Calcifications are one of the most important indicators for early breast cancer detection. We explore the feasibility of deep-penetration photoacoustic (PA) imaging of calcifications based on a medical ultrasound array imaging platform. Intralipid and chicken breast phantoms embedded with different-sized hydroxyapatite (HA) particles, which are the major components of calcifications, were imaged to verify the equipment’s capability and penetration depth for the visualization of calcifications. An optimal near-infrared excitation wavelength was selected to maximize PA signals of HAs, resulting in a better HA signal-to-blood ratio. We demonstrated that PA imaging is capable of visualizing 0.5-mm HA particles at a depth of 3 cm in chicken breast phantoms. The noise-equivalent penetration depth of the system for visualizing 0.5-mm HA particles in the human breast was estimated to be about 2.9 to 3.5 cm, which is clinically relevant as calcifications are usually found at a depth of 0.6 to 3.0 cm. Moreover, the feasibility of differentiating HA from blood by the PA spectroscopic technique was presented and the mechanism of the HA signal generation was discussed. The results show that PA imaging is a promising technique for real-time visualization of breast calcifications.
Breast calcification is one of the most important indicators for early breast cancer detection. In this study, based on a
medical ultrasound array imaging platform, we attempt to develop a real-time and high penetration photoacoustic (PA)
array imaging system for visualization of breast calcifications. Phantom studies were used to verify the imaging
capability and penetration depth of the developed PA array system for calcification imaging. Intralipid gelatin phantoms
with different-sized hydroxyapatite (HA) particles - major chemical composition of the breast calcification associated
with malignant breast cancers - embedded were imaged. Laser at 750 nm was used for photoacoustic excitation and a
custom-made 5-MHz photoacoustic array transducer with linear light guides was applied for photoacoustic signal
detection. Experimental results demonstrated that this system is capable of calcification imaging of 0.3-0.5 mm HA
particles. For the 0.5-mm HA particles, the imaging contrast was about 34 dB and the achievable penetration was 20 mm
where the axial, lateral, and elevational resolution of this PA array imaging system is 0.39 mm, 0.38 mm, and 1.25 mm,
respectively. The highest frame rate was 10 frames/sec limited by the laser pulse rate. Overall, our results demonstrate
that it is promising for PA imaging as a real-time diagnosis and biopsy guidance tool of breast micro-calcifications
outside mass lesion. Future work will focus on optimization of the photoacoustic transducer to further improve the
penetration depth and development of photoacoustic and ultrasound dual-modal imaging to enhance the calcification
In this study, an electromechanical modeling technique for characterization and optimization design of the postcomplementary-metal-oxide-semiconductor (pCMOS) capacitive microarrayed ultrasonic transducer (CMUT) is presented. A two-dimensional, axisymmetric finite element model is developed using the ANSYS parametric design language. Electromechanical simulations are performed to investigate the fundamental characteristics of the CMUT, such as collapse voltage, resonant frequency, capacitance, and electromechanical coupling coefficient. Both the numerical and analytical (experimental) results agree well to show the validity of the proposed approach. The study of the influence of each defined parameter on the collapse voltage and resonant frequency is also presented. An integrated design approach that couples the genetic algorithm (GA) with the commercial finite element method (FEM) software ANSYS is developed to obtain the best design parameters. The optimal results show that the design objective with the equality constraint, which are to minimize the collapse voltage while simultaneously achieving the customized resonant frequency, are satisfied. From the presented results, it is concluded that the GA/FEM coupling approach provides another useful numerical tool for multiobjective design of the pCMOS-CMUT.