An observer study for direct comparison of clinical efficacy of electronic to film portal images

PURPOSE: To directly compare clinical efficacy of electronic to film portal images. METHODS AND MATERIALS: An observer study was designed to compare clinical efficacy of electronic to film portal images acquired using a liquid matrix ion-chamber electronic portal imaging device and a conventional metal screen/film system. Both images were acquired simultaneously for each treatment port and the electronic portal images were printed on gray-level thermal paper. Four radiation oncologists served as observers and evaluated a total of 44 sets of images for four different treatment sites: lung, pelvis, brain, and head/neck. Each set of images included a simulation image, a double-exposure portal film, and video paper prints of electronic portal images. Eight to nine anatomical landmarks were selected from each treatment site. Each observer was asked to rate each landmark in terms of its clinical visibility and to rate the ease of making the pertinent verification decision in the corresponding electronic and film portal images with the aid of the simulation image. RESULTS: Ratings for the visibility of landmarks and for the verification decision of treatment ports were similar for electronic and film images for most landmarks. However, vertebral bodies and several landmarks in the pelvis such as the acetabulum and public symphysis were more visible in the portal film images than in the electronic portal images. CONCLUSION: The visibility of landmarks in electronic portal images is comparable to that in film portal images. Verification of treatment ports based only on electronic portal images acquired using an electronic portal imaging device is generally achievable.     

Studies on the kinetic mechanism of nitrate reductase from spinach (Spinacea oleracea)

Based on Lineweaver-Burk plots of the initial velocities, at different concentrations of NADH and nitrate, and product inhibition patterns, an Iso Ping Pong Bi Bi steady state kinetic mechanism is proposed for the spinach nitrate reductase. This mechanism incorporates the concept that the oxidized enzyme is present in two isomeric forms.     

Relationship between analgesia and extracellular morphine in brain and spinal cord in awake rats

Extracellular concentrations of morphine from the dorsal spinal cord, the periaqueductal gray (PAG) including the dorsal raphé, and the lateral hypothalamus were measured by microdialysis in awake rats after intraperitoneal (i.p.) administration of 2.5, 5.0 and 10 mg/kg morphine. Morphine concentrations in all areas showed similar time courses: morphine was detected in the first dialysate sample (13-15 min) and maximal concentrations were reached at 45 min after injection. When in vivo recoveries of morphine from the spinal cord and brain areas were taken into account, no significant differences between morphine concentrations in the various areas were found. The relationship between extracellular morphine concentrations and morphine-induced analgesic behavior was investigated by simultaneously measuring morphine in the dialysate and its analgesic effect in the paw-withdrawal and tail-flick tests. In all areas sampled, the extracellular concentrations of morphine at different times after i.p. injection, significantly correlated with the magnitude of behavioral analgesia assessed by either test. The highest correlation was obtained between extracellular concentrations of morphine in the spinal cord and PAG and behavioral analgesia assessed in the paw-withdrawal test. Our data indicate that, after systemic injection, morphine is evenly distributed throughout the spinal cord and brain including potential anatomical sites of morphine's analgesic action. We estimate that the minimal extracellular morphine concentration in spinal cord that is required to produced a significant increase in nociceptive threshold is approximately 100 pg/25 microl, which corresponds to a tissue concentration of about 100 mg/g of morphine.