Laser deflection with a split beam detection scheme for acoustic medical imaging.

Ultrasound imaging, a type of medical imaging used for diagnosis and treatment of various medical conditions, reflects high frequency sound waves through the body to create images of internal structures. Common ultrasound transducers rely on piezoelectric crystals, or more recently, on capacitive micromachined ultrasonic transducers (CMUTs), to generate and collect acoustic signals. We investigate using laser deflection with a split beam detection scheme to detect acoustic signals on the surface of the body with high sensitivity, potentially outperforming the signal resolution and bandwidth reception of current commercial ultrasonic transducers. This implementation could be used to localize energy signals within the body by exploiting the thermoacoustic effect, where deposited energy is transferred as an acoustic wave. A device based on this implementation could be used to locate and measure the dosage of various energy deposition therapies in real time, providing critical data to medical professionals. Furthermore, when triangulated, this detection scheme has the potential to create high resolution reconstructions of structures in the body. To make the detector more portable, we implement a split fiber bundle, with a face geometry designed to optimize the SNR. Preliminary experiments show the detector is able to pick up signals in the 100 kHz range, with displacements on the order of nanometers. Further experiments seek to characterize the operational bandwidth, NEP, and thermal limits of this detection scheme.