Master thesis presentation: Creatine Cest in Human Muscle by Esaú Poblador Rodríguez

On Thursday, November 19th at 11.15 am. Esaú Poblador Rodríguez will be presenting his master thesis “Creatine Cest in Human Muscle”. The examiner is Fredrik Kahl.

The presentation will take place in Lunnerummet (room 3311), Hörsalsvägen 11, 3rd floor at Chalmers.

Chemical Exchange Saturation Transfer (CEST) imaging is a relatively recent technique that allows the detection of endogenous and exogenous compounds (protons or molecules) with enhanced sensitivity. Its application to free creatine (Cr) could replace phosphorous MR spectroscopy (31P-MRS) as the gold standard due to its superior sensitivity and spatial resolution. It would then become a powerful tool for the assessment of treatment outcomes and diagnosis of skeletal muscular disorders (muscular dystrophy).

The present thesis is based on a working CEST MR imaging sequence for detection of Glycosaminoglycan (GAG-CEST) in cartilage and a CEST post-processing tool in Matlab for APT and GAG detection. The scope of the present work covers the implementations necessary to apply this method on phantoms for free Cr detection with maximum CEST effect, investigate how CEST contrast is affected by the RF saturation signal as well as by environmental factors, and finally, obtain an optimized MR sequence to achieve maximal contrast image.

For equal metabolite’s concentrations, free Cr was found to contribute to the CEST contrast around 80%, whereas the rest 20% came from PCr. In the ranges presented, the contrast was found linearly dependent with both pH and Cr concentration (gain of 0.6% per mMol). Parameters defining the saturation pulses, such as its amplitude, affect the proton’s exchange (in this case causing broadening of the CEST peaks). Others like the type of k-space readout, may yield to asymmetric spectra due to insufficient time between saturation periods. This knowledge is expected to be further applied for detection of dynamic changes of Cr in the human calf muscle during exercise.