Quantitative image quality evaluation of an order-statistic filter in x-ray fluoroscopic imaging

The use of x-ray fluoroscopy in complex interventional procedures can result in high patient dose leading to severe skin injuries. Simply reducing exposure degrades image quality. One solution is to acquire images at reduced exposures and digitally filter to reduce noise and restore image quality. We quantitatively evaluated image quality improvement from a bidirectional multi-stage (BMS) median spatio-temporal filter. Improvements were assessed using forced-choice measurement of detection and discrimination. Targets were vertical projected cylinders mimicking interventional devices such as catheters. Poisson white noise was added on uniform backgrounds to simulate low-dose x-ray fluoroscopy. The EMS filter improved detection by 20% and discrimination by 31% giving estimated dose savings of 31% and 42%, respectively. Minimal spatial and temporal blurring of targets was observed in filtered sequences.