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- Vatnitsky, S, et al.
(författare)
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Proton dosimetry intercomparison
- 1996
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Ingår i: Radiotherapy and Oncology. - 0167-8140 .- 1879-0887. ; 41:2, s. 169-77
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE: Methods for determining absorbed dose in clinical proton beams are based on dosimetry protocols provided by the AAPM and the ECHED. Both groups recommend the use of air-filled ionization chambers calibrated in terms of exposure or air kerma in a 60Co beam when a calorimeter or Faraday cup dosimeter is not available. The set of input data used in the AAPM and the ECHED protocols, especially proton stopping powers and w-value is different. In order to verify inter-institutional uniformity of proton beam calibration, the AAPM and the ECHED recommend periodic dosimetry intercomparisons. In this paper we report the results of an international proton dosimetry intercomparison which was held at Loma Linda University Medical Center. The goal of the intercomparison was two-fold: first, to estimate the consistency of absorbed dose delivered to patients among the participating facilities, and second, to evaluate the differences in absorbed dose determination due to differences in 60Co-based ionization chamber calibration protocols.MATERIALS AND METHODS: Thirteen institutions participated in an international proton dosimetry intercomparison. The measurements were performed in a 15-cm square field at a depth of 10 cm in both an unmodulated beam (nominal accelerator energy of 250 MeV) and a 6-cm modulated beam (nominal accelerator energy of 155 MeV), and also in a circular field of diameter 2.6 cm at a depth of 1.14 cm in a beam with 2.4 cm modulation (nominal accelerator energy of 100 MeV).RESULTS: The results of the intercomparison have shown that using ionization chambers with 60Co calibration factors traceable to standard laboratories, and institution-specific conversion factors and dose protocols, the absorbed dose specified to the patient would fall within 3% of the mean value. A single measurement using an ionization chamber with a proton chamber factor determined with a Faraday cup calibration differed from the mean by 8%.CONCLUSION: The adoption of a single ionization chamber dosimetry protocol and uniform conversion factors will establish agreement on proton absorbed dose to approximately 1.5%, consistent with that which has been observed in high-energy photon and electron dosimetry.
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- Isacsson, A, et al.
(författare)
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Social network, social support and the prevalence of neck and low back pain after retirement. A population study of men born in 1914 in Malmo, Sweden
- 1995
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Ingår i: Scandinavian Journal of Social Medicine. - 0300-8037. ; 23:1, s. 17-22
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Tidskriftsartikel (refereegranskat)abstract
- In this study we investigated the importance of social network and social support systems outside the workplace and workload and psychological job strain in former work for the prevalence of daily neck and low back pain. The study population (n = 621) comprised a random half of all male residents in Malmo, Sweden, born in 1914, of whom 500 (80.5%) participated. Two of the social network and social support indices (social anchorage and availability of material and informational support) were independent of life-style factors (leisure time physical activity, smoking and alcohol consumption) related to daily neck and back pain after retirement (OR = 2.0, 95% CI 1.2-3.4 and OR = 1.7, 95% CI 1.0-2.7, respectively), while the psycho-social and physical factors in former work were not. As no conclusion about the direction of the association can be drawn, prospective studies are needed to further explore these findings.
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