Automatic detection of fiducial markers from electronic portal images of prostate radiotherapy

Prostate cancer is the most common type of cancer afflicting Canadian men. Imageguided external radiation therapy of prostate cancer requires the accurate positioning of the patient in the treatment field. The alignment process is done using three fiducial markers implanted in the prostate. The current clinical practice involves the manual localization of these markers on pre-treatment, low-resolution electronic portal images (EPI). We propose an algorithm for the automatic detection of these markers. Our approach first enhances the quality of the EPI images using a fully automatic image enhancement approach. Next, fiducial markers are detected using template matching and a novel way of integrating information across multiple views. Experimental results show a significant improvement in the detection of fiducial markers in the left lateral view with respect to state-of-the-art results in related work. One should note that the left lateral view is the most challenging view due to the low resolution and the presence of occluding bony structures.