North Carolina State University Research on the Safety of Contrast-Enhanced Ultrasonography

We have had the unique privilege of interviewing Dr. Gabriela Seiler, a Associate Professor of Radiology at the Department of Molecular Biomedical Science at North Carolina State University.  Her latest paper, titled Safety of contrast-enhanced ultrasonography in dogs and cats: 488 cases (2002-2011). was published in the journal Journal of the American Veterinary Medical Association. The paper studies the incidence of adverse events within 24 hours after contrast-enhanced ultrasonography (CEUS) in dogs and cats..

Please tell me very briefly about your own background and research interests.

I am born and raised in Switzerland where I went to vet school, did a doctoral thesis and a residency in veterinary diagnostic imaging. After completion of the residency I took a faculty position at the University of Pennsylvania before accepting a position as Associate Professor of Radiology at NC State University. I am board certified in veterinary diagnostic imaging by the European College of Veterinary Diagnostic Imaging as well as the American College of Veterinary Radiology.  My research interest is in investigating the use and applications of advanced ultrasound methods in our veterinary patients.

What led you to this study?

In human medicine, CT (cat scans) and MRI are often the methods of choice to investigate abdominal and thoracic disease. These imaging modalities are also routinely available for our veterinary patients, but are less commonly used mainly because of their higher cost which most animal owners have to pay out of their pockets as pet insurance is not very common, and because animals have to be anesthetized to perform these studies. Therefore ultrasound is often the imaging modality of choice for our patients, particularly to investigate abdominal disease as it can be done in the awake patient, is non-invasive and less costly.

While I think it is a great imaging modality for our patients, as a radiologist I am also often somewhat frustrated with it, as it is very sensitive but not very specific. In other words, if there is a lesion in the liver, I am probably going to identify it with ultrasound, but I cannot tell in most cases if it is a benign lesion that can be ignored or if it is a malignant lesion that requires more aggressive treatment. We therefore typically have to do needle biopsy procedures to determine the nature of a lesion. Contrast-enhanced ultrasound is one of the advanced ultrasound methods available that can provide us with more information about abdominal, particularly liver lesions in a non-invasive way. It is able to show us the vascular supply which is different in benign and malignant lesions.

Contrast media are routinely used in other imaging modalities such as radiography, CT and MRI but ultrasound contrast media are relatively new and we did not know as much about their side effects prior to this study. In order to promote this method in a clinical setting and to provide owners and referring veterinarians with accurate information about the safety of these contrast agents we decided to undertake this multicenter study.

Tell us about your findings

Contrast-enhanced ultrasound is a very safe imaging method in dogs and cats. Any contrast agent that is injected into a vein can potentially cause an adverse reaction. In our study we did not observe any adverse reactions in cats, and adverse reactions were very rare (<1%) in dogs and were mild, self-limiting and not life-threatening. This percentage of side effects is similar to what we expect when we perform contrast studies with other imaging modalities which we do on a daily basis.

Whenever I propose to a pet owner or a referring veterinarian that contrast-enhanced ultrasound could be used in this patient go gather more information in a non-invasive way their first question of course is “is it safe” and “how safe is it”. The findings of this study allow me to give them a very precise answer and I don’t have to resort to something like “we don’t know of any side effects” or “in my experience it is pretty safe.” But I can tell them that there is a less than 1% chance that their dog will experience an episode of vomiting or dizziness after the procedure.

As outlined above it will help me provide better information to the pet owner or referring veterinarian. Also, ultrasound contrast media are currently very difficult to obtain for veterinarians. I am hoping that this data will facilitate distribution to veterinary radiologists in the US.

contrast-enhanced-ultrasoundConventional grayscale ultrasound image of  thyroid tumor in a dog (A). The structure of the tumor is heterogeneous. On the contrast-enhanced image (B) we can see that a portion of the tumor is very well perfused (displayed in gold color) whereas there is a large area that remains dark and is necrotic.