Gary To

Integration of UWB and Wireless Pressure Mapping in Surgical Navigation

Wireless technologies are becoming more prevalent in hospital environments. An ultra-wideband (UWB) indoor tracking system is outlined, which has dynamic 3-D real-time root-mean-square error in the range of 5.24-6.37 mm using line-of-sight signals in different experiments. This high 3-D accuracy opens up many new applications to UWB indoor wireless positioning, which includes its use for tracking smart surgical tools and its ability to register relevant objects in the scene such as a spacer block for real-time pressure mapping of the femoral condyles. Experimental results quantifying the operating room (OR) environment for UWB transmission fit to the IEEE 802.15.4a channel model are included. A simulation of our UWB positioning system with interference from an IEEE 802.11a source shows the need for a front-end bandpass filter at our UWB receiver. Both microcantilever and microelectromechanical systems-based wireless pressure sensors are presented including quantitative performance metrics (e.g., hysteresis, sensitivity). The data for these sensors is transmitted over the 315- and 433.92-MHz telemetry bands. These bands are examined for their performance in the OR.

Micro-cantilever Array Pressure Measurement System for Biomedical Instrumentation

An analog signal processing IC for micro-cantilever array is designed for pressure measurement in biomedical applications. The chip includes analog multiplexer, instrumentation amplifier, sample and hold circuit, on chip voltage reference, SAR ADC and digital control unit. The 8-b ADC attains 45.4 dB SNDR and 56.4 dB SFDR while operating at 772 KHz. The chip occupies an area of 1.54 mm2 and consumes 17.8 mW power with a single 3.3 V supply. The chip was fabricated in a 0.35 mum 2-poly 4-metal process.

Quaternionic Attitude Estimation for Robotic and Human Motion Tracking Using Sequential Monte Carlo Methods With von Mises-Fisher and Nonuniform Densities Simulations

In recent years, wireless positioning and tracking devices based on semiconductor micro electro-mechanical system (MEMS) sensors have successfully integrated into the consumer electronics market. Information from the sensors is processed by an attitude estimation program. Many of these algorithms were developed primarily for aeronautical applications. The parameters affecting the accuracy and stability of the system vary with the intended application. The performance of these algorithms occasionally destabilize during human motion tracking activities, which does not satisfy the reliability and high accuracy demand in biomedical application. A previous study accessed the feasibility of using semiconductor based inertial measurement units (IMUs) for human motion tracking. IMU hardware has been redesigned and an attitude estimation algorithm using sequential Monte Carlo (SMC) methods, or particle filter, for quaternions was developed. The method presented in this paper uses von Mises-Fisher and a nonuniform simulation to provide density estimation of the rotation group SO(3). Synthetic signal simulation, robotics applications, and human applications have been investigated.

No Strings Attached

The microwave community has recently seen a large increase in the research being done pertaining to medical applications. A few example applications include.

Microcantilever Array Pressure Measurement System for Biomedical Instrumentation

An analog signal processing integrated circuit for microcantilever array has been designed for pressure measurement in biomedical applications. The chip consists of analog multiplexer, instrumentation amplifier, sample-and-hold circuit, on-chip voltage and current references, successive approximation register analog-to-digital converter (ADC) and digital control unit. Root sum square (RSS) error from the overall pressure measurement system including microcantilever array and the application specific integrated circuit (ASIC) is only ±1.79 KPa within the measurement range of 0-300 KPa. The 8-bit ADC attains 45.4 dB signal-to-noise-and-distortion ratio (SNDR) and 56.4 dB spurious-free dynamic range (SFDR), while operating at 772 KHz. The integrated circuit has been fabricated using 0.35-¿m 2-poly 4-metal CMOS process technology. The chip occupies an area of 1.54 mm2 and consumes 17.8 mW of power with a single 3.3 V supply.

ASIC Design for Wireless Surgical MEMS Device and Instrumentation

There is an increasing demand on computerized surgical instrumentation and implants that can acquire intra-operative or in-vivo data for surgeons and engineers. The sensory system is gaining complexity in order to obtain more accurate measurements. Although many off-the-shelf components and chips exist, multiple components are often required to achieve the desired function. Since space is limited in biomedical applications, application specific highly compacted integrated circuits are preferable. In this study, a chip is designed to process an array of microcantilever readout used in an intra-operative soft-tissue balancing instrument

A Low-Power Wireless Piezoelectric Sensor-Based Respiration Monitoring System Realized in CMOS Process

This paper presents a methodology of monitoring respiration pattern using piezoelectric transducer incorporating CMOS integrated circuits for signal processing and data transmission. As a proof of concept, the system has been tested by placing electrodes on human chest using adhesive hydrogel to detect the pulsatile vibration due to respiration. The system can be used either as a wearable device itself or alternatively can be attached to a jacket or a chest belt. The front-end transducer is a piezoelectric material-based sensor, which is comprised of a ferroelectric polymer named polyvinylidene-fluoride (PVDF). PVDF is also biocompatible, which makes the sensor suitable to be used as a wearable device. The charge produced by the sensor is converted to a proportional voltage signal with the help of a charge amplifier designed in a standard 130-nm CMOS process with eight metal and one poly layer. The analog voltage signal acquired from the charge amplifier is then converted into a digital signal using a reconfigurable pipelined analog-to-digital converter for ease of transmission. An impulse-radio ultra-wideband transmitter operating in the frequency range of 3.1–5 GHz is designed for wireless transmission of the data. The smaller footprint, lighter weight, wireless telemetry, and low-cost material along with the low-power integrated CMOS circuitry for signal processing and data transmission make the proposed system an attractive choice for stable respiration monitoring system.

The Future of Ultra Wideband Systems in Medicine: Orthopedic Surgical Navigation

Ultra-wideband (UWB) technology has been utilized in low probability of detection radar and communications systems for decades since its inception from time domain electromagnetics in the 1960s (Fontana, 2004). Interest in UWB for unique indoor communications and positioning applications has skyrocketed since the FCC released its notice of inquiry in 1998 and then opened up the 3.1-10.6 GHz and 22-29 GHz frequency bands for UWB use in 2002 (FCC, 2002).

A low-power CMOS energy harvesting circuit for wearable sensors using piezoelectric transducers

In this paper, a low-power CMOS AC-to-DC full-bridge rectifier with a switch for piezoelectric transducers is presented. It consists of two NMOS and two PMOS transistors, which are configured to operate as a full-bridge rectifier along with an Op-Amp-based switch control circuit which is connected to a PMOS transistor of the main full-bridge rectifier. With a load of 45KΩ, the output rectifier voltage is 703mV and the input piezoelectric transducer voltage is 694mV. Simulated VOUT versus VIN conversion ratio is 98.7% with an efficiency of 46%. The circuit has been implemented in a standard 0.13µm CMOS process.

Powering wearable sensors with a low-power CMOS piezoelectric energy harvesting circuit

Piezoelectric vibration based energy harvesters have been widely researched as powering modules for various types of sensor systems due to their ease of integration and high energy density. A number of piezoelectric transducer based topologies have been reported in literature. In this paper a piezoelectric transducer in parallel with a switch along with a low-power CMOS full-bridge rectifier is presented as a solution for efficient energy harvesting system for potential application in medical electronics. It consists of two NMOS and two PMOS devices comprising a full-bridge rectifier coupled with a PMOS device driven by a comparator based switch control circuit. With a load of 45KΩ, the output rectifier and the input piezoelectric transducer voltages are 694mV and 703mV, respectably, while the VOUT versus VIN conversion ratio is 98.7% with a power efficiency of 46%. The proposed energy harvesting circuit has been designed using a 0.13µm standard CMOS process.