RESUMEN
Optical transition radiation (OTR) plays an important role in beam diagnostics for high energy particle accelerators. Its linear intensity with beam current is a great advantage as compared to fluorescent screens, which are subject to saturation. Moreover, the measurement of the angular distribution of the emitted radiation enables the determination of many beam parameters in a single observation point. However, few works deals with the application of OTR to monitor low energy beams. In this work we describe the design of an OTR based beam monitor used to measure the transverse beam charge distribution of the 1.9-MeV electron beam of the linac injector of the IFUSP microtron using a standard vision machine camera. The average beam current in pulsed operation mode is of the order of tens of nano-Amps. Low energy and low beam current make OTR observation difficult. To improve sensitivity, the beam incidence angle on the target was chosen to maximize the photon flux in the camera field-of-view. Measurements that assess OTR observation (linearity with beam current, polarization, and spectrum shape) are presented, as well as a typical 1.9-MeV electron beam charge distribution obtained from OTR. Some aspects of emittance measurement using this device are also discussed.
RESUMEN
Short gastric vessels (SGV) division is a controversial topic in antireflux surgery. Some surgeons do not divide the SGV routinely to perform a fundoplication; however, excessive tension of the gastric fundus (GF) forces this procedure necessary in some cases. This study aims to evaluate in a cadaveric model of Nissen fundoplication: (i) the correlation of GF tension with anatomic parameters; and (ii) the effect of SGV division on GF tension. In total, 23 fresh cadavers (18 men, mean age 62 years) were studied. The abdominal esophagus was dissected, and the GF transposed to a limit of 3 cm to the right border of the esophagus. A dynamometer was attached to the GF and the tension recorded. Cadavers were grouped according to the presence or absence of tension. SGV were divided and GF tension measured again. The presence or absence of initial GF tension was correlated to: (i) number of SGV; (ii) length of the GF; (iii) distance between His angle and the first SGV; and (iv) size of the spleen. The mean GF pressure was 0.5 N +/- 1.0 (0-2.5) before SGV division and 0.1 N +/- 0.3 (0-1.5) after SGV division (P= 0.002). Initial tension was absent in 12 (52.2%) cases. GF tension did not correlate with any of the anatomic parameters. Our results show that: (i) GF tension does not correlate with anatomic parameters; and (ii) SGV division affects GF tension significantly.
