Improvements of Liver MR Imaging Clinical Protocols to Simultaneously Quantify Steatosis and Iron Overload

International audiencePurpose : Fat accumulation and iron overload are important cofactors in chronic liver disease. Clinical quantifications of fat fraction and iron are currently assessed using MRI protocols. The purpose is to improve these measurements to simultaneously provide iron and fat maps from a single acquisition. Methods: Ten healthy volunteers and ten patients with steatosis underwent MRI for fat fraction (FF: IDEAL-IQ ®), iron overload concentration (IOC: Gandon, Starmap ®) and viscoelastic characterization (MR-Touch ®). IDEAL-IQ ® data, the clinical FF reference, were compared to the advanced Gandon protocol, post-treated with a 3pt Dixon method. The originality was to use IDEAL-IQ ® fat sequence to quantify iron volu-metrically using the Wood equation. To validate the iron data, the reference Gandon protocol was applied and improved to provide map of IOC. Then, IOC data were also compared to another clinical sequence (Starmap ®) which was also improved (scale, number of ROI). The estimated error associated with each method was evaluated with the coefficient of variation. Results: IDEAL-IQ ® and Gandon protocols were modified to provide simultaneously FF and IOC maps (2D, volume). Healthy FF were in the same range with all protocols (≈3%). For patients with steatosis, Gandon protocols underestimated the FF value (≈7%) compared to IDEAL-IQ ®. Healthy and fibrosis patients were correctly diagnosed (no hemochromatosis) with all the protocols and viscoelastic properties were in the same range. Conclusion: Manufacturer's tools were improved to simultaneously quantify liver markers saving time for the patient and the clinical setting. These parameters are of great value for clinical diagnostics and novel therapeutics to treat liver diseases

Low Frequency cMUT Technology: Application to Measurement of Brain Movement and Assessment of Bone Quality

International audienceFollowing recent advances in medical ultrasound imaging methods almost all human tissues can currently be examined. There are, however, two exceptions: the human skeleton and the brain, because bone tissue is a strongly attenuating and defocusing medium, rendering classical pulse-echo imaging methods inappropriate. Specific imaging approaches within low frequency bands, i.e. 200 kHz–2 MHz, have therefore recently been developed and the results are very promising: (1) the technique for the bone is axial transmission measurement, which consists of using elastic guided modes to characterize all elastic constants of the medium; (2) for brain exploration, it has been demonstrated that brain movement can be measured (i.e. brain pulsatility) with elastography techniques. However, there are certain limitations in the fabrication of low frequency probes with classical technology, which involve finding an alternative to the traditional PZT. Capacitive Micromachined Ultrasonic Transducers (cMUTs) can overcome these limitations and greatly improve these new imaging modalities. The study presented here represents technological development with several goals: (1) the design and fabrication of two different low frequency linear arrays for bone and brain exploration, respectively the testing of axial transmission measurements with a cMUT probe and; (2) comparison with a PZT probe; (3) the development of an imaging method based on the elastography of brain pulsatility, its implementation in a commercial ultrasound scanner and clinical trials for the validation. The results obtained with cMUT and PZT probes are compared

Development of a novel multiphysical approach for the characterization of mechanical properties of musculotendinous tissues

International audienceAt present, there is a lack of well-validated protocols that allow for the analysis of the mechanical properties of muscle and tendon tissues. Further, there are no reports regarding characterization of mouse skeletal muscle and tendon mechanical properties in vivo using elastography thereby limiting the ability to monitor changes in these tissues during disease progression or response to therapy. Therefore, we sought to develop novel protocols for the characterization of mechanical properties in musculotendinous tissues using atomic force microscopy (AFM) and ultrasound elastography. Given that TIEG1 knockout (KO) mice exhibit well characterized defects in the mechanical properties of skeletal muscle and tendon tissue, we have chosen to use this model system in the present study. Using TIEG1 knockout and wild-type mice, we have devised an AFM protocol that does not rely on the use of glue or chemical agents for muscle and tendon fiber immobilization during acquisition of transversal cartographies of elasticity and topography. Additionally, since AFM cannot be employed on live animals, we have also developed an ultrasound elastography protocol using a new linear transducer, SLH20-6 (resolution: 38 µm, footprint: 2.38 cm), to characterize the musculotendinous system in vivo. This protocol allows for the identification of changes in muscle and tendon elasticities. Such innovative technological approaches have no equivalent to date, promise to accelerate our understanding of musculotendinous mechanical properties and have numerous research and clinical applications