| I. Introduction | | | | in the hospital. It is located five floors above and |
| Timely management of medical imaging | | | | 1000 ft. (300 m) away from the Radiology |
| information is one of the greatest challenges | | | | Department. This busy unit has an average daily |
| facing medicine today. Patients with complex | | | | occupancy of 25.9 patients, and the average |
| medical problems may require a large number of | | | | duration of stay in the unit is 4.4 days. During |
| radiologic studies, which may be performed at | | | | their stay in the CCU, 72% of patients have at |
| physically separate locations; as a result, | | | | least one chest radiograph. On the average, 10 |
| preexisting studies may be inadvertently | | | | chest examinations are performed each day, |
| duplicated. Simultaneous access to radiologic | | | | about half of them with a mobile unit. Because |
| images may be needed for accurate | | | | use of the mobile unit is often indicative of the |
| interpretation. In addition, multiple physicians caning | | | | critical condition of the patient, a protocol has |
| for a patient may want to review the images. As | | | | been established to make these images (about |
| medical centers increase in size, illnesses increase | | | | five examinations per day) immediately available |
| in complexity, and the demand for rapid transfer | | | | to the CCU physicians through the digital viewing |
| of information increases accordingly, the capacity | | | | system. Traditionally, in order to view films, the |
| of film-based radiologic systems to meet these | | | | physician would have to walk to the Radiology |
| demands decreases. Films are often unavailable or | | | | Department to check out the patient's film jacket, |
| lost, and film storage costs are relatively high. | | | | a procedure that can be quite time-consuming. |
| Systems designed to store images in computers | | | | After a month long preclinical trial, the system |
| and display them on high-resolution monitors have | | | | was released to the CCU physicians for their use. |
| been developed over the past 10-12 years. These | | | | The system was available at all times, and |
| picture archiving and communication systems | | | | physicians could choose between the film-based |
| (PACS) attempt to overcome the limitations of | | | | viewing system and the digital viewing system. |
| film-based systems by providing economical | | | | The decision to release the system for clinical use |
| storage, rapid retrieval of individual images, access | | | | without restriction was based on the premise that |
| to images acquired with multiple modalities, and | | | | the functionality of a computer-based system |
| simultaneous access to the same image at | | | | ought to be defined and evaluated within the |
| multiple sites. However, acceptance of this new | | | | normal task environment. The usage and |
| technology has been limited by high capital costs, | | | | performance of the system were logged into a |
| limited spatial resolution of the display monitors, | | | | file to provide (1) the name and hospital |
| limited spatial resolution of digitization modalities for | | | | identification number of the patient reviewed, (2) |
| projection radiography, slow image display | | | | the date and time of viewing, (3) image |
| (compared with that in film-based systems), and | | | | manipulation function(s) used, (4) the identification |
| the need for system redundancy to provide | | | | of the image manipulated, and (5) the speed of |
| backup in case of component failure. Most PACS | | | | various operations. |
| in current use are prototypes intended for | | | | IV. DICOM Images |
| research, although recently some have been | | | | DICOM stands for Digital Imaging and |
| incorporated into segments of larger radiology | | | | Communications in Medicine. Its standard was |
| department | | | | created by the National Electrical Manufacturers |
| | | | Association (NEMA) to aid the distribution and |
| II. Picture archiving and communication system | | | | viewing of medical images, such as CT scans, |
| The principles of PACS were first discussed at | | | | MRIs, and ultrasound. Part 10 of the standard |
| meetings of radiologists in 1982. Various people | | | | describes a file format for the distribution of |
| are credited with the coinage of the term PACS. | | | | images. This format is an extension of the older |
| Cardiovascular radiologist Dr Andre Duerinckx | | | | NEMA standard. Most people refer to image files |
| reported in 1983 that he had first used the term | | | | which are compliant with Part 10 of the DICOM |
| in 1981. Dr Samuel Dwyer, though, credits Dr | | | | standard as DICOM format files. A single DICOM |
| Judith M. Prewitt for introducing the term. Dr | | | | file contains both a header (which stores |
| Harold Glass, a medical physicist working in London | | | | information about the patient's name, the type of |
| in the early 1990s secured UK Government | | | | scan, image dimensions, etc), as well as all of the |
| funding and managed the project over many | | | | image data (which can contain information in three |
| years which transformed Hammersmith Hospital in | | | | dimensions). This is different from the popular |
| London as the first filmless hospital in the United | | | | Analyze format, which stores the image data in |
| Kingdom. Dr Glass died a few months after the | | | | one file (*.img) and the header data in another file |
| project came live but is credited with being one | | | | (*.hdr). Another difference between DICOM and |
| of the pioneers of PACS Organizational techniques | | | | Analyze is that the DICOM image data can be |
| that enable small departments to function | | | | compressed (encapsulated) to reduce the image |
| efficiently often fail as departments become | | | | size. Files can be compressed using lossy or |
| larger. With the recent growth in imaging | | | | lossless variants of the JPEG format, as well as a |
| technology, the capacity of film-based systems to | | | | lossless Run-Length Encoding format (which is |
| meet the increasing needs of radiology | | | | identical to the packed-bits compression found in |
| departments has decreased. Electronic PACS have | | | | some TIFF format images). |
| been developed in an attempt to provide | | | | A. The DICOM header |
| economical storage, rapid retrieval of images, | | | | The below Image shows a hypothetical DICOM |
| access to images acquired with multiple modalities, | | | | image file. In this example, the first 794 bytes are |
| and simultaneous access at multiplies sites. Input | | | | used for a DICOM format header, which |
| to a PACS may come from digital or analog | | | | describes the image dimensions and retains other |
| sources (when the latter have been digitized). A | | | | text information about the scan. The size of this |
| PACS consists primarily of an image acquisition | | | | header varies depending on how much header |
| device (an electronic gateway to the system), | | | | information is stored. Here, the header defines an |
| data management system (a specialized | | | | image which has the dimensions 109x91x2 voxels, |
| computer system that controls the flow of | | | | with a data resolution of 1 byte per voxel (so the |
| information on the network), image storage | | | | total image size will be 19838). The image data |
| devices (both short- and long-term archives), | | | | follows the header information (the header and |
| transmission network (which serves local on wide | | | | the image data are stored in the same |
| areas), display stations (which include a computer, | | | | file).Furthermore, the DICOM header is shown. |
| text monitor, image monitors, and a user | | | | The DICOM requires a 128-byte preamble (these |
| interface), and devices to produce hard-copy | | | | 128 bytes are usually all set to zero), followed by |
| images (currently, a multiformat or laser camera). | | | | the letters 'D', 'I', 'C', 'M'. This is followed by the |
| The goals of PACS are to improve operational | | | | header information, which is organized in 'groups'. |
| efficiency while maintaining or improving diagnostic | | | | For example, the group 0002hex is the file meta |
| ability. A. Image Acquisition Modules | | | | information group, and (in the example on the |
| An image acquisition device is an electronic | | | | left) contains 3 elements: one defines the group |
| gateway to the PACS and may be an | | | | length, one stores the file version and the third |
| analog-to-digital converter or device that passes | | | | stores the transfer syntax. |
| along digital information from a digital imaging | | | | The DICOM elements required depends on the |
| device. The number of acquisition modules | | | | image type. For example, this image modality is |
| necessary for a PACS to function varies with the | | | | 'MR' (see group : element 0008:0060), so it should |
| system and is based on its size and the mix of | | | | have elements to describe the MRI echo time. |
| analog and digital input devices. | | | | The absence of this information in this image is a |
| B. Data Management System | | | | violation of the DICOM standard. In practice, most |
| The data management system is a specialized | | | | DICOM format viewers (including MRIcro and |
| computer that controls thenetwork, image | | | | ezDICOM) do not check for the presence of |
| storage devices, and image acquisition devices in | | | | most of these elements, extracting only the |
| order to maintain orderly traffic flow in the | | | | header information which describes the image size. |
| system. This computer manages patient | | | | The NEMA standard preceded DICOM, and the |
| information and images as well as the associated | | | | structure is very similar, with many of the same |
| reports. The data management system must | | | | elements. The main difference is that the NEMA |
| provide short- and long-term archiving capabilities. | | | | format does not have the 128-byte data offset |
| Usually, the short-term archive employs magnetic | | | | buffer or the lead characters 'DICM'. In addition, |
| media, and the long-term archive employs optical | | | | NEMA did not explicitly define multi-frame(3D) |
| media. The short-term anchive has low capacity | | | | images, so element 0028,0008 was not present. |
| but is frequently used (ie, high utilization), whereas | | | | Of particular importance is group : element |
| the long-term archive has high capacity and low | | | | 0002:0010. This defines the 'Transfer Syntax |
| utilization. | | | | Unique Identification'. This value reports the |
| C. Transmission Network | | | | structure of the image data, revealing whether |
| Data for images, text, and system commands | | | | the data has been compressed. Note that many |
| are transmitted over networks serving local or | | | | DICOM viewers can only handle uncompressed |
| wide areas. The network medium could be a | | | | raw data. DICOM images can be compressed |
| twisted-pain wire, coaxial cable, on fibenoptic cable. | | | | both by the common lossy JPEG compression |
| A variety of network topologies (eg, star) are | | | | scheme (where some high frequency information |
| available, each with its own advantages and | | | | is lost) as well as a lossless JPEG scheme that is |
| disadvantages. In addition, severalcommunication | | | | rarely seen outside of medical imaging (this is the |
| protocols (eg, transmission control protocol | | | | original and rare Huffman lossless JPEG, not the |
| internet protocol [TCP/IP]) exist for managing the | | | | more recent and efficient JPEG-LS algorithm). |
| information on the network. These protocols | | | | Note that as well as reporting the compression |
| provide instructions on how data will be moved on | | | | technique (if any), the Transfer Syntax UID also |
| the network. | | | | reports the byte order for raw data. Different |
| D. Image Display Stations | | | | computers store integer values differently, so |
| Image display stations are the principal area of | | | | called 'big endian' and 'little endian' ordering. |
| physician interface with a PACS. A display station | | | | Consider a 16-bit integer with the value 257: the |
| includes a computer with local stunage, a text | | | | most significant byte stores the value 01 (=255), |
| monitor, a variable number of image monitors, | | | | while the least significant byte stores the value 02. |
| and a user interface. A display station that can | | | | Some computers would save this value as 01:02, |
| duplicate the full range of tasks, speed of display, | | | | while others will store it as 02:01. Therefore, for |
| and spatial resolution available with film systems | | | | data with more than 8-bits per sample, a DICOM |
| has not yet been constructed. In fact, the cost of | | | | viewer may need to swap the byte-order of the |
| creating sucha station would be formidable. To | | | | data to match the ordering used by your |
| help minimize the potential costs, studies have | | | | computer. |
| been undertaken to determine the minimal spatial | | | | In addition to the Transfer Syntax UID, the image |
| and contrast resolution necessary to perform a | | | | is also specified by the Samples Per Pixel |
| variety of imaging tasks. This information may | | | | (0028:0002), Photometric Interpretation |
| then be used to create a series of workstations | | | | (0028:0004), the Bits Allocated (0028:0100). For |
| with different levels of sophistication so that | | | | most MRI and CT images, the photometric |
| appropriate equipment may be selected for the | | | | interpretation is a continuous monochrome (e.g. |
| task at hand. | | | | typically depicted with pixels in grayscale). In |
| E. Hard-Copy Devices | | | | DICOM, these monochrome images are given a |
| Although the major mode of storage and display | | | | photometric interpretation of 'MONOCHROME1' |
| with a PACS is electronic, provision must also be | | | | (low values=bright, high values=dim) or |
| made for creating a conventional im age on x-ray | | | | 'MONOCHROME2' (low values=dark, high |
| film. Multiformat cameras on laser cameras are | | | | values=bright). However, many ultrasound images |
| currently the most common way of meeting this | | | | and medical photographs include color, and these |
| demand. | | | | are described by different photometric |
| F. Interfaces to Other Systems | | | | interpretations (e.g. Palette, RGB, CMYK, YBR, |
| To function properly, the image management | | | | etc). Some color images (e.g. RGB) store |
| system must interface with other patient care | | | | 3-samples per pixel (one each for red, green and |
| management systems. These include but need | | | | blue), while monochrome and paletted images |
| not be limited to a radiology information system | | | | typically store only one sample per image. Each |
| (IllS) and a hospital information system (HIS). The | | | | images store 8-bits (256 levels) or 16-bits per |
| goals of interfacing the PACS to an RIS and an | | | | sample (65,535 levels), though some scanners |
| HIS are to maintain data integrity across the | | | | save data in 12-bit or 32-bit resolution. So a RGB |
| global system and to optimize the performance | | | | image that stores 3 samples per pixel at 8-bits |
| of each component system by using only the | | | | per can potentially describe 16 million colors' (256 |
| specific data needed fon each. The 1115 provides | | | | cubed). |
| basic patient histories, reporting of results, and | | | | B. ezDICOM |
| collection of data for department management. | | | | The ezDICOM is a software that is easy to use, |
| The HIS manages the demographic standards and | | | | mature (stable, few if any bugs) and can view a |
| distributes patient care information throughout the | | | | wide range of medical images including proprietary |
| medical center. | | | | formats as well as images in the DICOM standard. |
| III. A Radiologic Picture Archiving and | | | | For example, In addition, most free DICOM |
| Communication System for a Coronary Care Unit | | | | viewers only read a small subset of the DICOM |
| I chose the radiologic picture archiving and | | | | images available, while ezDICOM can view a broad |
| communication system for a coronary care unit | | | | range of images. In addition to DICOM images, the |
| (CCU) at a 700-bed teaching hospital ,as an | | | | software will automatically recognize and display |
| example in my project for PACS. The major | | | | Analyze, GE (LX, Genesis), Interfile, Siemens |
| components of this PACS module are located in | | | | (Magnetom, Somatom) and NEMA images. The |
| the Radiology Department and are shared with | | | | greatest strength of ezDICOM is that it is free |
| the Pediatric Radiology PACS. An important design | | | | and open source. There are many variations of |
| goal was to create a system in which acquisition, | | | | medical images 'in the wild' - many of these are |
| routing, and management of patients' image data | | | | poorly or incorrectly documented. By being free, |
| are accomplished with minimal operator | | | | ezDICOM has developed a wide user base, and |
| intervention. The automatic acquisition of images is | | | | this ensures the quality of the code. Thousands of |
| achieved through linkage of a computed | | | | people have used ezDICOM and sent in unusual |
| radiography (CR) unit, FCR-1 01 (Fuji Photo Film, | | | | and rare images, and the code is now mature and |
| Kanagawa, Japan) to an external host, VAX-i i | | | | able to read virtually all the popular medical |
| 750 minicomputer (Digital Equipment Corporation, | | | | images. |
| Maynard, MA.) These two components are | | | | Therefore, the users are the most important |
| integrated through an interface unit that was | | | | strength of this software. It is important to |
| developed in-house. The host computer is used to | | | | acknowledge the many people who shared their |
| manage the processing and flow of data from | | | | images with the developers. The advantage of |
| creation, storage, and archive to display. | | | | being open source is that programmers can |
| Under normal conditions, the only manual operation | | | | modify and improve the code if they want. The |
| required for data input and subsequent | | | | project was started by Wolfgang Krug and has |
| management of the data base is the entry of the | | | | been expanded and maintained by Chris Rorden. |
| patient's name, hospital identification (ID) number, | | | | Development was particularly aided by Earl F. |
| and hospital section code at the CR console. This | | | | Glynn's general programming tutorials and David |
| task is performed by the X-ray technologist at | | | | Clunie's medical imaging FAQ. This software is |
| the time the imaging plate is processed. Once this | | | | covered by the BSD open source license. You can |
| is completed, the remainder of the process is fully | | | | distribute both compiled projects and the source |
| automated. The software that is resident on the | | | | code. However, you should also distribute the |
| host computer detects the incoming imaging plate | | | | license (the compiled standalone program makes |
| and initiates the data transfer from the CR unit. | | | | this easy: the license is built into the 'about' |
| The hospital section code is used to route the | | | | window). The license also notes that the software |
| image to an appropriate data base (in this case, | | | | is provided 'as is', use it at your own risk. This |
| the CCU data base). The raw image data acquired | | | | software attempts to reproduce medical images |
| at 2048 x 2048 x 8 bit resolution are | | | | accurately. However, it is not designed for clinical |
| reformatted into the standard image file structure | | | | use: computer monitors can vary tremendously in |
| defined for the | | | | image quality. All grayscale images are rendered in |
| PACS and then archived. Subsequently, the image | | | | 256-levels of gray. |
| file is subsampled to 51 2 x 51 2 x 8 bit resolution | | | | The standalone ezDICOM for windows program is |
| for display purposes and the patient directory is | | | | a basic but useful tool for viewing medical images. |
| updated to include the new entry. Active patient | | | | This software will run on computers with |
| images are stored on magnetic disk for rapid | | | | Windows 95 or later and requires less than 300 |
| access. Forty-five megabytes of disk space have | | | | Kb of disk space. To view an image, you simply |
| been allocated for the CCU data base, which | | | | drag and drop the image onto the program (or |
| provides a maximum of 180 images on-line. The | | | | you can choose 'Open...' from the 'File' menu). |
| images are also automatically archived to an | | | | Despite the ease of use, ezDICOM has a number |
| optical disk library unit manufactured by Filenet | | | | of powerful features. For example, you can set |
| Costa Mesa, CA) and Hitachi (Tokyo, Japan). | | | | the brightness and contrast of an image with |
| When a patient is selected at the user terminal in | | | | great precision. You can also animate images that |
| the CCU, the image files are loaded on a Gould | | | | have multiple slices (e.g. see a heart beating over |
| 1P8500 image processor (Fremont, CA), and the | | | | time or see different depths into the brain). The |
| video output signals are transmitted in real-time to | | | | ezDICOM standalone application [version 1, release |
| the CCU via a broadband network. Three channels | | | | 19] is free software and is distributed as a |
| are multiplexed with Blonder-Tongue video | | | | compressed zip file - simply extract the files and |
| modulators (Oldbridge, NJ) operating with 8-MHz | | | | double click on ezDICOM.exe. Delphi source code is |
| bandwidths. The viewing station in the CCU | | | | also included, and a personal edition of this |
| consists of three 13-in. (30-cm) diagonal, 5i 2-line | | | | compiler is available for free. |
| display monitors (Panasonic Industrial Company, | | | | D. DCM2JPG console application |
| Secaucus, NJ) and a VT-i 00 terminal for user | | | | DCM2JPG is a simple command-line Windows |
| interface. | | | | program. If you drop a file on the program it will |
| A. User Interface | | | | create a JPEG version of the file (alternatively, if |
| The user interacts with the system through a | | | | you name the program 'dcm2png.exe' or |
| VT-i 00 terminal keypad. A directory of patients | | | | 'dcm2bmp.exe' it will create PNG or BMP format |
| and various image manipulation functions are | | | | images). You can also call the program from the |
| provided in a menu format. In a typical viewing | | | | command line, to do special functions like change |
| session, the clinician first selects a patient from | | | | the image brightness or contrast (most grayscale |
| the alphabetic active-patient directory. The | | | | DICOM images have much higher precision than |
| terminal prompts the user to wait while the data | | | | can be saved to standard bitmap formats). |
| base is searched. Images appear on the three | | | | Another nice feature is the ability to create nice |
| monitors in reverse chronological order, starting | | | | zoomed versions of DICOM images - e.g. save a |
| with the most recent image (Fig. 2). The | | | | 128x128 pixel image as a 192x192 pixel bitmap |
| information appearing at the bottom portion of | | | | (scaling is done using a bilinear-interpolation method |
| the image includes the patient's name and hospital | | | | to reduce any jaggy edges). Both a compiled |
| identification number, as well as the date and time | | | | program and the (ezDICOM-based) source code |
| of image acquisition. At this point, the viewer may | | | | can be downloaded from the internet. The |
| return to the directory, view more images of the | | | | program has some command as follows: |
| current patient, or apply an image manipulation | | | | b Brightness [window center]: a,h,-9999..9999 |
| function. The image manipulation functions include | | | | for auto, header, custom default: auto |
| zoom (by pixel replication), mean-and-window, | | | | c Contrast [window width]: a,h,0..9999 for |
| grayscale inversion, left-right reversal, and image | | | | auto, header, custom default: auto |
| rotation. | | | | -f Format of Output: b,p,j, txtfor bmp, png, |
| B. Data Bases | | | | jpg, txt default: jpg |
| The data bases use the indexed sequential access | | | | -o Output Directory, e.g. 'C:TEMP' default: |
| method (ISAM) files. The record for the patient | | | | source directory |
| data base contains information such as the | | | | -s Silent [errors not reported]: y,n for yes or |
| patient's name, hospital identification number, | | | | no default: no |
| number of images acquired to date, and the | | | | 14 |
| image code, which is issued automatically when | | | | -z Zoom of Output, e.g. ''1.5'' for 150% zoom |
| the patient is entered into the data base for the | | | | default: 1.0 |
| first time. The image code also serves as the | | | | V. Conclusion |
| primary key for the image data-base record, | | | | This report gave brief description about Picture |
| which provides information associated with the | | | | archiving and communication system PACs. It |
| individual image file, including the date of | | | | explains its setup components and how it works |
| acquisition, procedure, current location of the | | | | through an example of a Radiologic Picture |
| image (magnetic disk, optical disk, or both), and | | | | Archiving and Communication System for a |
| the volume and physical address of the optical | | | | Coronary Care Unit. It show also the format of |
| disk archive. The images are deleted from the | | | | the file extension of the image of the PACs and |
| magnetic disk according to a probability algorithm | | | | how it can be shown in ezDICOM software. |
| that determines which images are least likely to | | | | However, output format of the ezDICOM is can |
| be reviewed. | | | | be converted easily to other format according to |
| For a returning patient, the most recent image is | | | | the requirements such as jpg by using simple |
| retrieved.automatically from the optical disk library | | | | software called DCM2JPG console application. It is |
| for comparison purposes. | | | | really interesting in this life to see how science |
| C. Clinical Operation | | | | affected the life of the human being. |
| The CCU is one of the largest intensive care units | | | | |