Beschreibung:
<jats:title>Abstract</jats:title><jats:sec>
<jats:title>Purpose</jats:title>
<jats:p>To investigate the feasibility of a thermo-optical surface imaging (SGRT) system combined with room-based stereoscopic X‑ray image guidance (IGRT) in a dedicated breast deep inspiration breath-hold (DIBH) irradiation workflow. In this context, benchmarking of portal imaging (EPID) and cone-beam CT (CBCT) against stereoscopic X‑rays was performed.</jats:p>
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<jats:title>Methods</jats:title>
<jats:p>SGRT + IGRT data of 30 left-sided DIBH breast patients (1 patient with bilateral cancer) treated in 351 fractions using thermo-optical surface imaging and X-ray IGRT were retrospectively analysed. Patients were prepositioned based on a free-breathing surface reference derived from a CT scan. Once the DIBH was reached using visual feedback, two stereoscopic X‑ray images were acquired and registered to the digitally reconstructed radiographs derived from the DIBH CT. Based on this registration, a couch correction was performed. Positioning and monitoring by surface and X-ray imaging were verified by protocol-based EPID or CBCT imaging at selected fractions and the calculation of residual geometric deviations.</jats:p>
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<jats:title>Results</jats:title>
<jats:p>The median X‑ray-derived couch correction vector was 4.9 (interquartile range [IQR] 3.3–7.1) mm long. Verification imaging was performed for 134 fractions (216 RT field verifications) with EPID and for 37 fractions with CBCT, respectively. The median 2D/3D deviation vector length over all verification images was 2.5 (IQR 1.6–3.9) mm/3.4 (IQR 2.2–4.8) mm for EPID/CBCT, both being well within the planning target volume (PTV) margins (7 mm). A moderate correlation (0.49–0.65) was observed between the surface signal and X-ray position in DIBH.</jats:p>
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<jats:title>Conclusion</jats:title>
<jats:p>DIBH treatments using thermo-optical SGRT and X-ray IGRT were feasible for breast cancer patients. Stereoscopic X‑ray positioning was successfully verified by standard IGRT techniques.</jats:p>
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