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4.1 Blood and blood components are irradiated to predetermined absorbed doses to inactivate viable lymphocytes to help prevent transfusion-induced graft-versus-host disease (GVHD) in certain immunocompromised patients and those receiving related-donor products (1, 2).94.2 The assurance that blood and blood components have been properly irradiated is of crucial importance for patient health. This shall be demonstrated by means of accurate absorbed-dose measurements on the product, or in simulated product.4.3 Blood and blood components are usually irradiated using gamma radiation from 137Cs or 60Co sources, or X-radiation from X-ray units.4.4 Blood irradiation specifications include a lower limit of absorbed dose, and may include an upper limit or central target dose. For a given application, any of these values may be prescribed by regulations that have been established on the basis of available scientific data (see 2.6).4.5 For each blood irradiator, an absorbed-dose rate at a reference position within the canister is measured as part of irradiator acceptance testing using a reference-standard dosimetry system. That reference-standard measurement is used to establish operating parameters so as to deliver specified dose to blood and blood components.4.6 Absorbed-dose measurements are performed within the blood or blood-equivalent volume for determining the absorbed-dose distribution. Such measurements are often performed using simulated product (for example, polystyrene is considered blood equivalent for 137Cs photon energies).4.7 Dosimetry is part of a measurement management system that is applied to ensure that the radiation process meets predetermined specifications (see ISO/ASTM Practice 52628).4.8 Blood and blood components are usually irradiated in chilled or frozen condition. Care should be taken, therefore, to ensure that the dosimeters and radiation-sensitive indicators can be used under such temperature conditions.4.9 Proper documentation and record keeping are critical components of a radiation process. Documentation and record keeping requirements may be specified by regulatory authorities or may be given in the corporation’s quality policy.4.10 Response of most dosimeters has significant energy dependence at photon energies of less than 100 keV, so proper care must be exercised when measuring absorbed dose in that energy range.1.1 This practice outlines the irradiator installation qualification program and the dosimetric procedures to be followed during operational qualification and performance qualification of the irradiator. Procedures for the routine radiation processing of blood product (blood and blood components) are also given. If followed, these procedures will help ensure that blood product exposed to gamma radiation or X-radiation (bremsstrahlung) will receive absorbed doses with a specified range.1.2 This practice covers dosimetry for the irradiation of blood product for self-contained irradiators (free-standing irradiators) utilizing radionuclides such as 137Cs and   60Co, or X-radiation (bremsstrahlung). The absorbed dose range for blood irradiation is typically 15 Gy to 50 Gy.1.3 The photon energy range of X-radiation used for blood irradiation is typically from 40 keV to 300 keV.1.4 This practice also covers the use of radiation-sensitive indicators for the visual and qualitative indication that the product has been irradiated (see ISO/ASTM Guide 51539).1.5 This document is one of a set of standards that provides recommendations for properly implementing dosimetry in radiation processing and describes a means of achieving compliance with the requirements of ISO/ASTM Practice 52628 for dosimetry performed for blood irradiation. It is intended to be read in conjunction with ISO/ASTM Practice 52628.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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Terminology Relating to Radiation Measurements and Dosimetry

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4.1 The dichromate system provides a reliable means for measuring absorbed dose to water. It is based on a process of reduction of dichromate ions to chromic ions in acidic aqueous solution by ionizing radiation.4.2 The dosimeter is a solution containing silver and dichromate ions in perchloric acid in an appropriate container such as a sealed glass ampoule. The solution indicates absorbed dose by a change (decrease) in optical absorbance at a specified wavelength(s) ((3), ICRU Report 80). A calibrated spectrophotometer is used to measure the absorbance.1.1 This practice covers the preparation, testing, and procedure for using the acidic aqueous silver dichromate dosimetry system to measure absorbed dose to water when exposed to ionizing radiation. The system consists of a dosimeter and appropriate analytical instrumentation. For simplicity, the system will be referred to as the dichromate system. The dichromate dosimeter is classified as a type I dosimeter on the basis of the effect of influence quantities. The dichromate system may be used as either a reference standard dosimetry system or a routine dosimetry system.1.2 This document is one of a set of standards that provides recommendations for properly implementing dosimetry in radiation processing, and describes a means of achieving compliance with the requirements of ISO/ASTM Practice 52628 for the dichromate dosimetry system. It is intended to be read in conjunction with ISO/ASTM Practice 52628.1.3 This practice describes the spectrophotometric analysis procedures for the dichromate system.1.4 This practice applies only to gamma radiation, X-radiation/bremsstrahlung, and high energy electrons.1.5 This practice applies provided the following conditions are satisfied:1.5.1 The absorbed dose range is from 2 × 10 3 to 5 × 104 Gy.1.5.2 The absorbed dose rate does not exceed 600 Gy/pulse (12.5 pulses per second), or does not exceed an equivalent dose rate of 7.5 kGy/s from continuous sources (1).21.5.3 For radionuclide gamma sources, the initial photon energy shall be greater than 0.6 MeV. For bremsstrahlung photons, the initial energy of the electrons used to produce the bremsstrahlung photons shall be equal to or greater than 2 MeV. For electron beams, the initial electron energy shall be greater than 8 MeV.Note 1—The lower energy limits given are appropriate for a cylindrical dosimeter ampoule of 12 mm diameter. Corrections for displacement effects and dose gradient across the ampoule may be required for electron beams (2). The dichromate system may be used at lower energies by employing thinner (in the beam direction) dosimeter containers (see ICRU Report 35).1.5.4 The irradiation temperature of the dosimeter shall be above 0°C and should be below 80°C.Note 2—The temperature coefficient of dosimeter response is known only in the range of 5 to 50°C (see 5.2). Use outside this range requires determination of the temperature coefficient.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in 9.3.

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