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Teleradiology is the process of sending radiology images from one location to another through typically standard telephone lines, ISDN, T1, T3, or ADSL. Local (LAN) and wide (WAN) area networks can also be used for this purpose. Through Teleradiology, images can be sent to another part of the hospital or around the world. There are three classes of Teleradiology systems. (1) On-call; (2) Off-site; (3) In-hospital (Mini-Pacs).
On-call systems are most often used for after-hour, on-call applications. Typical on-call teleradiology systems consist of a transmitting unit and one or more receiving units. Usually, both the transmitting and receiving units are based on standard personal computers.
Off-site systems are most often used by radiology groups and hospitals to centralize reading and/or coverage, increase productivity, expand reading networks and consolidate subspecialty work. Off-site teleradiology systems are especially important to rural medical facilities.
In-hospital or Mini-Pacs systems are used to move images electronically throughout the facility (i.e, from radiology to ICU or the ER) over a local network.
The main feature DataView Imaging International, Inc. offers is the ability to mix and match components from all three system classes to form an integrated radiology imaging system that will serve the purposes of everyone using the system.
Telemedicine is the Telecommunicating of medical information technology to a global clinical and commercial audience. While Telemedicine includes Teleradiology, it can also include video conferencing, Telepathology, Telecardiology, and other electronic mediums.
Images can be captured either by a video capture (frame grabber) board which connects directly to the composite video signal of either the image processor or the modality console, or digitally by connecting directly from the modality to a workstation over a network (i.e., Ethernet). The least expensive method of acquiring digital data is through a DICOM file transfer.
Standard radiographs or plain film can be digitized by a film scanner designed to produce the optical density and spatial resolution acceptable to radiologists.
Film scanners come in two basic configurations, CCD (Charged Coupled Device) and laser. Laser film scanners are more expensive than their CCD counterparts but they yield a much better image.
DICOM or "Digital Imaging Communication in Medicine" is a standard that is a framework for medical imaging communication. It is based on the Open System Interconnect (OSI) reference model, which defines a 7 layer protocol. It is an application level standard, which means it exists inside layer 7 (The uppermost layer).
DICOM was developed by the ACR and NEMA, with input from various vendors, academia, industry groups, etc. It is referred to as "version 3" because it replaces versions 1 and 2 of the standard previously issued by ACR and NEMA, which was called the ACR-NEMA standard.
DICOM provides standardized formats for images, a common information model, application service definitions, and protocols for communication.
Depending on data transfer rate requirements and economic considerations, images can be transmitted by means of common telephone lines (twisted pairs of copper wire), digital phone lines (ISDN, Switched 56, ADSL), coaxial cable, fiber-optic cable, microwave, satellite, T1, and T3 telecommunication links.
Today most of the teleradiology systems run over standard telephone lines while the more bandwidth intensive Telemedicine systems tend to use ISDN or better. Over the next several years, we should see a substantial migration to ISDN lines which offer high speed and better line quality than standard dial-up phone lines. Other high-speed lines including ADSL, T1, and T3, will also become more popular as prices continue to fall and accessibility increases.
Digital images: those viewed on a computer monitor, transmitted over the phone line are pictures that have a certain spatial resolution. The spatial resolution, or size, of a digital image is defined a matrix with a certain number of pixels across the width of the image and down the length of the image. The more pixels, the better the resolution. This matrix also has depth. This depth is usually measured in bits and is more commonly known as shades of gray: 8 bit images = 128 shades of gray, 10 bit images = 1024 shades of gray, 12bit images = 4096 shades of gray.
Although images should be permanently archived as raw data or with only lossless data compression, hardware and software technology exists that allows teleradiology systems to compress digital images into smaller file size so that the images can be transmitted faster.
Compression is usually expressed as a ratio - 3:1, 10:1 or 15:1. A 10:1 compression factor means that the file size of the image is 1/10th the size as the original. Certain images such as CT and MRI contain a lot of black content. These areas compress greatly while the more subtle gray changes in the image compress very little. The resulting viewed images will show no signs of compression to the naked eye. The two widely used forms of lossy data compression are, JPEG and wavelet. JPEG compression time is normally much faster than wavelet but wavelet provides the greater image quality.
"How fast can you transmit an image?" is probably the most asked question of teleradiology sales reps. However, the answer is not as simple as you may think. An image is what is shown on the display monitor-, it could be a CT slice or an entire 14" X 17" film. If a vendor answewrs that question with "15 seconds", he is only giving you half the answer.
Image transmission time is directly proportional to the file size of the digital image after compression is applied, JPEG compression ratios vary depending on the grayscale make up of the image. Identical compression settings used to compress two vastly different images will produce vastly different file sizes even though the spatial resolution of the two images may be identical. Also a factor is the phone line speed. ISDN will yield much faster image transmission times than standard phone lines.
Image management is a process of managing the workflow of clinical images over internal and external networks. Images are then collected and stored to temporary or permanent archives, by means of a structured database or an image filing system.
There are various levels and configurations for archival storage of medical images. Optical disks and Juke Boxes are conventional means for storage. Robotic mass storage hardware systems utilize universal media components such as DAT and DLT Tape and Optical disks. There are various items that the radiology administrator should be concerned about. To see DataView's concerns about these issues, click here.
Pathway to PACS is the integration and building process, using open architecture software and hardware solutions, that manage workflow of clinical images. The end users immediate needs and abilities for growth will determine the pathway of integration, providing the end user with an upgrade path to a full PACS environment.
Images are routed to remote locations by various means. The most common means is by simple phone line connections point to point. A more robust approach would be to use our network store and forward software feature that allows for data to come in from a outside source (other hospital/clinic or capture device) and automatically routed to another location over ISDN, T1, DSL, Cable Modem, or T3 connections. Information is available by clicking here.
A quick answer is yes but there are concerns to address. The DataView Store and Forward software uses internet protocols for image transfer but using a 56K modem from home to access you images. This can only be accomplished if the hospital has a dedicated internet connection with at least ISDN bandwidth. DataView is in the process of developing a web browser enabled system that will allow refering physicians greater access to view studies.
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Copyright © 2000 DataView Imaging International, Inc.
Last modified: July 23, 2001