  Photoacoustic tomography (PAT) combines the advantages of the spectroscopic
optical absorption contrast and acoustic resolution with deep penetration, and
becomes an important novel biomedical imaging technology for scientific
research and clinical diagnosis. In this paper, an imaging size-adjustable PAT
system is proposed for clinical applications, which can adapt for different
size imaging targets. Comparing with the conventional PAT system setup which
with a fixed radius ring shape ultrasound transducer (UT) array, the proposed
system, which is based on sectorial ultrasound transducer array (SUTA), is more
flexible for different size targets imaging. There are 32 elements for each
SUTA, and four SUTAs form a 128-channel UT array for photoacoustic wave
detection. The four SUTAs are controlled by four stepper motors, and change the
SUTAs distribute positon that adapt for imaging applications. The radius of the
proposed system imaging region of interest (ROI) can be adjusted from 50 mm to
90 mm, which is much more flexible than the conventional full ring UT array PAT
system. The simulation results generated by the MATLAB k-wave toolbox very well
demonstrate the feasibility of the proposed system. To further validate the
proposed system for size-adjustable imaging, a vascular mimicking phantom and
ex-vivo pork breast with indocyanine green (ICG) injected are imaged to prove
its feasibility for clinical applications.
