The mean lethal dose (MLD) is defined as the dose that reduces survival fraction to what percentage?

The mean lethal dose (MLD) is defined as the dose that reduces survival fraction to what percentage?

• A. 25%
• B. 37%
• C. 50%
• D. 75%

Answer: (B)

The mean lethal dose (MLD) is a critical concept in radiobiology and refers specifically to the dose of radiation that causes a 37% survival fraction of a population of cells or organisms. This means that if the MLD is administered, approximately 63% of the cells or organisms will not survive, while 37% will live. This particular percentage is significant because it is derived from the exponential nature of cell survival following radiation exposure. The relationship between dose and survival often follows a linear-quadratic model, and the MLD corresponds directly to the point on the survival curve where a specific, standardized reduction in the surviving population is observed. Knowing that the surviving fraction is reduced to 37% provides critical insights into the lethality of a given dose, thereby forming a baseline for comparing different doses and their biological effects. Understanding the implications of MLD helps in planning radiation therapy and estimating treatment responses, making it a fundamental parameter in the fields of oncology and medical dosimetry.

The mean lethal dose (MLD) is a critical concept in radiobiology and refers specifically to the dose of radiation that causes a 37% survival fraction of a population of cells or organisms. This means that if the MLD is administered, approximately 63% of the cells or organisms will not survive, while 37% will live.

This particular percentage is significant because it is derived from the exponential nature of cell survival following radiation exposure. The relationship between dose and survival often follows a linear-quadratic model, and the MLD corresponds directly to the point on the survival curve where a specific, standardized reduction in the surviving population is observed. Knowing that the surviving fraction is reduced to 37% provides critical insights into the lethality of a given dose, thereby forming a baseline for comparing different doses and their biological effects.

Understanding the implications of MLD helps in planning radiation therapy and estimating treatment responses, making it a fundamental parameter in the fields of oncology and medical dosimetry.