A photoacoustic 3D tomographic breast imager: Bench & bedside experiences

Medical breast imaging is an important aid in diagnosing and guiding treatment of breast cancer, the cancer type with the highest incidence and mortality rates in females worldwide. Currently used imaging techniques are x-ray mammography, ultrasonography and magnetic resonance (MR) imaging. Research goes into the development of new modalities to image the breast in order to detect and/or diagnose tumors, of which photoacoustics is one. Photoacoustic imaging aims to make use of the strong optical contrast of the tumor-related environment, and combines this with the relatively high resolution of ultrasonic detection. The optical contrast originates from the often highly vascularized tumor(al region). The main goal of this work has been to assess the feasibility of photoacoustic breast imaging, specifically with our second generation Twente Photoacoustic Mammoscope (PAM 2): a three-dimensional (3D) tomographic prototype system.

This thesis shows the characterization of the PAM 2 system and its performance. Images of the breasts of healthy volunteers showed the breast contour, the nipple and the vascular anatomy within the breast. Next, the design, development and added value of breast-supporting cups to immobilize and position the breast are described. Clinical measurements on breast cancer patients were also performed. In a few cases, photoacoustic image features indicative of malignancy were seen. Another chapter describes the first steps towards longitudinal photoacoustic imaging, with the aim of investigating the influence of the menstrual cycle on photoacoustic breast appearance.

With PAM 2, we were able to visualize detailed vasculature, both in healthy volunteers as well as in breast cancer patients. Given the pathophysiological target of the imaging method (detecting enhanced tumor-related vasculature) this suggests that the technique might potentially add value in breast cancer management as a noninvasive, harmless imaging technique. The thesis ends with a general discussion of the work and a consideration of potential areas of application.