Presented at the 2012 AAPM Annual Meeting « Back

Accelerometer-Based Position-Adaptive Stimulation Technology

Keith A. Miesel, BSME, keith.miesel@medtronic.com¹, Timothy Denison, PhD1, (1) Medtronic, Inc., Minneapolis, Minnesota

Introduction: Accelerometers are used in a wide range of applications from video-game controllers to aircraft guidance and navigation. The RestoreSensor™ neurostimulator (Medtronic, Inc., Minneapolis, MN), contains a 3-axis accelerometer which provides information enabling determination of patient posture orientation and activity level. The AdaptiveStim™ feature uses this information to automatically adjust stimulation parameters with position changes based on predefined patient preferences. Discussion: An accelerometer measures acceleration resulting either from gravity or from a change in velocity of an object. Most accelerometers consist of two basic components (Figure 1): a. Proof mass mounted on a spring suspension: Acceleration is transmitted through the suspension to the proof mass, causing deflection of the mass relative to the surrounding body. b. Pickoff: The pickoff senses the deflection of the suspended proof mass and outputs a signal in proportion to the deflection, which is proportional to acceleration. A complete three-dimensional acceleration vector can be constructed by arranging three acceleration-sensing devices orthogonally. Modern microelectronics processing techniques have enabled the creation of ultra-miniature accelerometers in which the seismic mass, flexures, and pickoff can be formed in a single piece of silicon. The accelerometer used in the RestoreSensor neurostimulator has unique size/power/performance attributes needed for integration into an implantable medical device (Figure 2). Conclusions: Integration of 3-axis accelerometer technology into a spinal cord stimulation system enables the detection of patient posture and activity levels, which can be used to provide benefits of pain relief and convenience.

Funding: Development of the position-adaptive spinal cord stimulation technology described in the abstract was funded by Medtronic, Inc.