Share thisHigh frequency (17-25 MHz) real time linear array ultrasound technology for small lab animal imaging
Medical/veterinary ultrasound has been around for many years. Most standard systems, however, have had difficulties with imaging the very smallest of animal patients due to the lower frequency probes they can run (2-12 MHz) and the larger probe sizes used in relation to the size of the animal. Two technologies used to image small lab animals today employ mechanical sector probes or linear array probes. The mechanical probe oscillates (wobbles) or rotates a single crystal to form a sector (vector) shaped field whereas the linear array is comprised of multiple matched crystals in a line, designed to work in concert to produce and focus the ultrasound energy and results in a rectangular image (Figure 1). Our objective today is to understand more about the high frequency linear array technologies.
Linear array probes can vary in frequency and total size (length) based on the size of the crystals, the frequency of the crystals, and the users’ planned use or applications. For example, ribeye scanning a full sized cow requires a 17 cm long probe for complete coverage of the area of interest and a 2-4 MHz frequency range for adequate penetration and resolution. For scanning a horse’s tendon, a 4 cm long probe with an 8-12 MHz frequency range provides the resolution to see very small tears with enough penetration to view all the important structures. For scanning a mouse sized animal, the linear probe is just 2.4 cm long and offers a 17-25 MHz range to provide enough penetration to access all the structures and the resolution to better distinguish the various internal structures.
The operating frequency of the crystal effects both the penetration and resolution of the ultrasound image — a higher frequency than normal is required for very small animal imaging.
Ultrasound Inverse Rule: The higher the probe frequency, the higher the image resolution but the lower the penetration of the ultrasound beam.
By utilizing a linear array probe, the system has the ability to change or vary the number of crystals used (activated) to create a line of ultrasound data. This allows a user to control where the ultrasound beam is focused for optimal lateral resolution. The more crystals used in a single group, the deeper we can move the focus of the beam. Most linear array systems offer a selection of predefined focal depths so a user can easily and visually optimize their lateral resolution with the push of a button.