Person:

Stern, Robert

Magnetic resonance spectroscopic imaging (MRSI) is often used to estimate the concentration of several brain metabolites. Abnormalities in these concentrations can indicate specific pathology, which can be quite useful in understanding the disease mechanism underlying those changes. Due to higher concentration, metabolites such as N-acetylaspartate (NAA), Creatine (Cr) and Choline (Cho) can be readily estimated using standard Fourier transform techniques. However, metabolites such as Glutamate (Glu) and Glutamine (Gln) occur in significantly lower concentrations and their resonance peaks are very close to each other making it di!cult to accurately estimate their concentrations (separately). In this work, we propose to use the theory of ‘Spectral Zooming’ or high-resolution spectral analysis to separate the Glutamate and Glutamine peaks and accurately estimate their concentrations. The method works by estimating a unique power spectral density, which corresponds to the maximum entropy solution of a zero-mean stationary Gaussian process. We demonstrate our estimation technique on several physical phantom data sets as well as on invivo brain spectroscopic imaging data. The proposed technique is quite general and can be used to estimate the concentration of any other metabolite of interest.

We used cost-effectiveness analysis to compare the costs, risks, and benefits of two strategies for clearing papulopustular acne; topical therapy alone as initial therapy or a combination of systemic antibiotics and topical agents used at the first visit. Patients treated with combination therapy had fewer weeks of morbidity from acne, and lower dollar costs but have a greater risk of side effects. If the topical therapy alone was chosen to reduce the risk of side effects in a population of patients there would be an additional $764 in costs and 238 weeks of morbidity from acne to avert a single additional instance of side effects. Initial treatment of papulopustular acne with combined oral antibiotics and topical agents thus seems to be cost-effective. After clearing is achieved, maintenance therapy with topical agents should be considered.