Purpose: For breast radiation therapy treatments, the standard of care is traditionally to mark the patient with small tattoos which are used for alignment each day, though in over 1,700 oncology centers worldwide, optical surface guidance (SG) systems are used for patient positioning prior to receiving radiation. In this study, Cherenkov imaging metrics were analyzed in a clinic that utilizes SGRT for pre-treatment patient alignment (site 1) and compared to the metrics from a clinic that practices conventional tattoo/alignment (site 2). This was done to determine whether setup techniques were more consistent using one technique over the other.
Methods: Free-breathing breast treatments were recorded with Cherenkov imaging each day for n = 15 patients, (fx = 134 fractions) at site 1, and for n = 5 patients, (fx = 54 fractions) at site 2. A two-tailed t-test of unequal variance was carried out to determine significance for comparison of DICE analytics (% similarity) and MDC (Mean Distance to Conformity).
Results: MDC and DICE t-test results reveal that the null hypothesis could not be rejected, indicating that the setup techniques yield no significant difference (DICE, p = 0.432; MDC, p = 0.094). The p-value describing MDC comparison was smaller, however, possibly indicating that this may be the analytical metric more sensitive to changes in beam shape.
Conclusion: While SGRT may be a less invasive technique via the negation of tattoos and possibly a faster setup technique, ultimately, the Cherenkov data acquired in our two clinics showed no significant difference between the surface-guidance setup technique and the conventional skin marks/laser technique. In the two clinics studied, the quality or accuracy of patient setup was not compromised by using one setup technique over the other. Cherenkov imaging for clinical real-time monitoring was shown to provide a useful tool for this analysis.
Funding Support, Disclosures, and Conflict of Interest: Authors Prof. Brian Pogue, Prof. M Jermyn, Prof. P. Bruza, and Dr. Lesley Jarvis M.D. have competing interests with DoseOptics LLC, a company that manufactures Cherenkov cameras used to monitor radiation therapy.
Patient Positioning, Optical Imaging, Setup Errors
TH- RT Interfraction Motion Management: setup errors, immobilization, localization