Study on the application of thermo-optical surface monitoring + X-ray guidance system in DIBH for breast cancer.

OBJECTIVE

To evaluate the clinical value of thermo-optical surface monitoring + X-ray guidance system(ExacTrac Dynamic, ETD) in assessing inter-fraction setup accuracy and intra-fraction motion monitoring during deep inspiration breath-hold (DIBH) radiotherapy after breast-conserving surgery for breast cancer.

METHODS

Clinical data were collected from 31 female patients with breast cancer who had undergone breast-conserving surgery. Cone-beam computed tomography (CBCT) was used to verify inter-fraction setup during the first three treatment fractions, as well as the 6th, 9th, 12th, and 15th fractions. Triple thermo-optical surface tracking, intra-fraction CBCT, and X-ray imaging were employed to monitor intra-fraction motion. Setup errors and treatment duration were recorded. Linear mixed-effects models were applied to analyze inter-fraction setup errors derived from CBCT and intra-fraction errors measured by X-ray.

RESULTS

After X-ray correction, mean setup errors in all dimensions were not significantly different from zero (P>0.05) and were independent of breast volume. Treatment duration had no significant impact on intra-fraction deviations. Surface monitoring detected mid-treatment drift, which was corrected by X-ray guidance, keeping all values within clinical tolerance. The radiation dose from X-ray planar imaging was substantially lower than from CBCT. Calculated planning target volume (PTV) margins (van Herk formula) were 5.10 mm (lateral), 5.22 mm (longitudinal), and 5.78 mm (vertical).

CONCLUSION

ETD provides setup accuracy comparable to CBCT with lower radiation dose, making it appropriate for inter-fraction verification. It allows stable real-time intra-fraction monitoring and can enhance treatment precision with mid-treatment X-ray correction.