IHERO UseCase Prescription Automatation

1. Proposed Workitem: Comprehensive/universal radiotherapy treatment prescription format

• Proposal Editor: Sha Chang
• Editor: Sha Chang, May Wahab
• Date: N/A (Wiki keeps history)
• Version: N/A (Wiki keeps history)
• Domain: Radiation Oncology

2. The Problem

The problem: Current radiotherapy software systems do not have a consistent and comprehensive approach to record the treatment prescription, which describes the treatment intended by the patient’s physician. A comprehensive recording of the treatment prescription that is transferable and understandable by different RT software has become increasingly important today as the radiotherapy treatment technology as well as treatment objective becomes more complex and the need to consider previous treatments for today’s patient care increases.

The solution: To create a unified radiotherapy treatment prescription format that can be used by all RT systems (treatment planning systems and record & verify systems) to systematically record and interface treatment prescriptions of different complexity levels. For instance, it should work for the simplest form of treatment prescription – 6MV AP and PA fields, 200 cGy x 20 daily - and for complex treatment prescriptions that are anatomical structure specific and dose-optimized.

What are needed:

1. define the content of the comprehensive treatment prescription
2. define the format of the prescription.
   

Content: A comprehensive RT treatment prescription should contain all the information the physician would need in order to reconstruct the same treatment planning again). Suggested items in the comprehensive treatment prescription include: external/brachytherapy, total and fractional dose, fractionation scheme, treatment sites, treatment target volume names, margins to be used (in case of 3DCRT), dose constraints for organs at risk/normal tissue, beam energy, dose optimization and IMRT or not, gated treatment or not, immobilization to be used, image set(s) used for treatment planning, type of image-guided patient setup/treatment delivery (daily cone beam CT, radiographic, fluoro, ultrasound, etc.). Many of the above items can be extracted from the treatment planning system.

3. Key Use Case

1. Physician diagnoses the patient based on all information received from referring physician, imaging data, lab results, etc. He prescribes the treatment dose, OAR dose constraints, etc. (see the list of attributes above). The comprehensive prescription will be stored as part of the electronic medical record, and will be available electronically for dosimetry team to plan on. The original prescription will be also available for the rest of the care team, and will be used as a baseline for any changes, which will be done during the treatment course.
2. Patient comes in with prostate cancer having received external beam radiation using IMRT at another facility and is here for a brachytherapy boost. We need to integrate previous external beam plans with the brachytherapy plan and streamline the prescription as well. There should be a area in the prescription to reflect the previous dose. This also applies to head & neck re-treatment prescriptions, so the dose to the cord can be assessed in the current plan as well as cumulatively.

4. Standards & Systems

All treatment planning systems and record & verify systems will be involved in the problem and hopefully in the solution as well.
DICOM RT

5. Discussion

What can currently be found in DICOM
The DICOM Standard currently has a Prescription Module with specific elements that are used to convey some of the Dosimetric Intent. An attempt to summarize some of these are listed below, but for full information, it is the RT Prescription Module, Sec C.8.8.10 in DICOM PS3.3 - 2007:
Similarly, there is an RT Patient Setup Module (relating to imaging and patient setup). This can be found in in the RT Patient Setup Module, Sec 8.8.12 in DICOM PS3.3 - 2007

Relating to Dosimetric Intent
Dose Reference Structure Type (Point, ROI, Volume, Coordinates, Site)
Referenced ROI Number (if an ROI or a Volume is being prescribed to, this identifies which ROI or Volume)
Dose Reference Point Coordinates (if it is coordinates being prescribed to, e.g. if the Physician reviewed the CT and picked a pixel on the screen as the point to prescribe to).
Nominal Prior Dose (to this particular "thing" that is being referenced)
Dose Reference Type (Target, Organ at Risk)
Constraint Weight
Delivery Warning Dose
Delivery Maximum Dose
Target Minimum Dose
Target Prescription Dose
Target Maximum Dose
Target Underdose Volume Fraction (Percent allowed to be underdosed)
Organ at Risk Full-volume Dose
Organ at Risk Limit Dose
Organ at Risk Maximum Dose
Organ at Risk Overdose Volume Fraction (Percent allowed to be overdosed)

Some of what can be found in a particular commercial system
The following are abstracted from a particular commercial system, and are only intended as an aid in enumerating the particular "elements". These have some overlap with the DICOM RT Prescription mentioned above.

Site (Anatomic Name, Structure Name?)
Radiation Type (Photons, Protons, Electrons)
Technique (AP/PA, Four Field Box)
Modality (MV Photons with Energy, Ortho, Electrons with Energy)

Dose Specification Location (90%iso, D-Max, Depthdose, Isocenter, Isodose, Mid-plane, Plan, Point, Tumor)
Dose Specification Value (100, 90, 1)
Dose Specification Units/dimensionality (Percentage, centimeters)

Total Dose (in units of Gray or Cobalt Gray Equivalent)
Number of Fractions
Dose Per Fraction
(note that Total Dose = Dose Per Fraction * Number of Fractions, so there is redundant information)
Dose Semantics (Physical Dose vs. Biologically Equivalent Dose)

Fractionation Pattern (Start, End (# of times), Times Per Day, Daily, Weekly, Bi-Weekly,Every (n) Days, inclusion of Saturday,and/or Sunday, and/or Holidays

Dose Limits (Total Cumulative) in units of Gray, e.g. When additional radiation may accumulate from a separately irradiated Site.

Pattern?
Comment

Status [change] (Pending, Approved, On Hold, Closed, Completed, Exclusive, Voided)
Status [change] Date/Time
Status changer (a person's name, username, initials...whatever identifies the person who made/authorized the change in status)

Relating to Patient Setup

The RT Patient Setup module refers to Patient Position
Setup Images
Fixation Devices
Shielding Devices

Setup Technique where the Setup Device Type may be one of the following:
LASER_POINTER
DISTANCE_METER
TABLE_HEIGHT
MECHANICAL_PTR
ARC

Motion Synchronization and Respiratory Motion Compensation (Gating)
NONE
BREATH_HOLD
REALTIME = image acquisition shorter than respiratory cycle
GATING = Prospective gating
TRACKING = prospective through- plane or in-plane motion tracking
PHASE_ORDERING = prospective phase ordering
PHASE_RESCANNING = prospective techniques, such as real-time averaging, diminishing variance and motion adaptive gating
RETROSPECTIVE = retrospective gating
CORRECTION = retrospective image correction

Comments on what might also be needed
For a number of the kinds of information mentioned above, it will also be of considerable value to know if there are particular defined values that should be used, e.g. if in attempting to describe a target, one would want to use defined names such as PTV, CTV, GTV. Many of these do have definitions in the DICOM standard, and not all were enumerated completely in the above... In some cases the level of detail above is not critical to the description of the use case, but I hope that this detail will be helpful in guiding the editors/authors of the use case.