Accumulated dose

AH x-ray equipment must be periodically inspected and the output monitored and caUbrated to minimize the chance of accidental overexposure. Another concern involves radiation accumulation by medical personnel operating x-ray equipment. Although the dose to any one patient may be low, the accumulated dose to a clinician performing multiple exams each day over the course of a year is great. Therefore, personnel working with x-ray equipment must take precautions constandy to minimize and monitor exposure. Lead aprons and film badges are used to minimize exposure and to monitor accumulated dose, respectively. 

Chinese experiments with rats, inhaling radon and daughters for several weeks with accumulated doses up to 3500 WLM, did not show any increase in their chromosome aberration frequencies over that of the control group (Deng Zhi-cheng and Li Yuan-huy, 1983) Similar results on rats have been obtained in an unpublished investigation by Pohl-Riiling and Pohl. 

Another problem is degradation of the sensor due to the high UV dose. The radiation resistance of most photodiodes decreases with wavelengths. UV-enhanced Si photodiodes show a loss of 10% in sensitivity already after an accumulated dose of some hundred J/cm2 at X = 254 nm. This is the dose a sensor will have received over the lifetime of an Hg lamp. Special silicon nitride-protected photodiodes are stable up to 105 J/cm2. A filter combined with an attenuator may help to achieve the required selectivity and reduce the exposure of the detector. However, the radiation stability of the filter has to be guaranteed. 

In a case-control study (van Leeuwen et al. 1994) in which 98 cases of invasive endometrial carcinoma were diagnosed at least 3 months after diagnosis of primary breast cancer, it was observed that the use of tamoxifen was associated with a RR of 1.3. The risk appeared to have a tendency to increase during treatment, from 0.6 for less than a year to 3.0 for more than 5 years of treatment. It should be noted that the accumulated dose of tamoxifen was significantly associated with risk of endometrial cancer. However, the average daily dose used (20-40 mg/d) did not seem to influence risk. Other authors have also observed that the increase in risk is only detected when a determined accumulated dose is attained (van Leeuwen et al. 1994 De Muylder et al. 1991). 

According to results from clinical trials, the agonistic effects of tamoxifen detected in animals were also observed in the human uterus as it produces a trophic effect and an increase in the incidence of endometrial pathology, which is related to endometrial thickening (> 4 mm). Its use seems to be associated with an increase in endometrial cancer, which is related to the length of treatment and the accumulated dose of tamoxifen. Nevertheless, these tumors do not seem to be more aggressive or to have a worse prognosis than those found in women who do not follow this treatment or who receive hormone therapy. 

Two methods of documenting trends of oxidant concentrations during the 1968-1974 period at Rim Forest-Sky Forest express the accumulated dose as a sum of all hourly values in micrograms per cubic meter and as number of hours with a concentration of 0.08 ppm (the federal standard) or more for each month separately, June through September (Figure 12-5). The dose excludes background concentrations—those less than 59... 

Accumulation Dose, Dose Interval, and Plasma Level Fluctuation... 

A. Accumulation dose, dose interval, and fluctuation of plasma level... 

Gelinck GH, Warman JM (1996) Charge carrier dynamics in pulse-irradiated polyphenyle-nevinylenes effects of broken conjugation, temperature, and accumulated dose. J Phys Chem 100 20035... 

Dosimetry of residents at Chernobyl reactor accident28,29 and Techa River fuel processing plant has been reported.29,92 The World Health Organization (WHO) issued a report, Health consequences of the Chernobyl accident in which the extensive application to determine the accumulated dose of the residents up to 80-100 mGy with the accuracy of + 50 mGy. The measured dose appeared to be higher than 200 mGy.30... 

Figure 1. Typical ESR growth curve. Aliquots of enamel or other sample material are irradiated artificially and the increase in intensity measured A minimum of 10-12 points is required to provide statistical accuracy. The extrapolation of the growth curve to the x-axis gives the accumulated dose, AD.

Sample (subsamples) Accumulated Dose, AD (Gray) Weighted Mean Standard ESR Ages ... 

BLEOMYCIN ANTICANCER AND IMMUNOMODULATING DRUGS-CISPLATIN t bleomycin levels, with risk of pulmonary toxicity Elimination of bleomycin is delayed by cisplatin due to 1 glomerular filtration. This is most likely with accumulated doses of cisplatin in excess of 300 mg/m2 Monitor renal function and adjust dose of bleomycin as per creatinine clearance. Monitor clinically, radiologically and with lung function tests for pulmonaiy toxicity... 

Recent reports of the ICRP (ICRP 1991) and the NCRP (NCRP 1993) contain recommendations for lower worker dose limits. The ICRP recommends a limit on total effective dose of 2 rem/year averaged over 5 years, with the additional provision that the dose not exceed 5 rem in any single year. The NCRP s recommendations are that a worker s total accumulated dose should not exceed his or her age in years time 1 rem, and that the dose should not exceed 5 rem in any single year. These recommendations have not yet been incorporated into U.S. regulations. 

As an aside, it is worth mentioning that the study of primary radical cations in saturated hydrocarbon liquids presents a much greater purity problem than for excess electrons since many potential impurities and products of irradiation tend to have ionization potentials lower than that of the saturated hydrocarbon solvent. Rigid purification from unsaturated and even isomeric impurities, and very low accumulated doses are therefore imperative in such studies. 

The p -n diodes were irradiated with 6 MeV electrons using a linear accelerator. The flux of electrons was IxlO cm V and temperature of the samples during irradiation varied in the range of 300-800 K. The accumulated dose of electrons was 8xl0 cm. Thermal annealing of the irradiated structures was carried out in a furnace in nitrogen ambient. 

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