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Surgical correction of scoliosis is a complicated mechanical process. Understanding the loads applied to the spine and providing immediate feedback to surgeons during scoliosis surgery will prevent overloading, improve surgical outcome and patient safety. Long-term development of residual forces in the spinal instrument after surgery with the continual curvature changes over time has been unknown. The goal of this research work was to develop a wireless implantable sensor platform to investigate the loads during and after surgery. This thesis describes research leading to the design of a sensor platform that uses both 403 MHz and 2.45 GHz for wireless communication, and reports the resolution and accuracy of the built-in temperature sensor, the A/D accuracy of the sensing platform, the power consumption at different operation modes, the range of the wireless communication and the discharge characteristics of a potential capacitive power module. / Biomedical Engineering

The FCC allocated the spectrum of 402-405 MHz for MICS (Medical Implant Communication Services) applications in 1999. The regulations for MICS band apply to devices that support the diagnostic and/or therapeutic functions associated with implanted medical electronics. The implanted devices aid organs and control body functions of patients to support specific treatments, and monitor patients continuously so that necessary action can be taken in advance to avoid serious conditions. To enable to use MICS applications, several requirements must be satisfied. An implanted wireless device should have a small size, consume ultra-low power, and achieve the date rate of at least 200 kbps within 2 m distance. The major challenge is to realize ultra-low power devices. Thus the low-power design of the RF circuit is crucial for MICS applications as the power consumption of the wireless devices is mostly contributed by RF circuits. This thesis investigates low-power design of an LNA and a down-conversion mixer of a receiver for MICS applications. The key idea is to stack an LNA and a mixer, while the LNA operates in the normal super-threshold region and the mixer in the sub-threshold region. In addition, a gm-boosting technique with a capacitor cross-coupled at the LNA input stage is also adopted to achieve a low noise figure (NF) and high linearity, which is critical to the overall performance of the receiver. The mixer operating in the sub-threshold region significantly reduces power dissipation and relaxes the voltage headroom without sacrificing the LNA performance. The relaxed voltage headroom enables stack of the LNA and the mixer with a low supply voltage of 1.2 V. The proposed circuit is designed in 0.18 μm RF CMOS technology. The merged LNA and mixer consumes only 1.83 mW, and achieves 21.6 dB power gain. The NF of the block is 3.55 dB at 1 MHz IF, and the IIP3 is -6.08 dBm. / Master of Science

Objective: This present study aimed to evaluate whether cochlear implant (CI) surgery influences the patients’ postoperative work ability. Additionally, the influence of demographic, audiometric, and psychometric parameters on postoperative work ability was determined. This study also explored the contrasting relationship between the postoperative work ability of employed as well as pensioned patients and the above-mentioned influencing factors. Methods: In this prospective study, 79 patients were included. They responded to questionnaires and audiometric testing preoperatively and twelve months postoperatively. Work ability was evaluated with the Work Ability Index (WAI). Disease-specific health-related Quality of Life (HRQoL) was determined using the Nijmegen Cochlear Implant Questionnaire (NCIQ) and generic HRQoL was analyzed with the World Health Organization Quality of Life: Best Available Techniques Reference (WHO-QOL-BREF). Mental disorders (depression, somatoform disorder, stress) were assessed with the German Patient Health Questionnaire (PHQ-D). The patient’s personality was reviewed with the Big Five Personality Test (B5T). Speech comprehension was evaluated in noise with the Oldenburger sentence test. Results: The patients’ postoperative work ability was not significantly (p>0.05) affected by CI-treatment. However, employed patients displayed significantly (p<0.001) higher postoperative work ability than pensioners. The generic HRQoL, personality, and mental disorders were unaffected by CI-treatment (p>0.05). Instead, speech comprehension and disease-specific HRQoL displayed significant improvements (p<0.001) postoperatively. As shown through multiple regression analysis, age (ß = -0.275*, p<0.05) and the subdomain physical health of the patient’s generic HRQoL (ß = 0.471**, p<0.01) were significantly associated with postoperative WAI outcome scores. The influencing factors stress (ß = - 0.744**, p<0.01) and age (ß = -0.571*, p<0.05) displayed significant correlations with the postoperative work ability of employed patients. In contrast, the subdomain physical health of the patient’s generic HRQoL (ß = 0.805**, p<0.01) was significantly associated with the postoperative work ability of pensioned patients. Conclusions: Perceived stress, age, and physical health are strong predictive parameters for the patient’s postoperative work ability. The results indicate that preliminary multiprofessional and individualized counseling, the promotion of work accommodations, and physical activity during CI-(re)habilitation may contribute positively to the patient’s postoperative work ability. Additionally, a differentiated therapeutic approach between employed and pensioned CI- recipients is fundamental to bringing about better WAI outcome scores post-implant for each subgroup.

Wireless body area networks (WBANs) have tremendous potential to benefit from wireless communication technology and are expected to make sweeping changes in the future human health care and medical fields. While the prospects for WBAN products are high, meeting required device performance with a meager amount of power consumption poses significant design challenges. In order to address these issues, IEEE has recently developed a draft of IEEE 802.15.6 standard dedicated to low bit-rate short-range wireless communications on, in, or around the human body. Commercially available SoC (System-on-Chip) devices targeted for WBAN applications typically embed proprietary wireless transceivers. However, those devices usually do not meet the quality of service (QoS), low power, and/or noninterference necessary for WBAN applications, nor meet the IEEE standard specifications. This dissertation presents a design of low-power RF front-end conforming to the IEEE standard in Medical Communication Service (MICS) band of 402-405 MHz. First, we investigated IEEE 802.15.6 PHY specifications for narrow band WBAN applications. System performance analysis and simulation for an AWGN (additive white Gaussian noise) channel was conducted to obtain the BER (bit error rate) and the PER (packet error rate) as the figure of merit. Based on the system performance study, the link budget was derived as a groundwork for our RF front-end design. Next, we examined candidate RF front-end architectures suitable for MICS applications. Based on our study, we proposed to adopt a direct conversion transmitter and a low-IF receiver architecture for the RF front-end. An asynchronous wake-up receiver was also proposed, which is composed of a carrier sensing circuit and a serial code detector. Third, we proposed and implemented low-power building blocks of the proposed RF front-end. Two quadrature signal generation techniques were proposed and implemented for generation of quadrature frequency sources. The two quadrature voltage controlled oscillators (QVCOs) were designed using our proposed current-reuse VCO with two damping resistors. A stacked LNA and a down-conversion mixer were proposed for low supply and low power operation for the receiver front-end. A driver amplifier and an up-conversion mixer for the transmitter front-end were implemented. The proposed driver amplifier uses cascaded PMOS transistors to minimize the Miller effect and enhance the input/output isolation. The up-conversion mixer is based on a Gilbert cell with resistive loads. Simulation results and performance comparisons for each designed building block are presented. Finally, we present a case study on a direct VCO modulation transmitter and a super-regenerative receiver, which can also be suitable for an MICS transceiver. Several crucial building blocks including a digitally-controlled oscillator (DCO) and quench signal generators are proposed and implemented with a small number of external components. / Ph. D.

Antenna implants are used to establish a telemetry link to enable wireless data transfer, suitable for telemedicine and other medical applications. Inbody environments with water-based tissues lead to severe power absorption, making signal strength and radiation efficiency challenging yet central performance aspects of antenna implants. Fundamental performance limits exist regarding radiation efficiency; however, these limits consider theoretically ideal Hertzian dipoles. A semi-analytical model is used to evaluate the feasibility of previously determined fundamental bounds and the optimal dipole solution, both with respect to physical necessities of finite material conductivity and antenna size. This study uses a spherical model to represent a simplified in-body environment with various phantom compositions. Furthermore, the study focuses on implants operating within the Medical Implant Communication System (MICS) frequency band, but models and methods are not restricted to the considered frequency. The work contributes to the field of implantable antennas in several aspects; evaluating the feasibility of fundamental bounds, establishing more realistic performance limits, and determining the optimal dipole solution with respect to radiation efficiency. Other findings are presented in related areas, particularly concerning conductor loss and evaluation of the impedance for antennas inside a high-loss phantom. Moreover, the work presents a suggested method to measure electrically small magnetic dipole antennas. Methods and models are documented in a substantial theoretical derivation, and findings are verified using independent methods. Neglecting necessary antenna aspects like finite size and conductivity can lead to faulty conclusions on implant performance. Providing a more realistic performance target helps predict the performance of realistic antenna designs. Ultimately, increased knowledge of implanted antennas simplifies the design process to achieve high-performance implants. / Antennimplant används för att etablera en telemetrilänk som möjliggör trådlös dataöverföring, exempelvis användbart inom telemedicin och andra medicinska tillämpningar. Vattenbaserade kroppsmiljöer resulterar i kraftig absorption, vilket implicerar att signalstyrka samt strålningseffektivit blir utmanande men även centrala prestanda egenskaper för antennimplnatat. Det existerar fundamentala prestandabegränsningar för strålningseffektivitet, men dessa gränser är etablerade med hänsyn till teoretiskt ideala elementära dipoler. En semi-analytisk modell används för att utvärdera rimligheten av tidigare begränsningar samt den optimala dipolen, bägge med hänsyn till nödvändiga aspekter som ändlig konduktivitet och antennstorlek. Denna studie använder en sfärisk modell för att representera en simplifierad kroppslig miljö med olika vävnadskompositioner. Studien fokuserar på antennimplantat inom frekvensbandet dedikerat för Medical Implant Communication System (MICS) enheter, men modeller och metoder är typiskt inte begränsade inom omnämnt band. Arbetet bidrar till området för implanterbara antenner i flera aspekter; att utvärdera rimligheten av fundamentala gränser, fastställa mer realistiska prestandagränser samt bestämma den optimala dipolen med avseende på strålningseffektivitet. Andra resultat presenteras inom relaterade aspekter som metallförlust och utvärdering av en antenns last eller ingångs impedans inuti sfäriska och kroppsliga miljöer. Dessutom presenteras en metod för att mäta elektriskt små magnetiska dipoler. Metoder och modeller är dokumenterade eller demonstrerade via härledning, och centrala resultat har verifieras med oberoende metoder. Att förbise nödvändiga aspekter som ändlig storlek och konduktivitet kan leda till felaktiga slutsatser gällande prestanda. Däremot, att fastställa en mer realistisk gräns bidrar till att förutsäga prestandan i realistiska tillämpningar. I slutändan så resulterar ökad kunskap i en simplifierad designprocess som underlättar i strävan till att uppnå högpresterande antennimplantat.

<p dir="ltr">Decades of semiconductor technology scaling and breakthroughs in communication technology have miniaturized computing, embedding it everywhere, enabling the development of smart things connected to the internet, forming the Internet of Things. Further miniaturization of devices has led to an exponential increase in the number of devices in and around the body in the last decade, forming a subset of IoT which is increasingly becoming popular as the Internet of Bodies (IoB). The gradual shift from the current form of human-electronics coexistence to human-electronics cooperation, is the vision of Internet of Bodies (IoB). This vision of a connected future with devices in and around our body talking to each other to assist their day-to-day functions demands energy efficient means of communication. Electro-Quasistatic Human Body Communication (EQS-HBC) has been proposed as an exciting alternative to traditional Radio Frequency based methodologies for communicating data around the body. In this dissertation, we expand the boundaries of wearable and implantable IoB nodes using Electro-Quasistatic Human Body Communication and Powering by developing advanced channel models and demonstrating novel applications.</p><p dir="ltr">Leveraging the advanced channel models developed for wearable EQS-HBC, we demonstrate wearable applications like ToSCom which extend the use cases of touchscreens to beyond touch detection and location to enable high-speed communication strictly through touch. We further demonstrate an application of EQS Resonant Human Body Powering to demonstrate Step-to-Charge, allowing mW-scale wireless power transfer to wearable devices. With increasing connected implanted healthcare devices becoming a part of the IoB space, we benchmark RF-based technologies for In-Body to Out-of-Body (IBOB) communication using novel in-vivo experiments. We then explore EQS-HBC in the realm of IBOB communication using advanced channel modeling, revealing its potential for low-power and physically secure data transfer from implantable devices to wearable nodes on the body, demonstrating its potential in extending the battery life span of implantable nodes. Finally, an overview of the potential of IoB devices is analyzed with the use of EQS-HBC where we propose a human-inspired distributed network of IoB nodes which brings us a step closer to the potential for perpetually operable devices in and around the body.</p>