Applications in Medical Care

1. ISMICT 07 Overview of Wireless Sensor Networks Applications in Medical Care The Second International Symposium on Medical Information and Communication Technology Presenter: Professor Carlos Pomalaza-RáezDecember 11, 2007

2. B 11 13 A 16 15 6 17 F E C 19 18 12 11 10 9 8 5 4 3 1 20 14 7 2 D Topics Overview of Medical Applications Sensor Node Architecture IEEE 802.15.4 Routing Coverage Localization

3. Stage Model of the Medical Practice New and better medical devices are continuously introduced to detect vital signals and present them in a suitable format for healthcare givers The interpretation can be regarded as a data compression and data conformity process The physicians make a treatment prescription based on the patient’s medical history and current clinical reports by consulting the evidence-based database, pharmaceutical handbook and other resources Y. Shieh, et al., “Mobile Healthcare: Opportunities and Challenges,” Proceedings of Sixth International Conference on the Management of Mobile Business, July 9-11, 2007, Toronto, Ontario, Canada

4. Healthcare Wireless Network Expansion Each day more and more equipment is going “wireless” from pulse-oximeters to more complex patient vital signs monitors and ventilators Environments must scale from a few clients to 100’s on a single subnet External factors such as nearby TV and radio stations can affect overall performance. Interoperability profiles and standards are required to ensure plug-and-play operation in heterogeneous environments E. Sloane, et al., “Safety First! Safe and Successful Digital Network Wireless Medical Device Systems,” 2006 HIMSS Annual Conference February, San Diego

5. Wireless phone WiMax PDA Bedside PC PACS Server Telephone IP PC Laptop GSM Wi-Fi W-Fi Access point Camera Video Application servers Scanner Biomedical equipment RFID « Tag » RFID reader IP Convergence Integration of data, voice, image , video on a single traffic network based on the Internet protocol Eliminates the maintenance of a parallel voice network Decreases considerably the expenses on phone calls and fax transmissions Interoperability of networks, applications and devices used in information technology Allows the reuse of the existing data-processing infrastructure

6. Hospital systems Wired network Cellular phones PACS Radiology Laptop Lab Pharmacy Etc. Patient record Wireless router (Wi-Fi) Computer on wheels Tablet PC PDA (Personnel digital assistant) Mobile Devices Facilitates the mobility of doctors, practitioners and caregivers Allows access to patient information at any moment, everywhere and on real time Improves automatic data gathering through barcode or RFID reading Allows the immediate sharing of patient information and results Improves the internal communication within the caregiver team and with the support staff Helps to reduce paper

7. Room Topology Medical information collected by sensors on the patient’s body (WPAN) is displayed on a bedside monitor This information is also transmitted to another hospital location for remote monitoring, e.g., a nurses’ station) In case of emergency, when the patient is moved from his/her room to the intensive care unit, these communications need to be maintained D. Cypher, et al., “Prevailing over Wires in Healthcare Environments: Benefits and Challenges,” IEEE Communications Magazine, pp. 56-63, April 2006

8. Mobile reader Pharmaceutical product management Access point RFID Server Wall-mounted reader Equipment localization and tracking Bracelet Medical and chirurgical equipment tracking Fixed reader Patient Identification and tracking Radio frequency identification Facilitates the management of assets (wheel chairs, scanners, ambulatory equipment, etc) Improves patient localization and helps caregivers to provide services without delays Enhances the process of drug administration (identification, distribution, localization, returns and disposal) Facilitates the automatic data capture and the follow-up of blood and biological samples

9. Specialist Researcher Patient Doctor Telemedicine Utilization of different assets independent of their geographical location Multidisciplinary collaboration Facilitates the dissemination of medical knowledge to practicing doctors and medical students Allows doctors in remote and rural areas to consult with specialists in urban areas

10. Mobile monitoring platform Data capture Mobile device GSM GPRS WiMax Internet Real-time patient monitoring Remote monitoring Reduce the number of patients transferred to urban hospitals Allows tele-consultation and tele-diagnosis including the option of obtaining opinions of distant experts Facilitates the patient remote monitoring with instantaneous data transmission for analyses and follow-ups Allows remote handling of medical equipment (tele-surgery) and direct action of the expert on the patient Improves coordination of first-responders workers during in the event of catastrophes or emergency cases

11. Wireless Body Area Network E. Jovanov, et al., “A wireless body area network of intelligent motion sensors for computer assisted physical rehabilitation,” Journal of NeuroEngineering and Rehabilitation, 2005, 2:6

12. Wireless Body Area Network The personal server can be implemented on an Internet-enabled PDA or a 3G mobile phone, or a regular laptop of desktop computer. It can communicate with remote upper-level services in a hierarchical type architecture. Its tasks include: Initialization, configuration, and synchronization of WBAN nodes Control and monitor operation of WBAN nodes Collection of sensor readings from physiological sensors Processing and integration of data from the sensors Secure communication with remote healthcare provider

13. Wearable Monitoring Systems Fabric electrodes have been used to monitor EKG and respiratory activity M. Pacelli, et al., “Sensing Fabrics for Monitoring Physiological and Biomechanical Variables: E-textile solutions,” 3rd IEEE-EMBS International Summer School and Symposium on Medical Devices and Biosensors, Boston, Sept.4-6, 2006

14. Biomedical Measurements S. Arnon, et al., “A Comparative Study of Wireless Communication Network Configurations for Medical Applications,” IEEE Wireless Communications, pp. 56-61, February 2003

15. Wireless Technologies

16. Clinical Data vs Wireless Technologies M. Fadlee, et al., “Bluetooth Telemedicine Processor for Multichannel Biomedical Signal Transmission via Mobile Cellular Networks,” IEEE Transactions on Information Technology in Biomedicine, pp. 35-43, March 2005

17. Framework for Medical Image Analysis The remote medical image repositories communicate through different types of network connections with the central computing site that coordinates the distributed analysis. V, Megalooikonomou, et al., “Medical Data Fusion for Telemedicine,” IEEE Engineering in Medicine and Biology Magazine, pp. 36-42, September/October 2007

18. DICOM The Digital Imaging and Communications in Medicine (DICOM) standard is created by the National Electrical Manufacturers Association (NEMA) to aid the distribution and viewing of medical images. DICOM is the most common standard for receiving scans from a hospital. A single DICOM file contains both a header (which stores information about the patient’s name, the type of scan, image dimensions, etc), and all of the image data DICOM images can be compressed both by the common lossy JPEG compression scheme as well as a lossless JPEG scheme A single 500-slice MRI can produce a 68 MB image file

19. Transmission of DICOM Images The time values represent the total time, i.e. computing time (compression algorithm on each side of the communication link) plus the transmission time H. Lufei, et al., “Communication Optimization for Image Transmission in Computer-Assisted Surgery,” Proceedings of 2004 Congress of Neurological Surgeons, October 16-21, San Francisco, California

20. Activity Sensors They can be useful in monitoring patients undergoing physical rehabilitation such as after a stroke The Pluto custom wearable designed at Harvard incorporates the TI MSP430 microprocessor and ChipCon CC 2420 radio Pluto can run continuously for almost 5 hours on a rechargeable 120 mAh lithium battery It has a Mini-B USB connector for programming and to recharge the battery The software runs under TinyOS V. Shnayder, et al., “Sensor Networks for Medical Care,” Technical Report TR-08-05, Division of Engineering and Applied Sciences, Harvard University, 2005.

21. Pulse Oximeter • Non-invasive technology used to measure the heart rate (HR) and blood oxygen saturation (SpO2) • The technology used is to project infrared and near-infrared light through blood vessels near the skin • By detecting the amount of light absorbed by hemoglobin in the blood at two different wavelengths the level of oxygen can be measured • The heart rate can also be measured since blood vessels contract and expand with the patient’s pulse which affects the pattern of light absorbed over time • Computation of HR and SpO2 from the light transmission waveforms can be performed using standard DSP algorithms

22. Pulse Oximeter • Smiths Micro Power Oximeter Board • Length: 39 mmWidth: 20 mmHeight: 5.6 mm • 6.6 mA at 3.3 V, typical power:22 mW • Pulse range: 30-254 bpm SpO2: 0 to 99% • Data is transmitted from the oximeter board at a rate of 60 packets per second (5 bytes per packet) • Minolta Pulsox-2 • Size: W69xH60xD28 mm • Weight: approx. 70g (with 2 AAA batteries)

23. Electrocardiograph (EKG) • The most common type of EKG involves the connection of several leads to a patient’s chest, arms, and leg via adhesive foam pads. The device records a short sampling, e.g. 30 seconds, of the heart’s electric activity between different pairs of electrodes • When there is need to detect intermittent cardiac conditions a continuous EKG measurement is used. This involve the use of a two- or three-electrode EKG to evaluate the patient’s cardiac activity for an extended period • The EKG signal is small (~ 1mV peak-to-peak). Before the signal is digitized it has to be amplified (gain > 1000) using low noise amplifiers and filtered to remove noise

24. Electrocardiograph The P wave is associated with the contractions of the atria (the two chambers in the heart that receive blood from outside) The QRS is a series of waves associated with ventricular contractions (the ventricles are the two major pumping chambers in the heart) The T and U waves follow the ventricular contractions

25. Electrocardiograph IMEC has recently developed a wireless, flexible, stretchable EKG patch for continuous cardiac monitoring Placed on the arm or on the leg the same system can be used to monitor muscle activity (EMG) The patch includes a microprocessor, a 2.4 GHz radio link and a miniaturized rechargeable lithium-ion battery The total size is 60x20 mm2 Data is sampled between 250 and 1000 Hz an continuously transmitted The battery has a capacity of 175 mAh which provides for continuous monitoring from one day to several days

26. EKG Signals Various sampling rates and quantization levels are used when EKG signals are digitized In practice sampling frequencies between 128 Hz and 256 Hz are used The higher sampling rates and bit rates, e.g. 16 bits, are used to characterize EKG in sufficient detail

27. Interoperability There is need for intercommunication among medical devices and clinical information systems. This has been accomplished with a number of medical products. Infusion pumps and ventilators commonly have RS-232 ports, and these devices can communicate with many physiological monitoring instruments. Products to link medical equipment and personal communication devices exist as well However, virtually all of these are specialized applications—custom interfaces unique to the two devices being linked To address the medical device plug-and-play interoperability problem, a single communications standard is needed.

28. IEEE 1073.3.5 Project Transport standards associated with wireless data transport from IEEE 1073 point-of-care medical devices (POC) using personal area (WPAN), local area (WLAN), wide area (WWAN), and other networks It will make specific recommendations on the use of WPAN, WLAN, and WWAN wireless networks to facilitate medical data transport in various healthcare settings Specifically, technology protocols will be recommended to facilitate plug-and-play compatibility between (POC) medical devices and wireless networks to an end server or attending healthcare professional Medical data may range from non-critical to critical parameters, and expected quality of service (i.e., data throughput, latency, fidelity, network coverage) and acceptable performance parameters

29. MEDICAL INFORMATION BUS (MIB) MIB is published by the IEEE as the IEEE 1073 standard and follows the ISO OSI seven-layer communications model MIB is the name for a series of standards of connectivity between critical care bedside medical devices and hospital computer equipment Examples of these devices are: ventilators, pulse oximeters, patient monitors The heart of the MIB is the interface between the bedside communications controller (BCC) and one or more device communication controller (DCC) A medical device can function as both as BCC and DCC, i.e. a bedside monitor can be a BCC connected to a ventilator and an infusion pump DCCs, while at the same time it can be a DCC connected to a clinical information system acting as BCC

30. MIB

31. MIB – Logical Interface ACSE: Association control service ROSE: Remote operation service element CMDISE: Common medical device information service element MDIB: Medical data information base

32. HL7 Health Level 7 (HL7) standard is designed to enable different health care applications to exchange clinical and administrative data The most recent version of the HL7 specification uses XML messaging as its foundation HL7 also allows the use of trigger events, i.e. when a patient’s EKG waveform is available causes a request for that observation data to be sent to another information system

33. CodeBlue Infrastructure An ad hoc WSN Infrastructure for emergency medical care It is based on a publish/subscribe model for data delivery Designed to scale across a wide range of network densities an to operate on a range of wireless devices D. Malan, et al., “CodeBlue: An Ad Hoc Sensor Network Infrastructure for Emergency Medical Care,” Intl. Workshop on Wearable and Implantable Body Sensor Networks, April 2004.

34. Architecture of a Sensor Node

35. Sensors Everywhere Some current issues: • There are already many deployed sensors • Mobile phones • Surveillance cameras • GPS receivers • Motion and light sensors • How to organize them in networks • How to retrieve, store, and index data from sensors • Change the attention from “network” to “data” • Combine data processing with data delivery

36. The Traditional WSN Myth • The wireless sensor network paradigm was a myth from the late 1990s • Usual “assumptions”: • 1000s of homogeneous “sensing only” nodes • Mesh routing all nodes • This market is marginal Sink • Luckily, the ideas and algorithms that were developed can be applied to ubiquitous wireless applications • Huge research and market potential

37. Convergent WSNs • Convergent WSNs have real potential • Hierarchical part of other networks such as B3G • Ubiquitous embedded devices go wireless • Control & sensing • Ubiquitous services

38. Convergent WSNs • How do we integrate the Internet and Intranets with sensor networks? • Where is the intelligence? • Heterogeneous protocol interfaces? • Scalability and security are important issues • Mobility support • Gateways play an important role, as they communicate with TCP/IP and sensor networks • A proxy application often used to translate and shield one level from another

39. Convergent WSNs • Looking at the sales of uCs, there is a potential for billions of networked devices – much larger than the Internet itself • Huge impact also on the core Internet • IPv6 will be key to supporting convergent sensor networks • Intelligent data processing to reduce the network traffic

40. Embedded Meets Wireless • Microcontrollers are everywhere in embedded systems • appliances, watches, toys, cameras, industrial control, mobile phones, sensors, cars, automation • Microcontroller vs. microprocessor market • 15 x more microcontroller units sold yearly (8 billion) • 20 billion vs 43 billion USD market by 2009

41. Embedded Meets Wireless • Possibilities of wireless applications are endless • Projected sales of 802.15.4 chips are 150 million units by 2009 • Embedded systems have special characteristics • Academic community very computer science and protocol driven, often ignoring • Physical layer realities • Embedded system operation • Real-time capabilities

42. Device Architecture • Microcontroller and program code • Power supply • Power management • Renewable energy? • Memory (RAM, FLASH) • Sensors • Actuators • Communication • Input/output • Part of larger system?

43. Microcontroller • Main processing units of embedded devices • Special purpose and highly integrated • Integrated RAM, ROM, I/O, peripherals • Extremely good power to performance ratio • Cheap, typically 0.25 - 10.00 USD • Executes programs including embedded system control, measurement & communications • Usually time-critical requiring guarantees deadlines • Real-time performance a must in most applications • Pre-emptive scheduled tasks • Queues and semaphores

44. MSP430 • Texas Instruments mixed-signal uC • 16-bit RISC • ROM: 1-60 kB • RAM: Up to 10 kB • Analogue • 12 bit ADC & DAC • LCD driver • Digital • USART x 2 • DMA controller • Timers

45. ATmega AVR • Atmel AVR family • 8-bit RISC • RAM: Up to 4 kB • ROM: Up to 128 kB • Analogue • ADC • PWM • Digital • USARTs • Timers

46. ATmega AVR Current consumption VCC = 3 V is: The current consumption is a function of several factors such as: • operating voltage • operating frequency • loading of I/O pins • switching rate of I/O pins • code executed • ambient temperature The dominating factors are operating voltage and frequency

47. Power Management Power dissipation in CMOS systems modeled as Dynamic powerdepends on the switching behavior and the frequency of the circuit Static power (also called leakage component) depends only on the operational voltage In the past the static power has been assumed as very small when compared with . This is no longer possible as the CMOS technology is moving in the deep sub-micron range, e.g. 0.15 μm and smaller. These devices have large leakage currents which increases the amount of

48. Power Management Dynamic voltage scaling (DVS) is a standard technique for managing the power consumption of a system. In particular for CMOS circuits the power consumption,P, is proportional to the core voltageVand the frequencyf, The number of clock cycles needed to complete a computation is independent of the core frequency which means that the execution time is inversely proportional to the frequency. The total energy,E, is then proportional to the square of the voltage,

49. Dynamic Voltage Scaling Implementing an effective DVS system requires: • A variable power supply capable of a high voltage transition rate and minimum transition losses • A wide operational voltage range • A power scheduler that effectively computes the appropriate frequency and voltage levels needed to execute the various tasks

50. Dynamic Voltage Scaling The scheduler responsibilities include deciding when the processor can reduce its power and by how much. Its implementation assumes a preemptive operating system. This is not possible or difficult to implement in the small operating systems (OS) developed for microcontrollers used in WSN applications. These small OSs operate on an interrupt-driven policy and no “overseeing” program knows what other parts are doing. The implementation becomes even more complicated when the application requires the use of areal-time operating system.