High-frequency ultrasound is a versatile, non-invasive imaging modality that provides high-spatial-resolution (down to 30 micrometers), real-time imaging of soft tissue. In addition to anatomical information, high-frequency ultrasound is also able to provide Doppler flow (pulsed-wave, color, and power modes) information along with analysis of tissue motion (with tissue Doppler imaging or strain analysis).
The Vevo LAZR high-frequency ultrasonic-photoacoustic imager is the latest offering from VisualSonics’s suite of ultrasound-based small-animal imaging systems. This system is built around the Vevo 2100 high-frequency ultrasound platform, which affords it all of the standard functionality of this cutting-edge system. In addition, the Vevo LAZR add-on incorporates a laser source that allows for photoacoustic imaging, a technique in which tissue is irradiated with nanosecond pulses of low-energy laser light.
Through the processes of optical absorption followed by thermoelastic expansion, broadband ultrasonic acoustic waves are generated within the irradiated volume. Using an ultrasound transducer, acoustic waves can then be detected and spatially resolved to provide an image that is related to the local optical absorption of tissue constituents. The system is able to provide co-registered photoacoustic and ultrasonic images at a frequency of up to 55 MHz.
The system includes a Q-switched Nd:YAG laser with OPO that is capable of operating from 680-970 nm with a peak pulse energy of 45 mJ and repetition rate of 20 Hz. An integrated imaging station allows for volumetric acquisition, respiration gating, and ECG triggering.
Photoacoustic (PA) imaging, which is similarly non-invasive, non-ionizing, and real-time, provides functional and molecular/cellular imaging capabilities. PA functional imaging is primarily driven by the presence or oxygenation state of hemoglobin, which allows for assessment of angiogenesis, anemia, hypoxia, oxygen saturation, or ischemia in vivo. PA cellular/molecular imaging is based on the use of nano-sized contrast agents, such as plasmonic nanoparticles, that can be targeted to a particular cell receptor and tracked in real time.