Equivalent dose

The biological effectiveness of dose depends on the type of radiation and also on the mass and sensitivity of the irradiated tissue. For alpha irradiation, a quality factor of 20 is assumed (ICRP, 1981), and the dose in Sieverts is 20 times the dose in Grays. In addition, ICRP recommends a weighting factor of 0.12 for irradiation of the whole lung and 0.06 for irradiation of bronchial epithelium only. Thus the effective dose equivalent , symbol HE, is defined as the dose to the whole body which carries the same risk as the given dose to the organ or tissue. This, for irradiation of bronchial tissue is 20 x 0.06 = 1.2 times the dose to the organ in Gy. 

With this convention, the effective dose equivalent in the average indoor atmosphere is given in terms of the PAEC by 

The ICRP Task Group (1988) has recommended a conversion factor of 1.0 x 10-5 mSv per Bqh m-3 of equilibrium equivalent decay product concentration, with a possible 30% uncertainty either way depending on the value of fp. Since 1 Bq m 3 equilibrium equivalent gives 5.54 nj m-3 (Appendix 1.1) the ICRP recommendation is equivalent to 1.8 Sv per Jh m-3 or 6.3 mSv per WLM. 

Different assumptions on the volume of the bronchial tissue considered as critical in calculating the dose, and on the fraction of the PAEC which is carried by unattached daughter products, account for the variation in the estimates. 

The National Radiological Protection Board (1990) have adopted a slightly lower figure, 50 //Sv per Bq m-3 (coincidentally equivalent to Chamberlain Dyson 6.2 nGy per Bqh m-3). For the average UK indoor concentration of 20 Bq m-3 (Table 1.4), this gives 1 mSv annually, which is about equal to the total dose from all other natural sources of radiation (Clarke Southwood, 1989). 

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Ra.dia.tlon Units. Units in use for activity of a radionucHde, ie, the curie, the roentgen (exposure to x and gamma rays), the rad (absorbed dose), and the rem (dose equivalent), should eventually be replaced by the becquerel (Bq), coulomb per kilogram (C/kg), gray (Gy), and the sievert (Sv), respectively. 

Daily exposure in dose equivalents, using 17/ -estradiol aetivity for oestrogenieity (EQ) and TCDD for anti-oestrogenie aetivity (TEQ). 

I Dose equivalent limit-s tor lens of eye, skin and extremities 50 5... 

Absorbed Dose Equivalent to intake multiplied by an absorption factor... 

The dose equivalent is the actual dose modified to take into account the different destructive powers of the various types of radiation in combination with various types of tissue. It is obtained by multiplying the actual dose (in gray) by the value of Q for the radiation type. The result is expressed in the SI unit called a sievert (Sv) ... 

The former (non-SI) unit of dose equivalent was the roentgen equivalent man (rem), which was defined in the same way as the sievert but with the absorbed dose in rad thus, 1 rem = 10 2 Sv. 

A 2.0-kg sample absorbs an energy of 1.5 J as a result of its exposure to (1 radiation. Calculate the dose in rads and the dose equivalent in rems and in sieverts. 

Someone is exposed to a source of p radiation that results in a dose rate of 1.0 rad-d. Given that nausea begins after a dose equivalent of about 100 rem, after what period will that symptom of radiation sickness be apparent ... 

State whether the following statements are true or false. If false, explain why. (a) The dose equivalent is lower than the actual dose of radiation because it takes into account the differential effects of different types of radiation, (b) Exposure to 1 X 1 ()x Bq of radiation would be much more hazardous than exposure to 10 Ci of radiation, (c) Spontaneous radioactive decay follows first-order kinetics, (d) Fissile nuclei can undergo fission when struck with slow neutrons, whereas fast neutrons are required to split fissionable nuclei. 

Table 3-5. Sedative-hypnotic dose equivalency (equal to 30 mg of phenobarbital) ...

Simons PER, Lieberman PL, Read EJ Jr. Edwards ES Hazards of unintentional injection of epinephrine from auto-injectors a systematic review. Ann Allergy Clin Immunol 2009 102 267-272. Rawas-Qalaji MM, Simons PER, Simons KJ Sublingual epinephrine tablets versus intramuscular injection of epinephrine dose equivalence for potential treatment of anaphylaxis. J Allergy Clin Immunol 2006 117 398-403. 

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