Integrating cine EPID, dynamic delivery, and the off-axis Winston-Lutz test to enhance quality control in multiple brain metastasis stereotactic radiotherapy

• Published in: Physica medica Vol. 120; p. 103343
• Main Authors: Retif, Paul, Djibo Sidikou, Abdourahamane, Waltener, Alexandre, Letellier, Romain, Al Salah, Anwar, Pfletschinger, Estelle, Taesch, Fabian, Verrecchia-Ramos, Emilie, Michel, Xavier
• Format: Journal Article
• Language: English
• Published: Italy Elsevier Ltd 01.04.2024; Elsevier
• Subjects: Brain Neoplasms; Cine EPID; Diagnostic Imaging; Humans; Medical Physics; Multiple brain metastases; Phantoms, Imaging; Physics; Quality Control; Radiosurgery; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted; Radiotherapy, Conformal; Radiotherapy, Intensity-Modulated; Winston Lutz; Winston Lutz; Multiple brain metastases; Cine EPID
• ISSN: 1120-1797; 1724-191X; 1724-191X
• DOI: 10.1016/j.ejmp.2024.103343

•We designed a new dynamic off-axis Winston Lutz (DOAWL) test.•The test is ideal for assessment of multiple target cranial stereotactic radiotherapy.•It uses cine portal images acquired during arcs delivery.•It offers a wide view of the overall dose delivery process for complex SRT treatments. Stereotactic radiotherapy (SRT) has transformed cancer treatment, especially for brain metastases. Ensuring accurate SRT delivery is crucial, with the Winston-Lutz test being an important quality control tool. Off-axis Winston-Lutz (OAWL) tests are designed for accuracy assessment, but most are limited to fixed angles and hampered by local-field shifts caused by suboptimal Multi-Leaf Collimator (MLC) positioning. This study introduces a new OAWL approach for quality control in multi-brain-metastasis SRT. Utilizing cine Electronic Portal Imaging Device (EPID) images, it can be used with dynamic conformal arc (DCA) therapy. However, dynamic OAWL (DOAWL) is prone to more local-field shifts due to dynamic MLC movements. A two-step DOAWL is proposed: step 1 calculates local-field shifts using dynamic MLC movements in the beam-eye view data from the Treatment Planning System (TPS), while step 2 processes cine EPID images with an OAWL algorithm to isolate true deviations. Validation involved an anthropomorphic head phantom with metallic ball-bearings, Varian TrueBeam STx accelerator delivering six coplanar/non-coplanar DCA beams, cine EPID, and ImageJ's OAWL analysis algorithm. Inherent local-field shifts ranged from 0.11 to 0.49 mm; corrected mean/max EPID-measured displacement was 0.34/1.03 mm. Few points exceeded 0.75/1.0-mm thresholds. This two-step DOAWL test merges cine-EPID acquisitions, DCA, OAWL, and advanced analysis and offers effective quality control for multi-brain-metastasis SRT. Its routine implementation may also improve physicist knowledge of the treatment precision of their machines.