A UHF Radio Frequency Identification (RFID) System for Healthcare: Design and Implementation

A UHF Radio Frequency Identification (RFID) System for Healthcare: Design and Implementation A. C. Polycarpou 1, G. Gregoriou 1, A. Dimitriou 2, A. Bletsas 3, J. N. Sahalos 1,2 Cyprus Academic Research Institute (CARI) 1 Cyprus Academic Research Institute/Dept of ECE, University of Nicosia {gregoriou.g@unic.ac.cy, polycarpou.a@unic.ac.cy} 2 RCLab, Aristotle University of Thessaloniki {antodimi@mri.ee.auth.gr, sahalos@auth.gr} 3 Department of ECE, Technical University of Crete {aggelos@media.mit.edu} November 19, 2010 1

Outline of the Presentation Project Motivation Project Aims and Objectives Overview of RFID Technology System Design and Implementation Front-End Application: Graphical User Interface Challenging Issues and Research Findings Concluding Remarks November 19, 2010 2

Project Motivation Paper-based environments: medical errors approach 40 % (US Food and Drug Administration FDA) In-hospital medication errors: 44,000 deaths per year in the US, 700 deaths per year in Canada (Institute of Medicine, National Academic Press, 1999) Theft of equipment/supplies: $4,000 per hospital bed each year ($3.9 billion annually in the US) Asset Tracking: One third of personnel time is wasted in searching for medical equipment (e.g., infusion pumps, wheelchairs, etc) and patient files. Approximately 10 % of the inventory is lost annually. November 19, 2010 3

Outline of the Presentation Project Motivation Project Aims and Objectives Review of RFID Technology System Design and Implementation Front-End Application: Graphical User Interface Challenging Issues and Research Findings Concluding Remarks November 19, 2010 4

Project Aims and Objectives 1. Patient Identification 2. Inventory Control & Monitoring 3. Real Time Location Service November 19, 2010 5

Project Aim #1: Patient Identification Automatic and error-free patient identification Real-time uploading and updating patient s medical profile Paperless drug prescription Nurse/doctor accountability Patient treatment monitoring Drug administration monitoring Encrypted communication & securely stored patient data November 19, 2010 6

Project Aim #2: RTLS Scaled Down Implementation Hospital Ward B @BOCOC: Top View (34 m x 16 m) Room 23 Room 22 Room 21 Room 20 Room 19 Room 18 Room 17 Patient s Lounge Fixed Reader Room 16 Nurse Station Exam Room Inventory Room Room 15 Room 14 = RF Coverage = Directive Antenna Entrance November 19, 2010 7

On-Demand scan for: Wheelchairs Walkers Infusion Pumps Patient files Using a network of antennas connected to a fixed RFID Reader. November 19, 2010 8

Project Aim #3: Inventory Control & Monitoring Drug inventory room @ BOCOC: Real-time monitoring of drugs inside the inventory room Automatic update of the drug database Alarm activation due to possible expiration of drugs Alarm activation before medication is administered to the wrong patient November 19, 2010 9

RFID Technology: Active Vs Passive Feature Active Tag Passive Tag Power Battery Operated No Power Signal strength Low High Communication range Long range (100+ m) Short range (~3-5 m) Storage capability Large amount (128 kb) Small amount (128 b) Cost per tag $15-100 $0.15-5 Tag size Depends on application Sticker of credit card size Infrastructure cost Lower cheap interrogators Higher expensive fixed readers November 19, 2010 11

Available Spectrum for RFID Applications Near-field communication (inductive coupling) Backscatter communication (EM/RF coupling) 10-1 1 10 10 2 10 3 10 4 GHz LF 125-134 KHz HF 13.56 MHz UHF 433 MHz Microwave 2.45 GHz 5.8 GHz UHF: ETSI EN 302 208: 865-868 MHz (~3MHz) ETSI EN 300 220: 869.5-869.8 MHz (~300KHz) November 19, 2010 12

Block Diagram of a Passive RFID System RF Transmitter Interrogating RF Signal Up Converter Baseband Signal Processing Unit Circulator 1 2 Down Converter RF Receiver RFID Interrogator Backscattered RF Signal Tag antenna Chip RFID Tag November 19, 2010 13

Outline of the Presentation Project Motivation Project Aims and Objectives Overview of RFID technology System Design and Implementation Front-End Application: Graphical User Interface Challenging Issues and Research Findings Concluding Remarks November 19, 2010 14

Design and Implementation Wi-Fi Access Point Mobile Stations (Tablets) Database Patients Access Point RFID tags Assets Drugs Encryption/Security RFID Printer Antennas Computer Server Hospital Administrator Doctor s Office Nurse Station Pharmacy Stationary Readers LAN/WLAN November 19, 2010 15

Tablet PC/Handheld RFID UHF Gen 2 Reader UHF C1G2 RFID Wristband (GAO) C5 from Motion Computing USB UHF C1G2 IDtronic RFID Reader/Writer Easyconnect: USB/Ethernet clip-on module C5 with Easyconnect November 19, 2010 16

Graphical User Interface: Patient Identification November 19, 2010 18

Graphical User Interface: Inventory Control November 19, 2010 19

Graphical User Interface: RTLS November 19, 2010 20

Outline of the Presentation Project Motivation Overview of RFID technology Project Aims and Objectives System Design and Implementation Front-End Application: Graphical User Interface Challenging Issues and Research Findings Concluding Remarks November 19, 2010 21

Challenging Issues and Research Findings Short-range coverage for passive RFID systems Multipath and scattering from surrounding objects may reduce tag readability even at close proximity to the reader antenna Tags are affected by the attached surface (metal, liquids, etc.) Privacy/security issues Are the doctors and nurses willing to explore this technology in a healthcare environment? November 19, 2010 22

Best Chip Sensitivities time evolution Year Chip Sensitivity (dbm) November 19, 2010 23

Simulations & Optimization of Antenna(e) Position Using Ray- Tracing Algorithms z slice, z-field z slice, z-field x slice, z-field x slice, z-field 1 Reader Antenna 2 Reader Antennas with passive splitter (3-dB Tx power loss per antenna) November 19, 2010 24

Patient Room Coverage (Percentage) as a Function of Tag Sensitivity RFID tag at z=1.75m 1 Reader Antenna RFID tag at z=1.25m RFID tag at z=0.5m 2 Reader Antennas with passive splitter (3-dB Tx power loss per antenna) 80% Room Coverage @ -14dBm @ z=0. 5m Reader Antenna Transmit Diversity may substantially increase patient room coverage. Careful planning is needed (i.e. placing the antennas is tricky)! November 19, 2010 25

Concluding Remarks An UHF Gen 2 RFID system for healthcare applications was designed and implemented successfully in a laboratory setting. Major tasks include: Automatic and error-free patient identification Real Time Location Service of medical equipment within the premises of the hospital Quick and accurate monitoring of inventory (drugs, patient files, etc.) Tag readability and range were improved by using indoor propagation models and laboratory measurements in order to optimize antenna position inside the patient rooms. Tag polarization and space diversity was used with great results. A user-friendly Graphical User Interface that fully talks to the hardware (readers, printer, etc) via wireless/lan network was developed after close consultation with the medical staff of the Oncology Center A highly secured database with encryption was built on a server to house medical information and sensitive/private data associated with in-hospital patients Evaluation of the pilot RFID system at the Bank of Cyprus Oncology Center is under way Difficulties and challenges still exist; e.g., tags on metal surfaces or liquids, 100 % readability (?), long-range coverage, etc. November 19, 2010 27

As illustrated in the figures below, the reflection coefficient due to a possible mismatch between the chip impedance and the antenna impedance may significantly affect the maximum forward tag range. Enhancing chip power sensitivity increases the maximum forward tag range in a non-linear manner (Fig. 1) A higher reflection coefficient results in a lower maximum forward tag range (nonlinear dependence) (Fig. 2) f = 865 MHz P tx G = 2 W tag = 2 dbi PLF = 0.5 L c = 1.5 db Maxium forward tag range (m) 22 20 18 16 14 12 10 8 6 4 G tx = 7 dbi Gamma=0 Gamma=0.5 Gamma=0.9 Maximum forward tag range (m) 15 10 5 Chip Sensitivity = -14 dbm Gtx=5dBi Gtx=7dBi Gtx=10dBi 2-20 -19-18 -17-16 -15-14 -13-12 -11-10 Chip power sensitivity (dbm) 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Absolute Value of Reflection Coefficient November 19, 2010 28

Maximum Forward Tag Range Strongly dependent on the sensitivity of the chip, the impedance matching coefficient of the chip to the tag antenna, the polarization loss factor, the gain of the tag antenna, etc. P chip 2 2 ( )( 1 Γ )( ) Ptx GtxGtag PLF PL (min) = L λ PL = = Path Loss (line of sight) 4π r Solving in terms of r yields the maximum forward tag range r max c 2 ( PLF )( 1 Γ ) λ Ptx GtxGtag = 4 π LP (min) c chip 1 2 * 2 Zc Za 4RR c a 1 Γ = 1 = Z + Z Z + Z c a c a Conjugate match allows maximum power capturing from the interrogating signal Carrier Bit 0 ( Z L = Z 1 ) Bit 1 ( Z L =Z 2 ) 2 P tx = Effective radiated power (ERP = 2W for Europe: 865-868 MHz) Backscattered Signal from Tag to Reader November 19, 2010 29

Combined range: forward & return Power of the backscattered ASK modulated signal by the tag P received c1,2 ( PLF ) 2 Ptx Gtx λ σ = L 4πr 4π 2 2 λ Gtag σ = ρ1 ρ2 4π * Zc 1,2 Za ρ1,2 = Z + Z a 2 2 c 2 2 = Differential RCS ( ) State 1: Rc 1 + j Xc 1 + Xa ρ 1 ρ 2 ( ) State 2: Rc2 + j Xc2 + Xa Carrier 1 2 Bit 0 ( Z L = Z 1 ) Bit 1 ( Z L =Z 2 ) Backscattered Signal from Tag to Reader November 19, 2010 30

System Degradation due to Multipath Path Loss due to direct and multiple single reflections: N λ PL = 1+ Γ 4π r n= 1 2 ( d ) Γ = reflection coefficient for the n-th ray path n d = line-of-side path length d n jk d = n-th reflected ray path length N = total number of single reflections n d d n e n 2 Direct path d Single reflection path d n November 19, 2010 31