Room: Exhibit Hall
Purpose: On-board cone-beam CT (CBCT) has been developed on proton therapy for patient setup. It is desirable to utilize CBCT for daily dose calculation in adaptive proton therapy. Many image correction methods are being developed for CBCT for better image quality in contouring and patient setup, while its necessity in dose calculation is unknown, especially in brain CBCT images with similar image quality as planning CT. In this study, we evaluate the dose calculation accuracy on CBCT for proton therapy for brain cancer patients.
Methods: We retrospectively investigated a total of 10 treatment plans from 10 patients, each of whom has CT for original treatment planning and CBCT during treatment setup. The CBCT were firstly corrected using our learning-based method. The corrected CBCT (CCBCT) and original CBCT (OCBCT) were registered to planning CT for generating CCBCT-based and OCBCT-based treatment plans. The original planning CT-based plans served as ground truth. Clinically-relevant dose volume histogram (DVH) metrics were extracted from ground truth, OCBCT-based and CCBCT-based plans for comparison and evaluation. Gamma analysis was performed for the comparison of absorbed dose distributions between the CT-based and OCBCT/CCBCT-based plans of each patient.
Results: Mean absolute dose differences for all DVH metrics on planning target volumes (PTVs) between OCBCT/CCBCT-based and CT-based plans are 0.69%/0.73%, respectively. For both OCBCT and CCBCT, there is no significant dose difference from planning CT in all DVH metrics of PTV (pâ€‰<â€‰0.05). The average pass rates of gamma analysis for both OCBCT and CCBCT are over 99%.
Conclusion: The quantitative results indicate that the CBCT could provide comparable dose accuracy to the planning CT for brain proton treatment planning, which demonstrates on-board CBCT has great potential in CBCT-guided adaptive proton therapy. Additional image correction could help organs-at-risk delineation but not necessary for dose calculation on brain cancer patients.
Not Applicable / None Entered.