Localization Point → Isocenter Shift Calculator (DICOM LPS, Python Script)

Easily calculate localization-to-isocenter shifts directly from DICOM RT files.

This Python script reads:

• RT Plan: Extracts isocenter coordinates from beam control points.
• RT Structure: Finds POINT ROIs (e.g., "Localization" or "CT Lasers").

Outputs include:

• Patient position (e.g., HFS, HFP) from PatientSetupSequence
• Isocenter coordinates (shared or per beam)
• Localization point coordinates
• LPS vector (dx, dy, dz) from localization to isocenter — in mm, rounded to 0.1 mm
• Equivalent patient move directions for immediate interpretation (no sign confusion)

Why LPS?

• Patient-fixed coordinate system (+X=Left, +Y=Posterior, +Z=Superior)
• Works for supine, prone, or any orientation without extra transformations
• No couch coordinate conversions needed

Perfect for:

• Treatment planning QA
• Pre-treatment localization verification
• Medical physicists and dosimetrists