Natalia Golnik

A computer controlled ambient dose equivalent meter based on a recombination chamber

Abstract This paper is devoted to a description of a microcomputer controlled dose equivalent rate meter, based on a recombination principle and intended for routine use in radiation protection. The device displays, directly, the ambient dose equivalent rate H ∗ (10), the absorbed dose rate and the quality factor. The ionisation chamber of REM-2 type serves as a detector. An appropriate set of collecting voltages is sequentially applied to the chamber electrodes. Ions which have avoided initial recombination are collected at a capacitor connected to an electrometer. Then the collected charge is registered in the computer memory. The ambient dose equivalent is calculated in real time, taking into account the dependence of the initial recombination of ions on linear energy transfer (LET). The device can be used in radiation fields of any composition, usually with an accuracy not worse than 30%.

Comparison of multiscale entropy of healthy and cancer tissue imaged by optical polarimeter

Polarimetric observations of neoplastic changes in biological tissue may support its early diagnostics. A human breast tissue is observed in polarized light. Obtained images of healthy and cancer cases are decomposed by a trous wavelet algorithm. When multiscale representation of the tissue images is found their autocorrelation functions are compared. A comparison of new observables, multiscale entropy and mean entropy vectors is presented. It is found that these observables may indicate tissue changes as well as its condition.

Characterisation of radiation field for irradiation of biological samples at nuclear reactor—comparison of twin detector and recombination methods

Central Laboratory for Radiological Protection is involved in achieving scientific project on biological dosimetry. The project includes irradiation of blood samples in radiation fields of nuclear reactor. A simple facility for irradiation of biological samples has been prepared at horizontal channel of the nuclear reactor MARIA in NCBJ in Poland. The radiation field, composed mainly of gamma radiation and thermal neutrons, has been characterised in terms of tissue kerma using twin-detector technique and recombination chambers.

Recombination index of radiation quality of low-LET radiation

Recombination index of radiation quality (RIQ) wasmeas ured for X-raysranging from 40 to 230 kVp, for accelerator beams of photons with energy of 7 and 9 MeV and for several gamma and beta radiation sources. The obtained values ranged from 0.8 for high-energy photons to 1.3–1.9 for X-rays. The peak value was observed for 241 Am source and for 100 kVp X-rays with mean energy of about 55 keV. Values of RIQ reflect mean local ionisation density of investigated radiation and can be correlated with its relative biological effectiveness.

Determination of the photon-contribution of a 238Pu-Be source

Abstract Gamma radiation of a 238 Pu–Be source at CERN was measured with two neutron insensitive ionisation chambers, i.e. a graphite chamber filled with CO 2 and a steel chamber filled with argon, in order to determine the photon-contribution to ambient dose equivalent. These straightforward measurements were confronted with a novel method using a recombination chamber, with which a coarse spectrum in LET of the mixed radiation field can be obtained. The lowest LET part of the spectrum corresponds to the photon-contribution to the absorbed dose of mixed radiation. The comparison of the different methods showed very good agreement within the measurement uncertainties.

MEASUREMENTS OF THE IONISING RADIATION LEVEL AT A NUCLEAR MEDICINE FACILITY PERFORMING PET/CT EXAMINATIONS.

This paper presents the results of radiation level measurements at workplaces in a nuclear medicine facility performing PET/CT examinations. This study meticulously determines the staff radiation exposure in a PET/CT facility by tracking the path of patient movement. The measurements of the instantaneous radiation exposure were performed using an electronic radiometer with a proportional counter that was equipped with the option of recording the results on line. The measurements allowed for visualisation of the staffs instantaneous exposure caused by a patient walking through the department after the administration of 18F-FDG. An estimation of low doses associated with each working step and the exposure during a routine day in the department was possible. The measurements were completed by determining the average radiation level using highly sensitive thermoluminescent detectors.

Measurements of H*(10) in reference neutron fields using Bonner sphere spectrometry and LET spectrometry

Abstract A Bonner sphere spectrometer and the REM-2 recombination chamber were used for inter-comparison measurements of the neutron component of ambient dose equivalent, Hn*(10) in reference neutron fields. The 241Am–Be and 252Cf neutron sources were exposed either free-in-air or placed in iron or paraffin filters. The REM-2 recombination chamber was used as a LET spectrometer. The agreement of Hn*(10) values measured with both the methods was within experimental uncertainties of few percent. The determined neutron spectra were used for calculations of the REM-2 chamber response to H*(10).

Ambient dose equivalent measurements in secondary radiation fields at proton therapy facility CCB IFJ PAN in Krakow using recombination chambers

Abstract This work presents recombination methods used for secondary radiation measurements at the Facility for Proton Radiotherapy of Eye Cancer at the Institute for Nuclear Physics, IFJ, in Krakow (Poland). The measurements of H*(10) were performed, with REM-2 tissue equivalent chamber in two halls of cyclotrons AIC-144 and Proteus C-235 and in the corridors close to treatment rooms. The measurements were completed by determination of gamma radiation component, using a hydrogen-free recombination chamber. The results were compared with the measurements using rem meter types FHT 762 (WENDI-II) and NM2 FHT 192 gamma probe and with stationary dosimetric system.

A ring-shaped recombination chamber for hadron therapy dosimetry

An innovative recombination chamber has been designed for estimation of stray radiation doses and quality factors in hadron therapy. The chamber allows for determination of absorbed dose and recombination index of radiation quality in phantoms at small distances from simulated organs. The chamber body and electrodes are ring shaped, so the beam may be directed through the empty centre of the ring. The ionisation of the filling gas is caused by secondary or scattered radiation and can be related to the dose absorbed in the tissues close to the irradiated target volume.

Measurements of high level of iodine activity in thyroid with different radiation meters

Iodine activity in thyroid of female patient was measured with different radiation meters in order to estimate a possibility to use them in case of radiation accident. Two series of measurements were performed - first after diagnostic and second after therapeutic administration of iodine to the patient. The isotope activities were higher than those registered during routine radiation monitoring and similar to the activities which could be registered after radiation accident. The studies showed that simple dose rate meters may serve for identification and selection of contaminated persons which should be later subjected to the measurements with especially dedicated equipment. The initial measurements can be performed outside laboratory.