Objective A prototype magnetic resonance imaging (MRI)-compatible positioning device was used to move an MRIguided high intensity focused ultrasound (HIFU) transducer. The positioning device has three user-controlled degrees of freedom that allow access to various targeted lesions. Materials and methods The positioning device was designed and fabricated using construction materials selected for compatibility with high magnetic fields and fast switching magnetic field gradients encountered inside MRI scanners. The positioning device incorporates only MRI compatible materials such as piezoelectric motors, plastic sheets, brass screws, plastic pulleys and timing belts. The HIFU/MRI system includes the multiple subsystems (a) HIFU system, (b) MR imaging, (c) Positioning device (robot) and associate drivers, (d) temperature measurement, (e) cavitation detection, (f) MRI compatible camera, and (g) Soft ware. Results The MRI compatibility of the system was successfully demonstrated in a clinical high-field MRI scanner. The ability of the robot to accurately move the transducer thus creating discrete and overlapping lesions in biological tissue was tested successfully. Conclusion A simple, cost effective, portable positioning device has been developed which can be used in virtually C. Damianou · N. Milonas Frederick Institute of Technology (FIT), Limassol, Cyprus any clinical MRI scanner since it can be sited on the scanner's table. The propagation of HIFU can use either a lateral or superior-inferior approach. Discrete and large lesions were created successfully with reproducible results.

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A software platform written in MATLAB has been developed in order to control an MRI guided Focused ultrasound system. The software serves 7 main tasks: a) MRI imaging, b) transducer movement (the user may move the robot manually or automatically by specifying the pattern, the step and the number of steps), c) messaging (starting time, treatment time left etc), d) Camera control, e) Patient data (age, weight, etc), f) Controlling the parameters and activation of a signal generator and g) Temperature measurement. The motors are activated using a 24 V DC supply which is incorporate in an enclosure that includes the drivers of the motors. The motors are interfaced using a USB card (National instruments NI-6251). Feedback is provided using a timer card. The software controls a positioning device which can be used to treat patients with brain, liver, kidney, thyroid, pancreas and prostate cancer.

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