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

I would like to put a different view of the world.
The Use Case of the Radiotherapy Prescription
In the world of image-based & dosimetric planning, many of the parameters that were previously described & decided BEFORE planning (field size, field orientation) are now defined as a result of the planning. "The plan" is now just one of many operationally defined and acceptable solutions where the field sizes/orientation/intensity map/etc are set long after the intended prescription is set. In fact the only reason the prescription MAY change is because dose constraints can't be met.

In accordance with this dosimetric planning paradigm, the prescription is a simple statement [e,g, "Prostate", IMRT, 6MV X, 78Gy in 38Fx, ICRU reference point] which can be easily assessed according to the modern paradigm of ICRU50/62.

The Use Case of the Descriptors and Instructions associated with a Radiotherapy Plan
In the realms of plan construction & treatment delivery, there are a large number of specifications and instructions. I would pose the debate point that these can be considered to be NOT part of the prescription but more relevant to routine departmental protocol. Thus they need to be delineated but are not a requirement of the prescription. Some will be specified by RO, some by dosimetrist and some by sim RT. Instructions such as "empty rectum", "alpha cradle", "image fiducials" are not prescription per se.

The issue of how to get ROs to specify issues relating to GTV, CTV and PTV are very very vexatious. One ASTRO voluming course will quickly demonstrate that its a jungle out there when it comes to voluming. Certainly some standardised nomenclature could be easily introduced by manufacturers purely by inserting a base list [Use Case for standardised nomenclature BELOW], and altering some of the characteristics of drawn lines [e.g., not permit normal tissue contours to overlap as in Eclipse, not permit a PTV to be drawn, not permit a PTV to be altered, permit auto-expansion of PTV according to departmental defined protocols]

Sideline - Use Case for standardised nomenclature.
GTV relates abnormal image of either primary, nodes or metastases, thus GTVp, GTVn, & GTVm CTV relates to either the areas immediately around the GTV where there is soft tissue involvement, thus CTVp, CTVn, & CTVm (1:1 transformation from GTV>CTV); or the nodal areas that look normal but are at risk of involvement, thus CTVn0. PTV is a geometric dose envelope that relates to a covering isodose related to a prescription dose, thus PTV60, PTV70, ....

The Use Case of Fractionation
I have not worked out my thoughts completely on this yet. IGBTYL!

The Use Case of sequential plans (EBRT + brachytherapy boost)
The fundamental issue in this Use Case is the images on which the dose grid lies and whether they are capable of fusion, and if not can images/dose be distorted. The issue is whether these sequential plans should be stored separately (2 files, 2 plans), coalesced (1 file, 1 plan) or linked (1 file, 2 plans; maybe even 1 file, 1 integral dose plan, 2+ individual plans).

What will the future hold? A whole body CT scan with the first sim and then fusion of all subsequent plans? If there is the ability to morph CT images + dose, then dose deposition can be tracked from child to adult and between dissimilar techniques.