The modality and technique value sets were reviewed by the CODEX Radiation Therapy SMEs and deemed to be non-overlapping to the extent possible. Allowed combinations were also specified. Modality and Teqhnique will always be specified in tandem using the new http://build.fhir.org/ig/HL7/fhir-mCODE-ig/branches/modality-technique/StructureDefinition-mcode-radiotherapy-modality-and-technique.html extension, and the allowed combinations of modality and technique will be constrained using invariants to the combinations shown here: Treatment Type Modality Technique External Beam Radiotherapy Photons IMRT, VMAT, 3D, 2D, IORT External Beam Radiotherapy Electrons 3D, 2D, IORT External Beam Radiotherapy Neutrons 3D, NCT External Beam Radiotherapy Carbon Ions PPS, PSS, MIX External Beam Radiotherapy Protons PPS, PSS, MIX Brachytherapy Internal radiotherapy – permanent seeds Interstitial Brachytherapy Low Dose Rate using temp rad source Intracavitary, Interstitial, Surface Brachytherapy Pulsed Dose Rate Intracavitary, Interstitial Brachytherapy High Dose Rate Intracavitary, IMB, Interstitial, Intravascular, Intraluminal, IORT, Surface Brachytherapy High dose rate electronic Intracavitary, IMB, Interstitial, Intraluminal, IORT, Surface Brachytherapy Radiopharmaceutical Oral, Intravascular, Intracavitary, Interstitial Technique Acronyms: Acronym Meaning IMRT Intensity Modulated Radiation Therapy VMAT Volumetric Modulated Arc Therapy 3D Three Dimensional Planning 2D Two Dimensional Planning IORT Intraoperative Radiation Therapy NCT Neutron Capture Therapy PPS Particle Spot Scanning PSS Particle Passive Scattering   The BrachytherapyTreatmentPhase and Teleradiotherapy TreatmentPhase profiles are no longer in mCODE (there were moved to the new CODEX Radiation Therapy IG), so this extension is used only in the mCODE Radiotherapy Course Summary profile.