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Biomedical subjects

I Feher

Publications and source records attributed to I Feher.

16 recordsLinked to original sources

Dose measurements in space by the Hungarian Pille TLD system.

Exposure of crew, equipment, and experiments to the ambient space radiation environment in low Earth orbit poses one of the most significant problems to long-term space habitation. Accurate dose measurement has become increasingly important during the assembly (extravehicular activity (EVA)) and operation of space stations such as on Space Station Mir. Passive integrating detector systems such as thermoluminescent dosemeters (TLDs) are commonly used for dosimetry mapping and personal dosimetry on space vehicles. The well-known advantages of passive detector systems are their independence of power supply, small dimensions, high sensitivity, good stability, wide measuring range, resistance to environmental effects, and relatively low cost. Nevertheless, they have the general disadvantage that for evaluation purposes they need a laboratory or large--in mass and power consumption--terrestrial equipment, and consequently they cannot provide time-resolved dose data during long-term space flights. KFKI Atomic Energy Research Institute (KFKI AEKI) has developed and manufactured a series of thermoluminescent dosemeter systems for measuring cosmic radiation doses in the 10 microGy to 10 Gy range, consisting of a set of bulb dosemeters and a compact, self-contained, TLD reader suitable for on-board evaluation of the dosemeters. By means of such a system, highly accurate measurements were carried out on board the Salyut-6, -7 and Mir Space Stations as well as on the Space Shuttle. A detailed description of the system is given and the comprehensive results of these measurements are summarised.

Astronauts↗

In vitro cell irradiation systems based on 210Po alpha source: construction and characterisation.

One way of studying the risk to human health of low-level radiation exposure is to make biological experiments on living cell cultures. Two 210Po alpha-particle emitting devices, with 0.5 and 100 MBq activity, were designed and constructed to perform such experiments irradiating monolayers of cells. Estimates of dose rate at the cell surface were obtained from measurements by a PIPS alpha-particle spectrometer and from calculations by the SRIM 2000, Monte Carlo charged particle transport code. Particle fluence area distributions were measured by solid state nuclear track detectors. The design and dosimetric characterisation of the devices are discussed.

Alpha Particles↗

Extra dose due to extravehicular activity during the NASA4 mission measured by an on-board TLD system.

A microprocessor-controlled on-board TLD system, 'Pille'96', was used during the NASA4 (1997) mission to monitor the cosmic radiation dose inside the Mir Space Station and to measure the extra dose to two astronauts in the course of their extravehicular activity (EVA). For the EVA dose measurements, CaSO4:Dy bulb dosemeters were located in specially designed pockets of the ORLAN spacesuits. During an EVA lasting 6 h, the dose ratio inside and outside Mir was measured. During the EVA, Mir crossed the South Atlantic Anomaly (SAA) three times. Taking into account the influence of these three crossings the mean EVA/internal dose rate ratio was 3.2. Internal dose mapping using CaSO4:Dy dosemeters gave mean dose rates ranging from 9.3 to 18.3 microGy h-1 at locations where the shielding effect was not the same. Evaluation results of the high temperature region of LiF dosemeters are given to estimate the mean LET.

Calcium Sulfate↗

Doses due to the South Atlantic Anomaly during the Euromir'95 mission measured by an on-board TLD system.

During the Euromir'95 mission, a specially designed microprocessor-controlled thermoluminescent detector (TLD) system, called the 'Pille'95', was used by ESA astronaut Thomas Reiter to measure the cosmic radiation dose inside the Mir space station. One of the experiment's objectives was to determine the dose fraction on Mir due to the South Atlantic Anomaly (SAA) on an orbit inclined at 51.6 degrees and at an altitude of about 400 km. Using an hourly measuring period for 170 h in automatic mode, dose components both of galactic (independent of SAA) and SAA origin were determined. It was found that the maximum dose due to crossing the SAA was equal to 55 microGy. Averaging all the measurements it was calculated that the mean dose rate inside the Mir was 12-14 microGy h-1 and that half of this value was caused by the SAA.

Astronauts↗

Microprocessor controlled portable TLD system.

An up-to-date microprocessor controlled thermoluminescence dosemeter (TLD) system for environmental and space dose measurements has been developed. The earlier version of the portable TLD system, Pille, was successfully used on Soviet orbital stations as well as on the US Space Shuttle, and for environmental monitoring. The new portable TLD system, Pille'95, consists of a reader and TL bulb dosemeters, and each dosemeter is provided with an EEPROM chip for automatic identification. The glow curve data are digitised and analysed by the program of the reader. The measured data and the identification number appear on the LED display of the reader. Up to several thousand measured data together with the glow curves can be stored on a removable flash memory card. The whole system is supplied either from built-in rechargeable batteries or from the mains of the space station.

Computers↗

Thermoluminescent dose measurements on-board Salyut type orbital stations.

A small, vibration- and shock-resistant thermoluminescent dosemeter /TLD/ system--named PILLE--was developed at the Health Physics Department of the Central Research Institute for Physics, Budapest, to measure the cosmic radiation dose on board orbital stations. The first on-board measurements with this system were performed /by B. Farkas, the Hungarian astronaut/, on the Salyut-6 space station in 1980. The same instrument was used by other crews in the following years. Doses measured at different sites in Salyut-6 are presented. The dose rates varied from 0.07 to 0.11 mGy.day-1. After the first cosmic measurements, the system was further developed. The minimum detectable dose of the new TLD system is 1 microGy, i.e. less by on order of magnitude than that of the former system. The self-irradiation dose rate of the TLD bulbs is also reduced--by more than one order of magnitude--to 10 nGy.h-1, by the use of potassium-free glass for the bulb envelope. This new type of PILLE TLD system is currently on-board Salyut-7. The dose rates /0.12-0.23 mGy.day-1/ measured in 1983 are presented in detail.

Evaluation Studies as Topic↗

Results of cosmic radiation dose field measurements aboard the "Salyut-6" orbital station.

During the 3rd main expedition on board the "Salyut-6" orbital station in 1979 the integral characteristics of cosmic radiation were measured in various positions inside the manned modules (experiment "Integral"). Measurements were performed with thermoluminescent dosimeters, photographic films and solid state plastic detectors supplied for the experiment by specialists of the USSR, Bulgaria, Hungary, GDR and Romania. The dose gradient inside the manned modules of the station amounted to 70% for long intervals of time. During the experimental period the dose rate inside the station was 15 to 30 mrad per day. The mean flux of particles with Z > or = 6 and LET > or = 200 keV/micrometer was found to be 0.22 cm-2 or day-1.

Cosmic Radiation↗

A new thermoluminescent dosimeter system for space research.

A small, portable, vibration and shock resistant thermoluminescent dosimeter system was developed to measure cosmic radiation dose on board a spacecraft. The system consists of a small battery-operated reader and a special bulb dosimeter. Doses from 10 microGy up to 100 mGy can be measured. The electrical power consumption of the reader is about 5 W, its volume is about 1 dm3 and its mass is about 1 kg. Details are given for the construction and technical parameters of the dosimeter and reader.

Calcium Sulfate↗

The effect of E type prostaglandins on the proliferation of haemopoietic stem cells in vivo.

The ability of protaglandins E1 and E2 to stimulate the proliferation of haemopoietic stem cells (CFUS) was studied in vivo. PGE2, in a dose range of 10(-4) to 10(-1) microgram/g body weight and PGE1 in a dose range of 10(-5) to 10(-1) microgram/g body weight, produced a rapid cycling wave of CFUS. The increase in the number of CFUS in S phase was not followed by a rise in the femoral CFUS content, and except for a transient increase in femoral CFUC level, no increase in differentiation was found either. Therefore, it is proposed that haemopoiesis after PG-induced CFU stimulation is ineffective. PGE2 did not stimulate regeneration of CFUS in a perturbed state (after sublethal irradiation). All these findings support the idea that PGEs might represent potent stimulators of the haemopoietic stem cells acting in physiological doses. However, if acting concurrently with physiological control systems PGs lead to ineffective haemopoiesis (under normal conditions) or do not exert any measurable effect (after sublethal irradiation).

Animals↗

Secretory function of adrenal cortex in chronic alcoholis.

Three groups of male subjects (healthy subjects, chronic alcoholics with liver cirrhosis and patients with acute viral hepatitis) were included in a 24 hour pattern of excretion of the total and some fractions of 17-ketosteroids (KS), basal concentration of 11-hydroxycorticosteroids (11-OHCS) and dehydroepiandrosterone (DHEA) in plasma, as well as changes of concentration of the same steroids in plasma 15, 30 and 60 minutes after a single i.m. injection of insulin. In regard to healthy subjects and patients with acute viral hepatitis, chronic alcoholics with liver cirrhosis excrete decreased quantities of total and some fractions of 17-KS. In regard to healthy subjects, decreased excretion of the sum androsterone and etiocholanole was established as well as increased DHEA secretion in patients with acute viral hepatitis. In chronic alcoholics with liver cirrhosis basal concentrations of 11-OHCS in plasma and their increase after insulin administration are the same as in healthy subjects, but values of DHEA concentrations in plasma are decreased. It has been pointed to the possibility of damages of the secretory function of adrenal cortex in chronic alcoholics with liver cirrhosis. On the basis of above mentioned results, there is an assumption that adrenal gland primarily provides normal secretion of C21 steroid and thus, satisfying needs for these steroids, increases secretion of DHEA. Follow up of DHEA urinary secretion may provide insight into basal activity of adrenal cortex, whereas the functional state of the liver must be taken into account when interpreting the results.

Acute Disease↗

[Surgical trauma in laparoscopic and classical cholecystectomy].

INTRODUCTION: Accidental or surgical trauma stimulates a response and its intensity is proportional to extent of trauma. The aim of this prospective study was to compare the intensity of the acute-phase reaction and metabolic changes in patients undergoing elective cholecystectomy for chronic cholecystitis. PATIENTS AND METHODS: Sixty patients with cholelithiasis were divided into two groups: thirty patients underwent laparoscopic cholecystectomy (LC group) and thirty patients open cholecystectomy (OC group). Glucose concentration, mean cortisol concentration, C-reactive protein, albumin levels and lactate-dehydrogenase activity were measured preoperatively and postoperatively for up to 48 hours. RESULTS AND DISCUSSION: The examined groups of patients were comparable in regard to age and sex. The duration of operation was similar in both groups. Postoperative hospital stay after laparoscopic operation was significantly shorter than after open cholecystectomy (p < 0.05). The mean glucose concentration (s.e.m.) during the initial 24 hours after surgery was significantly higher (p < 0.05) following open cholecystectomy. The mean cortisol concentration was significantly higher (p < 0.05) following open in regard to laparoscopic operation. Increase in plasma C-reactive protein was significantly higher (p < 0.05) after open cholecystectomy, with maximal levels 48 h after operation. There was a statistically significant decrease (p < 0.05) in albumin concentration after open cholecystectomy. Serum concentration of intracellular enzyme lactate-dehydrogenase increased significantly (p < 0.05) following open in regard to laparoscopic cholecystectomy. CONCLUSION: According to these results, aspects of metabolic and acute-phase responses and tissue damage are reduced following laparoscopic cholecystectomy. The mean postoperative hospital stay was significantly shorter after laparoscopic cholecystectomy with rapid patient recovery.

Acute-Phase Proteins↗