Geometric optimal control of the contrast imaging problem in Nuclear Magnetic Resonance

The objective of this article is to introduce the tools to analyze the contrast imaging problem in Nuclear Magnetic Resonance. Optimal trajectories can be selected among extremal solutions of the Pontryagin Maximum Principle applied to this Mayer type optimal problem. Such trajectories are associated to the question of extremizing the transfer time. Hence the optimal problem is reduced to the analysis of the Hamiltonian dynamics related to singular extremals and their optimality status. This is illustrated by using the examples of cerebrospinal fluid / water and grey / white matter of cerebrum.Comment: 30 pages, 13 figur

Impact of rapid antigen detection testing on antibiotic prescription in acute pharyngitis in adults: FARINGOCAT STUDY: a multicentric randomized controlled trial

Dolor de garganta; Otitis media aguda; Prescripción de antibióticosSore throat; Acute otitis medium; Antibiotic prescriptionMal de gola; Otitis mitjana aguda; Prescripció d'antibiòticsBackground: Acute pharyngitis is one of the most frequent consultations to the general practitioner and in most of the cases an antibiotic is prescribed in primary care in Spain. Bacterial etiology, mainly by group A beta-hemolytic streptococcus (GABHS), accounts for 10-20% of all these infections in adults. The purpose of this study is to assess the impact of rapid antigen detection testing (RADT) to identify GABHS in acute pharyngitis on the utilization of antibiotics in primary care. Methods/design: Multicentric randomized controlled trial in which antibiotic prescription between two groups of patients with acute pharyngitis will be compared. The trial will include two arms, a control and an intervention group in which RADT will be performed. The primary outcome measure will be the proportion of inappropriate antibiotic prescription in each group. Two hundred seventy-six patients are required to detect a reduction in antibiotic prescription from 85% in the control group to 75% in the intervention group with a power of 90% and a level of significance of 5%. Secondary outcome measures will be specific antibiotic treatment, antibiotic resistance rates, secondary effects, days without working, medical visits during the first month and patient satisfaction. Discussion: The implementation of RADT would allow a more rational use of antibiotics and would prevent adverse effects of antibiotics, emergence of antibiotic resistance and the growth of inefficient health expenses.The study is funded by the Fondo de Investigaciones Sanitarias, theUniversity and Innovation Department of Spain (Reference number:PI061782), and from the Catalan Society of Family Medicin