Description
Breast cancer is a common cancer and a major health concern affecting the lives of many women worldwide. According to the World Health Organization (WHO) breast cancer has an estimated annual incidence rate of 2.1 million and is responsible for about 15% of all cancer related deaths around the world. We have previously introduced a novel photoacoustic tomography (PAT) system for breast cancer imaging, in which the object is illuminated omnidirectionally by using a cone and a conical ring mirrors. A ring ultrasound (US) transducer is used to acquire PA signals and to form the PAT images. The design of the system is intended to acquire data from entirety of a pendant breast up to the chest wall, without compressing the tissue, thus allowing for deeper detection of endogenous chromophores associated with breast cancer.
This work presents the characterization of the full-ring illumination/acquisition system through three different studies. In the first study, three different illumination methods, full-ring, diffused-beam, and point source illumination, and their efficacy for PAT imaging are compared. The results indicate that the full-ring illumination method is capable of providing a more uniform fluence irrespective of the vertical depth of the cross-section imaged, while the point source and diffused illumination methods provide a higher fluence at regions closer to the point of entry, which diminishes with depth. The omnidirectional ring illumination can provide a more uniform illumination pattern within the tissue and enable PAT imaging at deeper distances in the targeted cross-sectional area. In the second study, a set of experiments were conducted to determine the optimum position of ring-illumination with respect to the position of the acoustic detectors to achieve the highest signal-to-noise ratio. The last study was performed on breast-mimicking phantom, made out of human fat and embedded blood inclusions, to truly identify the capabilities of the developed PAT system and specifically the achievable in-plane penetration depth. The results demonstrate that the system is capable of imaging blood up to a cross-sectional depth of 30 mm. These three studies demonstrate the utility and advantages of the full ring-illumination system in imaging breast mimicking objects and paves the way for future development of the system towards a clinically translatable breast PAT scanner and can be part of a future diagnostic system.
