High-dose dosimetry

Fisher, D. R. Assessments for high dose radionuclide therapy treatment planning. Radiat. Prot. Dosimetry 105(1—4) 581—586. 2003. 

Irradiation techniques are more and more widely utilized for industrial applications for instance, for food preservation, medical sterilization, and polymer processing. Such techniques require specific rules of control by means of accurate dosimetry [89]. In this context, new promising dosimeters based on resistance measurements of organic conducting crystals have been reviewed by Zuppiroli et al. [89]. The crystals utilized as dosimeters are either small needles (0.01 x 0.01 x 3 mm3) or larger plates (0.1 x 0.5 x 3 mm3), and their electrical resistances ( 1 kfl in the first case, 1 H in the second) increase exponentially with the adsorbed radiation dose, up to quite high doses. 

There is considerable controversy over the shape of the dose-response curve at the chronic low dose levels important for environmental contamination. Proposed models include linear models, nonlinear (quadratic) models, and threshold models. Because risks at low dose must be extrapolated from available data at high doses, the shape of the dose-response curve has important implications for the environmental regulations used to protect the general public. Detailed description of dosimetry models can be found in Cember (1996), BEIR IV (1988), and Harley (2001). 

The overall accomplishments of the High-Dose Dosimetry Programme have been ... 

Lewtas J, Walsh D, Williams R, et al. 1997. Air pollution exposure-DNA adduct dosimetry in humans and rodents evidence for non-linearity at high doses. Mutat Res 378 51-63. 

There are uncertainties in the dosimetry we have used at the high dose rates, but as stated they are believed to be less 5%. Further the ratio of cyclohertene to bicyclohexyl does not depend on dosimetry. Another aspect of the comparison between low and high dose rates is the invariance of yields at the high dose rates up to 5 Mrads. 

A review is given on the experiences with the oxalic acid dosimeter. The system was first suggested by Draganic, who has carried out extensive investigations on the dosimetric properties. Further experiments have been carried out at various laboratories—e.g., in the United States, Japan, and Denmark. Although the system suffers from some systematic weaknesses, it can be applied successfully, when properly calibrated under the conditions where it is to be used. The present report describes its application for 60Co and high dose-rate electron dosimetry. 

The dosimetry is usually made in 0.01 mol dm air- or oxygen-saturated solution. Since the (SCN)2 ions disappear in a fairly slow bimolecular reaction with a rate coefficient of 3 x 10 moH dm s, this system is applicable for measuring high-dose pulses. The dose can be calculated from the increase of absorbance at 475 nm, AA, using Gs = 2.6 X 10 m J (Buxton and Stuart 1995)... 

The aqueous solution of nitro blue tetrazolium chloride was investigated (Kovacs et al. 1999) and it was observed that the NBT " ions were reduced radiolytically first to monoformazan (MF ) and then to diformazan (DF) having high linear molar extinction coefficients at the absorption maxima of 522 nm and 570-610 nm. The formation of formazans was found more pronounced in the presence of alcohol and the aqueous-ethanol nitro blue tetrazolium solutions were found useful for high-dose dosimetry in the dose range of 0.1-30 kGy. 

Taking into account all these observations, the use of TL materials for high-dose determination appears possible. The fact that there are very few examples of practical application for high-dose dosimetry can be explained with problems of supralinearity, energy dependence, limited accuracy (> 5%), and the difficulties originating from the repeated use of the systems (Burgkhardt et al. 1977). 

Glutamine has been found suitable for LL dosimetry. The glutamine system has been developed for high-dose dosimetry as routine dosimeter in radiation processing (Puite and Ettinger 1982 Temperton et al. 1984). The irradiation temperature coefficient for this dosimeter is about +0.35% (°C) in the temperature range of 10-40°C. Miller and Xie (1985) found no dose-rate dependence up to about 10 Gy s. ... 

The basic advantage of applying fluorimetry for dosimetry purposes is the high sensitivity of the method as compared to, e.g., spectrophotometry. Other advantages are the wide dynamic range, use for both passive and real-time dosimetry and for both low-and high-dose rates, variable geometries of the dosimeters (pellets, films, optical fibers, etc.), and inexpensive multiuse radiation detectors. 

Bartolotta A, Caccia B, Indovina PL, Onori S, Rosati A (1985) High-dose dosimetry. In Symposium proceedings, IAEA, STI/PUB/671, International Atomic Energy Agency, Vienna, p 245 Becker K (1973) Solid-state dogimetry, CRC press, Boca Rason, Florida. 

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