Electronic Thesis and Dissertation Repository


Master of Engineering Science


Biomedical Engineering


Dr. Hanif M. Ladak

2nd Supervisor

Dr. Sumit K. Agrawal

Joint Supervisor


Cochlear implants provide the sensation of sound to deaf individuals. An accurate estimate of cochlear duct length (CDL) is required for pre-operative implant electrode selection and can be obtained from clinical computed tomography (CT) by measuring the “A-value”.

The objectives of this work were to estimate the accuracy and variability in manual A-value measurements, and to automate measurements.

Four specialists repeatedly measured the A-value on clinical CT images from which the inter- and intra-observer variability were calculated. Accuracy was assessed by comparison to measurements on higher resolution micro-CT images. Motivated by this study, software was developed to automate the A-value measurement by registering an annotated atlas to unlabelled images.

There was significant variability in manual A-value measurements made using either standard clinical or multi-planar reformatted views with the latter exhibiting higher variability but better accuracy. The automated approach eliminated variability and improved accuracy, enabling the correct selection of electrode length.