Managing DICOM Image Metadata with Desktop Operating Systems Native User Interface

Transcription

1 Managing DICOM Image Metadata with Desktop Operating Systems Native User Interface Chia-Chi Teng, Member, IEEE Abstract Picture Archiving and Communication System (PACS) is commonly used in the hospital environment as the tool to manage radiological images which has standardized on the DICOM format. PACS usually consists of dedicated high performance server computers to provide functionalities of acquisition, storage, retrieval, editing (metadata), distribution and presentation. As the personal computers become more powerful, average desktop workstations can process large amount of data with performance comparable to the high cost dedicated systems. Recent desktop operating systems (OS) such as Microsoft Windows Vista have built-in indexing and search capability integrated with the graphic user interface (GUI) to allow fast retrieval and customized presentation for digital media and documents. Integrating DICOM image management into desktop OS GUI can reduce the cost of software acquisition, maintenance, and user training. We developed DicomProp as a Windows plug-in to provide an easy to use alternative for managing DICOM images on desktop computers. D I. INTRODUCTION IGITIAL Imaging and Communication in Medicine (DICOM) protocol has been the standard for processing and administration of medical image data. Picture Archiving and Communication System (PACS) is commonly used in the hospital environment as the tool to manage radiological images which has standardized on the DICOM format. PACS usually consists of dedicated high performance server computers to provide functionalities of acquisition, storage, retrieval, editing (image and metadata), distribution and presentation. Due to the high cost of the PACS, they are usually only installed in the large hospitals. Clinicians and researchers who work outside the large hospital environment often use a DICOM viewer application to work with images on personal computers or workstations that are not connected to PACS. As the personal computers become more powerful, common desktop workstations can process large amount of image data with performance comparable to the high cost dedicated systems. Recent desktop operating systems (OS) such as Microsoft Windows Vista and Apple Mac OS X have built-in indexing and search capability integrated with the graphic user interface (GUI) to allow fast retrieval and customized presentation for digital media and documentation. Integrating DICOM image management into desktop OS GUI reduces Manuscript received April 7, Chia-Chi Teng is with the School of Technology, Brigham Young University, Provo, UT USA (phone: ; fax: ; ccteng@byu.edu). the cost of software acquisition, maintenance, and user training. It provides a low cost and effective alternative for certain clinical and research environment where PACS is not a practical or suitable solution. Researchers often have to modify the metadata in DICOM image files to de-identify the data for HIPPA compliance or use the metadata to organize the images according the subject, project or other attributes. Additional information can also be added into the dictionary for annotation or other purposes. While some DICOM viewer applications are capable of modifying DICOM metadata, the process can be cumbersome and often non-intuitive. We are developing the software package DicomProp as a Windows plug-in to simplify the process by allowing users to view and modify DICOM image metadata through familiar operating system graphic user interfaces. Leveraging the native OS user interface and features provides other benefits in addition to reducing the cost of developing and managing separate applications. It improves productivity through ease of use. Language localization is also simplified through use of the operating system infrastructures. II. BACKGROUND There are many DICOM viewer applications available commercially, as freeware or as open source distribution. Escott and Rubinstein conducted extensive surveys and compared the functionality of many free viewers [1, 2]. While many of these viewers allow users to organize and edit DICOM images, their user interfaces are not always intuitive. Some of the DICOM applications had attempted to integrate DICOM viewer into the operating system GUI. For example, MicroDicom [3] and DicomShell [4] both implemented a Microsoft Windows shell extension which allows Explorer to display DICOM images as thumbnail and sort the files according to their metadata. QuickDicom s iidicom Framework [5] implemented a Spotlight plug-in for Apple Mac OS X which allows the user to search the DICOM files via to the metadata values, but does not allow editing. Some DICOM viewer applications also provide the functionality to edit the header information. For example, Sante DICOM Viewer Pro [6] includes a DICOM Header Editor which allows users to edit individual tag s values. This application can only edit one file at a time, and the

2 <?xml version="1.0" encoding="utf-8"?> <schema xmlns:xsi=" xmlns=" schemaversion="1.0"> <propertydescriptionlist publisher="byu" product="dicomprop"> <propertydescription name="byu.dicomprop.patname" formatid="{a691c6de-235c-4b41-88a9-51f8870c8267}" propid="101"> <description>this property indicates the patient name.</description> <searchinfo ininvertedindex="true" iscolumn="true" columnindextype="ondisk"/> <typeinfo type="string" multiplevalues="false" isviewable="true" isqueryable="true"/> <labelinfo label="patient name" invitationtext="specify patient name" /> <displayinfo displaytype="string" /> </propertydescription>... </propertydescriptionlist> </schema> Fig. 1. Property descriptions file for the DICOM property provider Fig. 2. Customized details pane and info tip for DICOM image file type displaying selected header information users need to run the viewer, then open the header editor in order to change a tag. Recent desktop operating systems such as Windows Vista have provided extensibility such that DICOM image file s metadata can be exposed and integrated in the native GUI and indexed by the desktop search engine. It is now feasible for users to manage DICOM header information through Windows Explorer instead of having to run another application. In Microsoft Windows Vista operating system, a property provider [7] can parse a given file and returns its metadata, both names and values, to the Explorer and search engine. With the DICOM header information being indexed, user can quickly search through and organize a large amount of files using various DICOM specific attributes. We are developing the DicomProp software package to provide the following functionalities that are missing in the DICOM tools currently available, - Ability to modify the tags (metadata) in-place from within the operating system GUI. - Customizable UI allowing users or organization to configure according to their needs. - Ability to modify multiple files at the same time. - Ability to search and organize DICOM image files according to their metadata using the native desktop OS GUI and search engine. III. METHODS Various mainstream operating systems have different programming interfaces for their GUI Shell and desktop search engine. Windows Vista allows programmers to expose metadata of any given file type through its property system as a shell extension. DicomProp currently includes a property provider and a preview handler for the DICOM

3 Fig. 3. In-place editing for DICOM header information within the Windows Explorer image file type (.dcm). The property provider extracts the metadata of the selected DICOM image(s) and returns the property values to both the Explorer and the search engine. The programming interface of the property system is documented in Microsoft Development Network (MSDN) [7]. The DICOM property provider uses the CTN DICOM library [8, 9] to parse and modify the dictionary in the image files. The software source code is written in C/C++ using Microsoft Visual Studio 2008 and Microsoft Windows SDK version 6. Windows Vista provides the extensibility for the property provider to define the types of custom properties that can be associated with the DICOM image files through a XML property description schema. The format of the schema is also described in MSDN; Figure 1 shows a subset of the current prototype schema. We selected a small subset of the DICOM dictionary to be returned from the property provider to the operating system. This set of properties can be easily expanded with addition property description and minimal change to the code. Windows Vista also provides the flexibility to customize the list of properties presented in various views such as details pane and info tip, which only requires a change to the registry without any modification to the code. Unlike most of the DICOM viewers, this implementation provides a solution that can be customized to user or organizational preferences. After the DICOM property provider is installed, the properties of the selected DICOM image file are displayed in the detail pane and info tip as shown in Figure 2. More importantly, users can click on the properties in the detail pane and modify their values. As shown in Figure 3, the Save and Cancel buttons are presented as soon as property values are modified; this example shows the user changing the patient name, ID and birth date of the selected file. Changes are only committed to the file when the user clicks the Save button. This is done within the Windows Explorer without having to run a viewer application. Any of the DICOM properties can be added to the Explorer s detail view as a column through Windows GUI and used to sort or group the file list. Figure 4 shows that a column Patient Name is added to the folder view and the files are grouped by the different patient names. Users can selected multiple files or a group of files and modify their property values at the same time, also as shown in Figure 4. This feature, for example, can be particular useful for deidentification where users can select a group of files and remove their private information altogether. The DicomProp property provider is also integrated with the Windows native desktop search engine. As opposed to being index as free text, DICOM image files are indexed with their property name and value pairs. For example, a DICOM file has patient name John Smith in the header; the word John Smith is recognized as the Patient Name property instead of just plain free text. This makes is possible to search and organize DICOM files with specific property values. For lack of a better method, researchers or medical workers who deal with large number of DICOM images on a non-pacs workstation usually use directory or folder structures to organize the images by patients, image date, or other attributes. This is inefficient and it can be difficult to search for a particular file or group of files. As the DICOM files properties are indexed, users can not only search the files from the search box, but also group and stack the files

4 Fig. 4. Modifying header information for multiple DICOM image files at the same time. according to one or more properties. Virtual folders [12] can also be used to quickly locate a list of files according to predefined search criteria regardless of where they are in the folder hierarchy. IV. EVALUATION DicomProp was developed using Microsoft Visual Studio 2008 and Windows SDK. We tested the prototype with a variety of DICOM images acquired from several repositories [10][11] including different image modalities, transfer syntax, size and other features. At the time of the submission of this manuscript, files with multi-frame compressed images are not yet supported. Performance of DicomProp was coarsely measured on an Intel Core 2 Duo PC with 3GB memory and Microsoft Windows Vista SP1 operating system. It takes approximately 7 seconds to commit DICOM header changes for 387 CT images at a time through Explorer s detail pane; each image is 512x512 in dimension and 520KB in size. It takes the same amount of time to commit changes of one property or multiple properties. V. CONCLUSION DicomProp is developed as a simple light weight plug-in for Microsoft Windows which integrates the DICOM image management functionality with the native operating system graphical user interface and desktop search engine. The integrated user experience in Windows Explorer makes it easy to modify the metadata of DICOM images as individual files or as a group of files. The software framework can support private tags of DICOM header to enable custom applications. However, adding or changing a private tag would require changing the source code and rebuild the executable in the current implementation. Future versions will allow users to define private tags through a definition file without having to modify the source code. There are great cost and productivity benefits from integrating DICOM image management with native desktop operating systems. We merely used Microsoft Windows platform as a starting point to prove the concept. We plan to implement plug-ins for other desktop OS s such as Linux and Apple Max OS X. While initial results are promising, more tests need to be done on a larger collection of DICOM images. Future work also includes performance improvements and more complete support for the DICOM header dictionary. REFERENCES [1] E.J. Escott, R. Rubinstein. Free DICOM Image Viewing Processing Software for Your Desktop Computer: What s Available and What It Can Do for You. RadioGraphics. vol. 23, pp , [2] E.J. Escott, R. Rubinstein. Free DICOM Image Viewing Processing Software for the Macintosh Computer: What s Available and What It Can Do for You. RadioGraphics. vol. 24, pp , [3] Accessed 4/7/2009. [4] Accessed 4/7/2009. [5] Accessed 3/7/2009. Accessed 4/7/2009. [6] Accessed 4/7/2009. [7] Accessed 4/7/2009.

5 [8] Moore SM, Hoffman SA, Beecher DE. DICOM Shareware: A Public Implementation of the DICOM Standard. Proc. SPIE 2165: , Medical Imaging 1994-PACS: Design and Evaluation, R Gilbert Jost; Ed. [9] Accessed 4/7/2009. [10] Accessed 4/7/2009. [11] Accessed 4/7/2009. [12] J. Durham and D. Torres, Microsoft Windows Vista Ultimate, Wiley, 2007, pp