Accuracy of an infrared marker-based patient positioning system (ExacTrac®) for stereotactic body radiotherapy in localizing the planned isocenter using fiducial markers

• Main Authors: Montes-Rodríguez María de los Ángeles, Hernández-Bojórquez, Mariana, Martínez-Gómez, Alma Angélica, Contreras-Pérez, Agustín, Negrete-Hernández, Ingrid Mireya, Hernández-Oviedo, Jorge Omar, Mitsoura Eleni, Santiago-Concha, Bernardino Gabriel
• Format: Conference Proceeding
• Language: English
• Subjects: ACCURACY; AGAR; FIDUCIAL MARKERS; GELS; Image acquisition; Infrared analysis; Markers; MONITORING; MONITORS; PATIENTS; PHANTOMS; QUALITY ASSURANCE; RADIATION DOSES; Radiation therapy; RADIOLOGY AND NUCLEAR MEDICINE; RADIOTHERAPY; Uncertainty
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/1.4901367

Stereotactic Body Radiation Therapy (SBRT) requires a controlled immobilization and position monitoring of patient and target. The purpose of this work is to analyze the performance of the imaging system ExacTrac® (ETX) using infrared and fiducial markers. Materials and methods: In order to assure the accuracy of isocenter localization, a Quality Assurance procedure was applied using an infrared marker-based positioning system. Scans were acquired of an inhouse-agar gel and solid water phantom with infrared spheres. In the inner part of the phantom, three reference markers were delineated as reference and one pellet was place internally; which was assigned as the isocenter. The iPlan® RT Dose treatment planning system. Images were exported to the ETX console. Images were acquired with the ETX to check the correctness of the isocenter placement. Adjustments were made in 6D the reference markers were used to fuse the images. Couch shifts were registered. The procedure was repeated for verification purposes. Results: The data recorded of the verifications in translational and rotational movements showed averaged 3D spatial uncertainties of 0.31 ± 0.42 mm respectively 0.82° ± 0.46° in the phantom and the first correction of these uncertainties were of 1.51 ± 1.14 mm respectively and 1.37° ± 0.61°. Conclusions: This study shows a high accuracy and repeatability in positioning the selected isocenter. The ETX-system for verifying the treatment isocenter position has the ability to monitor the tracing position of interest, making it possible to be used for SBRT positioning within uncertainty ≤1mm.