So we would assign the other radiation an RBE value of two. This value is used

primarily in the study of radiobiology.

d. The RBE demonstrated the need for a unit of dose that would take into

account biological damage. Thus, a unit of dose equivalent was established and called

the roentgen equivalent man (rem).

rem = rad x RBE (Radiobiology)

or

rem = rad x Q x N

where Q is the quality factor and N is any other modifying factor. This is used in

radiation protection.

e. Recently, a new name and unit of dose equivalent has been introduced. The

Sievert (symbol Sv) is the new unit of dose equivalent.

1 rem = 0.01 joule/kilogram = 0.01 Sv

Therefore, 1 Sv = 100 rem.

a. Up to now, we have discussed dose as a total quantity. A dose of radiation is

an expression of how much. A particular dose might be the result of a year's exposure

or a day's exposure to radiation.

b. This brings us to another term to consider--dose rate. The dose rate tells us

how fast or slow radiation is being delivered. Dose rate is to dose as miles per hour is

to total miles driven.

c. The dose rate is expressed as dose per unit of time, i.e., rads/hour,

roentgens/sec, etc.

d. Total dose is obtained by multiplying the dose rate by the time of exposure

where the dose rate remains constant.

Dose = Dose Rate x Time

MD0180

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