Design and implementation of a low-cost, tabletop MRI scanner for education and research prototyping.

While access to a laboratory MRI system is ideal for teaching MR physics as well as many aspects of signal processing, providing multiple MRI scanners can be prohibitively expensive for educational settings. To address this need, we developed a small, low-cost, open-interface tabletop MRI scanner for academic use. We constructed and tested 20 of these scanners for parallel use by teams of 2-3 students in a teaching laboratory.

Response surface model predictions of wake-up time during scoliosis surgery.

Background: With the use of previously published data, new sevoflurane-remifentanil interaction models of various degrees of sedation were created and adapted to desflurane-fentanyl by using minimal alveolar concentration and opioid equivalencies. These models were used to predict return of responsiveness in patients undergoing scoliosis surgery during a wake-up test. Our hypothesis was that one of the interaction models would accurately predict return of responsiveness during a wake-up test.

A simulation study of common propofol and propofol-opioid dosing regimens for upper endoscopy: implications on the time course of recovery.

Background: Using models of respiratory compromise, loss of response to esophageal instrumentation, and loss of responsiveness, the authors explored through simulation published dosing schemes for endoscopy using propofol alone and in combination with selected opioids. They hypothesized that models would predict adequate conditions for esophageal instrumentation and once drug administration is terminated, rapid return of responsiveness and minimal respiratory compromise.

Methods: Four published dosing regimens of propofol alone or in combination with opioids were used to predict the probability of loss of response to esophageal instrumentation for a 10-min procedure and the probability of respiratory compromise and return of responsiveness once the procedure had ended.

An exploration of remifentanil-propofol combinations that lead to a loss of response to esophageal instrumentation, a loss of responsiveness, and/or onset of intolerable ventilatory depression.

Background: Remifentanil and propofol are increasingly used for short-duration procedures in spontaneously breathing patients. In this setting, it is preferable to block the response to moderate stimuli while avoiding loss of responsiveness (LOR) and intolerable ventilatory depression (IVD). In this study, we explored selected effects of combinations of remifentanil-propofol effect-site concentrations (Ces) that lead to a loss of response to esophageal instrumentation (EI), LOR, and/or onset of IVD.

An evaluation of remifentanil-sevoflurane response surface models in patients emerging from anesthesia: model improvement using effect-site sevoflurane concentrations.

Introduction: We previously reported models that characterized the synergistic interaction between remifentanil and sevoflurane in blunting responses to verbal and painful stimuli. This preliminary study evaluated the ability of these models to predict a return of responsiveness during emergence from anesthesia and a response to tibial pressure when patients required analgesics in the recovery room. We hypothesized that model predictions would be consistent with observed responses.