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journa l homepage: www. int l .e lsev ierhea l th .com/ journa ls /cmpb

esign, development, exploitation and assessmentf a Cardiology Web PACS

arlos Costaa,∗, José L. Oliveiraa, Augusto Silvaa, Vasco Gama Ribeirob, José Ribeirob

University of Aveiro – DETI/IEETA, 3810-193 Aveiro, PortugalCentro Hospitalar de Vila Nova de Gaia, Portugal

r t i c l e i n f o

rticle history:

eceived 20 April 2008

eceived in revised form

0 October 2008

ccepted 30 October 2008

eywords:

a b s t r a c t

Healthcare institutions are increasingly turning to digital medical imaging systems to pro-

mote better diagnosis and treatment of their patients. The implementation of the Picture

Archiving and Communication System (PACS) clearly contributes to an increase in the pro-

ductivity of health professionals. However, despite the amount of research that has been

done in the past two decades, there are still several technological hurdles that hinder the

wide adoption of PACS in the Web environment.

In this paper, we present a Web-enabled PACS that through the inclusion of several DICOM

services and compression methods promotes medical image availability and greater acces-

ACS

ICOM

ardio-PACS

eb-PACS

elemedicine

sibility to users.

© 2008 Elsevier Ireland Ltd. All rights reserved.

them related to the huge volume of data, and to the lack of

elework

. Introduction

Picture Archiving and Communication System (PACS) is onef the most valuable tools supporting the medical professionoth in decision-making and during treatment procedures.t encompasses several technologies that are used in thecquisition, archiving, distribution, and visualization of digitaledical images [1]. The Digital Imaging and Communications

n Medicine standard (DICOM) [2] was a major contribution tohe facilitated exchange of structured medical imaging data,nd is now a key component in PACS’s success. Currently,lmost all medical imaging equipment manufacturers provideICOM digital output in their products.

The deployment of PACS has enabled faster and broaderccess to medical image data. The movement from film-basedrocesses to digital processes, allied to faster and more robust

∗ Corresponding author. Tel.: +351 234370500.E-mail addresses: carlos.costa@ua.pt (C. Costa), jlo@ua.pt (J.L. Oliveir

ibeiro), jri@chvng.min-saude.pt (J. Ribeiro).169-2607/$ – see front matter © 2008 Elsevier Ireland Ltd. All rights resoi:10.1016/j.cmpb.2008.10.015

network infrastructure, reduced the costs associated with thestorage and management of images, simplified data porta-bility, and has paved the way for the development of newapplications and working scenarios. A significant benefit ofdigital medical imaging is its availability, both within andbetween health institutions. Together with a new suite ofInternet Protocol (IP)-based applications, such as IP phone andteleconference, PACS presents a tremendous opportunity forthe introduction of telemedicine, telework, and collaborativeteams, which will help to bridge frontiers and overcome themedical resource asymmetries found in several regions [3,4].

However, several problematic issues still remain, most of

a), augusto.silva@ua.pt (A. Silva), vasco@chvng.min-saude.pt (V.G.

interoperability between distinct PACS products. For instance,dynamic image modalities (films) such as cardiac ultrasound(US) and X-ray angiography (XA) typically generate hundreds

erved.

274 c o m p u t e r m e t h o d s a n d p r o g r a m s i n b i o m e d i c i n e 9 3 ( 2 0 0 9 ) 273–282

of a

Fig. 1 – A multimedia container that allows the introductionprivate transfer syntax.

of MB of data for each study. To keep these exams permanentlyavailable to practitioners it is necessary to create robust andefficient storage and communication infrastructures.

There are no significant technical differences between thePACS used in cardiology and in radiology areas. However, theyare often separate systems that tackle distinct user needs,namely related to visualization and reporting protocols [5].Since almost all systems are DICOM compliant, it is possi-ble from a radiology workstation to query and retrieve imageslocated in a cardiology storage server, and vice-versa. Thehandicap is that an integrated system can lead to a moreefficient workflow and improved access to images and data[6,7].

This paper presents a Web-enabled PACS framework,entitled HIMAGE, which is specially designed to support

demanding cardiac imaging laboratories. HIMAGE enables theacquisition, storage, transmission, and visualization of DICOMcardiovascular sequences, providing a cost-efficient digitalarchive. The core of our approach is the implementation of

Fig. 2 – An example of a DICOM dump: DICOM “d

specific codec (MPEG4 in this case) inside the DICOM

a private DICOM transfer syntax that supports any videoencoder that best suits the specificities of a particular imagingmodality or working scenario. The major advantage of the pro-posed system stems from the high compression rate achievedby video encoding, while still maintaining diagnostic qualityin the medical image sequences. This approach ensures fullonline availability of the studies and simplifies the transmis-sion of medical data over the Internet

2. Methods and materials

2.1. Scenario

HIMAGE was developed in the CHVNG cardiology department

(Centro Hospitalar de Vila Nova de Gaia – Hospital of Gaia),which is supported by two imaging laboratories. The firstimplementation of HIMAGE was based on JPEG Baseline (JointPhotographic Experts Group) [8]. With this system, an echocar-

efault transfer syntax” vs. “private syntax”.

c o m p u t e r m e t h o d s a n d p r o g r a m s i n b i o m e d i c i n e 9 3 ( 2 0 0 9 ) 273–282 275

s an

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ooecouiobf

Fig. 3 – HIMAGE service

iography (US) study typically generates data between 20 and0 MB and an angiographic (XA) study between 40 and 60 MB,epending on the technical characteristics of the equipment,n the operator expertise, and on the procedure type [9].lthough this volume can be easily transferred inside an insti-

ution Intranet or through the Internet, the latency, especiallyn the latter case, may be a drawback for some scenarios. Oneossible solution can be the exploitation of lossy compres-ion techniques that still preserve the diagnostic quality ofhe existent JPEG solutions.

Over the years, several studies have investigated the impactf various compression ratios on image quality, and on thebserver performance for several diagnostic tasks. The gen-ral trend shown by the results of these studies is that optimalompression ratios for a modality are rarely achieved, as thebserver’s performance is tightly coupled with each partic-lar diagnostic task. Currently, guidelines are published by

nternational scientific and professional organizations, rec-mmending suitable algorithms and compression ratios for aroad range of diagnostic tasks (see [10–12] for XA and [13–15]or US).

Fig. 4 – HIMAGE Web components architecture.

d processes workflow.

2.2. Image compression

In cardiology, the majority of the data produced in the XA andUS procedures is related to cine-loop sequences, which havea significant time-space redundancy, especially in ultrasound.Because the JPEG-based DICOM compression algorithms onlyexplore the intra-frame image redundancy (space) [16], wedecided to investigate the utilization of a more powerful videoencoder that could also contemplate the inter-frame redun-dancy (time).

In general, distinct digital video codecs produce sig-nificantly dissimilar results and medical image sequencetypes (modalities, cine/still, color/grayscale, etc.). This occursbecause distinct sequences contain distinct kinds of informa-tion (motion, noise, etc.). As a result, it is not possible to selectthe very best among several codecs, to use for compression ofall types of image/video. In the particular case of US cardiovas-cular images, after several trials and result evaluations withdynamic encoders [9], we realized that Moving Picture ExpertsGroup (MPEG4) was the coding standard that provided the besttradeoff between image quality and storage requirements. Theemergence of MPEG4 [17] as a coding standard for multimediadata with object-based and other enhanced encoding facilitiesappears to be a good alternative for the cost-effective storageand transmission of cardiac digital cine-loop sequences. Withthis new codec, a typical US file rarely exceeds 200–300 kB [9].At this order of magnitude, it is already feasible to envisage apure online archive solution capable of handling all the reg-istered procedures whatever their clinical or epidemiological

life-cycle may be.

Another immediate consequence of our encodingapproach is that the reduced transmission times, either inIntranet mode or in Internet mode, may now be considered,

s i n

276 c o m p u t e r m e t h o d s a n d p r o g r a m

in the worst cases, minor drawbacks in the overall imagingworkflow.

2.3. DICOM private transfer syntax

Since MPEG4 is not a DICOM native coding schema, sub-sequent image transmission, decoding and reviewing isaccomplished through a specifically designed DICOM privatetransfer syntax. Moreover, to ensure that HIMAGE has the flex-ibility to support other modalities/encoders, it was decided notto insert the MPEG4 directly in the Tag Length Value (TLV) ofthe DICOM data structure [18]. Instead, we developed a multi-media container that dynamically supports several encoders(Fig. 1). The container includes a field that stores the encoderID code, which is similar to the field used by the Audio VideoInterleave (AVI) RIFF headers [19]. This approach representsthe best modular software solution, as we simply need to

change a single parameter in the HIMAGE conversion engineif a more efficient codec is developed.

In Fig. 2 it is possible to compare parts of the DICOMrepresentation of the “default transfer syntax” against our

Fig. 5 – HIMAGE main infra-structure insid

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“private syntax,” in the specific case of a US 25-frame imagesequence, with a RGB 576*768 matrix. Two important aspectsare noticeable. First, the DICOM transfer syntax identifier ischanged (from DefaultTransferSyntaxUID to PrivateTransfer-SyntaxUID). Second, the “PixelData” field size is reduced 120times (from 33177600 to 275968).

3. Results

3.1. Software engineering

In the initial versions of HIMAGE, the main objective was toreduce data volume through the implementation of a privatetransfer syntax that was capable of supporting multiple videoencoders. In the current version herein described, another

attained goal is the provisioning of a Web-based PACS thatcan be accessed easily and securely through a common Webbrowser with no further need for complex local installation ofsoftware.

e the CHVNG cardiology department.

c o m p u t e r m e t h o d s a n d p r o g r a m s i n b i o m e d i c i n e 9 3 ( 2 0 0 9 ) 273–282 277

ation

afiuw((

Fig. 6 – Himage Integr

Web solutions can be created using one of the current avail-ble architectures [20–22]. Our approach is based on the .NETramework, which allows for smooth integration with exist-ng code (in C, C++ and Visual Basic). All of the core functions

sed to manipulate the images and the DICOM structuresere written in C++ and packed as Dynamic-link Library

DLL) components. We have developed a DICOM C++ SDKSoftware Development Kit) that allows manipulation of the

Fig. 7 – Main interface o

Engine (CIS + PACS).

DICOM persistent object (i.e. structured files) and implementsseveral HIMAGE (DICOM) network services such as Storage,Query/Retrieve and Modality Worklist (Fig. 3) [23].

The graphical components supporting all image-related

tasks (visualization, reporting, etc.) were developed as VisualBasic plugins (ActiveX) and are directly embedded in the ASPX.NET pages (Fig. 4). The ActiveX viewer allows the direct inte-gration of private DICOM files with the Web content. The

f the Web HIMAGE.

278 c o m p u t e r m e t h o d s a n d p r o g r a m s i n b i o m e d i c i n e 9 3 ( 2 0 0 9 ) 273–282

wind

Fig. 8 – Web HIMAGE–viewer

communication between the dynamic HTML contents and theActiveX binary is performed by JavaScript code.

To be visualized or processed, the study images must bedownloaded from the server to the client platform. All DICOMpersistent object transfers (retrieves) are supported by a WebService developed in C#. Though the Web Services are actuallyusing XML-SOAP (Extensible Markup Language-Simple ObjectAccess Protocol) [24] to transfer data, the XML [25] does noteasily handle embedded binary data, which can create prob-lems for DICOM file transfer. There are several issues, suchas memory size and computation costs, that are associatedwith the conversion of binary data into base64 format (whichis treated as a string). This encoding schema (base64) typicallyincreases the original object size by 33% and also increasesthe processing time relative to binary-text-binary conversion[26]. To bypass this XML-SOAP drawback, it was necessary todevelop a parallel gateway channel (HTTP encapsulated) totransfer DICOM files in a more efficient way.

3.2. System workflow

Our clinical facility (CHVNG) is equipped with nine echocar-diography machines distributed over three geographicallydispersed hospital units. They have standard DICOM3.0 out-put interfaces and a configuration that ensures an automaticDICOM SCU (client) storage service at the end of each medi-cal procedure. Daily output to the network typically reaches

approximately 1200 DICOM files (both still and cine-loops).The ultrasound image data is sent to the Acquisition Pro-cessing Unit (APU) in DICOM default transfer syntax, i.e.uncompressed format (Fig. 5).

ow (Normal/Compare Mode).

The received procedures are analyzed (the alphanumericdata is extracted from DICOM headers) to detect eventualexam/patient ID errors and, if format conditions are verified,the exam is added to HIMAGE with the image data compressedand embedded in a new DICOM private syntax file. The resultis then passed into the “Storage Server” that makes it perma-nently available to the PACS users. The original raw images arealso saved, but they are only kept online for 6 months.

The developed client application consists of a Web DICOMviewer (Fig. 7) that handles medical images and films availablein the HIMAGE database, formatted in standard DICOM or inDICOM extended with our private syntax. Since the HIMAGEclient solution is completely developed in Web technology, theaccess to the exams is controlled by appropriate security rules.Authentication is performed through a username/passwordpair and communication security is assured by an HTTPS con-nection.

3.3. Integration with a cardiovascular informationsystem

Implementation of an integrated healthcare access inter-face to patient clinical data represents the core element toaccomplish new healthcare services with improved qualityand efficiency. After the emergence of PACS as a funda-mental infrastructure of any digital imaging department, thefocus turned to the possibilities of integrating the medical

image with other sources of information. Cardiologists needstructured reports including images and related patient infor-mation. In our CHVNG scenario, a commercial CardiovascularInformation System (CIS) handles this additional information.

c o m p u t e r m e t h o d s a n d p r o g r a m s i n b i o m e d i c i n e 9 3 ( 2 0 0 9 ) 273–282 279

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tiiTMdqtcat

pempd

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Fig. 9 – Web HIMA

Integration of the PACS with the existing CIS is an impor-ant feature for the healthcare professional. Besides thenterface conformance, on network and application protocols,t is crucial to ensure data consistency among several systems.o implement this requirement, HIMAGE provides a DICOModality Worklist SCP service that is connected to the CIS

atabase. It enables modalities (using C-FIND command) touery the server for patient and study-related informationhat will be thereafter inserted in the DICOM header. This pro-ess ensures consistency between both information systemsnd also that all PACS studies can be correctly referenced fromhe CIS.

Concerning integrated access to information, the HIMAGErovides smooth integration of patient image data in the CISnvironment. The inclusion of PACS images in other environ-ents is easy due to DICOM private transfer syntax container

ortability. A “Himage Integration Engine” module (Fig. 6) waseveloped with two integration options:

. Multimedia AVI container: the engine can extract theMPEG4 encoded image data from the DICOM and encap-

sulate it in an AVI file to be, for instance, inserted in the CISWeb document;

. Plug-in module: an ActiveX application viewer is available,allowing the direct integration of the HIMAGE DICOM files

eporting module.

in both Winforms and Web environments. This plug-indownloads the image data from HIMAGE archive and dis-plays it.

3.4. Web-enabled interface

During the last 5 years, the ubiquity of Web interfaces haspushed practically all PACS suppliers to develop client appli-cations in which clinical practitioners can receive and analyzemedical images using conventional personal computers andWeb browsers [20,21]. Because of security and performanceissues, use of these software packages has mostly beenrestricted to Intranets. Paradoxically, one of the most impor-tant advantages of digital imaging systems was to enablethe widespread sharing and remote access to medical databetween healthcare institutions.

The HIMAGE Web version is fully operational, provides allthe necessary functionality, and has the same performanceand flexibility as the previous desktop version [9]. The applica-tion setup is very simple. It is downloaded from the Web serverand is automatically installed when given explicit authoriza-

tion by the user.

Graphically, the HIMAGE main window includes a grid boxwith a list of patients and a movie preview of three sequencesfor the current selection (Fig. 7). The user can search all

s i n b i o m e d i c i n e 9 3 ( 2 0 0 9 ) 273–282

Table 1 – CHVNG cardiology department—US statistics.

Number of procedures (exams) 36,418Number of images (still + cine-loops) 856,215Total size 230,984,532,254 bytes

(215 GB)Average procedure size 6.05 MB

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procedures using criteria such as patient name, patient ID,procedure ID/type/date, source institutions and equipment. Asecond graphical application layer provides interfaces to thesystem modules: communications to telecardiology, DICOMviewer (Fig. 8), report (Fig. 9) and export.

In the DICOM viewer window (Fig. 8), it is possible to visu-alize the image sequences (still and cine-loops) and to selectframes from various sequences that are then sent to thereport area. Other traditional functions have been includedsuch as image manipulation tools (contrast/brightness), print-ing capability, and the export of images in distinct formats(DICOM3.0 default transfer syntax, AVI, BMP, JPEG). It is alsopossible to copy a specific image to the clipboard and paste itonto some other external application.

In the compare mode, the viewer window can work ineither of two ways: automatic or manual. The automatic modeis used for a specific type of procedure—the “Stress eco” (Fig. 8).In this case, the visualization technique is based on the infor-mation stored in the DICOM file headers. HIMAGE provides asimultaneous and synchronized display of the several “Stages”of a heart “View.” The term “Stage” is defined as a phase in thestress echo exam protocol. The “View” is the result of a partic-ular combination of the transducer position and orientationat the time of the image acquisition. Manual mode allows theuser to select among distinct images of the same and/or differ-ent procedures that can then be displayed in a defined windowmatrix.

In the report module (Fig. 9), the user can arrange the

location of the image(s) or delete some frames using a drag-and-drop functionality. Finally, the output image matrix (2 × 3or 3 × 3) is bundled with the clinical report to generate an RichText Format (RTF) file that is compatible with common text

Fig. 10 – HIMAGE standa

Average file size 263.5 kBAverage files/procedure 23.5 (majority of

cine-loops)

editors. The user can customize the base template used togenerate the report file. For example, one could include theinstitution logo and report headers.

The export module allows the procedure to be saved in aCDROM or DVD-ROM, using the uncompressed DICOM defaulttransfer syntax format or the AVI format. A standalone fullycompliant DICOM viewer application is also stored (Fig. 10),which starts automatically whenever the disk is used.

3.5. Exploitation

The HIMAGE is installed in two central hospitals and threesmall diagnostic centers. Our main installation and researchlaboratory is the CHVNG cardiology department with approx-imately 65,000 patient records. In Table 1 it is possible toobserve some general statistics relative to the CHVNG US data.

Concerning transmission times, the Web HIMAGE imagesare downloaded in packs of 3 sequences (due to preview mode)

based on the user selection. In a telework environment, sup-ported by a 4 Mbits ADSL (Asymmetric Digital Subscriber Line),a complete pack of 3 cine-loops takes typically less then 10 sto download, decompress and display, including the overhead

lone DICOM viewer.

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ntroduced with an encrypted SSL (Secure Sockets Layer) chan-el.

. Discussion

e have described a Web-enabled PACS software solution thats specially oriented to support demanding cardiac imagingaboratories. It provides a cost-efficient digital archive, ensuresull online availability of studies and simplifies the transmis-ion of medical data over the Internet. The benefits obtainedrom the availability of all historical image data in a simple,ast and integrated Web interface are unquestionable to prac-itioners and to patients, and are likely to induce a significantmprovement in the overall quality of healthcare services.

In our main installation, two years after the introductionf HIMAGE in the echocardiography laboratory, and main-aining the human resources, one realize an increase ofrocedures/year from 4000 to 7000, which is a good indica-ion considering other reported results of PACS productivitymprovements [27–29]. Although this result can be explainedy several factors, to an increase on patient demand andn optimized workflow process, an informal and continu-us assessment performed near the physicians suggest thatIMAGE was a major driving to this change: (a) the dead

imes and the information handling mistakes were consid-rably reduced; (b) since HIMAGE is ubiquitously available, theemote diagnostic can be easily performed without movinghe patient or his records between several buildings; (c) theatient history (CIS reports and PACS images) is permanentlyvailable, which avoids the need for CD or other media storageanual handling.One main HIMAGE advantage is associated with its trans-

er rate efficiency. Healthcare professionals do not adoptelemedicine or telework platforms if they need to wait, fornstance, 2–3 h to receive/download a clinical image study withiagnostic quality.

The advantage of the proposed system stems from themplementation of a private DICOM transfer syntax that sup-orts any video encoder. In the cardiac US we are using aPEG4 codec that provides high compression and maintains

iagnostic quality. Qualitative assessments have been made ofhe previous HIMAGE Desktop version (no Web interface) [9].n a simultaneous and blind display of the original against theompressed cine-loops, 37% of trials have selected the com-ressed sequence as the best image. This suggests that otheractors related to visualization conditions are more likelyo influence observer accuracy than the image compressiontself.

The interoperability of HIMAGE with other DICOM PACSmplies the decompression of private MPEG4 images ton uncompressed normalized format like, for instance, theICOM Default Transfer Syntax. However, we believe that, in

he future, MPEG4 will be adopted by the DICOM standard thaturrently only supports MPEG-2 [30].

Finally, a major constraint of the presented solution is its

ependency on Windows and on Internet Explorer browser.his has to do with the richness of the interface that requirespowerful platform to work (like ActiveX or Flash). The resultill not be possible using pure web2.0 technologies. This deci-

i o m e d i c i n e 9 3 ( 2 0 0 9 ) 273–282 281

sion provides a Web interface supporting all the requirementsof a DICOM viewer. In the future, it is planned to updatethe HIMAGE platform to Microsoft .NET Silverlight technology,which is multi operating system compliant.

5. Conclusions

In this paper, we have presented the Web HIMAGE software,a DICOM conformant Web PACS. Reducing the size of examimages, while preserving the diagnostic quality, is a majornovel feature of this HIMAGE application. This is especiallyimportant for ensuring time-effective transmission throughInternet connections. We successfully demonstrated the util-ity of HIMAGE (started with the HIMAGE desktop version) ina telemedicine project established between CHVNG (Portu-gal) and the Central Hospital of Maputo (Mozambique). TheWeb version of HIMAGE is currently being used in clinicalenvironments with different requirements, from small privatelaboratories to public central hospitals. In the main installa-tion, (CHVNG), we have made more than 36,000 US procedurespermanently available through this system (850,000 cardiovas-cular digital sequences).

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