M e s o t h e l i o m a

The amount of radiation absorbed by the tissues is called the radiation dose (or dosage). Before 1985, dose was measured in a unit called a “rad” (radiation absorbed dose). Now the unit is called a gray (abbreviated as Gy). One Gy is equal to 100 rads; one centigray (abbreviated as cGy) is the same as 1 rad.
Different tissues can tolerate various amounts of radiation (measured in centigrays). For example, the liver can receive a total dose of 3,000 cGy, while the kidneys can tolerate only 1,800 cGy. The total dose of radiation is usually divided into smaller doses (called fractions) that are given daily over a specific time period. This maximizes the destruction of cancer cells while minimizing the damage to healthy tissue.
The doctor works with a figure called the therapeutic ratio. This ratio compares the damage to the cancer cells with the damage to healthy cells. Techniques are available to increase the damage to cancer cells without doing greater harm to healthy tissues. These techniques are discussed in Questions 8, 9, and 15.