests that the short-T2 signal observed in SKM might arise from interstitial connective tissue, further investigation is necessary to confirm this statement. Magn Reson Med 78:997-1008, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Interest of surgical vascular reconstructions aiming at preserving hemodialysis access.

BACKGROUND: Vascular hemodialysis access is a very precious asset for patients with end-stage renal failure. Ideally complications in these accesses should be detected early in order to treat them in time. The aim of this study was to evaluate the effectiveness of vascular reconstructions to preserve the vascular access for hemodialysis and to examine their benefits in terms of conserving the venous network, using hemodialysis catheters, time of cannulation after surgery, patency and postoperative morbi-mortality, by comparing them to those of newly created arterio-venous fistula (AVF). METHODS: This was a retrospective, descriptive and comparative study, performed from September 2012 to February 2015. It concerned patients operated for complications of their native AVF. Two groups were compared: reconstructed AVF (group 1) and newly created AVF (group 2). Demographic characteristics, comorbidities, preoperative clinical and paraclinical data, surgical techniques and outcomes were recorded. This data was analyzed and compared between the two groups. RESULTS: We collected 151 surgical interventions divided into two groups: 55 surgical reconstructions and 96 new AVF. The average age was 59.9±1.3 years [19.1-88.9], with a male predominance (59.6%). The two groups were comparable in terms of age, gender and comorbidities. Reconstructions were mostly indicated for stenosis (47.3%) and new vascular accesses for venous thrombosis (92.7%). Reconstruction had significantly better successful exploitation rates (95.7%) and time of cannulation (26.6 days) (respectively P=0.025 and P=0.000). Its primary failure rate was null. Its primary patency and primary functional patency were respectively 94.2% and 97.7% at 1 month and 82.2% and 87.1% at 2 years. Morbidity's global rates were comparable between both groups (41.8% vs. 43.8%). The rates of early morbidity and stenosis were significantly higher for reconstructions (respectively P=0.037 and P=0.047), while late morbidity and thrombosis' rates were significantly higher for new AVF (respectively P=0.021 and P=0.023). Mid-term permeabilities were better for reconstructions, but the differences were not statistically significant. CONCLUSION: Surgical reconstructions seem to be an effective alternative for the treatment of complicated AVF. Our results appear to be comparable to those of the literature. The benefits of these surgical techniques in terms of conserving venous network, use of hemodialysis catheters, time for cannulation after surgery, patency and postoperative morbi-mortality appear to be undeniable.

Prior knowledge, random walks and human skeletal muscle segmentation.

In this paper, we propose a novel approach for segmenting the skeletal muscles in MRI automatically. In order to deal with the absence of contrast between the different muscle classes, we proposed a principled mathematical formulation that integrates prior knowledge with a random walks graph-based formulation. Prior knowledge is represented using a statistical shape atlas that once coupled with the random walks segmentation leads to an efficient iterative linear optimization system. We reveal the potential of our approach on a challenging set of real clinical data.

Comprehensive longitudinal characterization of canine muscular dystrophy by serial NMR imaging of GRMD dogs.

The Golden Retriever Muscular Dystrophy (GRMD) dog is the closest animal counterpart of Duchenne muscular dystrophy in humans and has, for this reason, increasingly been used in preclinical therapeutic trials for this disease. The aim of this study was to describe the abnormalities in canine dystrophic muscle non-invasively, quantitatively, thoroughly and serially by means of NMR imaging. Thoracic and pelvic limbs of five healthy and five GRMD dogs were imaged in a 3T NMR scanner at 2, 4, 6 and 9months of age. Standard and fat-saturated T(1)-, T(2)- and proton-density-weighted images were acquired. A measurement of T(1) and a two-hour kinetic study of muscle enhancement after gadolinium-chelate injection were also performed. Ten out of the 15 indices evaluated differed between healthy and GRMD dogs. The maximal relative enhancement after gadolinium injection and the proton-density-weighted/T(2)-weighted signal ratio were the most discriminating indices. Inter-muscle heterogeneity was found to vary significantly for most of the indices. The body of data that has been acquired here will help in designing and interpreting preclinical trials using dystrophin-deficient dogs.