General: the role of Ultrasound within AMIE

Ultrasound is one of the most universally used methods in medical diagnostics. Ultrasound is a fast, real-time, non-invasive technique. Abdominal organs such as liver, spleen, kidneys, bladder, prostate, womb and the heart can be properly visualised with (Doppler) ultrasound and be studied for anomalies. Furthermore, only ultrasound permits a non-invasive evaluation of embryo development. The depth of penetration is related to the frequency of the sound wave. The lower the frequency, the deeper the penetration. However, the lower the frequency, the lower the resolution. Therefore, high-frequent ultrasound is preferred for small animals or for intravascular application, for which deep exploration is not required.

A specific example of application of ultrasound is transrectal ultrasonography (TRUS) of a mouse or rat prostate, a new technique developed by the departments of Urology and Experimental Cardiology. The technique makes use of a rectal, vascular ultrasound probe that has the capacity to visualise prostate volume. The technique has been validated and implemented in several pre-clinical studies and is now being optimized for the new application. The possible usefulness of this application in other model systems/research areas has not yet been explored.

Ultrasound-contrast agent is made of tiny micro bubbles that can be destructed regionally. These contrast agents are promising carriers for drugs or genes to be delivered locally. Also, ligand-conjugated micro bubbles can be aimed at any target of choice, enabling molecular imaging of vascular wall related processes.

Specific benefits of Ultrasound in biomedical research

Ultrasound is a relatively easy real-time method to visualise the inside of a small experimental animal. Real-time mapping of organ perfusion and tissue identification are not much of a problem with ultrasound. In addition it enables to study the physiological, anatomical, biochemical and functional characteristics of transgenic or treated animals without major interventions. Ultrasound owes its popularity to its real-time, non-invasive character, one of the things that makes it useful in large longitudinal studies. Within AMIE ultrasound in itself will prove to be of value, but it can also be well combined with other techniques such as CT, PET/SPECT and Optical Imaging.

Interaction with other technologies

Ultrasound guidance during electrophysiological interventions such as transseptal puncture and RF ablations makes these procedures easier and more efficacious. Another option is real-time evaluation of radiation therapies and jugular-vein catheterisation. In addition, ultrasound guidance provides for biopsy punctures for further analysis, or giving controlled injections for therapy.

Desired configuration for Ultrasound

At present experimental animal ultrasound equipment operating at 10 MHz frequency is available in the department of Experimental Cardiology. It is suited to study the anatomy of mice. However, a high-frequency (50 MHz) ultrasound machine is badly needed for smaller structures and contrast-guided local administration of drugs in small experimental animal. The Vevo 770 (Visual Sonics) is an ultrasound tool at frequencies > 50 MHz and was specifically developed and programmed for use in small animals. It offers a resolution five-fold that of the 10 MHz machine, i.e. 30 µm.

At present the department of Urology has two functioning ultrasound imaging machines for TRUS in use that could be placed in a central Animal Imaging Facility.