|ECR 2015 / C-1009|
|Virtual Navigator Real-time Ultrasound-MRI Fusion Imaging of leg muscles in supine and weight bearing|
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Aims and objectives
Preliminary study to determine the feasibility to perform real-time MRI and Ultrasound fusion imaging of leg muscles. Tests were carried out by first acquiring leg muscle images while subject was lying supine and then standing using an Esaote MRI GScan Brio system. GScan Brio (Fig. 1) is a tilting MRI system equipped with a permanent magnetic unit (0.25T) that is able to rotate magnet and patient’s bed from 0 to 90 degrees while scanning muscles in conventional (supine) and weight-bearing (standing) positions [1, 2].
This feature is especially useful as the MRI image sequence allows us to assess leg muscles’ biomechanical and physiological changes as they shift from a standing (weight-bearing) to a supine (conventional) position.
Being able to attain MRI images of muscles in both positions, lets us study muscle structures at different stress and fatigue levels, possibly opening new valuable prospects in the assessment of rehabilitation treatments (for instance in order to study leg muscles’ deep magnetic stimulation) and in the follow-up of patients with degenerative muscular structure diseases.
Virtual Navigator fusion imaging technology was used to enhance real-time Ultrasound scans with double position MRI acquisitions, thereby supplementing MRI data [7, 8] with morphological (B-Mode), hemodynamic (Colour, Power and Pulsed Wave Doppler) [3-6] and stiffness (Elastosonography) data. Fusing together these real-time diagnostics supplied by Ultrasound with the highly detailed anatomical images offered by MRI, allows the operator to display in real-time a virtual space where the different imaging modes are merged and where Ultrasound scanning plane spatial data is correlated with three-dimensional MRI volumes. This allows for an easier navigation that is based on the geometrical and spatial relationships between the real-time data and pre-acquired data.
Virtual Navigator is based on electromagnetic tracking technology used in conjunction with Ultrasound probes (and biopsy instruments for instance) and accurate Motion Compensation Sensor. This sensor is placed on the body being examined to counteract voluntary and/or involuntary movements and to enable continuous motion compensation which preserves the previously set co-registration between two, or more than two, imaging modes.
This preliminary study aims to show the potential of real-time fusion imaging for MSK clinical applications that are not limited to relaxed muscles supine assessments, but include the examination of weight bearing muscles structure in standing position. Virtual Navigator technology could also visually aid muscle biopsies in the assessment of pathologies, rehabilitation and follow-up after therapies as well as to display biopsy needle thanks to the Virtual Biopsy technology . In vivo tests for Virtual Navigator real-time fusion imaging between MRI and Ultrasound, both in standing and supine positions are being presented.
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