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CFMRI Force Project:

MRI Compatible Force Measurement Device

Project Motivation

There are many applications in which being able to take force measurements while simultaneously conducting a functional magnetic resonance imaging (fMRI) scan is useful. Here at UC San Diego (UCSD) the Center for fMRI (CFMRI) performs MRI scans for many research groups that have interests in these applications. For example, at UCSD there is a group that is studying the rehabilitation of patients who have undergone tendon transfer surgery to recover function of their thumbs after spinal cord injuries. The group is interested in measuring lateral pinch forces of these patients while in an fMRI to better understand the rehabilitation process and why some recover motion while others do not. Another application can be seen in research being done by a collaborating group in Brazil that is interested in measuring the leg bracing of patients with Parkinson's Disease as compared to healthy patients. At a larger level, this kind of study using the fMRI in conjunction with force measurements could be performed on patients who have undergone different tendon transfer surgeries, have other injuries and diseases, etc. to help us better understand the brain and these different diseases.

Project Objectives

Our objective is to design and build a device that can measure lateral pinch forces inside an fMRI scanner. The device must meet the following requirements:

• • Measure forces within a range of 0.1-100 N and a resolution of 0.02 N

• Have minimal signal interference from the MRI

• MRI-Compatible

• Time synchronize with the MRI brain scans

• Handheld

• Setup in less than 15 minutes

• Keep to a $600 budget

Our Design

Our device consists of four main components: (1) Grip (2) Cable (3) Filter (4) Data Acquisition. The components come together as seen in the diagram below. The grip is strapped to the patient's hand and rests upon the side of his or her index finger. The patient can pinch the top of the grip with his or her thumb, transmitting the force to the FlexiForce sensor. The signal is passed through shielded cable to the penetration panel that separates the MRI scan room and the control room. Inside the control room the signal is filtered with a 1st order active low pass filter and passed into LabView through a 16-bit data acquisition system.

Testing and Device Performance

The following is a video of our test in the MRI. In addition to doing some baseline noise test and calibration tests, we had the opportunity to stick one of our teammates into the scanner with the device to test how it would actually be used. More information on the performance of the device can be found under the "Design Process" tab.