This report specifies the following information objects: 1) A DICOM Image Information Object for Radiotherapy. It specifies the semantic content of RT Images. It is commonly abbreviated to the RT Image IOD. It also includes the corresponding Storage SOP Class so that this IOD can be used in Network and Media Storage exchanges. The scope of the RT Image IOD is radiotherapy images which have been obtained on a conic imaging geometry, such as that found on conventional simulators and portal imaging devices. It can also be used for calculated images using the same geometry, such as digitally reconstructed radiographs (DRRs). 2) A DICOM Dose Information Object for Radiotherapy. It specifies the semantic content of RT Doses. It is commonly abbreviated to the RT Dose IOD. It also includes the corresponding Storage SOP Class so that this IOD can be used in Network and Media Storage exchanges. The scope of the RT Dose IOD is radiotherapy dose distributions which have been calculated on a radiotherapy treatment planning system, represented as two- or threedimensional dose grids, groups of named or unnamed dose points, isodose curves, and dose-volume histograms (DVHs). 3) A DICOM Structure Set Information Object for Radiotherapy. It specifies the semantic content of RT Structure Sets. It is commonly abbreviated to the RT Structure Set IOD. It also includes the corresponding Storage SOP Class so that this IOD can be used in Network and Media Storage exchanges. The scope of the RT Structure Set IOD is radiotherapy patient-related structures which have been identified on devices such as CT scanners, virtual simulation workstations, or treatment planning systems. 4) A DICOM Plan Information Object for Radiotherapy. It specifies the semantic content of RT (Treatment) Plans. It is commonly abbreviated to the RT Plan IOD. It also includes the corresponding Storage SOP Class so that this IOD can be used in Network and Media Storage exchanges. The scope of the RT Plan IOD is geometric and dosimetric data specifying a course of external beam and/or brachytherapy treatment. This report includes a number of addenda to existing Parts of DICOM; therefore the reader should have a working understanding of the Standard. 1. Part 3 Addenda (Extension to the body, Annex A, B, C and D) 2. Part 4 Addenda (Extension to Annex B) 3. Part 6 Addenda (Extension to Section 6 and Annex A)