The quality factor of x-rays/gamma rays as one is realistic?

Akber, Syed F.

doi:10.1017/s1460396912000349

Cited by 3 publications

(4 citation statements)

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“…Direct comparisons are also hampered by the different radiation exposure deliveries. Indeed, despite the fact that a quality factor of 1 is assigned for both x rays and gamma rays, the reliability of this assigned value has been called into question [ 20 , 21 ], more so for different tissues in vivo [ 21 ]. Within these acknowledged limitations, a tentative comparison is worth presenting, as it may help gain insights into this area of radiobiological research where much uncertainty persists.…”

Section: Discussionmentioning

confidence: 99%

Acceleration of atherogenesis in ApoE−/− mice exposed to acute or low-dose-rate ionizing radiation

et al. 2015

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There is epidemiological evidence for increased non-cancer mortality, primarily due to circulatory diseases after radiation exposure above 0.5 Sv. We evaluated the effects of chronic low-dose rate versus acute exposures in a murine model of spontaneous atherogenesis. Female ApoE−/− mice (60 days) were chronically irradiated for 300 days with gamma rays at two different dose rates (1 mGy/day; 20 mGy/day), with total accumulated doses of 0.3 or 6 Gy. For comparison, age-matched ApoE−/− females were acutely exposed to the same doses and sacrificed 300 days post-irradiation. Mice acutely exposed to 0.3 or 6 Gy showed increased atherogenesis compared to age-matched controls, and this effect was persistent. When the same doses were delivered at low dose rate over 300 days, we again observed a significant impact on global development of atherosclerosis, although at 0.3 Gy effects were limited to the descending thoracic aorta. Our data suggest that a moderate dose of 0.3 Gy can have persistent detrimental effects on the cardiovascular system, and that a high dose of 6 Gy poses high risks at both high and low dose rates. Our results were clearly nonlinear with dose, suggesting that lower doses may be more damaging than predicted by a linear dose response.

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Section: Discussionmentioning

confidence: 99%

Acceleration of atherogenesis in ApoE−/− mice exposed to acute or low-dose-rate ionizing radiation

et al. 2015

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“…10 For example, take cobalt 60 (Co-60) (1?25 MeV) RWF as one. Determine the mean lethal dose (Do) of a cell line in the mitotic phase of a given energy.…”

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confidence: 99%

“…This created an unprecedented problem in computing E. First of all, if we use RWF as 1, there is no differentiation/demarcation whether the exposure is in kV range or MV range or the calculated E is in kV or MV exposure. In addition, Akber 10 has shown that, as energy decreases, the potency of radiation at low energy increases. The relative biological effectiveness value increases as kV energy decreases.…”

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confidence: 99%

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The clinical efficacy of effective dose

Akber¹

2014

J Radiother Pract

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Effective dose (E) is proposed by the International Commission on Radiological Protection (ICRP) 1 in 1975 to replace effective dose equivalent. Effective dose as defined by the ICRP is a dose quantity of health determinant due to scholastic effects from being exposed to low doses of ionising radiation. One of the goals of ICRP in proposing E is to quantitate radiation exposure for establishing and providing ionising radiation dose limits for radiological protection. E reflects the health determinant aspect from an ionising radiation exposure to any section of the human body whether it be external or internal exposure to uniform body ionising radiation exposure for a reference person.To conceive the concept of E, the ICRP 1 relied on health determinant from ionising radiation exposure and using linear no-threshold (LNT) model to yield a single-dose value from internal and external exposure.where E is the the effective dose; Dm the dose/ exposure in a medium; TWF the tissue-weighting factor; and RWF the radiation-weighting factor.To compute E, there are many innate uncertainties. These are as follows.Effective dose (E) can only be calculated with inherent uncertainties. Direct measurement of E is not possible.Exposure/dose measurement (Dm). The penetrating beam quality in kilovoltage is characterised by an X-ray tube potential (kVp) and the half value layer (HVL), although host of other factors also affect the beam quality. 2 It has been reported that clinically used energy (kVp) have a wide range of HVL values for a given kVp. 2,3 The HVL ranges from 0?31 mm of pure aluminium (Al) for mammography to 2?31 mm Al equivalent for 80 kVp for X-ray unit, to 3?01 mm for fluoroscopy unit and 4?01 mm Al for computerised tomography (CT) at 120 kVp. Let us assume that an X-ray unit with 2?5 mm Al HVL at 80 kVp yields an exposure of 1 R at 100 cm source to chamber distance to the human liver and so does CT. Is the effective dose for the liver the same?Chambers-related factors also contribute to uncertainties in computing E. 3-7

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