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Microwave imaging to diagnose breast cancer

Microwaves are an attractive imaging method for finding breast tumours as the contrast between healthy tissue and tumour is very high. However the resolution is low. We are working   to improve the interpretation of the data gathered from both phantoms and clinical images using microwave clinical imaging system developed in Bristol University. A spin out company from Bristol University has one of the few clinical systems in use worldwide, which has been used in trials in Frenchay Hospital. This work is funded by EPSRC.

Skin rejection artefacts: time delay beamforming

To keep the system compact the trasnmitter and receivers are placed in a hemisphere around the breast.  A large reflection artefact occurs at the skin, and with no correction dominates the image in the time delay beamforming, the method preferred for good turnaround. The skin artefact may be removed by subtractig two images with a small degree of rotation between them, as shown on the left for a single insertion phantom.  As shown on the right, a method adapted from image registration to idencity the exact angle of rotation allows the images ot be combined with compensation for the rotation, removing the artefact.

Velocity map estimation

Tomography is often seen as a gold standard for imaging, providing estaimtes of essential paramters as well as an image,  but it is computationally intensive. A simple allied technique based on modelling the velocity profile across a slice of the image provides a rapid method to approximate the profile. It estimates the velcoity across a set of radial basis functions through measurements of tme of flight between sets of antenna.

Time reversal methods

These are showing promise in locating tumours.

Contributors:

Dr Jean Francois Deprez, Dr Navid Ghavami

In addition we are investigating an acousto-microwave system which offers both high contrast and improved resolution, and developing a new ultrasound array.