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Regional Basic Professional Training Course in Korea

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<strong>Regional</strong> <strong>Basic</strong> <strong>Professional</strong> <strong>Tra<strong>in</strong><strong>in</strong>g</strong> <strong>Course</strong> (BPTC) on Nuclear Safety<br />

joule (J) of energy absorbed from any ioniz<strong>in</strong>g radiation <strong>in</strong> one kilogram (kg) of any<br />

material. In symbolic form:<br />

1Gy = 1 J·kg ‐1<br />

The former unit of absorbed dose is known as the rad. The relation between rad and gray<br />

is very simple:<br />

1 rad = 1 · 10 ‐2 Gy = 1 cGy<br />

Therefore, any absorbed dose values expressed <strong>in</strong> rad can be expressed directly <strong>in</strong><br />

centigray (cGy). Many older table of absorbed dose are expressed <strong>in</strong> terms of rad.<br />

Frequently it is of importance to know not only the total absorbed dose, but also the time<br />

period over which that absorbed dose was acquired. This is expressed as the absorbed<br />

dose divided by the time period and is known as the absorbed dose rate. The common<br />

derived unit of absorbed dose rate is gray per second (Gy·s ‐1 ).<br />

2.2.3. Equivalent dose<br />

The concept of Relative Biological Effectiveness (RBE) is used to relate the biological<br />

response of tissue to absorbed dose from radio‐therapeutic beams of different qualities.<br />

Publication 103 of the ICRP [1] redef<strong>in</strong>ed this relation by mak<strong>in</strong>g use of two parameters.<br />

the Equivalent Dose <strong>in</strong> an organ, and<br />

the Effective Dose.<br />

For the sole purpose of express<strong>in</strong>g dose limits, Equivalent Dose and Effective dose have<br />

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