Thanks for your detailed suggestion. We appreciate your advice/request to leverage the existing fields within the procedure and serviceRequest resources for their intended usage. We will change the profiles to use only standard elements to reference the Device from the ServiceRequests and Procedure. Concerning the modalityAndTechnique. We prefer to leave the collection of information in the modalityAndTechnique extension together as a top-level extension, since we are building on mCODE, and because we think it is clearer. These are properties of the procedure/servicerequest, not properties of the device. We propose to pull the devices out of that extension and include them as follows: Within ServiceRequests (RadiotherapyCoursePrescription, RadiotherapyPlanPrescription, RadiotherapyPhasePrescription, RadiotherapyPlannedCourse, RadiotherapyPlannedPhase, RadiotherapyTreatmentPlan), we will slice the ServiceRequest.performer field by profile (open slicing), and include a slice – that references a RadiotherapySeedDevice or a RadiotherapyTreatmentDevice. Within Procedures (RadiotherapyCourseSummary, RadiotherapyTreatedPhase, RadiotherapyTreatedPlan) we propose to slice by profile with open slicing: usedReference ( description : Items used during procedure) to include a slice for TreatmentDevice. (which is not implanted, and is used in the procedure) focalDevice.manipulated ( description : Manipulated, implanted, or removed device / Device that was changed ) to include a slice for SeedDevice (which is implanted) Procedure.performer.actor  ( description : The people who performed the procedure / The reference to the practitioner.) seems inappropriate for both TreatmentDevices and SeedDevices.