Public examination of a doctoral dissertation in the field of medical physics
Doctoral candidate: M.Sc. Tuomas Virén
Date and venue: 22.6.2011, at 12 noon, L22, Snellmania, Kuopio campus
Osteoarthritis (OA) is a progressive degenerative joint disease which causes pain, stiffness and abnormal remodeling of the joints. Currently, no healing cure exists for the disease, but with early diagnosis, the progression of the OA may be slowed down. Unfortunately, the earliest changes related to OA are not detectable with the current clinical imaging techniques. Furthermore, the development of surgical cartilage repairing techniques has created the need for novel quantitative techniques for evaluating of the integrity of articular cartilage and subchondral bone.
Quantitative ultrasound imaging is a sensitive technique for the detection of artificial degeneration of cartilage as well as the early signs of spontaneous osteoarthritis. Furthermore, with ultrasound, the integrity of spontaneously or surgically repaired cartilage can be evaluated. However, clinically applicable ultrasound imaging devices for arthroscopic evaluation of articular cartilage have not yet been introduced.
In the present thesis, a novel arthroscopic ultrasound technique is introduced and evaluated. First, the technique was tested by imaging phantoms with variable surface characteristics and with mechanically or enzymatically damaged cartilage samples. Furthermore, the ability of the technique to evaluate the integrity of spontaneously healed and surgically repaired animal cartilage was investigated in vitro and the technique was compared with the optical coherence tomography (OCT), another high resolution imaging technique proposed for arthroscopic use. Finally, the clinical applicability of the proposed ultrasound technique was tested in arthroscopy of bovine knee joints ex vivo and human knee joints in vivo.
Ultrasound arthroscopy proved to be suitable for the detection of mechanical and enzymatical degeneration of articular cartilage. Furthermore, the integrity of spontaneously healed and surgically repaired cartilage could be determined with the technique. Significant correlations were detected between the ultrasound and OCT parameters. Mechanically degraded and spontaneously degenerated cartilage could be distinguished from intact cartilage by arthroscopic ultrasound evaluation of bovine (ex vivo) and human (in vivo) knee joints. Furthermore, the ultrasound evaluation of human knee articular cartilage provided important information on the integrity of the tissue not available from conventional arthroscopy.
The present results indicate that the ultrasound arthroscopy is a sensitive method for evaluation of the integrity of articular cartilage. Furthermore, ultrasound could provide valuable information on the integrity of repaired tissue. The introduced ultrasound technique was found to be suitable for arthroscopic use and to produce valuable diagnostic information. However, further technical development of the arthroscopic ultrasound catheters will be needed to enable more straightforward and reproducible clinical measurements.
The doctoral dissertation of Tuomas Virén entitled Arthroscopic ultrasound imaging of articular cartilage will be examined at the Faculty of Science and Forestry. The opponent in the public examination is Research director Pascal Laugier from University Paris 6 and the custos is Professor Juha Töyräs of the University of Eastern Finland.
Photo available for download at http://www.uef.fi/vaitoskuvat
Contact: Tuomas Virén, tel. +358 40 355 3930, firstname.lastname@example.org
Publishing year: 2011Back to this years article listing