Journey into the Middle Ear




A walk-through virtual experience of the middle ear anatomy.

External Auditory Canal: 360 degree panoramic rendering

This was my first of two experiments aimed at creating a virtual reality middle ear walk-through.

After hand editing the relevant slices of a CT scan and volume rendering to create a 3D model, I found that the resulting 3D file was too large and complex for the processor to handle. As an initial workaround, I used Blender's camera to take a virtual stereoscopic panorama. The left eye feed is shown above.

I wasn't quite satisfied with this result as it felt like "fake VR", so I tried again and succeeded. Click ahead to see my process.

3D Slicer Images of CT Head

The source file I had available was in the public domain. It was a 1mm slice DICOM file. The resolution is far too crude to see all the complex middle ear anatomy, and I had to hand edit some of the artifact out.

I'm trying to source a high resolution CT scan or fine histology slices of the middle ear for my next iteration. Please contact me if you have knowledge of or access to this type of data!

Volume Rendered CT Head

Axial (horizontal) slices taken at 1mm intervals during scanning.

These are put together to produce a three dimensional model in a process called volume rendering.

Low resolution or a degree of noise is common in CT scanning where a balance needs to be struck between radiation dose and quality. Therefore it is often necessary to edit serial slices by hand to pick out the finer details. 3D slicer does help, with features which allow you to watershed some of your selections into adjacent slices.

Rendering a Virtual Photo in Blender

In order to reduce load on the processor, I initially attempted to create a virtual stereoscopic panorama of the complex 3D model I had created from the CT images. I used Blender to do this and rendering the high resolution images took many hours on my standard i7/4GB RAM system.

I ultimately decided against this technique and created a full 3D VR environment.

Rendered Panorama of External Auditory Canal

One of the early renderings of the External Auditory Canal.

Volume Rendering in Invesalius

Brilliant software which allows you to set a density threshold and visualise and export 3D model data from a DICOM CT scan image.

3D Model of Soft Tissues and Bones of the Head

I had to find a balance when thresholding in order to capture the soft tissue contours of the external auditory canal whilst exposing enough bone to clearly show the middle ear anatomy.

Ear Anatomy Surface Model

I painstakingly stripped out all unnecessary data so the virtual reality experience would be as smooth as possible. This was the model when almost complete, showing the external auditory canal and middle ear inside surfaces.

Positioning the Camera in Unity

Importing the model and placing the starting point for the camera.