Radiotherapy Treatment Simulation

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Radiotherapy Treatment Simulation

  1. 1. CT-to-TPS-to-verification summary of simulation process Vibha Chaswal, Ph.D.
  2. 2. Know the co-ordinate system TPS uses Patient co-ordinate system (not used in Pinnacle) CT co-ordinate system
  3. 3. Image data on acquisition on CT • Image request form: Patient positioned using lap lasers (ct bb’s on lap lasers) • Immobilization devices marked • Orientation and technique (protocol) selected in CT • Topogram acquisition • CT scan acquisition • Dicom images send to TPS and archive
  4. 4. TPS processes • Image data imported • Scanning information verified ( patient position, orientation) • CT bb’s are localized w.r.t. CT room lasers co-ordinate system • ROIs are contoured and isocenter is defined w.r.t machine co-ordinate system • Shifts from ct-bb’s to isocenter are given w.r.t treatment table (up/down, L/R, in/out) • Segmentation, TP (beams, blocks, dose) and DRRs generated (set-up and field) • Transfer TP to record and verify (LEX), DRRs to machine (coherence)
  5. 5. Verification processes • • • • Set patient to CT-bb’s Get shifts to isocenter from DRR’s, make shifts Check SSD Take portal image using field DRRs or Set-up DRRs (orthogonal and oblique DRRs) • Compare DRR with portal image and verify shift (orthogonal gives sup-inf and left-right info oblique gives A-P) • Mark lasers on patient if everything matches, these are treatment isocenter localization marks
  6. 6. • Bite-block – physicist verifies the physical positioning of bite-block before CT scan, radiocam localization no ct bb’s • Cone-beam – Cone beam field with CT image and segmented structures sent to machine, MVCT image compared with the help of bony land-marks and contours
  7. 7. Thank You!
  8. 8. Thank You!

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