International Journal of Medical Informatics (2003) 71, 157—163

Technical communication

Wireless and PDA: a novel strategy to accessDICOM-compliant medical data on mobile devices

Rafael Andrade*, Aldo von Wangenheim1, Mariana Kessler Bortoluzzi

Department of Computer Sciences-INE, Federal University of Santa Catarina, Caixa Postal 476,Trindade, Florianópolis SC CEP 88040-900, Brazil

Received 21 January 2003 ; received in revised form 5 June 2003; accepted 9 June 2003

KEYWORDSPersonal digitalassistants;DICOM;Wireless;Medical imaging;PACS

Summary The medical procedures at the patient bedside are out of the scope ofcurrent HIS/RIS systems, which means that patient record and image data access dur-ing the medical visit or the execution, recording and confirmation of the medicineprescriptions, still do not enjoy computerized support. As a consequence, the neces-sary inclusion of new data to the patient record, still needs to be carried out throughnotations on paper and later typed, causes delays on the availability of this infor-mation (Mobile computing in a hospital: the Ward-In-Hand project. SAC 2000-ACMSymposium on Applied Computing, Março, 2000, Villa Olmo, Como, Italy). This paperpresents a software technology where the medical and nursing staff will be equippedwith a handheld computer connected by radio to a central server that provides accessto the electronic patient records and that will actively inform about tasks pendingdistribution. The server acts as a database for multimodal electronic patient recordinformation, storing patient data from computerized tomography (CT), ultrasonogra-phy (US), magnetic resonance (MRI) images and also medical findings, observationsand prescriptions coded as DICOM Structured Reports (Digital Image and Communi-cations in Medicine). The prototype described in this article implements a medicalimages and structured reports server that makes the search and recovery of datastored in the DICOM standard possible.© 2003 Elsevier Ireland Ltd. All rights reserved.

1. Problem description

Many health care organizations (HCO) already pos-sess local or long distance computer networks tomanage administrative, pharmaceutical, patientrecord, laboratory and image and signal informa-tion. The availability of this information dependsdirectly on the integration between the Hospital

*Corresponding author. Tel.: +55-48-331-9117;fax: +55-48-331-9770.

E-mail addresses: andrade@inf.ufsc.br (R. Andrade),awangenh@inf.ufsc.br (A.v. Wangenheim), mariana@inf.ufsc.br(M.K. Bortoluzzi).

1Tel.: +55-48-331-7552/9498

Information Systems (HIS) and the Picture Archiv-ing and Communication Systems (PACS)/RadiologyInformation Systems (RIS) and their hospital-wideavailability. The increasing need to standardizestorage and transmission of clinical and administra-tive data is forcing the interoperability of systemsof various manufacturers and accelerating the ac-ceptance of standards for parts of the electronic pa-tient record, like the DICOM Structured Report [1].

Despite all the advantages in the use and develop-ment of PACS-related systems, it is still very difficultto connect different parts of a public health systemand to make the information accessible everywherewhere patient care takes place in the HCO. Thediversity of necessities found in institutions that

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deal with public health increases the complexity ofthe interface between PACS and other componentsof a HIS. It is common to find different implemen-tations of an information system in different placeswith the objective to solve this diversity [2]. As aconsequence, there is much important information,for example, the clinical workflow, image data andthe diagnosis text that cannot be accessed duringa medical visit to the patient bedside or in emer-gency situations.

This situation can be improved through the use ofmobile computers connected through a local wire-less network to central databases [3] and the use ofa software tool for the access of all kind of patientrecord data including images of all kinds, the inser-tion of new data like prescriptions and observationsand the support of the workflow distribution tasks.

1.1. Material and methods

Currently, for the storage and exchange medicaldata, three standards have been established: DICOM(Digital Imaging and Communications in Medicine)[10], HL7 (Health Level Seven) [4] and CEN/TC251[5]. The great majority of equipment that dealswith digital medical information supports the DI-COM standard. The use of accessible and cheap net-work technologies (TCP/IP or OSI) and the use of aservice protocol for the communication with otherdevices that support the DICOM standard do guar-antee that this standard could easily be integratedin an already existing PACS. The DICOM standardsupports the image and signal data codification, as-sociated information, and the definition of diverseservice classes (storage, recovery, search and imageprinting). Special formats used in the image storageand procedures for the association negotiation forthe transmission of image data through networksare also part of this standard.

With the creation of the DICOM Structured Repor-ting—DICOM-SR, in the year 2000, the standard leftthe scope of images and signals of PACS-only systemsand started to include also normalized structuresdescribing medical textual data, thus implementingan important part of the electronic patient recordin a structured and manufacturer-independent way.The DICOM-SR standard establishes a method forconstructing and transferring information objectsthat encode structured documents, which may befindings, laboratory results, clinical reports, pre-scriptions or any another type of clinical document.Structured reports ease the search for specific infor-mation, report translation and comparison betweendifferent findings. A report in the DICOM-SR stan-dard uses a controlled terminology, like SNOMED, asa way to prevent ambiguities of natural languages.

It can contain references to images, electrocardio-grams, audio files and another DICOM objects.

The HL7 standard specifies the rules for the com-munication and format of medical and HCO dataexchange at the application level of the OSI-TCP/IPmodel (level 7, according to International Stan-dards Organization—ISO) for open systems intercon-nection. It is an application-oriented standard andindependent of the software, hardware or network,providing the user with freedom in the search foroptimization. With this norm, it will be possible tomanipulate all the high-level tasks of communica-tion of a HCO providing considerable improvementsto their efficiency. For the transmission of images,HL7 references the DICOM standard [2].

The CEN/TC251 is a standard being developedby the European Union that was adopted as anISO-norm under number TC215, being developedtogether with ANSI-HISB (American National Stan-dards Institute, Healthcare Informatics StandardsBoard). This standard includes both DICOM and HL7scopes, and among the three standards mentionedit is supported more intensely in governmental andsupranational bodies. This standard also includes:architecture of information, standards for trans-ference of data, security and protection [4].

1.2. Methodology and architecturedescription

In this paper, we present the first prototype devel-oped at our research group. This prototype imple-ments only the patient record storage and recoverycompliant to DICOM SR standard, besides DICOM im-age consultation and manipulation facilities.

Using DICOM client [6] the basis was a mobileclient/server application called ‘Cyclops PDA DI-COM Editor’ (Fig. 1), already implemented by theCyclops project [8,9]. It was developed in a pilotexperiment realize in University Hospital of theFederal University of Santa Catarina in Brazilformanagement of information, coordination of thework of the hospital medical team and organizationof the work of the medical staff in general.

In this experiment, a mobile client/server ap-plication was developed for management of infor-mation, coordination of the work of the hospitalmedical team and organization of the work ofthe medical staff in general. The experiment ex-plores the use of handheld computers of low costand high portability, integrated through a wirelesslocal computer network within the IEEE 802.11bstandard. It supports the authentication of usersvia password and the access to encrypted data.It makes access and updates possible through a

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Fig. 1 Example of database list visualized in a webbrowser.

graphical user interface especially developed forhandheld computers and allows access to the elec-tronic patient record, and graphical data such asCT scans, US images or MRI data (Fig. 3).

As a starting point for the implementation of ourmobile application, we used the DICOM server andclient technologies already developed at the Cy-clops Project, called ‘Cyclops DICOM Server’ and‘Cyclops DICOM Editor’, respectively. The CyclopsDICOM Server is a DICOM Service Class Provider—SCP for storage, searches, recovery and notifica-tion of medical images compliant to the DICOMstandard. This system uses the DICOM upper levelprotocol for TCP/IP, which allows different imagemodality modes and supports equipment such asCT scanners, Ultrasound devices, MRI devices orradiological workstations supporting the DICOM

Fig. 2 Example of patient list visualized in a PDA.

standard, to establish connections through TCP/IPcomputer networks. The DICOM service classescurrently supported by the Cyclops DICOM Serverare verification, storage and search/recovery. Thesupported modalities are CT (Computerized Tomog-raphy), MR (Magnetic Resonance), US (Ultrasound),Waveforms (EEG, ECG, Hemodynamics) and patientrecords coded as DICOM-SR. It is important to pointout that the support to additional modes can easilybe implemented, due to the use of object-orientedtechnology [10]. Another characteristic that mustbe noted is the possibility for this system to bemulti-platform, (Linux, Solaris, SGI, AIX, HP/UX,AD/UX, PowerMac and Windows). As a DatabaseManagement System, the Cyclops DICOM Servercan use PostgreSQL, Oracle or MySQL (via ODBC).This DICOM server was used to provide data for thetests performed with our technology [6].

1.3. DICOM editor functionality

Cyclops DICOM Editor is a complete DICOM clientthat provides access to the information storedin a DICOM server and runs on Windows PCs orUnix/Linux workstations. After selecting a DICOMserver to be accessed and a particular patient, theinformation from all studies is loaded. Likewise,after one study is selected, all its series are loaded,and when a series is selected all its contained im-ages are loaded, being shown on the screen as athumbnail. Another important function of the Cy-clops DICOM Editor is to allow the launching ofdiverse image processing tools on the recoveredimages, for example, the Cyclops DICOM Series Edi-tor, a visualization tool for a series of images capa-ble of executing diverse important operations forradiologists on the images: graphical landmarks ofareas in the image, measurements, commentaries,sending of selected images to emails, changes tovisualization window and zoom [6].

2. Results

Using our DICOM client as a basis, an HTTP serverapplication was developed. This HTTP application,called ‘Cyclops PDA DICOM Editor’, is a special mid-dleware that acts in one direction as a DICOM client,communicating with the DICOM server, and in theother direction, as an HTPP server, generating dy-namical HTML pages formatted to be visualized ina PDA web browser running on a 200×320 moni-tor. This middleware can provide encrypted accessto DICOM data, through wireless network accesspoints. Each access point connected to the physi-cal network functions basically as a traditional HUB

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Fig. 3 Example of tomographic image visualized usinga handheld computer.

generating a radio network cell, providing access tothe wireless devices, using the IEEE 802.11b com-munication standard for the encrypted transmissionof the data in a fast and safe way on a rate up to11 Mbps.

2.1. Application scope

Since the Cyclops PDA DICOM Editor was basicallydeveloped as an HTTP server, it is also possible toaccess the data from any station connected to thenetwork of a hospital, using any web browser, whichallows a universal network interface with platformindependent functions. The application offers dif-ferent modes of consultation of radiological imagesand patient record data (findings, prescriptions andobservations, all coded as DICOM SR documents),besides allowing the adjustment to the radiologicalwindow of the computer tomography and magneticresonance images. Fig. 4 shows the application lay-out this technology.

The visualization of tomography and magneticresonance images in Cyclops PDA DICOM Editor,based on the form in which the images have beenloaded from the database, can be affected in twodistinct ways:

� Original settings: the images are loaded withoutmodifications to their pallet of colors, normally12- or 16-bit DICOM images, and presented withthe window settings under which they werestored;

� User-set window: the color pallet is modifiedtaking into account window width and windowcenter values provided by the user. Such valuesindicate the width of pallet (amount of different

gray shades) and the center of the scale in theHounsfield scale for radiological density. Sincean interactive setting of the window via an HTTPserver with generation of intermediary-valuedimages would be prohibitively slow, the systemprovides a pull-down menu where the user canselect one of a list of preset window settings,such as ‘chest’, ‘lung’, ‘bone’ and so on. Whenthe user select a new window setting, the Cy-clops PDA DICOM Editor receives a request forregenerating the images sent to the mobile de-vice and the displayed images are refreshed,now with the new window settings [7].

Due to the fact that the application manipulatesconfidential information of several patients, theaccess to the server is restricted to the authorizedusers, as a means of preserving the privacy andsecurity of the information. After the authentica-tion of the user, it is possible to visualize a windowshowing all the DICOM servers registered in thehospital, organized by modality. Based on a searchcriterion sent to the server, the Cyclops PDA DICOMEditor returns a list of the patients who satisfythe criterion (Fig. 2). When selecting determinatepatients, a new query is submitted to the server,which returns all the studies from this patient in anew window to the requester.

In the same way, when a study is selected all itsseries are loaded. After the selection of a series, allthe pertaining images are loaded and shown directlyon the web browser, making it possible to interactwith these images.

For the visualization of the images the applica-tion converts them to JPEG (Joint PhotographicExperts Group) format and stores them in a tempo-rary directory. When a new query is submitted or

Fig. 4 Schematic visualization of the application layoutof the developed technology.

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Fig. 5 Example of visualization of one MR slice in thedefault window.

when the system is quit, the images are deleted.When a new window selection is applied, a newquery is sent to the server, which generates a newvisualization of the images in the chosen radio-logical window setting. In order to generate thiswindow, some pre-defined values of the HU scaleare used, thus facilitating the visualization of theseimages in the PDA.

The application was developed to be visualizedin a PDA, thus only highly important information,for the medical staff, is shown. Fig. 5 shows a snap-shot of one MR slice accessed through an especiallydeveloped DICOM client who functions as an imageserver, reformatting radiological images and mak-ing them available in the PDA in real time.

The Cyclops PDA DICOM Editor can also access SRdocuments, which are shown as text. Fig. 6 showsa DICOM SR document visualized with the PDA.

2.2. Image quality and colorresolution issues

A typical PDA from the pocket PC family, like theiPAQ, disposes of only 48—64 MB of memory, whichhas to hold operating system, programs and data.To avoid overloading the mobile devices with thehuge DICOM data structures, we chose to generatecompressed JPEG images for the specific windowsetting of the chosen images directly on the DICOMmiddleware and to send them to the mobile devicein a ‘ready to see’ format with a fixed pallet. Thisraises the question whether the quality of the JPEGimages is enough for a correct visualization and

Fig. 6 Visualization of a DICOM SR document.

whether the mobile devices offer enough displayquality.

The typical pocket PC models currently on themarket have color displays with a 12 bit color depthand they only tend to become better. This alreadyallows palettes of 4096 colors. Supposing the oper-ating system will reserve about 64 pallet entries forthe window decoration colors, this leaves us withmore than 4000 possible gray shades that can berepresented.

The grayscale JPEG images that we generate are8 bit images, which have only 256 pallet entries.Since these images are generated for their specificradiological window settings and typical windowwidths range from 200 to 600 H.U., the pallet com-pression will be much less than one would supposelooking at the theoretical range of radiological den-sity of −1000 to +3000 H.U. It could be even noneat all if you have a CT series with a window width of250 H.U. On the other side, one has to consider thata human can normally distinguish only 40—60 shadesof gray and that the PDA application is intended forconsultation of the images and not for image pro-cessing. A lot of radiological workstations still inuse today use 8-bit displays and are considered ade-quate. The US images are 24 bit color JPEG images.

JPEG compression is, however, a quality loss fac-tor. But JPEG images can be generated with manydifferent degrees of compression. Most radiologi-cal images, since they are grayscale images, havelots of black background and have few local texturevariations, can achieve a high degree of compres-sion even with very conservative compression set-tings, showing no quality loss at all for the human

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Fig. 7 CT image visualized in original resolution.

observer when these parameters are observed. Thecompression rate of the Cyclops PDA DICOM Editorcan be parameterized to achieve the standards pre-ferred by the medical staff.

2.3. Zooming and image manipulationresources

Since the mobile device is an HTTP client, almostall image manipulation tasks have to be processedremotely in batch mode by the Cyclops PDA DICOMEditor. Presently, we implemented only the possi-bility of changing the radiological window settings,

but other image processing tasks implemented onthe workstation version of the Cyclops DICOM Editorcould be provided, given it makes sense to havethem run as batch jobs and from a mobile device.

There is, however, one visualization task that canbe performed locally on the mobile device. Thistask is zooming. The images are sent to the mobiledevice on their original resolution and convertedon the PDA to a format that places the whole im-age on the screen, thus reducing its resolution to200×200 pixels. The user can choose to see the im-age in the original resolution, normally 512×512,and navigate through the image to inspect it moreaccurately (Figs. 7 and 8).

Fig. 8 US image visualized in original resolution.

2.4. Access speed

The data access speed depends on three factors:radio network speed, generation of the HTML pagesand DICOM server access. The radio network speedvaries from 2 Mbps on areas with poor reception upto 11 Mbps when the signal is good and can be influ-enced by the number of access points distributedthrough the hospital. The total time varies depend-ing on the task at hand: a consultation of new DI-COM data takes more time than regenerating theimages for a new radiological window setting. Thetable below shows some results.

Modality Series size Resolution Colordepth

Firstaccess

Regeneration timeafter window change

CT 43 slices 512×512 8 bit 2′05′′ 0′55′′

MR 20 slices 256×256 8 bit 0′20′′ 0′10′′

US 11 snapshots 600×400 24 bit 0′30′′ n/a

3. Discussion and future work

Normally medical images obtained from radio-logical examinations such as the ultrasonography,conventional radiology, computerized tomography,magnetic resonance and nuclear medicine are fre-quently used in radiological clinics and hospitalsaiding the diagnosis of a series of illnesses. Theinterrelation between clinics, hospitals, depart-ments of radiology and other departments, mainlythe Intensive Care Unit and emergency unit, isof fundamental importance and increasingly de-pends on the accessibility of these images from any

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physical localization inside or outside the hospitalor clinic of origin.

The first archetype version of the system isbeing tested in the Telemedicine Lab of the Uni-versity Hospital of the Federal University of SantaCatarina—UFSC Brazil, where the viability of thesystem for use in assisting the hospital clinical bodywill be evaluated.

This system offers some advantages in the use ofhandheld computers to access the medical imagesand findings: the system is based on a web inter-face, allowing the integration of different systemsand DICOM applications and an efficient and flexi-ble access to the image database.

It is intended in the future to implement an ap-plication resident in the PDA, making it possible tohave access to medical findings stored in the DICOMSR standard format. The access to CT and RM imagesand ECG signals stored in DICOM format will also bepossible. The application will allow the off-line vi-sualization and editing of the patient record datawhen the equipment covers the wireless networkarea. The data update will be affected when theuser returns to the coverage area.

This preliminary study shows that it is possibleto use handheld computers in the visualization,evaluation, and manipulation of images and clin-ical reports in a medical hospital environment,without compromising the mobility of the healthprofessionals.

References

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[3] European Committee For Standardisation, A mobile e-health system based on workflow automation tool. Infor-mation Society RTD Standards Implementation Report, May,2002.

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