IHERO 2007UseCase Residual Dose Optimization

IHERO 2007 Use Case Multi Modality Residual Dose Optimization

1. Proposed Workitem: Multi Modality Residual Dose Optimization inc. Brachytherapy

Proposal Editor: Firas Mourtada & Nick Linton
Profile Editor: Kevin Albuquerque & Nick Linton
Domain: Radiation Oncology

Summary It is difficult to account for previously delivered radiation dose for individual patients when planning a second (or subsequent) treatment with a different vendor radiotherapy treatment planning (RTP) system. DICOM (RT objects) in principle should contain the required information and communication protocol to transfer information between different vendor RTP systems.

A Multi Modality Residual Dose Optimization profile could require compliant RTP systems (also Oncology Information Management systems which act as a centralized data store) to support the transaction(s). The market interest as represented by the member clinics of the IHE-RO P.C. is high.

A rationale is expressed below.

> Many patients have more than a single course of Radiation Therapy.

> Even with rigid body registration (research groups and vendors are working on deformable registration) the ability to take previously delivered dose into account is a must.

> Unfortunately the TPS of the external beam therapy (Elekta/CMS XiO) and the TPS for the brachytherapy (Varian Brachyvision) are not compatible, hence the requirement for this use case.

2. The Problem

Goal: Provide a mechanism for repeated courses of radiation therapy while taking the accumulated dose(s) from previous course(s) into account.

Summary: A patient arrives for a second (or subsequent) course of radiation therapy (traditional / 3D conformal or IMRT external beam or brachytherapy or particle therapy), dose has already been delivered to the treatment volume, and a radiation oncologist desires to account for previously delivered radiation dose in the new plan created on a different treatment planning system.

Examples: Brachytherapy specific problems we find common in clinics:

Problem (1): After the course of HDR/LDR/PDR brachytherapy for GYN, nodal boost with IMRT might be needed. It would be of great help if the dose distribution from the brachytherapy fractions (4-5 fractions for HDR, 2 fractions for PDR) can be displayed on the CTs/MRs acquired for the IMRT boost so the IMRT planning is done in an efficient manner. Connectivity issues exist between brachytherapy TPS and external beam TPS, so this is currently done in a manual fashion. The nodes are far away from the GYN implant so issues with tissue deformation due to the rigid applicator might not be an issue.

Similar Problem: Addition of 3D conformal or IMRT dose distributions to critical structures from High Dose Rate or Pulsed Dose Rate brachytherapy

Problem (2): Patient has already received external beam therapy and brachytherapy at the same institution and now comes with a recurrent tumor that will require more therapy. The problem is similar in that one has to get the external radiation therapy treatment(s) isodose distribution(s) and brachytherapy and integrate this information with the newly planned brachytherapy treatment for salvage of recurrence so that one can meaningfully administer dose to the remaining tumor without causing severe toxicity.

Problem (3): Currently there is no ability in brachytherapy planning systems to add the doses from (multiple) previous High Dose Rate brachytherapy fractions; one simply does mathematical addition of these doses. The ability to create a composite dose is useful particularly from fraction to fraction as the movement of the applicators and the change in the volume of the tumor may shift the high-dose regions from the critical structures, particularly if these high-dose regions are not the same from fraction to fraction. And one can technically escalate the dose because these high-spot regions move.

Problem (4): The change of shape of the cervical tumor from the initial external beam planning and the presence of a smaller and more displaced volume during brachytherapy requires some deformable registration software to estimate how the dose to the bowel has changed over the time period between the new scan and the previous scan.

Example: Particle Therapy With the (potential) growth in Particle Therapy availability, proton treatments accounting for previously delivered dose (e.g. brain radiation therapy on linear accelerator or Leksell Gamma Knife) will have increasing demand.

Example: Adaptive Therapy Future: This issue will be even more common when cone beam CT can be used for dose calculation and dose accumulation A TPS may accumulate the dose for each fraction using the image data (such as kV or MV cone beam image studies) used for IGRT localization & patient (re)positioning.

Now describe the Value Statement: what is the underlying cost incurred by the problem, what is to be gained by solving it. If possible provide quantifiable costs, or data to demonstrate the scale of the problem.

3. Key Use Case

Actors: Patient, Radiation Oncologist, Treatment Planner (Dosimetrist or Medical Physicist).

Preconditions: Patient has completed radiation therapy course with planned dose distribution or has aborted treatment at known time and therefore delivered dose distribution can be calculated. Original therapy is any modality from photons and/or electrons, brachytherapy (LDR, HDR, or PDR), particle therapy (protons or ions; scanned or scattered beams). Electronic retrieval and transfer of 3-D dose grid from storage in treatment planning system, oncology information system, or DICOM (RT) archive is possible.

Triggers: Patient arrives at same institution for subsequent treatment. Or/ Patient transfers to alternate institution for subsequent treatment.

Basic course of events: Patient has Prescription (dose, fractionation), image studies, contouring (manual) and segmentation (manual and/or automatic); treatment planning and dose calculation for first treatment course. Treatment course is completed according to plan. (Therefore the planned dose distribution is assumed to be the best available representation of the delivered dose distribution).

or/ treatment course is interrupted or abandoned such that remaining Prescription, new image studies, new contouring and segmentation, new treatment planning and dose calculation is required.

Then/ patient requires subsequent radiation therapy and the radiation oncologist desires to account for already delivered dose, physical or radiobiological. The existing 3D dose grid (DICOM RT DOSE), anatomical structures (DICOM RT Structure Set) and Image Studies (assuming for all external beam modalities that CT is required for dose calculation purposes) are available for import into the new treatment planning system.

Alternate paths: Optionally the DICOM RT DOSE is not used, and the existing DICOM RT PLAN is imported and used as the basis for a new dose calculation (dose is recalculated with a beam model in the new TPS that is used in institution #2 and different – perhaps more accurate, dose calculation implementation). The DICOM RT Structure Set is used to recalculate and bin dose to create a new DVH. Radiobiological considerations, if the fractionation was known, displayed and renormalized as if given at the standard 2Gy / fraction regimen.

Postconditions: New treatment plan is completed and ready for delivery.

Business Rules: Assumes that the Use Case for ‘Dose Compositing’ has been implemented. Also assumes that the new TPS can display dose from both plan #1 and plan #2, as well as the composite. Optionally the imported dose may be used on a per structure basis (an IMRT optimizer should not be constrained to include the original target and organs at risk doses). As an example, the user could select to include (bias) dose for the spinal cord (serial organ) as a limit, whereas for the (tumor) target, this may not be the case (user may not wish to compensate for dose cold spots in the original plan).

Notes: In theory, all statements above for 3D image study data could be applied to 4D data (respiratory correlated image studies from CT or CT + PET).

Authors, Date: Nick Linton & Richard Popple; 8/17/2009

Second use case scenario for Brachytherapy.

Preconditions: The patient has already received External Beam Radiation Therapy (EBRT; planned with CMS XiO) and chemotherapy at another center. A patient is referred to a specialized center to receive ICBT for cervical cancer, and is now planned to have brachytherapy at the specialized center (this is a fairly common scenario given that the incidence of cervical cancer is decreasing).

Triggers: According to the radiation oncologist who administered the initial EBRT, the patient has had severe diarrhea during the course of EBRT. Images of the planning CT scan and a CD of the initial EBRT treatment plan has been sent to the specialized center prior to the HDR brachytherapy. These images have been reviewed by the brachytherapist and it appears there is extensive small bowel close to the cervix. If one plans to administer a curative dose to the cervix there is going to be tremendous amount of small bowel dose. It would be useful to estimate the brachytherapy dose to the small bowel and combine it with the dose from the EBRT. The addition of the brachytherapy dose and the EBRT dose would allow the brachytherapist to estimate the dose toxicity to the small bowel.

Basic course of events: The brachytherapist plans the ICBT using MRI guidance, hence we have to provide multi-modality registration for MR and CT based planning for the brachytherapy in addition to be able to get the isodoses from the external beam in a meaningful fashion onto the HDR brachytherapy plan (fusion or side-by-side display).

Authors, Date: Firas Mourtada & Kevin Albuquerque; 8/17/2009

4. Standards & Systems

DICOM (RT) – version ?? HIPAA – version ?? IEC 62083 – version ?? ICRU (various) – Reports 24, 42, 55, 60, ?? Level of support by system vendors is in principle high. References for obtaining detailed information, contact standards bodies. Systems affected include: Treatment Planning Systems Oncology Information Systems DICOM RT Archive

5. Technical Approach

This section can be very short but include as much detail as you like. The Technical Committee will flesh it out when doing the effort estimation. Outline how the standards could be used/refined to solve the problems in the Use Cases. The Technical Committee will be responsible for the full design and may choose to take a different approach, but a sample design is a good indication of feasibility. If a phased approach would make sense indicate some logical phases. This may be because standards are evolving, because the problem is too big to solve at once, or because there are unknowns that won’t be resolved soon.

Existing actors Actors: Patient, Radiation Oncologist, Treatment Planner (Dosimetrist or Medical Physicist).

New actors List possible new actors

Existing transactions Indicate how existing transactions might be used or might need to be extended.

New transactions (standards used) Describe possible new transactions (indicating what standards would likely be used for each. Transaction diagrams are very helpful here. Feel free to go into as much detail as seems useful.

Impact on existing integration profiles Indicate how existing profiles might need to be modified.

New integration profiles needed Indicate what new profile(s) might need to be created.

Breakdown of tasks that need to be accomplished A list of tasks would be helpful for the technical committee who will have to estimate the effort required to design, review and implement the profile.

6. Support & Resources

List groups that have expressed support for the proposal and resources that would be available to accomplish the tasks listed above.

7. Risks

List technical or political risks that could impede successfully fielding the profile.

8. Open Issues

Assumption: The plan (DICOM RT PLAN) is required as a link between dose and structure set but is not relevant to the summation – all dose information is in the 3D dose grid.

Assumption: the Prescription is not required as the treatment intent.

Assumption: for Radiobiological summation, the fractionation and time sequence for prior radiation therapy must be known.

Open issue: It must be clear to the new Treatment Planner which structures are relevant to the original Prescription (the imported Structure Set may include anatomical structures, ‘Helper’ or ‘Avoid’ structures from IMRT plans, and/or IGRT structures such as ‘masks’ or ‘clip regions’). The new Treatment Planning System must be able to import the prior data, register the prior image study (at least, that which is associated with the 3D dose grid) to new data, combine (merge) or augment the structures, account for the delivered dose in the new plan/optimization, create and maintain the single dose matrices and the summed (by physical or radiobiological weighting) doses, display single and composite 3D dose grids.

Assumption: the new TPS must be able to perform rigid body image registration (i.e. there is not a requirement for deformable registration in this Use Case).

Assumption: that the new treatment plan requires some form of automatic optimization (depending upon delivery modality, inverse planning for photon IMRT, could also be for brachytherapy or proton therapy) as accounting for delivered dose by manual re-planning is complicated and unlikely.

Point out any key issues or design problems. This will be helpful for estimating the amount of work and demonstrates thought has already gone into the candidate profile. If there are no Open Issues at Evaluation Time, it is usually a sign that the proposal analysis and discussion has been incomplete.

9. Technical Committee Evaluation

The technical committee will use this area to record details of the effort estimation, etc.

Effort Evaluation (as a % of Technical Committee Bandwidth): 35% for ...

Responses to Issues: See italics in Risk and Open Issue sections

Candidate Editor: TBA