History of Absorbed Dose

Absorbed Dose:Absorbed dose is the amount of energy that

ionizing radiation imparts to a given mass of matter. In other words, the dose is the amount of radiation absorbed by an object.

Under normal circumstances, the larger the absorbed dose, the larger will be the hazard.

The unit of absorbed dose is Gray, whose symbol is Gy and sievert (Sv) .

Conversions from the SI units to other units 1 Gy = 100 rad1 mGy = 100 mrad1 Sv = 100 rem1 mSv = 100 mrem1 rem = 1 rad

HistoryMedical physics is concerned with protecting people

from the harmful effects of ionizing radiation while allowing its beneficial use in medicine, science and industry.

100 years ago, when the radiations were discovered, The limits were based on preventing the onset of such obvious effect as skin ulcerations that appeared after intense exposure to radiation fields.

Later limits were based on preventing delayed effects such as cancer that had been observed in populations of people receiving high doses, particularly from medical exposures and from the atomic-bomb exposures in Hiroshima and Nagasaki.

Radiation and LifeDifferent organs of the body vary in their

sensitivity to absorbed doses of radiation. The most sensitive organs are generally those

with the highest rate of cellular replication.These are bone marrow, lung, thyroid, bone,

gonads and female breast.

History of Protection Standards:Early ignorance of the hazards of radiation resulted in

numerous unexpected injuries to patients, physicians, and scientists and as a result, some researchers took steps to publicize the hazards and set limits on exposure.

In July 1896, only one month after the discovery of x rays, a severe case of x-ray-induced dermatitis was published, and in 1902, the first dose limit of about 10 rad per day (or 3000 rad per year), was recommended. The 10 rad-per-day limit was based not on biological data but rather on the lowest amount that could be easily detected, namely, the amount required to produce an observable exposure.

By 1903, animal studies had shown that x rays could produce cancer and kill living tissue and that the organs most vulnerable to radiation damage were the skin, the blood-forming organs and the reproductive organs.

In September 1924 at a meeting of the American Roentgen Ray Society, Arthur Mutscheller was the first person to recommend a “tolerance” dose rate for radiation workers. He based his recommendation on observations of physicians and technicians who worked in shielded work areas. He estimated that the workers had received about 60 rad per month as measured by the x-ray-tube current and voltage, the filtration of the beam, the distance of the workers from the x-ray tube, and the exposure time.

Radiation Detection and SafetyMonitors used for detection of radioactivity

Radiation Detection and Safety

film badge

electronic dosimeter

finger ring (TLD) Thermo luminescent dose meter (TLD)

Radiation Detection and SafetyThe 3 methods of reducing external exposure

relate to:

Time of exposure (the less the better)

Distance to the source (the more the better)

Appropriate Shielding (the more the better)

Thank You!