Using Mimics to Monitor Changes in Bone Mineral Density of Femur during Electrical Stimulation Therapy of Denervated Degenerated Thigh Muscles. *Thórdur Helgason, *Paolo Gargiulo, †Páll Ingvarsson, †Stefán Yngvason *Department of Research and Development, HTS, Landspitali-University Hospital; and †Department of Rehabilitation Medicine, Landspitali-University Hospital, Reykjavik, Iceland Abstract In a spinal cord injured (SCI) patients with lower motor neuron lesion the associated muscles degenerate as a consequence of inactivity. If the motor neuron does not recover and the muscles are not connected to the spinal cord they denervate and are unable to contract. In several years this leads to severe degeneration of the muscle to the point that no contractile elements can be detected. Side effects are thinner skin with higher risk of decubitus ulcer, lower capillary density, lowering of bone mineral density with higher risk of bone fracture and other side effects. To date the side effects are treated but there has been no treatment keeping the muscl- es active, maintaining their volume and force. In a European project RISE (QLG5- CT-2001-02191) [1] a novel method for treating denervated degenerated muscles has been developed. Muscle fibres are directly stimulated electrically with higher current intensities than are recommended in international standards and are available in current commercial simulating devices. Results of the RISE project show that muscles can regain their volume and to a great extent their force through stimulation therapy once a day for one to five years depending on degree of degeneration of the muscles in the beginning of therapy. To monitor this treatment, that is changes in muscle and other tissue volume, shape and density a method has been developed using spiral computer tomography (CT). Thereby the thigh is scanned from the hip joint to the knee joint with 1,25 mm thick slices. This scanning is done regularly every four to six months during electrical stimulation therapy period. From this information a three dimensional models of muscles, bones, veins are made using the Mimics software. Comparing the models the tissue changes can be detected. In this work bone mineral density is specially addressed. Quantified CT is made using calcium hydroxyapatide as a calibration material. The bone tissue is segmented according to six Houndsfield unit (HU) intervals. This gives six models, each for one density interval and therefore of a part of the femur. Shape, structure and statistics of the models for each scanning are compared using the Mimics tools. Results show that the total amount of bone tissue is not changing, that remodelling of the bone takes place with an increase in the densest part of the bone at locations where force is expected from the stimulated muscle but a decrease at other location. This suggests that the electrical stimulation therapy is contributing to remodelling of the femur bone. Introduction Spinal cord injured (SCI) patients with a lower motor neuron lesion suffer from degeneration of muscles below the injury. This is due to inactivity, as the muscles are never contracting. In comparison paraplegic patients with an intact lower motor neuron tend to develop spasm, activated through the motor neuron and the muscles do contract but without control. This muscle activity means that they do not degenerate