IHERO UseCase brachy

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1. Proposed Workitem: Brachytherapy

• Proposal Editor: Firas Mourtada
• Editor: Kevin Albuquerque
• Date: N/A (Wiki keeps history)
• Version: N/A (Wiki keeps history)
• Domain: Radiation Oncology

2. The Problem

In general, we need a method to add brachytherapy dose distributions to those from external beam (traditional and IMRT). Following are 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 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 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

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A patient is referred to a specialized center to receive ICBT for cervical cancer. The patient has already received external beam radiation therapy (using Xio-CMS) 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 external beam therapy. The addition of the brachytherapy dose and the external beam therapy 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). 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.

4. Standards & Systems

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5. Discussion

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