China
Africa
Explore chapters and articles related to this topic
Radiometry
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
The energy dependence of a detector is of concern not only in spectrometric applications. Also, for non-spectrometric instruments, such as dose and dose rate meters, it is important to consider. The factors mainly affecting the energy dependence of photon detectors are the thickness of the detector casing, atomic composition of the detector material and the detector size. The detector casing will cause attenuation of low energy photons, resulting in a low efficiency at these energies. A detector designed for measuring dose rate will therefore underestimate the dose rate from low-energy photons, unless this is compensated for. For example, so-called energy compensated GM tubes are equipped with a metal filter to increase the attenuation of medium and high energy photons as well (Figure 5.8).
Brachytherapy Treatment Planning
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
Margaret Bidmead, Dorothy Ingham, Peter Bownes, Chris D. Lee
The overall time and the temporal pattern of irradiation should be recorded. The irradiation time is the time during which a radioactive source is present in the patient. The overall treatment time is the total time elapsed from the beginning of the first irradiation to the end of the last one. The instantaneous dose rate is the dose per fraction divided by the irradiation time for that fraction. The average overall treatment dose rate is the total dose divided by the overall treatment time.
Radiation Dose and Exposure Indicators
Published in Ken Holmes, Marcus Elkington, Phil Harris, Clark's Essential Physics in Imaging for Radiographers, 2021
Exposure occurs over time, of course. The more Sieverts absorbed in a unit of time, the more intense the exposure. So we express exposure as an amount over a specific time period, e.g. 5 mSv per year. This is called the ‘dosage rate’. In the UK, the dose rate from background radiation, the sum of all natural radiation, is about 2.5 mSv per year.
Cohort profile – MSK radiation workers: a feasibility study to establish a deceased worker sub-cohort as part of a multicenter medical radiation worker component in the million person study of low-dose radiation health effects
Published in International Journal of Radiation Biology, 2022
Lawrence T. Dauer, Meghan Woods, Daniel Miodownik, Brian Serencsits, Brian Quinn, Michael Bellamy, Craig Yoder, Xiaolin Liang, John D. Boice, Jonine Bernstein
Previous attempts to estimate cancer and non-cancer risk from radiation exposures at low doses (<100 mGy) and low dose rates (<5 mGy per hour) have significant uncertainties, but have suggested that risks following low-dose rates may be as harmful as those reported among Japanese atomic-bomb survivors. Even today, 70 years after the exposure, 18,443 atomic-bomb survivors exposed to >100 mSv form the basis of radiation protection standards (NRC 2006; Cardis 2007; ICRP 2007; UNSCEAR 2008; Jacob et al. 2009; Wakeford 2005; Dauer 2011; NCRP 2018a) and scientific and medical committees grapple over how best to estimate and apply a ‘dose and dose rate effectiveness factor’ (ICRP 2005; Tubiana et al. 2006; ICRP 2007; Tenforde and Schauer 2008; NCRP 2018a) to scale the risks to situations involving chronic exposures relevant to occupational, environmental, and medical imaging circumstances.
The γH2AX DSB marker may not be a suitable biodosimeter to measure the biological MRT valley dose
Published in International Journal of Radiation Biology, 2021
Jessica A. Ventura, Jacqueline F. Donoghue, Cameron J. Nowell, Leonie M. Cann, Liam R. J. Day, Lloyd M. L. Smyth, Helen B. Forrester, Peter A. W. Rogers, Jeffrey C. Crosbie
The Australian Synchrotron functioned at a constant ring current of 200 mA, in so-called Top-Up mode. We used high purity in vacuo copper, aluminum, and molybdenum filters to produce a polychromatic X-ray beam generating mean energies of approximately 95 keV for MRT and 125 keV for BB irradiations (Stevenson et al. 2017). The dose rate for the BB exposures was 41.5 Gy/s and 12.2 Gy/s, and for MRT, 279.3 Gy/s and 357.9 Gy/s for skin and cell studies respectively. The dose rate was determined using previously published methods (Lye et al. 2016; Livingstone et al. 2017) and was based on full-scatter reference conditions. The dose rate measurement methods are described in the Supplementary Methods section. A dynamic motorized stage was used to vertically move the mouse jig through the beam at precise velocities. The irradiations were carried out across 2 separate beam-times separated by approximately 6 months.
Low dose gamma irradiation attenuates cyclophosphamide-induced cardiotoxicity in rats: role of NF-κB signaling pathway
Published in International Journal of Radiation Biology, 2021
Amira Abd-ElRaouf, Ahmed S. Nada, Nour El-Din A. Mohammed, Hany A. Amer, Sahar S. Abd-ElRahman, Rania M. Abdelsalam, Hesham A. Salem
Low doses of radiation were administered through two different dose rates:Low dose rate (LDR): radiation with the dose 0.05 Gy (source: 137Cs with dose rate 2.21 mGy/h obtained from the National Center for Nuclear Safety and Control (NCNSC)). Prior to the irradiation process, the dose rate was measured using TLD dosimeter (Automass, Wenzenbach, Germany. Measuring range: 0.1 μSv/h–10 mSv/h).High dose rate (HDR): radiation with the dose 0.25 Gy (source: 137Cs irradiation unit [Gamma cell-40] provided by the Atomic Energy of Canada Limited, with dose rate 0.46 Gy/min obtained from the NCRRT).