Room: Exhibit Hall
Purpose: This study was undertaken to compare and evaluate the positioning reproducibility of shoulder position for head and neck patients with and without shoulder depressors.
Methods: 10 patientsâ€™ positions without the shoulder suppressor (ORFIT, Be) and with the shoulder suppressors (Qfix, PA, USA) positioning device were evaluated. CT on rails (CToR) was used twice a week as image guidance for these patients amounting to approximately 200 CT scan evaluations. The shoulder position was evaluated once fusion was done to align the PTVs. The humeral head position in the superior/inferior (SI) and anterior/posterior (A/P) direction of the CToR were compared to the treatment planning scan.
Results: The maximum deviation in the SI direction for both shoulders without and with the shoulder suppressor was 1.6 cm and 1.1 respectively. The maximum deviation in the AP direction for both shoulders without and with the shoulder suppressor was 1.8 cm and 1.1 cm respectively. The standard deviation without the shoulder depressor in the SI and AP direction was 0.3 mm larger than with the shoulder depressor, suggesting slightly better reproducibility in patient set up.
Conclusion: Our data indicate that the use of the shoulder depressor seems to be able to both replicate and repeatedly reproduce treatment planning position better. However, even with the shoulder depressor , we did not achieve reproducibily of less than 0.5 cm. Futher studies will be carried out to evaluate the dosimetric implication in patient set up variability.