The principle of long-pulse photoacoustic signal generation and its applications

Emily Zheng and Wenhan Zheng

Theoretical overview of LDPA effect.

Theoretical overview of LDPA effect

Undergraduate Student Project


Diagnostic imaging have greatly improved our ability to diagnose and treat pediatric illness, and it is also one of the most revolutionary innovations in the medical world. For example, advanced imaging technique allows medical professionals to peer into the interior of a living human body without having to cut it open. In this poster we're going to introduce one of the novel imaging technique:  photoacoustic, and the application of LDPA effect.

My name is Emily Zheng, a senior Biomedical Engineering student at University at buffalo. Last summer I conducted research in the optical and ultrasound imaging lab, which focus on the development of novel optical and ultrasonic imaging techniques, especially photoacoustic tomography. My project focuses on the application of long pulse induced photoacoustic sensing (LDPA).

Compared to the traditional short-pulse photoacoustic sensing, LDPA uses long pulses to quantify the object's mechanical and thermal properties. It has a broad application in the field of medical imaging, such as super-resolution PA imaging and non-linear contrast agent development. In this study we analysis how the emitted pulse width influences the signal amplitude and energy efficiency in the LDPA system.


Photoacoustics is the production of acoustic waves by the absorption of light. As a hybrid technique, photoacoustic tomography combines the advantage of two imaging techniques: it possesses the high spatial resolution of ultrasonic imaging and the strong contrast of optical imaging.

For effective signal generation, the photoacoustic light source should meet both stress and thermal confinement. Otherwise, dual photoacoustic signals will be generated. This phenomenon is called the long laser pulse induced dual photoacoustic (LDPA) effect. LDPA generates two PA signals named P1 and P2 induced by the rising and falling edge of the pulse, respectively.

The non-linear characteristics of LDPA signal opens up a broad range of applications. For example, since the thermal and stress confinement times of the material/tissue are determined by its thermal-mechanical properties, the LDPA effect can be used as a material/tissue characterization tool. Using a portable light source and ultrasound transducer, we successfully demonstrated LDPA in our study.

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