EFSUMB Young Investigator's Award 2006

Table of Contents

Each year, each member society of EFSUMB is invited to nominate a member of their society to present a paper in the Young Investigator's Award session of the EUROSON Congress. Applicants must be under 35 years of age at the opening date of the Congress, and must be a paid up member of the nominating society. The member society must agree to sponsor their candidate for the cost of their travel and accommodation expenses, and the organising committee of the conference offer the candidates free registration at the meeting. One or two prizes of €1.000 are awarded to the candidates, judged by an ad-hoc committee to be best in terms of scientific content and quality of presentation. This year entries were received from 5 national societies (Denmark, Italy, Norway, Netherlands, UK), and as always the quality of the presentations was excellent. The winner on this occasion was Martijn Frijlink from the Netherlands with his outstanding presentation on 'Harmonic Intravascular Ultrasound'. I would like to encourage all societies to consider nominating one of their outstanding young members for the 2007 competition to be held in Leipzig in October of this year. I would also commend attendance at the Young Investigators session to the membership in general; for me it is one of the highlights of the meeting.

Prof David Evans

EFSUMB President

First Prize

CV Martijn E. Frijlink

Martijn E. Frijlink was born in Gravenhage, the Netherlands in 1976. He received his M.Sc. degree in electrical engineering from the University of Technology, Delft, Netherlands in 2001. In September 2006 he completed his Ph.D. dissertation on the topic of "Harmonic Intravascular Ultrasound" at the Biomedical Engineering department of the Thoraxcenter at the Erasmus Medical Center in Rotterdam, Netherlands. From February 2007 he will be with the Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway. His current research interests include transducer development and high-frequency harmonic imaging.

Abstract

Title: Harmonic Intravascular Ultrasound

Authors: M.E. Frijlink¹, D.E. Goertz¹,², D. Tempel¹, H.J. Vos¹,²,³, A. Gisolf³, R. Krams¹, N. de Jong¹,² and A.F.W. van der Steen¹,^{2 1}Erasmus MC, Rotterdam, the Netherlands, ²Inter University Cardiology Institute of the Netherlands, the Netherlands, ³Delft University of Technology

Aims: Intravascular ultrasound (IVUS) is an important imaging technique for therapy guidance, clinical research, and the detection and evaluation of atherosclerotic lesions. In Echocardiography, at conventional diagnostic frequencies (<10 MHz), second harmonic imaging has been shown to suppress unwanted tissue image artifacts and enhance contrast agent detection. Therefore, we investigated the potential of Harmonic Intravascular Ultrasound (HIVUS) to improve tissue image quality. Furthermore we investigated the harmonic detection of microbubble contrast agents in the vasa vasorum, the microvascular network supplying large vessel walls. Despite the increasing recognition of the key role that vasa vasorum play in plaque progression and vulnerability to rupture, there is currently no clinically available tool to detect them in the coronary arteries.

Materials and Methods: A prototype HIVUS imaging system, including a custom-made single-element IVUS catheter with a dual-frequency response was developed to transmit at a fundamental frequency of 20 MHz (F20) to obtain second harmonic signals at 40 MHz (H40) in pulse-echo mode. The performance of Tissue Harmonic Imaging (THI) was studied in vivo by situating the IVUS catheter in atherosclerotic abdominal rabbit aortas (n = 4) and transmitting high-pressure F20 pulses. The feasibility of harmonic detection of a modified clinically approved contrast agent (Definity^TM, Bristol-Myer Squibb Medical Imaging, MA, USA) with HIVUS in vivo was studied using the same set up and proximally releasing a bolus of contrast agent through a second delivery catheter. Presence and location of microvasculature was post mortem validated against histology and microCT.

Results: Cross-sectional images of rabbit aortas as acquired in H40 mode with the dual-frequency catheter in vivo demonstrated an increased image quality as compared to F20 mode. HIVUS results at 40 MHz showed reduced sheath artifacts and high-resolution images with a good signal-to-noise ratio while maintaining penetration depth. For the in vivo contrast experiments, HIVUS enabled the detection and visualization of contrast agent within the main aortic lumen and within adventitial microvessels following the bolus release of contrast. Histology and microCT revealed presence of these microvessels in the adventitia. They were not detected using fundamental IVUS imaging.

Conclusions: The potential of Harmonic IVUS to improve tissue image quality has been shown in vivo using a prototype HIVUS system. These results also demonstrate the feasibility of contrast harmonic IVUS as a new technique for vasa vasorum imaging, which has potential to be a unique tool for assessing rupture prone coronary plaques.

Acknowledgement: this project was funded by the Dutch Technology Foundation (STW)