I. Introduction
Breast cancer is one of the common cancers that women suffer from. It is a reason of death more than 0.5 million women in 2012 [1], [2]. An early detection of breast cancer will lead to increase the percentage of the survive rate [3], [4] . As a part of the diagnosis pathway for breast cancer, a needle biopsy of the sentinel lymph node (SLN) is taken for analysis. When ultrasound imaging is used, it will be difficult to differentiate between the SLN and other lymph nodes [5]. Therefore, researchers investigate photoacoustic imaging to guide the needle. In photoacoustic imaging, exogenous contrast agents such as indocyanine green (ICG) are injected near the tumour. This contrast agent that has a narrow optical absorption spectrum propagates through the lymphatic system. As a result, the location of the SLN is defined by generating photoacoustic images of these agent [5], [6].