Q. What is Teleradiology?
A. Teleradiology is the process of sending radiologic images from one point to another through digital, computer assisted, typically over standard telephone lines or over a local area network (LAN). 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 especially are important to rural medical facilities.

In-hospital or mini-PACS systems are used to move images electronically throughout one facility (i.e., from radiology or to ICU or ER) over a local network.

Q. How are images captured from modalities such as CRT, MR, ultrasound and nuclear medicine?
A. 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 console, or digitally by connecting directly from a modality to a workstation over a network (i.e., ethernet). The least expensive method of acquiring digital data is through a DICOM (see below) file transfer.

Q. How are plain film (standard radiograph) images captured?
A. Standard radiographs can be digitized by either video camera or a film scanner.

Video cameras (commonly referred to a "camera on a stick") were in fact the method of digitizing any images from transmission as recently as 3 years ago, video based on film. Typical camera systems utilize a light box designed to illuminate radiographs, an extension arm for holding the camera above the film, and a high sensitivity video camera with zoom lens. This is an inexpensive, but mostly a poor method of image acquisition.

Q. What is DICOM?
A. DICOM or "Digital Imaging Communications in Medicine" is a standard that is a framework for medical imaging Communication. It is based upon 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 a "version 3 " because it replaces versions I 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.

Q. Which telecommunications media can be used in teleradiology?
A. 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, etc.), coaxial cable, fiber-optic cable, microwave, satellite, and T-I telecommunication links.

Today most teleradiology systems run over standard telephone lines. Over the next couple of years, we should see a substantial migration to switched-56 and ISDN lines, which offer high speed and better line quality than standard dial-up phone lines. Other high- speed lines, including T-1 and SMDS will also become more popular as prices continue to drop.

Q. What is meant by image BIT size?
A. Digital images: those viewed on a computer monitor, transmitted over a phone line, are pictures that have a certain spatial resolution. The spatial resolution, or size, of a digital image is defined as 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: 6 bit images=64 shades of gray-, 7 bit images- 128 shades of gray- 8 bit images=256 shades of gray; 12 bit images=4096 shades of gray, and then by indicating the number of bits in tile shades of gray as the depth.

Q. What does image compression mean?
A. 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 bit sizes 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 for each piece of information in the original image's matrix, ten are dropped. Certain images can withstand a certain amount of compression without a visual difference - CTs and MRs have large areas of black surrounding the actually patient image information on virtually every slice. The loss of some of those pixels does not impact on the perceived quality of the image nor does it significantly change the reader interpretive performance.

Q. How do you calculate image transmission times?
A. "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 single CT slice or an entire 14"x17" film. If a vendor answers that question with "15 seconds", he is only giving you half an answer.

Image transmission time is directly proportional to the file size of the digital image. The greater the amount of digital information in an image, the greater the time required to transmit the image from one location to another.

Q. What is client/server computing?
A. Client/Server computing was developed from the need to move application development and operations systems from expensive mainframes to more efficient, less expensive yet just as powerful workstations. Client/server architecture involves the use of two types of computers: a client's computer, which runs applications and makes requests for data and other resources, and a server, which processes the client's requests by distributing the requested resources.

Q. What is spent annually on teleradiology?
A. Over $1.5 million is spent annually on teleradiology.

Q. What is a teleradiology overread network?
A. While most teleradiology systems purchased over the last decade were for on-call purposes, the past two years have seen a rapid increase in the use of teleradiology to link hospitals and affiliated satellite facilities, other primary hospitals and imaging centers. A number of the enabling technologies needed for effective overread networks are enhancing the accessibility and quality of health care, especially for rural hospitals, which make up about 60% of all US hospitals. Radiologists are also experiencing a decrease in reimbursement for services- teleradiology allows them to use their time more efficiently, thus increasing volume without substantially increasing costs.