**5. References**


In this chapter, brief explanations of modern communication strategies are explained and the limitations of their use in swallowable telemetry systems are described. Selections of the RF band and modulation methods are described and compared with each other. Since the human body attenuates high frequency RF power, their use in sophisticated communication

I'd like to thank Qun Wei and Zia Moth-Un-Din for their support of drawing the pictures. This book was supported by a grant of the Institute of Biomedical Engineering Research,

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[2] Hawkins, P., *Telemetry in the field: Practical refinements to improve animal welfare.*

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[4] Johnson, D.S., et al., *A general framework for the analysis of animal resource selection from* 

[5] Kong, W., et al., *A semi-implantable multichannel telemetry system for continuous electrical,* 

[6] Kutsch, W., *Telemetry in insects: the "intact animal approach".* Theory in Biosciences, 1999.

[7] Nations, C.S. and R.C. Anderson-Sprecher, *Estimation of animal location from radio telemetry* 

[8] Salvatori, V., et al., *Estimating temporal independence of radio-telemetry data on animal* 

[9] Walisser, J., et al., *Optimizing Telemetry Stock Animal Quality: Implementation of Monthly* 

[10] Ko, W.H., et al., *Studies of MEMS Acoustic Sensors as Implantable Microphones for Totally* 

[11] Yoon, K.W., et al., *Telemetry capsule for pressure monitoring in the gastrointestinal tract.*

[12] Browning, C., et al., *A New Pressure Sensitive Ingestible Radio Telemetric Capsule.* The

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Ieice Transactions on Fundamentals of Electronics Communications and Computer

**3. Conclusion** 

**4. Acknowledgment** 

**5. References** 

Kyungpook National University, Republic of Korea.

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is limited.


**1. Introduction** 

fusion (Hnat et al., 2008).

corpectomy model fixture.

**3** 

*USA* 

**Inductively Coupled Telemetry in** 

**Spinal Fusion Application Using** 

Ji-Tzuoh Lin, Douglas Jackson, Julia Aebersold, Kevin Walsh, John Naber and William Hnat

Titanium or stainless steel rods are implanted to stabilize vertebrae movement during spinal fusion surgery, which allows bone grafts to fuse two or more vertebrae. Radiograph images (x-rays), computed tomography scans (CT) and magnetic resonance imaging (MRI) procedures are used to assess fusion progress and diagnose problems during patient recovery. However, the imaging techniques yield subjective results (Vamvanij et al.,1998) and as a consequence, result in unnecessary exploratory surgeries to ascertain the efficacy of the spinal fusion surgery. As the grafted bone fuses, the bending strain of the implanted rods decreases as the load is transferred to the fused vertebrae (Kanayama et al., 1997). Strain is measurable on the spinal fusion fixture, normally a stainless or titanium rod. In other words, the amount of strain is an indicator of the load applied to the rod. Therefore, it is proposed that the strain on the implant rods can be used as an alternative and non-invasive method to monitor the progress of spinal

This chapter will demonstrate the realization of a telemetric strain measurement system for the spinal fusion detection as illustrated in Fig. 1. The system is composed of three major components: a sensitive strain sensor, a battery free transducer circuit that wirelessly interfaces the strain sensor, and an external interrogating reader that provides power to the implant as well as collects strain information from the transducer circuit. Research has shown that less power is consumed by a capacitive sensor than the resistive counterpart (Puers, 1993). In addition, the sensors require high sensitivity to eliminate the need for amplification that would require additional power. Therefore, the novel capacitive strain sensors are developed to meet both the power and sensitivity demand. Additional, in making the measurements a bodily-like situation, the sensor system, including the transducer circuit, is assembled on a housing (Aebersold et al., 2007) that is capable of transferring the strain from the rod to the sensor and accommodating for the size constrain. The testing loads on the rods will be provided by a material test system (MTS) with a

Although most strain sensors are capable of measuring axial strain due to tension and compression or their equivalents derived from bending, a sensitive bending strain sensor

**Capacitive Strain Sensors** 

*University of Louisville* 

