Towards the objective assessment of fluoroscopy systems: development of a framework to aid the design of tasks and metrics

The purpose of this work is to propose a framework that could help to accelerate the development of task models and figures of merit for fluoroscopy applications. Our final goal is to use this framework to establish an imaging task based on pediatric vesicoureteral reflux (VUR) diagnosis, and to assess a reader study design that mimics contrast medium uptake. The proposed framework is based on task and observer study fine-tuning after consecutive virtual trials. Radiographs of neonates were selected by a radiologist for phantom and observer study development. Ureter depictions of five VUR grades were segmented from published references and used as imaging tasks. A tool to simulate patient+task images was developed based on well-known x-ray imaging models. To validate this tool, two quality assurance phantoms were simulated and compared to actual acquisitions, having as result a good agreement in terms of maximum resolvable line-pair frequency and contrast resolution. In addition, the noise texture and magnitude were very similar. To facilitate virtual trials, a web-based application was developed, which displays simulated images and asks the observer to grade them. Preliminary tests have shown that the application is practical, accessible and provides the needed flexibility for testing different study designs. In conclusion, a framework to facilitate phantom profiling and observer study design has been developed. With this framework it has been possible to simulate and score pediatric VUR diagnostic tasks embedded in realistic anatomical backgrounds, with the goal of developing a study design that can be performed in real time.