Wireless Telemedicine Systems: An Overview

Rapid advances in information technology and telecommunications - and, more specifically, wireless and mobile CO~mUnica-tions - and their convergence (“telematics”) are leading to the emergence of a new type of information infrastructure that has the potential of supporting an array of advanced services for healthcare. The objective of this paper is to provide a snapshot of the applications of wireless telemedicine systems. A brief review of the spectrum of these applications and the potential benefits of these efforts will be presented, followed by successful case studies in electronic patient record, emergency telemedicine, teleradiology

elemedicine can be defined as the delivery of health care and T the sharing of medical knowledge over a distance, using telecommunication means.It aims at providing expert-based medical care to any place where health care is needed.Telemedicine, as a concept, was introduced about 30 years ago, when telephone and fax machines were the first telecommunication means used.In recent years, several telemedicine applications have been successfully implemented over wired communication technologies like POTS (plain old telephone system) and ISDN (integrated services digital network).However, nowadays, modem wireless telecommunication means, such as the GSM (Groupe Speciale Mobile - Global System for Mobile Communications), GPRS (General Packet Radio Service), and the forthcoming UMTS (Universal Mobile Telecommunications Systems) mobile telephony standards, as well as satellite communications, allow the operation of wireless telemedicine systems, freeing the medical personnel and/or the subject monitored from being bound to fixed locations [l-31.The objective of this paper is to present a review of wireless health systems.
Telemedicine applications, including those based on wireless technologies, span the areas of emergency health care: telecardiology, teleradiology, telepathology, teledermatology, teleophtlalmology, teleoncology, and telepsychiatry.In addition, health telematics applications, enabling the availability of prompt and expert medical care, have been exploited for the provision of health-care services at understaffed areas, such as rural health centers, ambulance vehicles, ships, trains, and airplanes, as well as for home monitoring [4-lo].
The structure of this paper is as follows.In Section 2, wireless-technologies are introduced, followed by Section 3, on the transmission of digital images and video.In Section 4, an overview of wireless telemedicine systems, documented through published conference or journal papers, is given.This is followed by a brief summary of completed and ongoing European Union (EU)-funded projects, in Section 5. Selected case studies of these systems are presented in Section 6, followed by Section 7 with concluding remarks.A shorter version of this paper was published in [l 11.In this section, we briefly describe the main wireless technologies that have been used in wireless telemedicine systems: GSM, satellite, and wireless local-area network (WLAN).These systems are summarized in Table 1.GSM is a system currently in use, and is the second-generation (2G) of mobile-communication networks.When it is in the standard mode of operation, it provides data-transfer speeds of up to 9.6 kbps.Through the years, a new technique was introduced in the GSM standard, called High Speed Circuit Switched Data (HSCSD).This technology makes it possible to use several time slots simultaneously when sending or receiving data, so the user can increase the data transmission rate to 14.4 kbps (an increase of 50%), or even triple it to 43.3 kbps

WI.
Their is an evolution of mobile telecommunication systems from 2G to 2.5G (IDEN, 64 kbps; GPRS, 171 kbps; EDGE, Enhanced Data rate for GSM Evolution, 384 kbps) and, subsequently to 3G (W-CDMA, wideband code-division multiple access; CDMA2000, TD-CDMA) systems.This will facilitate the provision of faster data-transfer rates, thus enabling the development of telemedicine systems that require high-data-transfer rates, and that are currently only feasible on wired communication networks [12].Satellite systems are able to provide a variety of datatransfer rates, starting from 2.4 kbps, and moving to high-speed data rates of up to 2 x 64 kbps, and even more.Satellite links also have the advantage of operating all over the world [ 131.
WLAN is a flexible data-communications system, implemented as an extension to or as an alternative for a wired LAN.Using radio frequency technology, WLANs transmit and receive data over the air, minimizing the need for wired connections.Thus, WLANs combine data connectivity with user mobility.They are becoming very popular in a number of vertical markets, including healthcare, retail, manufacturing, warehousing, and academia.These industries have profited from the productivity gains of using hand-held terminals and notebook computers to transmit real-time information to centralized hosts for processing.Today, wireless LANs are becoming more widely recognized as a general-purpose connectivity alternative for a broad range of applications.We fore-

Transmission of Digital Images
The use of digital imaging in medicine has benefited from the formation of the Digital Imaging and Communications in Medicine (DICOM) committee [14].The committee was formed in 1983, by the American college of Radiology (ACR) and the National Equipment Manufacturers Association (NEMA).For still images, DICOM has adopted various JPEG variants, such as lossless JPEG and JPEG-LS [15], and it is expected to adopt JPEG 2000 [16].For digital video, the DICOM committee may adopt the MPEG-2 standard [17].
There are essentially no theoretical bandwidth requirements for transmitting medical images.In effect, lack of bandwidth can be compensated for by longer transmission times.Yet, high-quality medical images, such as a single chest radiograph, may require from 40 to 50 MB.In practice, it is desirable to at least be able to transmit medical images during a single patient visit, so as to avoid a follow-up visit.
Due to the diagnostic use of medical images, medical imagecompression techniques have primarily focused on lossless methods, where the image can be reconstructed exactly from its compressed format [18][19].Unfortunately, lossless methods can only provide limited compression ratios, usually ranging between 2 and 3.7 [20].With lossy compression methods, the original image is only approximately reconstructed from its compressed format.Hence, adoption of lossy image-compression techniques requires the careful evaluation of the effect of compression on diagnostic performance [2 11.In general, optimum performance requires the study of the impact of compression on different diagnostic situations.Clearly, though, the background of most images is of no diagnostic value.Hence, "region of interest" (ROI) techniques can be used to avoid compression of the background, and thus provide substantial improvements in compression ratios [22].For example, where the region of interest covers about 20% of the entire image, average compression ratios of about 15.1 have been reported using PEG-LS, while an average compression ratio of only 2.58 is possible using the entire image as the region of interest [22].
Another solution is to provide a simple perceptual test, where the participants are asked to identify the original image in a set that is composed of compressed images and the original image.Clearly, i,f the original image cannot be identified, then the compressed images that are confused as original will also not impact the diagnosis [22].This technique leads to near-lossless techniques, where the uncompressed image differs from the original in only a small number of levels (+1, +2, out of a possible 4096 levels).For comparison, JPEG-LS in lossless mode provides for an average compression ratio of 2.58, which improves to 3.83 in the near-lossless mode (+I levels) [22].In addition, for a region of interest that covers 20% of the image region, the average compression ratio improves from 15.1 to 22.0 [22].

Transmission of Digital Video
As mentioned earlier, the DICOM committee has not yet adopted any standard for digital video compression.The adoption of MPEG-2 is possible, but this is limited by the MPEG-2 requirement for the constant-delay method for frame synchronization [ 17, 231.The constant-delay requirement is not supported by ATM (asynchronous transfer mode) networks, making it difficult to deliver real-time MPEG-2 video over ATM [23].On the other hand, the transmission of offline video is still possible.
It is important to distinguish among the requirements for real-time video transmission, offline video transmission, medical video and audio for diagnostic applications, and non-diagnostic video and audio.Real-time video transmission for diagnostic applications is clearly the most demanding.Offline video transmission is essentially limited by the requirement to provide patientdoctor interaction.Real-time diagnostic audio applications include the transmission of stethoscope audio, or the transmission of the audio stream that accompanies the diagnostic video.Good-quality diagnostic audio at 38-128 kbps using Dolby AC-2 has been achieved, while MPEG-1 Layer 2 audio (32-256 kbps) or Dolby AC-3 (96-768 kbps) may also be used [23].For non-diagnostic applications, such as teleconferencing, H.26 1 (64 kbps -1.92 Mbps) and H.263 (15-64 kbps) may be acceptable [23].A typical application will require a diagnostic audio and video bit stream, in addition to a standard teleconferencing bit stream.
Due to the high bandwidth requirements and the framesynchronization problem, successful methods for real-time diagnostic video transmission will most likely require the adoption of the MPEG-4 standard [23-251.The frame-synchronization problem is alleviated in MPEG-4 via the use of timestamps on each frame [24-251.A possible method for achieving acceptable video compression for diagnostic purposes may be through the use of objectbased encoding and decoding.In object-based encoding and decoding, different bit rates are allocated to different parts of the digital video, according to the level of diagnostic importance.The advantage of this approach is that it can significantly reduce the required bandwidth, while maintaining high-quality video images of the regions of diagnostic interest.As an example, it is important to note that most of the bandwidth in digital-video transmission is spent on tracking moving objects in video images.Clearly, if there is no motion between successive images, then high-quality video can be achieved by simply encoding the small differences between video frames.This would be automatically detected in all videocompression standards.Furthermore, in many clinical applications such as in personal injuryit is clearly the case that the stationary part of the video is of significant importance, as opposed to moving objects in the background.A disadvantage of object-based coding is that it is not always clear which part of the video is of diagnostic importance.This obstacle can be overcome by using interactive video, where the user can interactively select a region of interest.

Wireless Telemedicine Systems
The INSPEC and MEDLINE databases were searched with the following keywords: telemedicine and mobile, telemedicine and GSM, telemedicine and GPRS.The number of papers (including both conference and journal papers) published under these categories in the years 1979 to 2001 was 132.Out of these reports of wireless telemedicine systems published in the literature, a total of 35 selected applications are briefly summarized in Table 2.These systems cover a significant component of the whole spectrum of health telematics applications.They are grouped in Table 2 primarily under the wireless technologies of GSM, satel-lite, radio, and wireless LAN.Under each of these technologies, the systems are grouped into the areas of emergency healthcare, telecardiology, teleradiology, telepsychology, teleopthalmology, and remote monitoring (including monitoring at rural health centers, home monitoring, and subject monitoring at distant or isolated locations).In addition, in Table 2 the data transmitted are coded under the following columns: "Signals" for bio-signals, "IMG' for medical imaging or video, "EPR' for electronic patient record, and   2 gives some comments characterizing the system described.
The majority of these applications (1 7) used the GSM network, and the papers were published between the years 1999 and 2001.These applications covered the areas of emergency telemedicine (7), remote monitoring (4), and telecardiology (3).Satellite links were also used in many, telemedicine applications (12).
Most of these systems were used for remote monitoring (8), followed by emergency telematics (2) and telecardiology (2).Satellite systems have the advantage of worldwide coverage and offer a variety of data transfer speeds, even though satellite links have the disadvantage of high operating cost.A few analog radio telemedicine systems were developed for the support of aircraft and ships in isolated areas.Finally, WLAN technology is an emerging technology, already being applied for emergency telematics and teleradiology.

EU-Funded Projects in Wireless Telemedicine
Distance  4 summarizes the ongoing projects under the Fifth framework program.Both tables are structured similarly.In Table 3, the first column gives the project name/program/duration/total cost and funding, the second column gives the area of application, and the third column gives the technology employed.The fourth column, "Data Transmitted," is structured similarly to Table 2 in that it is subdivided under "Signals," images, electronic patient records, and teleconferencing mode.The last column gives the number of partners and countries involved.
Table 3 shows that most of the projects carried out under the two programs in the time span 1990-1998 fall under the area of rural-area support (6), followed by projects for emergency telematics (4).These projects exploited mainly the GSM and satellite wireless technologies.Most of the ongoing projects (1 998- 2002) fall under the areas of hospital support (3) and remote monitoring (3) (see Table 4).These projects exploit Bluetooth, UMTS, and GPRS wireless technologies.

VI. Case Studies
In this section, case studies of successful wireless telemedicine systems in emergency health telematics, telecardiology, teleradiology, electronic patient record, and home monitoring are given.

Emergency Telemedicine: The Ambulance and Emergency-I 12 Projects [41-[81
The availability of prompt and expert medical care can meaningfully improve health-care services in understaffed rural or remote areas.The provision of effective emergency telemedicine and home-monitoring solutions is the major field of interest of the Ambulance HC 100 1 and Emergency-1 12 HC4027 projects, which were partially funded by the European Commission/DGXIII Telematics Application Programme.An overview of the concept of both projects is shown in Figure 1.portable medical device for emergency telemedicine.The system enables the transmission of critical bio-signals (ECG, BP, HR, gency site to an emergency call center.It thus enables physicians to direct pre-hospital care in a more efficient way, improving patients' outcome and reducing mortality The system was designed to operate over several communication links, such as satellite, GSM, POTS, and ISDN.In Emergency-112, emphasis was given to maximizing the system's future potential application through the utilization of several communication links (both fixed and wireless).as well as throueh the increase of the overall svs-P SpO,, temperature), and still images of the patient, from the emer- Baas-Consultation I tem's usability, focusing on an advanced user interface and ergonomics.The system comprises two different modules.The first is the patient unit, which is the unit located near the patient (see Figure 2).This unit can operate automatically over several communication means, and has several operating features (depending on the case used).The second unit is the physician's unit, which is the unit located near the expert doctor.This unit can operate over several communication links fdeoendine on the dace where the exvert -zz3,l 9 1 doctor is located) The final system was used to provide emergency health care over several communication links (from ambulances, rural hospital centers or any other remotely located health center, and navigating ships), and for patient home monitoring.Emergency-I 12 has been used successfully in three European countries (Greece, Italy, and Cyprus) since 1998.The network infrastructure for the island ofCyprus is shown in Figure 3.

ECG Telecardiology Service [61]
In this study, the diagnostic accuracy of a telecardiology service, employed in the daily activity of 150 general practitioners, was evaluated.Each practitioner was equipped with a 12-lead ECG portable electrocardiograph (Card-Guard 7100), which was connected to a mobile (GSM) or fixed (POTS) connection.At the consultation site, a specialized cardiologist was available, in order to give directions to the general practitioner.The system was tested for one year, in which 3456 calls took place.At the time of the ECG recording, 44% of patients were symptomatic.ECG teleconsultation satisfactorily supported all the problems for 2452 (71%) of the patients, whereas futher diagnostic tests were requested for 862 (25%) of the patients.For 142 (4%) of the patients, referral to the emergency department was given.Cardiological diagnosis was confirmed in 95 (73%) of the patients, while anxiety or gastritis was presumed in 35 (27%) of the patients.In the group of patients ( n = 3314) for whom the cardiologist solved the problem without referral to the emergency department, there were five patients who were admitted to the emergency department for myocardial ischemia in the 48 hours following the teleconsultation.The study concluded that the telecardiology service, when compared to emergency-department admission, showed a sensitivity of 95%, a specificity of 97.5%, and a diagnostic accuracy of 92.5%.The aim of the Ambulance [SI project was the development of a portable emergency telemedicine device, which supports realtime transmission of critical bio-signals, as well as still images of the patient, using the GSM link.This device can be used by paramedics or non-specialized personnel who handle emergency cases, in order to get directions from expert physicians.The system comprises two different modules: (I) the mobile unit, which is located in an ambulance vehicle near the patient; and (2) the consultation unit, which is located at the hospital site, and can be used by the experts in order to give directions.The system allows telediagnosis, long-distance support, and teleconsultation with mobile healthcare providers by experts located at an emergency coordination center or a specialized hospital.

A Teleradiology System Using a
Mobile CT Van and High-speed Satellite Communication [45] In this system, a mobile van houses a whole-body spiral computed-tomography (CT) scanner, and a second van houses the sat-ellite communications equipment.This system was used for CT scanning, online two-way transfer of image data, and teleconferencing to a consultation center with various specialists.The system personnel consist of two drivers, a radiology technician who operates the CT scanner, and the telecommunications unit.The mobile CT van is 12 m long, and is equipped with a whole-body CT scanner, designed for lung-disease screening.In addition, the van houses a PC for CT data transmission, teleconferencing equipment, an image printer, a facsimile machine, and resuscitation equipment.The stationev diagnostic center is equipped with a Sun Sparc 1000 server, equipped with a 209 GB, RAID 7 disk array, and an image-observing station with two 21 in, 1728 x 2304 monochrome monitors, and a 1280 x 1600 color monitor.The mobile and stationaly stations communicate at 155 Mbps in asynchronous transmission mode (ATM) via satellite or ISDN.The protocol used for image communication is DICOM 3.0, and, for online diagnosis to screen CT images, it takes 10min for the transmission of 16.5 MB.The system was applied for the screening of 19117 residents in 29 districts of Japan.This resulted in the identification of 75 cases of early lung cancer, which were subsequently treated by partial pneumonectomy.In addition, the system was applied to providing medical services in rural areas, at sporting events, and for home monitoring.The usefulness of the proposed system is limited by the high initial cost for building the system (US$ 8,000,000), hy the number of subjects scanned, as well as by the satellite-communications fee.These costs can be significantly lowered via the manufacture of IO similar CT vans, doubling the number of subjects examined, and transmitting the images via the use of a multi-port format and in compressed format.

Electronic Patient Record:
Mobile Medical Data (MOMEDA) [36,[55][56][57]621 Adequate, continuous information ahout patients during advanced medical procedures is a major factor in the patients' overall satisfaction.Moreover, patients, while hospitalized, need to continue their daily routine, or they at least need to be able to communicate through modem means (via e-mail or fax, for example) with the outside world.On the other hand, specialized physicians who are moving inside or outside the hospital need to have complete and continuous information ahout a patient's record, in order to be able to provide the best medical practice.These are the main issues addressed by the Momeda HC4015 telemedicine project [62], which was partially funded from the European Commission/DGXIII.Telematics Application Programme.The system consisted of two modules, as illustrated in Figure 4: (I) the patient's information module, and (2) the doctor's information module.The main objective of the patient's information module was the development of a demonstration unit called the Personalized Medical System (PMIS) [55, 561.This system allows access to customized disease-specific information from patients about their medical problem, the planned medical procedures, and what lifestyle they should have during hospitalization, and afterwards.
The main objective of the doctor's information module was the development of a demonstration unit that allows the consulting physician to access electronic patient records, using a hand-held companion device, connected to the GSM network [36, 571.A module based on the Nokia Communicator 9110 was developed (see Figure 5 ) and tested through the project.The user of this module was able to connect to the hospital's main server, and to receive electronic records and medical images, such as MRIs.The project was successfully tested in three European countries (Finland, Italy, and Greece).by a coordinated team of professionals.Home-based care of chronic illnesses (e.g., cancer) by a team of professionals is often a necessity, due to the protracted length of the illness.In contrast, hospital-based treatment is limited, and is often demand-based for short periods of time.As it is not possible for the health-care team to be physically present with the patient at all times while the patient is undergoing treatment, a principal aim of the current project is to overcome this problem, through a network for medical collaboration called DITIS (AITHC in Greek, which stands for Network for Medical Collaboration) [9, lo].DITIS is a system that supports virtual medical teams dealing with the home healthcare of cancer patients in Cyprus, and it is currently exploited at the European level.It aims to support the creation, management, and coordination of virtual medical teams for the continuous treatment of the patient at home, and, if needed, for periodic visits to places of specialized treatment and at home.
The design and development of the DITIS telecooperation system (the infrastructure of which is given in Figure 6) is based on Intemet and GSM/WAP (wireless application protocol) connectivity.It includes four modules.The first module consists of mobile agents, e.g., IBM's Aglets workbench, Mitsubishi's Concordia, and Voyager, for the implementation of a flexible communication infrastructure for the support of mobile users.The mobile agents may be extended to offer intelligence and cooperation.The second module is a Web-based database for the storage and processing of the Electronic Medical Record.The third module is a telecooperation system for the sharing of information, team communication, and the coordination of team activities.The fourth module is an adaptive intelligent interface for database access from a variety of access units, such as mobile computing units with GSM Intemet connectivity, and fixed units with Internet access supporting telecooperation.

Concluding Remarks
This paper has attempted to give a snapshot of completed, ongoing, and emerging applications of wireless information-technology applications in health systems.Wireless telemedicine technologies -linked with emerging technological trends such as pervasive computing (enabling seamless human-computer interactions with multimedia databases, "smart" cards), intelligent-agent technology, electronic-commerce applications in the healthcare sector, high-bandwidth Web, and citizen-centered services -provide promising solutions for forthcoming healthcare applications [63].These trends, together with more work and needed efforts in the areas of interoperability, standards, security, and legal issues [2] at both the national and international levels, will facilitate wider application of healthcare telematics, including wireless, for the whole health-care sector.This will enable offering better service to the citizen.
In conclusion, the following are some recommendations that will help enable the wider spread of wireless health systems: 1. High-level political and managerial decisions (including government and private sector), commitments, and leadership for the immediate promotion and application of wireless health systems in hospital operations and in rural-health-center services.
2. Training of physicians, paramedical, and administrative staff in the use and benefits of wireless information technology in medicine.
3. Clarification of the legal and ethical issues.
for audio (A), image (I), or video (V) teleconferencing.The last column of Table

Figure 3 .
Figure 3.The Emergency-I12 network infrastructure for the island of Cyprus.

Figure 4 .
Figure 4.An overview of the Momeda project.

Figures.
Figures.The doctor's handheld device, as shown on the Momeda project Web site (from the Momeda web page 1621, 01999 Momeda HC4015, used with permission).

Figure 6 .
Figure 6.The DITIS network infrastructure for medical collaboration (from the DITIS Web page 191, 01999 DITIS project, used with permission).

5. 5
DITIS: Collaborative Virtual Medical Team for Home Healthcare of Cancer Patients [9, I O ] Complex and chronic illnesses, such as cancer, demand the use of specialized treatment protocols, administered and monitored IEEE Antenna's and Propagation Magazine, Vol.44, No. 2, April 2002

Table 1 . The main wireless communication networks/standards.
IL, Ka band 2.4 kbps see that this technology will penetrate the health sector in the near future.