ESTRO 2024 - Abstract Book

S5590

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2024

In the new workflow patients had a planning CT and treatment in open face mask. A treatment plan was generated with a single isocenter for all PTV’s. During treatment the head adjuster and the SGRT system were used to monitor and correct for position, including rotations. The head adjuster is an adjustable headboard which allows to manually correct the head of the patient for pitch, yaw and roll. If CBCT shows rotations out of tolerance, this will be corrected with the head adjuster and a repeat CBCT before treatment. Treatment only starts if translations and rotations are in tolerance. At the SGRT system tolerances of 1 degree rotations and 1.5 mm for translations and a 2 mm tolerance for the 3D vector were used.

Results:

Figure 1 shows the results per fraction of the absolute CBCT registration results for rotations after patient setup and couch shift for new SGRT (ten patients) and the old (seven patients) workflow. Patient setup with SGRT in combination with head adjuster showed significant smaller rotations using T-test. Patients lay stable during treatment and deviations monitored are within tolerance.

Figure 1:

Absolute CBCT registration results for rotations (Pitch, Roll and Yaw in degrees) per fraction after patient setup using SGRT and head adjuster (blue columns) versus old clinical workflow (red columns).

Conclusion:

Using open-face masks in the new workflow gives patients more comfort as is shown in other studiesi,i[i]. Rotations can be easily corrected with the head adjuster within 0.1° before CBCT is made and therefore shows less deviations in the patient group using the new workflow. Treatment time is reduced by treating multiple PTVs with a single isocenter (less CBCT scans and single patient setup for multiple PTVs). Patients can be treated within the applied tolerances, because their position is stable and deviations are small enough for different couch angles. Another benefit is patients position can be monitored during treatment and movement out of tolerance can be detected using