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Teleradiology for Primary Diagnosis

The purpose of this section is to answer some of the frequently asked questions, about how to implement teleradiology and how much it will cost.

First, the image is translated into a computer file. For films, that requires the use of specialized film digitizers which convert the film into a dense matrix of dots. For digital modalities, 1)the data can be directly outputted into a computer, 2)or the image on the console of the modality can be "grabbed" via devices called frame grabbers. Once converted into a computer file, the file can be compressed to reduce the amount of time to transmit the data. Then it is transmitted using regular phone lines, specialized phone lines, satellites, etc. After being received by the computer on the other end, the image is decompressed to turn it back into an image file. Then it can be viewed by the viewing application.

What is the resolution of the digitized image?

For the digital modalities, the resolution is the same as the console or the printed film. If a frame grab method is used, you'll get the same 8 bits of color data as you would get from the film (i.e. 256 shades of gray). If you use a direct digital interface, such as DICOM-3, you could have all 12 bits of data (i.e. 4096 shades of gray). On film, the resolution is dependant on the scanner and may be selectable. The ACR recommends a resolution of 2.5 lp/mm, 10 bits deep for film digitization for primary needs. This translates into about 1800 x 2200 by 1024 shades of gray. Most film digitizers will output 12 bits of grayscale data (4096 shades of gray), but not all of those bits have "real" information. A good digitizer will give you 10 "good" bits, though.

What are the differences between film digitizers?

There are three basic technologies used: camera-on-the-stick, CCD and laser. Camera-on-the-stick shines a light through the film, much like an overhead projector and takes a picture of the film. Both cost and the quality are low. It isn't recommended. CCD's use a specialized fluorescent bulbs to shine through the film and CCD arrays as detectors. Lasers use a laser to illuminate the film and photomultiplier as detectors. The lasers do not have the "bleeding" - overlap from pixel to pixel caused by light scattering - seen in the CCD technology and they also have a larger dynamic range, mainly because the dark regions of the film get better illuminated. Laser are also more expensive than CCDs. The technologies are quite comparable in achievable resolution - both can support 4k by 4k.

Do I lose image information when I compress the data?

You can compress the data by about 2 or 3:1 without any loss of data; this is called lossless compression. Once you get above that ratio, there will be loss, regardless of the compression technique used. There are several well known methods of compression, including several newer methods, such as wavelet compression. They vary in the amount they compress data and the quality of the reproduced image, including the types of artifacts produced. For primary reads, we recommend low or lossless compression algorithms;. the ACR is silent on this.

How long does it take to send the image?

The charts below show the approximate times to transmit different types of medical images by various networks (28.8 modems, 56 kb, ISDN, T-1) using different compression ratios. Please note the scale is logarithmic!

What resolution is required on the monitor to provide primary interpretations?

All of the digital modalities can be viewed at their full resolution using monitors supporting 1280 x 1024, which are common on PC platforms. The ACR refers to the images produced by digital modalities as "small matrix". They recommend 1K viewers with 50ftl of brightness. To achieve this level of brightness requires a grayscale monitor. Grayscale monitors of this resolution are no more expensive than a high quality 20" color monitor. For primary diagnosis of large matrix images (from film or CRs), the ACR recommends 2.51lp/mm (approximately 1800 x 2200) viewers with 50 ftl brightness. This requires specialty hardware and is very expensive for home systems (start at $30k) when compared to a PC solution. However, part of the image can be viewed at full resolution on the PCs and you can then scroll around the image. This may not be efficient for high volumes, but should work fine for emergency cases. Of course, each radiologist must judge for him or herself. At BRIT, we would be happy to show you a wide range of images displayed side-by-side on monitors of varying resolutions. Or bring us your most challenging films for your comparison.

How much does it cost to implement teleradiology?

The costs in implementing teleradiology include:

  1. Digitizing
  2. Transmitting
  3. Viewing the image

Besides resolution, what other considerations do we have in the quality of the monitor?

Unfortunately, you can seldom judge the quality of a monitor for medical image display from the monitor's specification sheets. Some parameters to consider are:

  1. Brightness and contrast - are very closely related, and make more difference in the perceived quality of the medical images than other parameters. Grayscale monitors are generally brighter and have better contrast than colored ones. Different models of grayscale monitors have a broad range of brightness and contrast. The ACR guidelines call for a brightness of 50ftl, which excludes all color monitors. Almost all grayscales will meet this. On monitors that support the 25.1p/mm specifications, almost all will run at 65 ftl or more. If you use the highest-end graphic card available, it delivers 10 bits to the monitor, or 1024 shades of gray. To have a chance of distinguishing even half of these (500 Just Noticeable Differences - JND), the monitor should be set at 100 ftl or brighter.

  2. Dot pitch - for referral and review purposes, the monitor's dot pitch should be 0.26 or smaller, but you would have to know how each manufacturer measures their dot pitch in order to compare apples to apples. Dot pitch is not relevant with a color monitor.

  3. Distortion - for large, high resolution monitors, distortion can be a real problem. In addition to skew, barrel distortion and such; large monitors with a large curvature of the CRT's glass have images which are subjectively distorted.

  4. Image "blooming" - the spreading of bright regions into neighboring regions.

At BRIT, we send monitors through a series of tests to determine the overall clarity of the image produced. One might think that this is quite subjective, but it doesn't appear to be. At least all radiologists seem to like the same, most highly rated display!

1.)Digitizing: If you are supporting all modalities (i.e. film plus CT, etc.), then the least expensive route in digitizing the image is the use of a film digitizer because it can support everything. If you are only interested in digital modalities, then using a frame grab system will be less expensive than the film digitizer. BRIT recommends that you use a laser, rather than a CCD digitizer for primary diagnosis. The laser has a larger optical density range than the CCD. This means that the range of color produced is greater - the blacks are blacker, the whites are whiter. The laser also does a better job "reading" the dark portions of the film. Some CCD scanners achieve better optical density ranges by digitizing the film twice: once to determine the overall range and the second time to spread that range across a wider spectrum. Obvioulsy, this is more time consuming. CCD also has significantly more "bleeding" - that is the colors run together due to light scattering during digitization so the images aren't as sharp. Both laser and CCD can have the same spatial resolution. We are most often asked to compare the Lumiscan 75 with their Lumiscan 20. When dealing with the Lumiscan 75 laser vs. the Lumiscan 20 CCD, there is a difference in the spatial resolution on smaller films. The Lumiscan 75 will adjust the spacing between scans of the laser so that you get 2000 x 2500 pixels, regardless of the film size. Lumiscan 20 has a fixed grid. You get 2000 x 2500 on 14" x 17" films only. The number of pixels is directly proportional to the film size on the Lumiscan 20. This can be an issue if you are reading small films, such as hands. The lasers digitizers are more expensive than the CCDs, however. BRIT would be more than happy to show you a wide range of images digitized using both methods and let you decide if the CCD technology is acceptable. The laser digitizers start at approximately $33K; the CCD ones cost approximately $23k (fully integrated and installed, in both cases).

2.)Transmitting: The cost to transmit images will vary with the type of transmission facility used, your location and perhaps line usage. You will need to select the facility based on the speed you require, considering both the capacity of the line (i.e. how many images can be sent in a day) and the time to transmit a given image. The diagrams below should help you size your line requirements.

If 28.8 kbs modems suffice, then you'll have the cost of the phone lines on both ends and whatever long distance charges incur. Note: phone lines rated at 28.8 are not available everywhere. The 33.6 modems do not always run faster than the 28.8 modems. The ability to achieve a given rate is dependant on the quality of the phone line, which is partially dependant on the distance between the modem and the phone company's switching facility.

ISDN is a newer, faster technology that runs at either 56kb/sec or 64 kb/sec or twice these numbers. This technology runs over regular phone lines, although the switch at the phone company is different. It acts as a plain old telephone (POTS) line in several aspects: it can carry regular voice traffic and it is dial access (as opposed to a dedicated line). ISDN is not available everywhere and where it is available, the prices vary tremendously. In Dallas, for example, Southwestern Bell charges about $100 for installation and $60/month for two 64 kbps "channels"- unlimited usage (of course, this doesn't include long distance charges). If, however, you are served by GTE in Dallas, the installation charge is about $800, the monthly usage is about $60 plus they charge per minute!

Where ISDN isn't an option, 56kb lines may be available. These tend to be quite a bit more expensive than the ISDN and are typically dedicated. Next up are the T-1 lines( 1.54 mb/s) or partial T-1 lines. The price of the T-1 line depends on many factors, such as the distance from the send and receive locations to the phone company's facilities. Typically, they start at about $1000/month. Texas has passed a House Bill, though making these lines much more affordable for nonprofit healthcare organizations. They may be available for as little as $250/month for a dedicated line.

There are more expensive and faster speed connections available than these, such as ATM. There are also networked solutions, such as frame relay, which can save you money with as few as three end points. We'd be glad to discuss these with you, as needed.

How about using the Internet?

Yes, the Internet can be used. Most Internet providers now charge a flat rate/month based on the speed of your connection. If the cost of the Internet service on both the send and receive ends is less than you'd expect to pay for long distance phone calls, then it may be a good idea. For example, the Internet cost of one channel (64kbps) ISDN service here in Dallas is $30/month. The receiving end must also have the Internet ISDN service for us to transmit near those speeds. So, that may be an additional $40/month. Therefore, if your long distance phone bill would be more than $70/month, you should consider the Internet (Note that you must still pay for the ISDN lines from our local phone companies in either the Internet or the long-distance carrier scenario). There are several caveats, though. First, the providers on both ends have to be able to handle our large file sizes in order to store and forward them. Some are not equipped to handle files over 1MB. Second, you need to understand how fast they will guarantee movement through the net. How often do they run their store and forward for files? They may not tell you, but a trial for a month will give you a good idea. Third, nobody really manages the Internet. So, if the files don't make it, you may have a hard time figuring out why or when they might arrive. This means that you'll always need a back-up. This isn't difficult to provide; you just direct dial the other computer and incur the cost of that long distance call. Of course, the Internet connection does not need to be dedicated to this tasks; you can use it for surfing. So, the total monthly cost would be: ISDN Line@ send side + ISDN Internet send side +ISDN Line receive side + ISDN Internet receive side. Add to that any long distance charges for when the Internet fails.

3) Viewing: The price of BRIT viewing software applications start at $1200 for Windows which must be placed on a properly configured PC (minimum of 256MB memory, 2 MB VRAM on the video board, 1280 x 1024 monitor, some transmission method). This hardware is quite inexpensive, since it is produced in high volumes. You will want a grayscale monitor for primary diagnosis of small scale matrix images. These cost about the same as a good 19" color monitor.

The next step up in quality is the 1600 x 1200(landscape) or 1200 x 1600 (portrait mode). The displays and graphics are a bit more expensive, especially if you want to maintain the refresh rates on the monitors (slow refresh rates can cause eye fatigue and can cause screen flicker, especially if used with fluorescence lights). Grayscale monitors can a run a bit more money, too, since they are not produced in high volumes. The price of a system with 1200 x 1600, 21" portrait display is approximately $10k.

Above 1200 x 1600, we get into specialty systems, which cost more than double the 1200 x 1600. A system which supports a display the ACR guidelines of 2.5lp/mm starts at about $20k.

If my business case does not justify the purchase of a teleradiology system for reading emergency films, are there any other benefits that can be included in the financial analysis?

Of course, the PC and Internet can be used for other purposes, such as education, finances, word processing and entertainment. Even if you purchase a higher end UNIX system, you can still run your Windows programs with an emulator.

NOTE: BRIT Systems is now a reseller of MedSpeak, IBM's voice recognition application which allows radiologists to speak continuously while the compute transcribes. Using viewers and this transcription tool, radiologists can now quickly and remotely 1)interpret exams and 2) provide the report.

Conclusions

Primary diagnosis can be achieved using today's teleradiology systems. The costs of these systems vary depending on many factors, including the cost and availability of phone services in your area. BRIT Systems can help you determine your costs and select a system to meet your particular needs.