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Biomedical: Robot Arm Positioner for Focused Ultrasonic Transducers

Client

Laboratory for Medical Ultrasonics, Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts.

Problem

To provide for the positional control of a set of rotating ultrasonic transducers focused at one point in space. System must provide continuous three dimensional translation of focal point along a desired path within a deep seated tumor volume under a computer control program.

Solution

An existing support frame was strengthened and modified. An extension arm providing X,Y,Z, translation was designed to support a frame having 45 degrees of adjustment to either side of the theta-X and theta-Y, while theta-Z was under continuous rotation. Such Rotation demanded the use of a hollow drive shaft and brush commutators designed for the high frequency in use. Four cables of coaxial type passed through the rotating shaft carrying the power to the transducers. rotation was providd by means of a stepping motor and gear-belt drive enclosed in a gray plastic cover for safety. A bayonet mount facilitated the removal of the transducer systems. Up to four transducers can be mounted at one time. System has been in use since 1981. A more complex robot has been designed and and about to be built.

Picture of the Robot Arm Positioner