Impact of localized diminished illumination for needle targeting procedures in optical see-through head-mounted...

The use of Optical see-through (OST) Head- Mounted Displays (HMDs) in Surgical Navigation Systems (SNSs) has seen a stark increase in recent years due to the release of consumer-grade HMDs such as the Microsoft HoloLens 2. Despite the promise of in situ visualization methods in enhancing surgical navigation for minimally-invasive procedures, failure to address the incorrect occlusion cue will lead to errors in depth perception, eliciting potential procedural mistakes from the physician. Rendering methods alone fall short in addressing this limitation, as lighting from the physical world, in contrast to Video see-through devices, cannot be digitally manipulated in OSTs. We propose the incorporation of a "black hole" projector into an OST-based Augmented Reality (AR)-SNS to mitigate these perceptual issues. In the context of surgical needle guidance, we integrated electromagnetic tracking into the HoloLens 2 environment through a co-calibration process to enable accurate needle tracking with no user-centric line-of-sight limitations. Employing a generic foam-based phantom with a skin-mimicking layer on top, we conduct a user study (n = 16) to evaluate the efficacy of our projector approach for needle insertion procedures against standard surgical lighting conditions. Quantitative results from the study show that, while the BlackHole projector had no significant impact in pure depth estimation capabilities, when employed to a needle targeting task it significantly improved the mean relative targeting error from 4.58mm with the standard lighting conditions to 2.69mm with the BlackHole approach (p = 0.047). Qualitative results showed the projector effectively reduced the mental strain associated with both depth estimation and needle targeting tasks.