4.1 The radiochromic liquid dosimetry system provides a means of measuring absorbed dose in materials (5-7). Under the influence of ionizing radiation, chemical reactions take place in the radiochromic solution modifying the amplitudes of optical absorption bands (8-10). Absorbance values are measured at the selected wavelength(s) within these affected absorption bands (see also ISO/ASTM Guide 51261).

4.2 In the use of a specific dosimetry system, a calibration curve or response function relates the dosimeter's response to an absorbed dose traceable to a nationally or internationally recognized standard (11, 12).

4.3 The absorbed dose that is measured is usually specified in water. Absorbed dose in other materials may be evaluated by applying the conversion factors discussed in ISO/ASTM Guide 51261.

NOTE 2-For a comprehensive discussion of various dosimetry methods applicable to the radiation types and energies discussed in this practice, see ICRU Reports 14, 17, 34, 35, and 37.

4.4 These dosimetry systems may be used in the industrial radiation processing of a variety of products, for example the sterilization of medical devices and radiation processing of foods (5, 7, 13).

4.5 The available dynamic range indicated in 1.2.1 is achieved by using a variety of radiochromic leuco dyes (Table 1) in a variety of solutions (Table 2).

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4.6 The ingredients of the solutions, in particular the solvents, can be varied so as to simulate a number of materials in terms of the photon mass energy-absorption coefficients, (μen/ρ), for X-rays and gamma-rays and electron mass collision stopping powers, [(1/ρ) dE/dx], over a broad spectral energy range from 0.01 to 100 MeV (18). For special applications certain tissue-equivalent radiochromic solutions have been designed to simulate various materials and anatomical tissues, in terms of values of (μen/ρ) for photons and [(1/ρ) dE/dx] for electrons (18) (see also ICRU Report 44). Tabulations of the values of (μen/ρ) for water (19), the anatomical tissues (17, 19), and three specially designed radiochromic solutions, for photons over the energy range from 0.01 to 20 MeV, and tabulations of the values of [(1/ρ) dE/dx] (17) for water, the tissues and the radiochromic solutions for electrons over the energy range from 0.01 to 20 MeV are given in Refs (12, 13, 18). For additional information see ISO/ASTM Guide 51261, ASTM Practice E 666, and ICRU Reports 14, 17, 35, 37, and 44.