Radiotherapy Planning CT

What it does

Radiotherapy Planning CT contours the simulation CT before a treatment plan is made. Upload the planning CT series as it leaves the CT simulator, couch, immobilisation mask and all; the run recognises the treatment site (head and neck, thorax, abdomen or pelvis) and contours the full organ-at-risk set for that site.

The contours come back as a DICOM RT Structure Set that a treatment planning system can import, with structure names following AAPM TG-263, organ volumes and contour quality-assurance flags. For lung and for nasopharyngeal and other head and neck cancers the run also proposes an editable gross tumour volume (GTV).

Intended use

Contouring support for the radiotherapy team. Organ-at-risk delineation is repetitive manual work that delays planning; the run returns the full organ set as editable contours, ready to import into the planning system.

Who it is for

Radiation oncologists, dosimetrists, medical physicists and radiotherapy departments. Developers connect the run to the department's DICOM node so that structure sets arrive in the planning system alongside the simulation CT.

Accepted input

• Planning CT series as CT Image Storage or Enhanced CT.
• Simulation set-up: flat couch, thermoplastic masks and other immobilisation devices are expected in the images.
• PET or MR of the same patient may accompany the planning CT to support the GTV proposal.

Requirements

Requirement	Why
Frame of Reference UID	The RT Structure Set must reference the planning CT geometry exactly
Image Position and Orientation (Patient) and Pixel Spacing	Contours are written in patient coordinates on the original slices
Field of view covering the body outline	A truncated field of view affects body and skin contours and is flagged
Treatment site within head and neck, thorax, abdomen or pelvis	The organ set is chosen per site

Dental metal and implant streaks are reported as quality flags on the structures they cross.

Optional context

The treatment site and the tumour type can be stated in clinical_context; otherwise the site is detected from the anatomy in the scan.

The result

A JSON result with structure volumes and QA flags, and the RTSTRUCT that carries the contours.

Section	Content
Organs at risk	Site-specific OAR contours for head and neck, thorax, abdomen or pelvis, with volumes and QA flags
GTV proposal	Editable gross tumour volume for lung and nasopharyngeal or head and neck cancer
Draft report	Opt-in (options.report): an English narrative that interprets the result for the reader (findings, impression, limitations); every number is checked against the findings

Standards

• DICOM: RT Structure Set Storage (RTSTRUCT) referencing the planning CT, with SEG available as an alternative encoding; SR TID 1500 Measurement Report for structure volumes.
• Nomenclature: AAPM TG-263 standardised structure names, which match planning templates and dose-constraint lists.

Quality assurance

Every structure carries contour QA flags. Structures near dental metal, immobilisation devices or the edge of a truncated field of view are marked.