Understanding Isodoses in Radiation Oncology

In radiation oncology, an isodose is a line or surface of equal dose in a treatment plan. It represents the amount of radiation that will be delivered to a specific area of the body. Isodoses are used to determine the dose distribution in the patient's body and to ensure that the tumor receives an adequate dose of radiation while minimizing damage to surrounding healthy tissue.

Isodoses are typically represented as contours on a dosimetry map, with each contour representing a specific dose level. The dose levels are usually expressed in gray (Gy) or millisieverts (mSv). For example, an isodose line might be labeled "20 Gy" if it represents the dose level at which the radiation therapy will deliver 20 Gray to the tumor.

Isodoses are important in radiation oncology because they help clinicians plan and deliver precise doses of radiation to the tumor while minimizing side effects. By analyzing the isodose distribution, clinicians can identify areas of the body that may receive excessive or inadequate doses of radiation and make adjustments to the treatment plan as needed.