Author: Jonathan Dowell, Grace Francis, Wei Luo, Shane McCarthy, Janelle A. Molloy, Markus Murphy 👨🔬
Affiliation: University of Kentucky, Department of Radiation Medicine, University of Kentucky, Iridesce Solutions, Inc. 🌍
Purpose: A novel radiation therapy quality assurance (RT QA) device has been designed, constructed and tested. The nüFilmTM machine QA system provides a method for collecting light, mechanical and radiation data, along with automated data processing routines. In so doing, it yields RT QA measurements that are more efficient, precise and objective than existing methods.
Methods: A semi-transparent radiosensitive screen is supported above a novel optical system that collects light and radiation data in a compact form factor. Image processing routines are integrated with task-specific software utilities to yield precise, objective machine performance metrics.
Results:
The light field walk out utility measures mechanical axes to within 0.1mm. An “Isocenter Manager” records the locations of 5 rotational axes (collimator, gantry, couch, plus pitch and roll for 6DOF couches) so that coincidence can be documented to within 0.1 mm. A radiation star shot analyzer has similar functionality, allowing all 5 radiation isocenters to be compared. These utilities can be used in real time while collecting beam data, or offline. Couch pitch and roll can be measured using the star analyzer, which reports the angles of individual spokes.
Light/radiation coincidence is measured by quantitative comparison of automatically-identified field edges. This measurement is objective, repeatable and precise to within 0.1 mm. Flatness and symmetry constancy are monitored by reporting the average intensities within user-defined, symmetric regions of interest. The user interface is designed to simulate typical daily QA devices. Operational efficiency is enhanced since a single field can be used for multiple measurements, e.g. flatness/symmetry and light/radiation.
Conclusion: The nüFilm machine QA system can collect, analyze and document comprehensive data sets objectively and precisely. Comprehensive comparison of mechanical characteristics is achieved with a precision of 0.1 mm.
This technology was supported in part by Kentucky ( CED 2021-001-009) and US HHS ( R44CA295373).