In vivo time course studies of the tissue responses to resorbable polylactic acid implants by means of MRI.

Magnetic resonance (MR) imaging and relaxation time measurements of bioresorbable implants made of polylactic acid (PLA), as well as the surrounding tissues, were carried out over a period of 6 months to monitor the implant state and the body's responses, and to determine how these processes are reflected in MR data. Twelve rabbits each received two subcutaneous PLA implants (45 x 10 x 2 mm). Changes in tissue relaxation rates demonstrated inflammation and tissue healing time courses but were not simply linear functions of the tissue water content and so provide new insight into MR characterization of inflammatory processes.