M. Budzanowski

Development of a Method for Passive Measurement of Radiation Doses at Ultra-High Dose Range

The thermoluminescent (TL) detectors are an old-established method of passive dose measurement. In the last several years MCP-N (LiF:Mg,Cu,P) detectors have been widely used in modern TL dosimetry due to their very high sensitivity (at microgray level) and a simple signal-dose relation. Their dose response does not show any supralinearity up to saturation at about 1 kGy. Only recently we have discovered their quite unexpected properties at high and ultra-high doses, which enable us to use them for measurements of doses from micrograys up to a megagray. The presented method is based on these properties. This method is also suitable for measurements of doses in mixed radiation fields.

Development of a method of passive measurement of radiation doses at ultra-high dose range

Thermoluminescent (TL) detectors are an established method for passive dose measurement. Over the last several years MCP-N (LiF:Mg,Cu,P) detectors have been widely used in modern TL dosimetry due to their very high sensitivity (at the microgray level) and their simple signal-dose relation. Their dose response does not show any supralinearity up to saturation at about 1 kGy. Only recently we have discovered their quite unexpected properties at high and ultra-high doses, which enable us to use them for measurements of doses from micrograys up to a megagray. Significant changes of the glow-curve shape occur for doses higher than a few kGy and what is most important, a new peak appears in their glow-curve at exposures above 50 kGy, the position of which shifts towards higher temperatures with increasing dose. The presented method is based on these properties. This method is also a promising way of measurements of doses in mixed radiation fields.

Dosimetry properties of Tm-doped single CaF2 crystals

Abstract The dosimetry properties of thermoluminescence CaF 2 : Tm detectors with thulium concentrations of 0.1%, 0.3%, 0.5%, 0.6% and 0.7%, developed from single crystals grown by the Stockbarger method at the Institute of Geochemistry, Irkutsk, Russia, were investigated. The relative TL efficiency, η, after 5.3 MeV Am-241 α-particle irradiation and the Cs-137 γ-ray dose response after doses up to 10 Gy , of interest for radiation therapy, were evaluated. Linearity and reproducibility of the dose response, the shape of the glow-curve (ratio of area under peaks 3 and 5 for α- and γ-radiation) were studied and referred to the properties of standard Harshaw TLD-300 detectors. The relative TL α-particle efficiency, η, for the high temperature peak 5 was found to grow with increasing Tm concentration, from 0.13 for 0.1% Tm, 0.17 for 0.3% Tm to 0.92 for 0.5% Tm where the corresponding values of η for peak 3 were 0.073, 0.059 and 0.211. Detectors with 0.6 wt % Tm appear to reproduce the properties of TLD-300 quite well, showing a similar shape of the glow curve and a similar ratio of peak areas under peaks 5 and 3. The highest ranges of linear dose-response for 137Cs γ-rays for peaks 3 and 5, were obtained for detectors with 0.5% Tm. These detectors, due to their high efficiency after high-LET irradiation and extended linearity range are most suitable for dosimetry of high-LET radiotherapy beams.

Supralinearity of peak 4 and 5 in thermoluminescent lithium fluoride MTS-N (LiF:Mg,Ti) detectors at different Mg and Ti concentration

The dose–response ofsintered MTS-N (LiF : Mg ; Ti) thermoluminescent detectors in which the concentration ofMg was varied between 30 and 920 ppm and the Ti concentration varied between 13 and 260 ppm, has been studied after Cs-137 gamma-ray and fast proton irradiation (average energy 147 MeV) in the dose range between 0.5 and 37:5 Gy. Peak 4 and peak 5 were extracted from the TL glow curve by deconvolution, assuming >rst-order kinetics. We have observed a decrease in the supralinear response ofLiF : Mg ; Ti at increasing Mg concentration. The e-ect ofvarying the concentration ofTi on the dose response was less pronounced. No signi>cant di-erence in the linearity index measured after Cs-137 gamma-ray and fast proton beam irradiation was observed at all the studied Mg and Ti concentration values. The data are discussed with reference to some models ofTL supralinearity. The extended range oflinearity ofthe high Mg-doped LiF : Mg ; Ti materials may make them better suited for clinical dosimetry. c

Dose levels of the occupational radiation exposures in Poland based on results from the accredited dosimetry service at the IFJ PAN, Krakow

Individual dosimetry service based on thermoluminescence (TLD) detectors has started its activity at the Institute of Nuclear Physics (IFJ) in Krakow in 1965. In 2002, the new Laboratory of Individual and Environment Dosimetry (Polish acronym LADIS) was established and underwent the accreditation according to the EN-PN-ISO/IEC 17025 standard. Nowadays, the service is based on the worldwide known standard thermoluminescent detectors MTS-N (LiF:Mg,Ti) and MCP-N (LiF:Mg,Cu,P), developed at IFJ, processed in automatic thermoluminescent DOSACUS or RE2000 (Rados Oy, Finland) readers. Laboratory provides individual monitoring in terms of personal dose equivalent H(p)(10) and H(p)(0.07) in photon and neutron fields, over the range from 0.1 mSv to 1 Sv, and environmental dosimetry in terms of air kerma K(a) over the range from 30 μGy to 1 Gy and also ambient dose equivalent H*(10) over the range from 30 μSv to 1 Sv. Dosimetric service is currently performed for ca. 3200 institutions from Poland and abroad, monitored on quarterly and monthly basis. The goal of this paper is to identify the main activities leading to the highest radiation exposures in Poland. The paper presents the results of statistical evaluation of ∼ 100,000 quarterly H(p)(10) and K(a) measurements performed between 2002 and 2009. Sixty-five per cent up to 90 % of all individual doses in Poland are on the level of natural radiation background. The dose levels between 0.1 and 5 mSv per quarter are the most frequent in nuclear medicine, veterinary and industrial radiography sectors.

Energy response of different types of RADOS personal dosemeters with MTS-N (LiF:Mg,Ti) and MCP-N (LiF:Mg,Cu,P) TL detectors

The photon energy response of different RADOS (Mirion Technologies) personal dosemeters with MTS-N (LiF:Mg,Ti) and MCP-N (LiF:Mg,Cu,P) thermoluminescence (TL) detectors was investigated. Three types of badges were applied. The irradiation with reference photon radiation qualities N (the narrow spectrum series), and S-Cs and S-Co nuclide radiation qualities, specified in ISO 4037 [International Organization for Standardization (ISO). X and gamma reference radiations for calibrating dosemeters and doserate meters and for determining their response as a function of photon energy. ISO 4037. Part 1-4 (1999)], in the energy range of 16-1250 keV, were performed at the Dosimetry Laboratory Seibersdorf. The results demonstrated that a readout of a single MTS-N or MCP-N detector under the Al filter can be used to determine Hp(10) according to requirements of IEC 61066 [International Electrotechnical Commission (IEC). Thermoluminescence dosimetry systems for personal and environmental monitoring. International Standard IEC 61066 (2006)] for TL systems for personal dosimetry. The new RADOS badge with the experimental type of a holder (i.e. Cu/Al filters) is a very good tool for identifying the radiation quality (photon energy).

Occupational exposure in orthopedic procedures under fluoroscopic control

BACKGROUND In interventional radiology the highest radiation doses are usually recorded for both the medical staff and the patients. Interventional procedures with X-rays are implemented in a number of medical specializations. This paper concerns the exposure of interventional teams performing orthopedic procedures under X-rays control. MATERIAL AND METHODS Doses for interventional teams were measured in the 3 Łódź hospitals. Thermoluminescent dosemeters were applied to measure the following dose equivalents: Hp(3) for eye lens, Hp(0.07) for palm skin, Hp(10) at the level of the neck without a protective shield (i.e., collar) and Hp(10) for the whole body on the front surface of the trunk (measured under the protective apron at the level of the chest). RESULTS Doses for the operator who performs surgery, assisting physicians and scrub nurse were measured during 95 procedures. The highest doses were received by the operator the dose for eyes per 1 procedure did not exceed 0.1 mSv, the highest dose for hands was 1.6 mSv and the highest recorded effective dose was 0.02 mSv. CONCLUSIONS On the basis of the results of measurements and their comparison with the values reported in the literature it may be concluded that the obtained results fall within the published reference range (for non-vascular procedures). This proves the compatibility of practice in the monitored Łódź hospitals with routine methodology applied in other interventional departments. The measurement results confirm that the usage of thermoluminescent dosimetry is fully adequate for the evaluation of exposure in interventional radiology and that the usage of at least 2 dosemeters for that staff is necessary. Med Pr 2017;68(2):221-227.

Czynniki wpływające na poziom narażenia personelu medycznego podczas zabiegów ortopedycznych pod kontrolą fluoroskopii

BACKGROUND Extended control of staff exposure in interventional radiology has been legally required over the last few years. This is determined by a number of factors, including the type of procedure, technical conditions and methodology. In orthopedic procedures fluoroscopy is used to control surgical reconstructions. An influence of particular factors on the registered values of doses received by the members of medical team performing osteosynthesis for limb fractures is presented in this paper. MATERIAL AND METHODS Doses received by individual interventional team members performing specific functions, operator, assisting physicians and scrub nurse, during a series of the procedures were measured. Each person was equipped with 4 dosimetric tools, containing thermoluminescent dosimeters, to measure the equivalent doses for the eyes, hand skin and the neck (outside the shield) and to evaluate effective doses. The investigations were performed in operational theatres of 3 hospitals in Łódź. RESULTS The equivalent doses per one procedure for the eyes and hand skin of the operator were 0.029-0.073 mSv and 0.366-1.604 mSv, respectively. Significantly higher doses were noted during the procedures of intramedullary osteosynthesis, especially for the operator. An average age and body mass index (BMI) of patients treated in the monitored hospitals did not differ statistically. CONCLUSIONS Based on the dosimetric measurements the following conclusions can be drawn: in orthopedic procedures of interventional radiology (IR) the exposure of the staff is mostly determined by the type of procedure and more precisely by its complexity and by the optimized use of X-ray unit, including pulsed fluoroscopy. It is also revealed that the operator is the most exposed person in the interventional team. Med Pr 2017;68(1):75-83.

APPLICATION OF PTTL METHOD FOR DOSE REASSESSMENT IN EXTREMITY DOSIMETRY

Wide and common applications of ionising radiation require continuous improvement of radiation safety and dosimetry methods. The thermoluminescent (TL) method is well known and very popular. Apart from its advantages, it also carries certain disadvantages. The erasure of the TL signal on detector readout and the resulting impossibility of post-readout dose reassessment is one of them. At the Institute of Nuclear Physics, Polish Academy of Sciences (IFJ PAN), a method for dose reassessment based on phototransferred thermoluminescence (PTTL) has been developed. This method has been applied for dose reassessment to MTS-N (LiF:Mg, Ti) detectors used in individual whole-body dosemeters and adjusted to an automatic reader used in routine measurements. The next step was to extend and adapt this method for extremity dosemeters. With the use of the PTTL method, it is possible to reassess relatively high doses measured on individual whole-body and extremity dosemeters collected from our customers after routine use. The influence of PTTL background has greater impact in extremity dosemeters where it is only one and thinner MTS-N detector compared with four MTS-N detectors in whole-body dosemeters. The minimum dose was determined as 5 mSv for extremity dosimetry. Below 5 mSv, the impact of PTTL background is comparable to the signal, and the estimated uncertainty of reassessed dose is at the level of reassessed dose.

HOW DO HOSPITAL STERILISATION PROCEDURES AFFECT THE RESPONSE OF PERSONAL EXTREMITY RINGS AND OF EYE LENS TL DOSEMETERS

Stringent standards of hygiene must be applied in medical institutions, especially at operating blocks or during interventional radiology procedures. Medical equipment, including personal dosemeters that have to be worn by medical staff during such procedures, needs therefore to be sterilised. In this study, the effect of various sterilisation procedures has been tested on the dose response of extremity rings and of eye lens dosemeters in which thermoluminescent (TL) detectors (of types MTS-N and MCP-N, respectively) are used. The effects of medical sterilisation procedures were studied: by chemicals, by steam or by ultraviolet (UV), on the dose assessment by extremity rings and by eye lens dosemeters. Since it often happens that a dosemeter is accidentally machine-washed together with protective clothing, the effect of laundering on dose assessment by these dosemeters was also tested. The sterilisation by chemicals is mostly safe for TL detectors assuming that the dosemeters are waterproofed. Following sterilisation by water vapour, the response of these dosemeters diminished by some 30 %, irrespectively of the period of sterilisation; therefore, this method is not recommended. UV sterilisation can be applied to EYE-D™ eye lens dosemeters if their encapsulation is in black. The accidental dosemeter laundry in a washing machine has no impact on measured dose.