What Are DICOM RT Objects?

What Are DICOM RT Objects

Radiotherapy uses a family of DICOM objects that describe a treatment rather than an image.

An RT Structure Set (RTSTRUCT) holds the contours drawn on the planning images: the target volumes and the organs at risk, each as a named set of outlines with a frame of reference tying it to the CT it was drawn on. An RT Plan describes how the treatment is to be delivered — beams, segments, fractions. An RT Dose carries the computed dose as a three-dimensional grid, displayed as isodose lines over the anatomy or as a color wash.

The dose-volume histogram (DVH) summarizes that grid against the contours: for each structure, how much of its volume receives at least a given dose. It is the standard way to check that a plan covers the target while sparing what surrounds it, and it can be stored in the RT Dose object or recomputed from the dose grid and the structures.

Read together, these objects let a viewer show contours, isodoses and the DVH against the planning images — which is a different task from reading a diagnostic study, and why viewers treat them separately.

In Weasis, see DICOM RT viewer.