Adaptation of a Haptic Robot in a 3T fMRI

This video demonstrates how to use a phantom haptic robot during FMR imaging with an ultimate goal of assessing brain activity during motor tasks in humans. When the robot's arm is manipulated by a subject, precise measurements can be made of the arm position and the force applied by the subject. In order to record FMRI in conjunction with haptic robotic manipulations, it is important to avoid having the robot interfere with the FMRI output by introducing too much electrical noise and also to avoid damage to the robot from the MRI's magnetic field.

To accomplish this, the robot is first encased in an aluminum shielded box. In addition, the shielded robot is attached to an eight foot effector handle that will be used by the subject during the experiment. The shielding and eight foot handle minimize the disruptive electrical and magnetic fields when the phantom robot is used with the MR scanner.

When a subject is placed in the MRI and manipulates the phantom robot's effector arm via the eight foot handle, virtual reality experiments can be done of naturalistic reaching passive displacement of the limb and haptic perception adaptation, learning in varying force fields, and texture identification. Ultimately, this setup can be used to correlate brain activity with movement and planning through functional MRI recordings and kinematic analysis of the robot data. The main advantage of this technique over existing methods like using compressed air or water Tory, the sensory motor interaction is that the haptic robot responds with millisecond latencies even to complex dynamic objects.

This method can help answer key questions in the study of neuro control of movement. For example, the brain regions active during haptic interaction with virtual objects. To begin place a rolling table with an aluminum shielded box outside the MRI scanner door.

The free end of the table should be supported and the exterior end of the long handle effector detached assure that the robot is switched off. Then place the robot in the table socket and secure the aluminum safety plate over the robot with two screws. Next, attach the end effector to the robot handle and check that it moves freely.

Then attach the 10 foot parallel cable with aluminum shielding to the robot, and check that the shielding is intact. Add extra foil if needed. Place the aluminum shielding box over the robot being careful to place the parallel and power cables into the groove on the back.

Carefully screw on the shielding box. Pack aluminum foil into the cable groove on the shielding box, and be sure the foil makes contact with the shielding on the parallel cable. Prepare to enter the high magnetic field environment by removing any and all metallic objects and non MR Safe items.

Moving the robot into the MRI room requires two people in order to assure that the setup can be brought into the magnetic field safely. With one person holding the free end of the robot table and another person stabilizing the box end roll, the free end forward until the robot just enters the door of the room. The researcher holding the box end should now clip the security rope tethered to an anchor hole on the back of the shielding case.

Assure that the other end is firmly attached to a wall Anchor next working together. Roll the table into the room and attach it with Velcro straps to the foot of the FMRI table. The robot end of the table must stay as far away from the scanner as possible.

Now attach the robot's parallel cable to the custom filter on the pass through to the control room and plug in the robot. The shielding foil on the parallel cable should make contact with the filter. Finally, attach the exterior part of the end effector being the long handle that the subject will reach to the robot.

Verify that the handle will be able to enter the bore of the FMRI cleanly without hitting the side. Once the robot is set up in the scanner, start up the control computer. Then assure only the custom filter is on the interior part of the pass through and attach the six foot parallel cable to the robot.

Next, check that the robot motors are turned off. Then start up the phantom calibration routine and verify that the position readouts of the motors are stable. Now turn on the robot by opening the port on the back of the shielding box and activating the switches within the box.

Restart the calibration routine with the end effector approximately centered at the end of the conical wave guide. Step through the calibration and check that the calibration box has the appropriate haptic interaction. To begin the experiment, set up any extra equipment for the experiment, such as a visual display system.

Here, the Nordic Neuro Lab Incorporated vision system is used, which provides stereo viewing of visual displays. Now have the subject lie down on the scanner table and assure that he or she will be comfortable for the duration of the experiment. Place the head coil and cushioning.

Then adjust the distance of the robot by the hand screws and sliding the top of the table until the subject can reach the effector handle and move comfortably. Guide the table into the MRI bore manually by holding onto the robot end while the table is moving. Make sure the end effector is directed into the bore and does not catch on the outside.

Finally, run the FMRI experiment. Begin by obtaining an anatomical scan to check for any imaging artifacts. Then run the functional scans while the subject performs the functional task designed for the experiment such as a naturalistic reaching paradigm, the haptic robot and FMRI should not interfere with each other.

If the robot is being affected by the FMRI, then the readout of the motors will oscillate rapidly and the online representation of the robot will move even when the robot itself is not moving. In general, this happens when the robot's parallel cable is not properly shielded and filtered. This can be fixed by double checking the aluminum shielding on the cable that the Ferris core is properly placed on the parallel cable near the robot, and that the only filter to the robot is the custom filter on the scanner room side of the pass through.

Detecting errors in the FMRI is really only possible after the data have been reduced and analyzed. But an anatomical scan should be taken early in the study and checked for zipper effects or other artifacts indicative of correlated noise. Frequently such noise comes from metal on metal contact and can be cleaned up by tightening all the screws on the robot table, especially the hand adjustment screws on the side of the table.

Once mastered, this technique can be completed in about 15 minutes, which is very important for the FMRI. Since time is so expensive While attempting the procedure, it's urgently important to keep in mind the MRI safety protocols since the robot could potentially be drawn into the bar of the MRI.