Orthovoltage RT

Development of a treatment planning system for orthovoltage RT

Participants (alphabetical):

ctcreate is used to create the “phantom” input for DOSXYZnrc, and is called with two input files

Input 1: File list text file that simply lists the CT slice files
- Ingrid has a Matlab script that creates this file, which may help (CCSEO - done)
- Sample file list file will be needed to verify that the automatical generation is correct (CCSEO - done)
- External Beam Planning (EBP) Orthovoltage plugin will generate the text file from the DICOM file list of the CT loaded into Slicer (PerkLab - done)
Input 2: RED curve (could be changed later if needed, but default will be fine for now) (CCSEO - done)
Anonymized pelvis phantom CT scan will be sent to the PerkLab (CCSEO - done)
ctcreate will be called from Slicer from Python environment with the two files (PerkLab - done)
- Need the ctcreate executable to be packaged with or downloaded by SlicerRT (see ScreenCapture module for example) (PerkLab)
- Sample output “phantom” file will be needed to verify that the conversion within Slicer is correct (CCSEO - done)
- There is a limit on the number of voxels (~512x512x28)
  - Can change limit in ctcreate, but need to change in DOSXYZnrc too (DOSXYZnrc_user_macros)
  - Cropping will be needed for faster execution
    - Automated cropping (margin around the PTV and OARs, plus the region superficial from that area) (PerkLab)
    - Good margin to determine (need to verify that calculation is the same as for the whole volume) (PerkLab)

(Contains phantom file path, beam geometry, and various dose engine parameters)

Expose dose engine parameters in the EBP Orthovoltage plugin
- List of those parameters and their default values are needed: check papers using EGSnrc for orthovoltage to see what they use (CCSEO)
- Add parameters on the beam settings UI (PerkLab) (see screenshot)
- Simple plan will be created with one or two beams (AP+LR) in Eclipse and saved along the CT and the structures (CCSEO)
- Ascertain that input beam geometry and phantom geometry relationship is as expected. (CCSEO)
Sample input file to DOSXYZnrc is needed for this plan to verify that automated generation of this in Slicer is correct (CCSEO)
- Input file automatically generated in Slicer using the phantom file, the RT plan and its beams, and the selected engine parameters (PerkLab)
Beam geometry is specified in the regular IEC (linac) coordinate system (this work will be done using an MV plan following IEC)
- This plan will be delivered manually using the orthovoltage machine
Call DOSXYZnrc from Slicer - need to discuss ways of doing this, and how SlicerRT will access DOSXYZnrc (PerkLab/CCSEO)

Implement file reader in SlicerRT (PerkLab - done)
Export dose as DICOM-RT (PerkLab - done)
Will need sample dose calculated with the manual workflow to verify that the Slicer workflow is correct (CCSEO)
- Exact match will be expected, because MC is deterministic if the same seed is used

Model orthovoltage unit in BEAMnrc and validation (CCSEO)
Simulate phase space at a certain plane for each applicator cone used (CCSEO)
- Option: create phase space for the largest field and truncate as needed
- Option: use smaller pencil beams and assemble the particular field
Ask Adrian, the head of the company about modeling of the head (John)
Ask Tommy Knoos about orthovoltage spectrum (John)

Clinics need to go through the same hurdles, because they do not have a well established workflow (similar problem that the GelDosimetry slicelet solves)

(will be useful for Anna’s report and conference paper)

Current clinical workflow for orthovoltage and electron:
- Pen marks around GTV (will not need this with surface scanning)
- Patient immobilization mask on head, CTV or PTV cut out.
- Wires (manufactured by Beekley) around cutout for contouring on CT (will not need this with surface scanning)
  - Wires create artifact in CT that skews dose calculation, so need to be exluded from the CT (will not need this with surface scanning)
  - Anonymized screen capture from CCSEO with a patient with the wires (CCSEO) – will be useful for understanding and the papers
- Electron only: bolus on top of mask and wires
Lead shielding with a cutout of the shape of the lesion is added on the applicator
- Could be designed automatically in Slicer based on PTV and beam geometry (PerkLab)