dvh

Dose-volume histogram (DVH) is a plot used in radiotherapy treatment planning to summarize the distribution of radiation dose within structures such as target volumes and organs at risk. It provides a compact representation of how much of a structure receives a given dose, aiding evaluation of plan quality and safety.

In a DVH, the relationship between dose and volume is shown for a structure. A cumulative DVH plots dose on the x-axis and the volume fraction (or volume) of the structure receiving at least that dose on the y-axis. A differential DVH shows the amount of tissue receiving doses within small intervals. DVHs can be presented as relative data (percent of the structure) or absolute data (volume in cubic centimeters).

Commonly reported quantities include Vx, the volume (or percent) of the structure receiving at least dose x Gy, and Dx, the minimum dose to x percent of the structure. Dmean and Dmax are also used. For example, V20 is often cited for the lung, and D95 or D98 indicate target coverage. DVHs are generated from treatment planning systems by mapping the planned dose to the structure contours on the patient’s anatomy.

Applications of DVHs include comparing treatment plans, verifying dose constraints for targets and organs at risk, and guiding optimization. Limitations include the loss of spatial information, since two different dose distributions can yield identical DVHs for a given structure; results can be sensitive to contour delineation and dose calculation resolution. Complementary analyses, such as full dose distributions and 3D visualization, are routinely used to assess plans.