Response of current dosemeters to new operational quantities in rotational geometry.

Recently, the ICRU released Report 95, where new operational quantities for external radiation exposure are defined. The new quantities are defined in close relation to the protection quantities. This change affects the practice use of dosemeters. That is why the instruments must be adapted to the measurement of new quantities before their implementing as legally binding. The discrepancies depend on radiation spectra-particle type, energy of particles and direction of incidence. To analyse the performance of currently used instruments, irradiations in photon and neutron fields of various energies were performed for personal and area dosemeters. In this work, the response of photon and neutron personal dosemeters in conditions of rotational geometry is presented. The difference between the responses with respect to the new or old operational quantity was not large, which corresponded to the similar reference values for this irradiation geometry. The mutual ratio depended on the specific radiation quality and geometry. The behaviour of different types of dosemeters varied too.

RESPONSE OF CURRENT AREA DOSEMETERS TO NEW OPERATIONAL QUANTITIES.

New operational quantities for external radiation exposure presented by the ICRU brought changes, which can affect the use of current dosemeters. Dosemeters calibrated in the old quantities should be tested, and the results obtained should be analyzed with respect to the new quantities. The difference between the old and new quantities depends primarily on photon energy. This work concerns instruments for area monitoring, which were exposed to reference photon and neutron spectra of mean energies from 65 to 1250 keV and from 0.02 to 10 MeV, respectively. As expected, it was revealed that the current photon dosemeters overestimate the new quantity ambient dose. For the measurements within the energy interval chosen, it seems to be acceptable to implement a correction factor to optimize the response. For the purposes of measurements of photons of lower energies, further research would be needed. To adapt the response of the neutron dosemeter tested, recalibration or redesign can be considered, but no fundamental changes seem to be necessary for the investigated spectra.

Comparison of luminescence detectors of Al2O3:C, CaF2:Mn, LiF:Mg,Cu,P and quartz with respect to retrospective dose reconstructions using bricks.

In the aftermath of an orphan radiation source find, a complex retrospective dose reconstruction can be required to estimate doses of persons who were staying in the vicinity. In retrospective dose reconstructions based on luminescence measurements of quartz extracted from bricks, high sensitivity thermoluminescence detectors (TLD) can be used as an ancillary tool for dose distribution measurements or natural radiation background measurement. We investigated the potential and limits of Al2O3:C, CaF2:Mn and LiF:Mg,Cu,P detectors for such applications. We measured depth-dose profiles in bricks using quartz and the TLDs. We factored in important dosimetry characteristics such as dose response, energy response and detection threshold. The work included Monte Carlo simulations. Depth-dose profiles and radiation spectra inside of the bricks were calculated for purposes of comparison and interpretation. The measurements and calculations were performed for two different photon spectra with mean energies of 662 and 118 keV. As regards comparison of the measured and Monte Carlo calculated depth-dose profiles, the best agreement was found for LiF:Mg,Cu,P. Quartz, Al2O3:C and CaF2:Mn tend to overestimate dose for lower photon energies and greater depths in bricks. The overestimation was the most marked for CaF2:Mn. For measurements related to quartz, especially for natural radiation background dose measurement, the most suitable TLDs are Al2O3:C and LiF:Mg,Cu,P. CaF2:Mn is the least useful material.

RETROSPECTIVE DOSE RECONSTRUCTION WITH MOBILE PHONES AND CHIP CARDS.

Mobile phones and common chip cards are very widespread items that almost everyone owns. They contain some radiation-sensitive materials that can be used for dosimetry based on stimulated luminescence. We investigated and compared reproducibility, dose response and fading of luminescence signal for the particular materials. Subsequently, we performed an experiment of a dose reconstruction using mobile phones and chip cards, which were fixed to a slab phantom and irradiated by a 137Cs radiation source in our laboratory. Doses obtained were compared with reference values. The materials investigated can be used for dosimetry in cases of serious radiation accidents or malevolent acts with radioactive materials, when it is extremely important to identify as quickly as possible individuals who received high-radiation doses.

Retrospective dosimetry with alumina substrate from electronic components.

Alumina substrate can be found in electronic components used in portable electronic devices. The material is radiation sensitive and can be applied in dosimetry using thermally or optically stimulated luminescence. Electronic portable devices such as mobile phones, USB flash discs, mp3 players, etc., which are worn close to the body, can represent  personal dosemeters for members of the general public in situations of large-scale radiation accidents or malevolent acts with radioactive materials. This study investigated dosimetric properties of alumina substrates and aspects of using mobile phones as personal dosemeters. The alumina substrates exhibited favourable dosimetry characteristics. However, anomalous fading had to be properly corrected in order to achieve sufficient precision in dose estimate. Trial dose reconstruction performed by means of two mobile phones proved that mobile phones can be used for reconstruction of personal doses.

NaCl as a retrospective and accident dosemeter.

NaCl is a cheap and widely available material. This study investigated the potential of NaCl in the form of a household salt as a retrospective and accident dosemeter using optically stimulated luminescence (OSL). Samples of the investigated household salt were stimulated using blue light of linearly modulated power. Attention was concentrated on sensitivity, dose dependence of the OSL signal, fading, optimisation of the read-out procedure and application of analytical protocols that do not require a specific calibration. A potential of NaCl as a complementary dosemeter within emergency preparedness was considered. The behaviour of the OSL signal observed was found to be favourable for dosimetry.

Lethal events in V79 cells irradiated by low-energy protons and correlations with distribution patterns of energy deposition, radical concentration and DNA damage.

Published survival data of V79 cells irradiated by 0.5-5.0 MeV (7-40 keV/microm) protons have been analyzed with a detailed radiobiological model to estimate the per-track yields of lethal lesions. Their correlations with distribution patterns of deposited energy, radical concentrations and with the yields of specific classes of DNA damage have been studied. The observed correlations indicate a potential interpretation of DNA damage lethal for the cell and the initial physical and chemical processes leading to such damage.

Concurrent versus sequential chemoradiotherapy with cisplatin and vinorelbine in locally advanced non-small cell lung cancer: a randomized study.

PURPOSE: The superiority of chemoradiotherapy (CRT) over radiation alone in locally advanced non-small cell lung cancer (NSCLC) has been proven, but the relative merits of a concurrent schedule versus their sequential administration are less clear. This study compared the safety and efficacy of concurrent and sequential CRT, with chemotherapy (CT) consisting of a cisplatin and vinorelbine regimen, in patients with locally advanced NSCLC. PATIENTS AND METHODS: One hundred and two previously untreated patients (aged 42-75 years) with locally advanced, stage IIIA (n = 15) or stage IIIB (n = 87) NSCLC were entered into the study. The CT schedule consisted of up to four cycles of cisplatin 80 mg/m(2) on day 1, and vinorelbine 25 mg/m(2) at the first and fourth cycles (12.5 mg/m(2) during the 2nd/3rd cycles) on days 1, 8, 15 of a 28-day cycle. Radiotherapy (RT) was prescribed at a dose of 60 Gy/30 fractions, given as five fractions per week for 6 weeks. In the concurrent arm (arm A), RT was started on day 4 of cycle 2; whilst in the sequential arm (arm B), RT started within 2 weeks after completion of CT. Fifty-two patients were randomized to concurrent treatment and 50 to the sequential schedule. RESULTS: Overall survival was significantly longer in arm A (median survival 16.6 months) versus arm B (median survival 12.9 months) (P = 0.023 by means of log-rank test; hazard ratio HR = 0.61, 95% CI of HR (0.39-0.93)), and time to progression (TTP) was also significantly longer in arm A (median time to progression 11.9 months) versus arm B (median time to progression 8.5 months) (P = 0.024 by means of log-rank test; HR = 0.62, 95% CI of HR (0.38-0.93)). Ninety-eight patients were evaluable for response and 101 for toxicity. The overall response rate was significantly higher in arm A, 80% (with 21% complete response (CR)) compared with 47% (with 17% CR) in arm B (P = 0.001 by means of chi(2)-test). WHO grade 3 or 4 toxicity was more frequent in arm A than in arm B, with a significantly greater incidence of leucopenia (53% versus 19%, P = 0.009 by means of chi(2) test) and nausea/vomiting (39% versus 15%, P = 0.044 by means of chi(2) test). There were no treatment related deaths. CONCLUSION: In this study population, concurrent CRT demonstrated significant benefit in terms of response rate, overall survival and time to progression over sequential CRT. The concurrent CRT schedule was associated with higher toxicity; however, the adverse event profile was acceptable in both arms.

Thermoluminescent dosimeters (TLD) quality assurance network in the Czech Republic.

INTRODUCTION: The Czech thermoluminescent dosimeters (TLD) quality assurance network was established in 1997. Its aim is to pursue a regular independent quality audit in Czech radiotherapy centres and to support state supervision. MATERIALS AND METHODS: The audit is realised via mailed TL dosimetry. The TLD system consists of encapsulated LiF:Mg,Ti powder (type MT-N) read with Harshaw manual reader model 4000. Basic mode of the TLD audit covers measurements under reference conditions, specifically beam calibration checks for all clinically used photon and electron beams. Advanced mode consists of measurements under both reference and non-reference conditions using a solid multipurpose phantom ('Leuven phantom') for photon beams. The radiotherapy centres are instructed to deliver to the TLD on central beam axis absorbed dose of 2 Gy calculated with their treatment planning system for a particular treatment set-up. The TLD measured doses are compared with the calculated ones. Deviations of +/-3% are considered acceptable for both basic and advanced mode of the audit. RESULTS: There are 34 radiotherapy centres in the Czech Republic. They undergo the basic mode of the TLD audit regularly every 2 years. If a centre shows a deviation outside the acceptance level, it is audited more often. Presently, most of the checked beams comply with the acceptance level. The advanced TLD audit has been implemented as a pilot study for the present. The results were mostly within the acceptance limit for the measurements on-axis, whereas for off-axis points they fell beyond the limit more frequently, especially for set-ups with inhomogeneities, oblique incidence and wedges. CONCLUSIONS: The results prove the importance of the national TLD quality assurance network. It has contributed to the improvement of clinical dosimetry in the Czech Republic. In addition, it helps the regulatory authority to monitor effectively and regularly radiotherapy centres.