A Study in Scatter: Investigating Low-Contrast Image Contents Outside the X-Ray Collimation

Heiko Maier, Shahrooz Faghihroohi, Philipp Steininger, Felix Wirth, Angelos Karlas, Nassir Navab

Keywords: X-Ray Imaging, Minimally Invasive Surgery, Interventional Radiology, Collimation

TL;DR: We investigate if residual information in detector parts outside of the collimated area of x-ray images can be used to reconstruct bones and medical devices in these areas

Abstract: Fluoroscopy is a widely used modality that provides vision to surgeons in minimally invasive surgery, but inherently raises concerns about radiation exposure. Collimation is a technique to reduce exposure by narrowing the radiation to a smaller area, with the trade-off of field-of-view limitations. However, the constraint the collimator shutters form for the x-ray beam is not absolute. Due to the non-ideal properties of the x-ray imaging and collimation process, small amounts of radiation are detectable outside the collimated area. This is a source of additional information, freely available as a byproduct of the imaging process, yet currently left unregarded. We explore whether this information can be used to provide additional knowledge about the surgical scene. In particular, we investigate whether it can be used to detect and visualize anatomical landmarks and surgical devices outside of the collimated area. We discuss the origins of this phenomenon, and perform experiments to evaluate its properties under different x-ray source parameters. Using anthropomorphic phantoms and a set of surgical guidewires, we investigate how well and under which conditions different landmarks and devices can be visualized with the proposed concept. We hope this work can open a path to provide additional information to interventional radiologists, while making use of every bit of radiation the patient is exposed to.

Submission Number: 15