Biomedical subjects
J C Landry
Publications and source records attributed to J C Landry.
A patient rotator for stereotactic radiosurgery.
A new technique for stereotactic radiosurgery by use of a patient rotator is described. Using the rotator with a small collimated beam of 6 MV x-rays, a small well-defined region of the brain can be irradiated to a high dose with rapid fall off of the dose outside the target volume. Since the linear accelerator gantry does not move during therapy the possibility of a collision between the gantry and the patient or stereotactic equipment is eliminated. The system is also independent of the rotational stability of the linear accelerator gantry axis and turntable axis. Dose distributions measured in a Lucite head phantom with film exhibited properties well suited for radiotherapy. Tests carried out to evaluate the ability to irradiate a selected target point within the brain with the rotator system showed a maximum positional error of 1.0 and 2.0 mm for angiography and CT localisation respectively.
Accidental bromine exposure in an urban population: an acute epidemiological assessment.
In November 1984, because of an accident at a chemical plant, the population of a large area in the town of Geneva, Switzerland, was exposed to toxic bromine gas during several hours at concentrations above the short-term exposure limit. We describe the development of the disaster, the reactions of the fire brigade, the police and the first aid services as well as the breakdown of communications that occurred. On-the-spot epidemiological assessment of the exposed area and of the characteristics of the exposure syndrome was combined with the emergency care of 91 self-referred patients that were seen at the University Hospital. Follow-up was obtained one month later. The clinical course was moderate (eyes and upper airways irritation) and self-limiting in all cases. Immediate definition of the exposed population permitted effective follow-up. Such early evaluation could prove to be of crucial importance for managing more serious accidents of a similar nature.
[Bromine cloud in Geneva. Epidemiologic study of the short-term effects on a population sample].
In November 1984, due to an accident at a chemical plant, toxic bromine gas spread into the town of Geneva, Switzerland, at concentrations over five times the maximal admissible concentration (MAC). Monitoring of atmospheric brome concentrations allowed the determination both of the duration of exposure and the geographical area concerned. Description of the immediate measures taken at the time of the accident illustrates how mass panic reactions can be generated or controlled, and clearly shows the vital importance of an effective communication network: it was lacking in this case and caused further insecurity for the population and isolation of the hospital. Immediate and systematic data collection enabled us to carry out an "acute" epidemiological survey of the accident. It is the first report of mass bromine intoxication in the medical literature. 91 patients with symptoms of bromine exposure were seen in the outpatient and casualty departments of the cantonal Hospital, but the clinical course was mild and self-limited in nearly all cases. One patient was admitted for 24 hours. The most common symptoms were upper respiratory tract symptoms, cough and headache. In 20-30% of cases these pesisted for more than three days, and sometimes up to one month. Recording the location of patients at the time when their first symptoms occurred made it possible to define the exposed area with precision. When the initial data collected in this "acute" fashion is reliable, it should be possible to undertake more elaborate epidemiological studies at a later stage if necessary.
[Manganese in the water supply of the town of Beaucaire: origins and solutions].
Changes in domestic water supply appearance and quality linked with increasing manganese amount and iron at a lesser degree, having been found by the inhabitants of Beaucaire (Rhône Valley), a study was made by chemists, hydrogeologists and biologists to detect the origin. The problem is not specific to this town and can frequently be found in the Saône and Rhône valleys. The results show that we have to deal with an aquifer with semi-captive groundwater whose supply is double: the Rhône and calcareous mountain masses. The low-oxygen waters are enriched, by dissolution from gravel, with manganese and iron which are preferentially fixed on porous and cracked surface elements. The conditions for manganese liberation are connected with the presence of organic matters, bacteria (capable to reduce the manganic compounds) and anaerobiosis. The supply does not seem to be the only cause in the low-oxygen contents; the action of heterotrophic microorganism using organic matter and consuming oxygen, at the groundwater periphery, must be taken into account. Thus the central part of the groundwater system is a reducing environment which allows the modification of the bacterial metabolism towards a ferric and manganic compounds reduction process. The result is the transformation of insoluble manganic and ferric compounds into manganous and ferrous compounds which are liberated into the groundwater.