Identifying Visible Tissue in Intraoperative Ultrasound Images during
  Brain Surgery: A Method and Application
Alistair Weld Luke Dixon Giulio Anichini Michael Dyck Alex Ranne Sophie Camp Stamatia Giannarou
Intraoperative ultrasound scanning is a demanding visuotactile task. It
requires operators to simultaneously localise the ultrasound perspective and
manually perform slight adjustments to the pose of the probe, making sure not
to apply excessive force or breaking contact with the tissue, whilst also
characterising the visible tissue. In this paper, we propose a method for the
identification of the visible tissue, which enables the analysis of ultrasound
probe and tissue contact via the detection of acoustic shadow and construction
of confidence maps of the perceptual salience. Detailed validation with both in
vivo and phantom data is performed. First, we show that our technique is
capable of achieving state of the art acoustic shadow scan line classification
- with an average binary classification accuracy on unseen data of 0.87.
Second, we show that our framework for constructing confidence maps is able to
produce an ideal response to a probe's pose that is being oriented in and out
of optimality - achieving an average RMSE across five scans of 0.174. The
performance evaluation justifies the potential clinical value of the method
which can be used both to assist clinical training and optimise robot-assisted
ultrasound tissue scanning.