Assessment of the mean glandular dose using LiF:Mg,Ti, LiF:Mg,Cu,P, Li2B4O7:Mn and Li2B4O7:Cu TL detectors in mammography radiation fields
| Autor: | Joana Pereira, M. Pereira, J. V. Cardoso, Joao G. Alves, L. M. Santos, Mário João Fartaria, Cláudia Reis, V. Holovey, Ana Pascoal, Carlos Augusto Fernandes de Oliveira |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Materials science
Thermoluminescence Analytical chemistry Sensitivity and Specificity 030218 nuclear medicine & medical imaging Ionizing radiation Radiation dose assessment Thermoluminescence detectors 03 medical and health sciences Kerma 0302 clinical medicine Dosimetry Humans Radiology Nuclear Medicine and imaging Mammary Glands Human Reproducibility Dosimeter Radiological and Ultrasound Technology business.industry Radiation Dosimeters Radiation quality X-Rays Reproducibility of Results 030220 oncology & carcinogenesis Measurement uncertainty Female Thermoluminescent Dosimetry Thermoluminescent dosimeter Radiology Mean glandular dose Nuclear medicine business Mammography |
| Zdroj: | Repositório Científico de Acesso Aberto de Portugal Repositório Científico de Acesso Aberto de Portugal (RCAAP) instacron:RCAAP |
| ISSN: | 1361-6560 |
| Popis: | The aim of this paper is the characterization of four thermoluminescence detectors (TLD), namely, LiF:Mg,Ti, LiF:Mg,Cu,P, Li2B4O7:Mn and Li2B4O7:Cu for the measurement of the entrance surface air kerma (ESAK) and estimation of the mean glandular dose (MGD) in digital mammography examinations at hospitals and clinics. Low-energy x-ray beams in the typical energy ranges of mammography, produced with a tungsten target and additional 60 µm molybdenum filtration were implemented and characterized at the Laboratory of Metrology of Ionizing Radiation at Instituto Superior Tecnico. These beams were used for the characterization of the TLDs in terms of sensitivity, linearity, reproducibility, energy dependence and fading at 40 °C. The energy dependence test was further extended using clinical beams produced by mammography units at hospitals and clinics. The method proposed by the International Atomic Energy Agency was used for the measurement of ESAK and assessment of MGD. The combined standard uncertainty for the measurement of ESAK (and MGD) was determined in accordance to the Guide to the expression of uncertainty in measurement. The x-ray beams generated in the 23-40 kVp range presented HVL values from 0.36 to 0.46 mm Al. The beam produced at 28 kVp (HVL 0.39 mm Al) was considered as reference. The radiation field defined a circle with 84 mm diameter with a maximum variation of the beam intensity of less than 1% at the top flat (plateau) within 4 cm of the central axis. The estimated total uncertainty for the measurement of air kerma was 0.42%. All the TL detectors tested showed good performance except the commercial Li2B4O7:Mn (or TLD-800) which was excluded due to its poor sensitivity in our experimental set up. Both lithium fluorides showed better linearity and reproducibility as well as lower energy dependence and fading when compared to lithium borates. The stable behaviour of LiF:Mg,Ti and LiF:Mg,Cu,P detectors is reflected in the low combined standard uncertainty of ±5.6% and ±4.3% respectively (or ±5.1% and ±3.6% if fading is neglected). In general a total combined uncertainty lower than ±10% for the measurement of ESAK was obtained for the four TL materials studied. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|