Variable angle stereo imaging for rapid patient position correction in an in-house real-time position monitoring system

Purpose: To develop and validate a variable angle stereo image based position correction methodology in an X-ray based in-house online position monitoring system. Materials and methods: A stereo imaging module that enables 3D position determination and couch correction of the patient based on images acquired at any arbitrary angle and arbitrary angular separation was developed and incorporated to the in-house SeedTracker real-time position monitoring system. The accuracy of the developed system was studied by imaging an anthropomorphic phantom implanted with radiopaque markers set to known offset positions from its reference position in an Elekta linear accelerator (LA) and associated XVI imaging system. The accuracy of the system was further validated using CBCT data set from 10 prostate SBRT patients. The time gains achieved with the stereo image based position correction was compared with the manual matching of seed positions in Digitally Reconstructed Radiographs (DRRs) and kV images in the Mosaiq record and verify system. Results: Based on phantom and patient CBCT dataset study stereo imaging module implemented in the SeedTracker shown to have an accuracy of 0.1(sigma = 0.5) mm in detecting the 3D position offset. The time comparison study showed that stereo image based methodology implemented in SeedTracker was a minimum of 80(4) s faster than the manual method implemented in Mosaiq R&V system with a maximum time saving of 146(6) s. Conclusion: The variable angle stereo image based position correction method was shown to be accurate and faster than the standard manual DRR-kV image based correction approach, leading to more efficient treatment. (C) 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.