The ability to detect, capture, and analyze motion with microelectromechanical systems (MEMS) has become a commonplace feature on consumer and mobile devices. Where technological advances have provided high-precision motion capture, applications have extended into industrial fields. Many potential medical diagnostic and instrumentation applications can benefit from merging the precision of industrial devices with the mobility and economies of consumer devices.
In some cases, the complexity of medical motion capture rivals that of high-end military systems. For instance, precision navigation, typically associated with applications developed for land, air, and sea vehicles, is increasingly being used in medical applications ranging from surgical instrumentation to robotics. Also, while the design requirements of a surgical navigation system share broad similarities with traditional vehicle navigation, there are distinct new challenges posed by the environment and the level of required performance.
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This article first introduces some of the fundamentals of MEMS motion sensing, including key understandings needed for component selection. It also looks at the unique challenges of medical navigation applications, and explores possible solutions ranging from various sensor mechanisms, to necessary sensor processing, to the unique system characteristics and data processing required to provide optimal solutions. Critical sensor specifications will be reviewed and explained for their individual contributions and, more importantly, the potential error and drift mechanisms will be discussed to aid in sensor selection. Opportunities and approaches for sensor enhancement through integration, sensor fusion, and sensor processing (such as Kalman filtering) will be highlighted as well.
Motion capture enables innovation and value in healthcare
Silicon-based accelerometer and gyroscope sensors known as MEMS (Figure 1) are commonly found today in a wide range of devices. These inertial sensors detect and measure motion, with minimal power and size, and are valuable to nearly any application where movement is involved, and even those where lack of motion is critical. Table I outlines some of the basic pertinent medical applications by motion type. Later, more advanced applications where combinations of motion, in complex scenarios that present additional challenges, will be discussed.
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Fig.1: MEMS silicon structures sense acceleration and rotation and convert this to an electrical signal with the help of signal processing.
Table I: Inertial sensors accurately capture varied and complex motion to drive widespread medical applicability.