1. CT-to-TPS-to-verification
summary of simulation process
Vibha Chaswal, Ph.D.

2. Know the co-ordinate system TPS
uses
Patient co-ordinate system (not
used in Pinnacle)
CT co-ordinate system

4. 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

5. 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)

6. 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

8. • 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

9. Thank You!

10. Thank You!