Purpose: Accurate dose delivery in deep-inspiration breath-hold (DIBH) radiotherapy for patients with breast cancer
relies on precise treatment setup and monitoring of the depth of the breath hold. This study entailed performance
evaluation of a 3D surface imaging system for image guidance in DIBH radiotherapy by comparison with cone-beam
computed tomography (CBCT).
Materials and Methods: Fifteen patients, treated with DIBH radiotherapy after breast-conserving surgery, were included.
The performance of surface imaging was compared to the use of CBCT for setup verification. Retrospectively, breast
surface registrations were performed for CBCT to planning CT as well as for a 3D surface, captured concurrently with
CBCT, to planning CT. The resulting setup errors were compared with linear regression analysis. For the differences
between setup errors, group mean, systematic and random errors were calculated. Furthermore, a residual error after
registration (RRE) was assessed for both systems by investigating the root-mean-square distance between the planning
CT surface and registered CBCT/captured surface.
Results: Good correlation between setup errors was found: R2=0.82, 0.86, 0.82 in left-right, cranio-caudal and anteriorposterior
direction, respectively. Systematic and random errors were ≤0.16cm and ≤0.13cm in all directions,
respectively. RRE values for surface imaging and CBCT were on average 0.18 versus 0.19cm with a standard deviation
of 0.10 and 0.09cm, respectively. Wilcoxon-signed-ranks testing showed that CBCT registrations resulted in higher RRE
values than surface imaging registrations (p=0.003).
Conclusion: This performance evaluation study shows very promising results