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18 March 2010

Answer to Question #4875 Submitted to "Ask the Experts"

Category: Historical Issues/Applications

The following question was answered by an expert in the appropriate field:

I would like to know why H_T is used as a symbol for equivalent dose and where the term came from.

The term equivalent dose used in International Commission on Radiological Protection (ICRP) Publication 60 is a replacement of the previous term dose equivalent originally defined in ICRP Publication 26 and given by the arbitrary symbol H_T for a particular target organ or tissue T by the equation for a particular radiation type:

H_T in units of sieverts = D Q N,

where D is the absorbed dose in units of j kg^-1, Q is the quality factor for the radiation type, and N is the product of all other dose-modifying factors, which are currently taken as unity.

Ken Skrable, CHP, PhD

Answer posted on 27 October 2005. The information and material posted on this Web site is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of materials and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Web site. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.