On-Line Mobile Organ Tracking for Non-Invasive Local Hyperthermia

Magnetic resonance (MR) systems can be used to monitor temperature changes in and around a treated region during an hyperthermic ablation procedure. Dynamic temperature monitoring allows on-line prediction of cellular destruction during the intervention. However, organ displacements due to physiological activity (respiratory cycle) may induce important artifacts in computed temperature maps. In addition, focused ultrasound (FUS) is an extra-corporal heating device which makes possible to perform local hyperthermia non-invasively. For intervention on mobile organs, the position of the focal point must be adjusted dynamically to track the targeted pathologic tissue. Without such corrections, treatment is inefficient or may induce unwanted destruction of healthy tissue. In this paper, image processing methods are developed to propose an efficient solution to correct on-line motion artifacts on temperature maps, and to adjust the focal point position of the FUS device in order to track the targeted organ moving.