21-09-2013, 02:46 PM
A SEMINAR REPORT ON DIGITAL IMAGING AND COMMUNICATIONS IN MEDICINE (DICOM)
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Abstract
Digital technology has in the last few decades entered almost every aspect of medicine. There has been a huge development in noninvasive medical imaging equipment. Because there are many medical Equipment manufacturers, a standard for storage and exchange of medical images needed to be developed. DICOM (Digital Imaging and Communication in Medicine) makes medical image exchange more easy and independent of the imaging equipment manufacturer. Besides the image data, DICOM file format supports other information useful to describe the image. This makes DICOM easy to use and the data exchange fast and safe while avoiding possible confusion caused by multiple files for the same study.
Digital Imaging and Communications in Medicine (DICOM) Standard is an image archive system which allow itself to serve as an image manager that controls the acquisition, retrieval, and distributions of medical images within entire picture archiving and communication systems
(PACS). The DICOM technology is suitable when sending images between different departments within hospitals or/and other hospitals, and consult". However, some hospitals lack the DICOM system. This paper presents an easy and practical MATALB program that is devised CO view medical images stored in DICOM format and converts them to other common formats. Consequently, the images can be seen using personal computers, instead of using the DICOM
System software. Thus, patients each have their x-rays, Computed Tomography (CT)'s. Magnetic Resonance Image (MRI)'r and other types of medical images in their computer. This also allows the images to be sent to physicians and anywhere without worrying about the imaging viewing software they are using.
INTRODUCTION
DICOM (Digital Imaging and Communication in Medicine) is a standard that specifies a non-proprietary data exchange protocol. Current version (3.0) is published by NEMA (National Electrical Manufacturers Association) in 1993. This standard is developed by workgroups every year to satisfy virtually any medical branch.
Overview of DICOM
The contents of the DICOM standard go far beyond a definition of an exchange format for medical image data. DICOM defines
Data structures (formats) for medical images and related data,
Network oriented services, e. g.
image transmission,
query of an image archive (PACS),
print (hardcopy), and
RIS - PACS - modality integration
Formats for storage media exchange, and
Requirements for conforming devices and programs.
History of the DICOM
As the development of digital computers and equipment started in the 1970's an idea of using digital imaging equipment in medicine has become a reality. ACR (American College of Radiology) and NEMA (National Electrical Manufacturers Association) formed in 1983 a joint committee whose mission was to develop a standard for connection of displays and similar devices to medical imaging equipment from different manufacturers. The first version named ACR/NEMA Standard Version 1.0 was published in1985. Two revisions of the standard, in October1986 (No. 1) and in January 1988 (No. 2), followed the initial version 1.0. In 1988 new material was included in the new revision of the standard and version 2.0 was created. Both versions 1.0 and 2.0allowed point-to-point connection and that represented a problem for modern communication networks which do not use absolutely dedicated channels. Because of that a new revision of the standard had to be presented. In 1993 a new version, named DICOM Version 3.0, was released. DICOM Version 3.0 uses networked environment instead of point-to-point connection environment for imaging system connections. This allows cost-effective connections over large geographical areas with the use of a prebuilt network infrastructure. Since its release in 1993 DICOM Standard has been revised many times, mostly on yearly bases. Research indifferent medical fields are done by different workgroups, each with specific area of research. The DICOM Standards Committee nowadays creates and maintains international standards for interchange of digital medical imaging and associated data. It has become a leading standard used by all major vendors of diagnostic medical equipment. If not already, DICOM will soon be used in every medical branch that utilizes imaging, for example: cardiology, mammography, radiology, surgery, endoscopy, dentistry, pathology, etc. Today DICOM allows effective medical imaging storage and transfer overlarge geographical areas, making a basis for picture archiving and communication systems (PACS)
Conversion of DICOM Images to Common Standard Format
MATLAB is a popular scientific package [4]. In this work, a MATLAB program is developed to extract an image from a given DICOM file and convert it to another format [3]. The supported formats are common standard formats as follows:
1. Portable Network Graphics (PNG).
2. Windows Bitmap (BMP).
3. Tagged Image File Format (TIFF)
4. Joint Photographic Experts Group (JPEG)
This variety of formats is meant to satisfy different users. The flow chart given in next page describes how the program deals with the DICOM file. The first part of the program is for users. It describes how to use such program. After that, the number of inputs is examined.
The program needs to know the source DICOM file and the destination file and its format. For example, if the user did not write them in the command line, user-friendly interfaces do ask for these data. The existence of the source file is checked to avoid errors of misspelled names. The program then begins reading the source file. Here, the length of the file is important information enable to proceed further with obtaining the image. Most Magnetic Resonance Imaging (MRI) DICOM files, for example, have a specific length. This length can vary depending on the data stored in the file. MRI images commonly have two sizes: 512 by 512 and 256 by 256 and they come at the end of the DICOM file. The file length determines the image size and so it could be easily extracted. Sizes of other images can be extracted from the DICOM file. It is more efficient in these cases to use the commands DICOMINFO and DICOMREN) to get the images since these commands scan the whole file and extract all of its information.
Experimental Results
The program presented is simple to apply and limited to some modality types, mainly
MRI DICOM images. Using a Guide User Interface (GUI) can more enhance the program. Generally speaking, the DICOM file has data about the exam, patient, image, etc. Data are arranged by this, manner as standard for the DICOM format. To extract more information from the DICOM file, the location of what is looked for should be obtained first. The file is composed of data elements having different tags. The image pixel values are preceded by important information about it such as the number of rows and columns of the image, number of
Samples per pixel, pixel encoding [1].
DICOM images
Image displaying under DICOM Standard does not define how images are displayed or annotated. Besides the image data, DICOM includes data structures that are of importance to the image. Those structures are placed in a header that contains object's description, patient's data, name of the institution and other information such as performed procedures or reports. Information Object Definitions (IODs) are the most important components of data structures. IODs are tables of attributes that define information objects. Information objects are models that are abstracted versions of real-world objects, for example "patient" is an information object that has "patient name" and "patient ID number" as attributes. DICOM Standard supports different types of images for different medical applications. For X-Ray imaging intensity images are used, while for some Computed Tomography applications color images are often used. DICOM supports multi-dimensional multiframe images. Data compression relies on widely used compression standards like JPEG, JPEG Lossless, JPEG 2000, or MPEG-2 for multi-image (video) sequences [6]. Different medical applications require different level of image quality. Mammography images require very high resolution, so the compression used is mostly lossless because small details need to be preserved. That is the reason why mammography image files are large even though images are grayscale.
Advantages and disadvantages of DICOM
DICOM has standardized the exchange of medical information. The general idea was to provide a standard for cost-effective interconnection of different medical systems to provide a transparent
and easy to use environment. It is very important to have a standard which is being used in all hospitals for the same or similar examination processes. A unique standard helps in avoiding problems that occur if patient moves from one hospital to another. DICOM also provide interconnectivity between diverse medical systems. That made the DICOM Standard stand in front of other separate standards developed by manufacturers of medical equipment .DICOM's big advantage also lies in supporting all medical branches, and that makes it so comprehensive. Different workgroups that work in development of DICOM Standard are in charge of developing only a small part of the standard that is specific to their line of duty. DICOM also has an
Advantage when compared to storage of analogue images and data because it takes up less space for digital storage and digital data are easy to transmit over the large geographical area.
SUMMARY
DICOM systems have become important in the medical environment. They ease and speed up the communication between different departments in a hospital and also between hospitals around the globe. Using the simple program presented, other environments will also benefit from the DICOM images. The program can be improved, transferred to other languages, and it can also be transformed into a single independent executed file.
This Standard has evolved throughout the years as an indispensable component for the integration of digital imaging systems in the field of medicine. The standard has offered many solutions for the problems in the transmission, reporting, and analysis of medical images.