Treatment Delivery and Setup
Treatment Delivery and Setup examines the execution end of the workflow: reproducing the simulated setup, verifying it with imaging, delivering the approved plan, and managing everything that goes wrong while the patient is on the couch.
Before beam on
- Two patient identifiers plus a formal time-out covering name, site, laterality, fraction number, and any devices.
- Setup follows the simulation record exactly: indexed immobilization in the recorded slot, tattoos aligned to isocenter lasers, bolus in place and marked, extremities in the documented position.
- The record-and-verify system must hold the signed, current plan revision; a mismatch between plan and prescription is a stop-work condition.
Image guidance and action levels
- Orthogonal kV or MV pairs for bony or fiducial matching; CBCT for soft-tissue targets such as prostate, head and neck, and SBRT.
- Apply shifts in the convention your system uses, and re-image when the residual exceeds the site action level (commonly 3 mm for prostate and head and neck, 1-2 mm for intracranial SRS).
- Six-degree-of-freedom couches correct roll, pitch, and yaw; confirm with a repeat scan after a large rotational correction.
Motion and special procedures
- For DIBH or gating, verify the surrogate (spirometry, surface imaging, fiducial) sits inside the window at beam-on and stays there.
- For SBRT, check collision before each arc and image again to check intrafraction drift.
- If delivery is interrupted, record the delivered MU and resume per protocol; never restart the fraction from zero without physics direction.
Worked example
A prostate CBCT shows the patient 4 mm anterior, 2 mm left, and 3 mm superior of reference. The site action level is 3 mm, so the shift is applied rather than dismissed. The therapist enters the translation so the couch moves the patient 4 mm anterior, 2 mm left, 3 mm superior; in systems that accept patient displacement values, the entered numbers already carry the correct sign. A confirm CBCT shows residual within 2 mm and the fraction proceeds.
Traps
- Reversing the left/right or anterior/posterior sign convention of the couch.
- Skipping the confirm scan after a large rotational correction.
- Treating a plan whose revision date postdates its approval signature.
- Altering bolus, arm position, or immobilization index without documenting the change.