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

Editor: Kevin Albuquerque & Nick Linton

Date: N/A (Wiki keeps history)

Version: N/A (Wiki keeps history)

Domain: Radiation Oncology

2. The Problem

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

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

In general, we need a method to add brachytherapy dose distributions to those from external beam (traditional / 3D conformal and IMRT).

Following are 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 fraction for HDR, 2 fractions for PDRs) can be displayed on the CTs/MRs acquired for the IMRT boost so the IMRT planning is done in an efficient manner. Currently, this is done in a manual fashion. This is a connectivity issue between brachytherapy treatment planning systems and external beam TPS from different vendors. 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 isodose distribution of the external radiation therapy treatments and brachytherapy and integrate this information with the current new and planned brachytherapy for salvage of recurrence so that one can meaningfully administer dose to the remaining tumor without causing severe toxicity.

Another problem with brachytherapy planning systems is the ability to add the doses from previous(multiple) brachytherapy fractions. Currently there is no other ability to create a composite dose from previous High Dose Rate brachytherapy fractions and one simply does mathematical addition of these doses. This 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 (3): Change of shape of 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.

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 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 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, 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 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 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 modalities that CT remains that for dose calculation purposes) are available for import into the treatment planning system.

Alternate paths: (Included with Or/)

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

Business Rules: Assumes that the Use Case for ‘Dose Compositing’ has been implemented.

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).

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) may have increasing demand.

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

Second use case scenario for Brachytherapy.

Basic course of events:

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

Planning Process: 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).

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

4. Standards & Systems

Treatment Planning Systems, Oncology Information Systems, DICOM RT Archive

DICOM (RT), HIPAA, IEC 62083, ICRU (various)

5. Discussion

Details from orginal proposal.

Retrieves (planned or delivered?) dose distribution, CT image, RTSS, and Prescription (out of band). Residual Dose Optimization (“Dosimetric planner with prior dose”)

• Base dose input
• Single, multiple FOR; registration
• Display composite, new dose (radiobiological issues)
• Need RTSS, (RT Plan) for existing dose
• Merging vs. augmenting structure sets
• Maintain three dose matrices: existing, new, composite

Why IHE would be a good venue to solve the problem and what you think IHE should do to solve it:

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

Evern 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.

This issue will be even more common when cone beam CT can be used for dose calculation and dose accumuation.

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

What might the IHE technical approach be? Existing Actors? New Transactions? Additional Profiles?:

A profile with multi- vendor treatment planning seems appropriate.

What are some of the risks or open issues to be addressed?

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.

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.

Future: A treatment planning system 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.

<This is the brief proposal. Try to keep it to 1 or at most 2 pages>