Direct augmented reality computed tomographic angiography technique (ARC): an innovation in preoperative imaging

Abstract

Background

Since the advent of free tissue transfer approximately 40 years ago, constant improvement particularly in the preoperative planning phase has led to flap success rate reaching 99% and improved patient outcomes. The use of imaging, such as computed tomographic angiography (CTA) or magnetic resonance angiography (MRA), for preoperative planning is now routine. However, current image modalities are restricted by being represented in two dimensions (2D) and have led to clinicians seeking novel methods of utilising the scan data, such as augmented (AR) or virtual reality (VR) and holograms. These mixed-reality devices facilitate a natural mode of visual perception and have the capacity to introduce tactile feedback. However, most AR devices are currently expensive, bulky and complicated and require tedious image registration processes. We illustrate our projector-based direct AR technique using CTA, or ARC, for preoperative planning.

Methods

Our bespoke ARC method consists of compact, affordable hardware (MacBook, Philips pocket projector and a 15-cm ruler) and free, open-source software (OsiriX). We have utilised this technique in six cases of perforator flaps of the thigh and abdomen (anterolateral thigh (ALT), transverse upper gracilis (TUG) and deep inferior epigastric artery perforator (DIEP) flaps.

Results

In all cases, 3D-reconstructed images of perforators from CTA were accurately projected onto the donor site. System calibration was rapid and convenient to use.

Conclusions

We illustrate a novel technique of projector-based AR CTA (or ARC) for preoperative planning in perforator flaps. The technique is affordable and readily reproducible.

Level of Evidence: Level IV, diagnostic study.