Contrast Imaging
Contrast enhanced ultrasound (CEUS) imaging has been developed in order to visualize the micro-circulation in tissue, that is, the blood flow in very small blood vessels. For flow assessment in relatively large blood vessels, ultrasound Doppler methods perform well in many situations. However, for assessment of the micro-vasculature and for perfusion measurements (the amount of blood that flows through a volume of tissue), the blood velocities are so low that they cannot be detected with ordinary, non-invasive Doppler techniques. In these situations, the use of an ultrasound contrast agent is necessary.
Ultrasound contrast agents are typically made as solutions of gas micro-bubbles in a fluid that can be injected into the blood flow to increase the scattering from blood, which is weak compared to the scattering from soft tissue. The gas bubbles have high compliance relative to the surrounding blood and when insonified by medical ultrasound pulses, they resonate and generate a steady stream of harmonics. State-of-the-art CEUS methods aim at detecting the harmonics emitted by the contrast agent while suppressing the tissue signal.
The contrast bubbles are normally smaller than the red blood cells (order of 3 um), but large enough not to penetrate through the endothelial cells lining the inside of all blood vessels and will thus not diffuse out into tissue. Ultrasound contrast agents are hence true blood pool agents. They can potentially be used for improved diagnosis and therapy in several clinical situations, e.g. evaluation of cardiac chamber size and function such as the left ventricular function, assessment of myocardial perfusion, detection of reduced blood flow due to vascular stenosis or thrombosis, evaluation of aneurysms, and for evaluation of the micro-vasculature and perfusion of organs in general, for example with respect to cancer tumor diagnosis. In tumor diagnosis, the contrast agents may also potentially be injected directly into the tumor interstitial fluid in order to trace lymphatic drainage of the contrast agents to sentinel lymph nodes for evaluation of possible metastases. In near future, targeted contrast agents that will attach to specific molecular tissue signatures, i.e. pathology-specific micro-bubble adherence, will perhaps be available opening for molecular or functional ultrasound imaging. There is also interesting work being done with respect to using microbubble ultrasound contrast agents for transient increase in cell membrane permeability potentially opening for efficient drug and gene delivery.
The video shows CEUS ultrasound in a kidney. |
Research activities at the department
To differentiate between the ultrasound signal received from tissue, and received contrast agent signal, special contrast agent detection techniques must be applied. It is in this field where the research at the Department of Circulation and Medical Imaging is concentrated.
The SURF Imaging method has been at the core of the contrast agent detection research performed in Professor Bjørn Angelsen's group. More detailed information about this research can be found under the link below.
| Professor | Phone: +47 728 28015 |
Svein-Erik Måsøy Post. Doc. Area of interest: ultrasound, reverberation cancellation, nonlinear propagation, | Office: Prinsesse Kristinas gt. 3 , AHL, 3.etg rom 342.03.033, |
