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Transmitting digital images is key to telemedicine
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Optometrists around the world are switching from traditional film-based photography to digital imaging. There are myriad systems out there, ranging from inexpensive digital cameras and in-line analog cameras, such as the BioVID, to high-end analog cameras attached to beam-splitters on slit-lamps and retinal cameras.
If telemedicine is to become a common part of optometric practice, doctors need to become comfortable in moving the images these instruments create via the Internet. The emergence of a standard protocol in medical image transmission hasn't been realized, so, until then, already adopted standards for basic file transmission via the Internet e-mail suffice as long as doctors learn a few rules.
What is a file attachment?
E-mail is the most common form of Internet-based communication today. While the World Wide Web gets most of the press, plain e-mail is where most of the work gets done. As long as you know the e-mail address for the person you wish to contact, you can send him or her mail.
When you send e-mail, the text you write is converted into digital code and sent across the endless connections that comprise the Internet until it reaches its destination in the recipient's mailbox. It's up to the programmers to make sure data gets sent properly and is reassembled on the other end.
The importance of this lies in the fact that e-mail protocols currently support the attachment of other data to the text-based e-mail messages we send and receive every day. The process of doing this is called a "file attachment" or simply "file attach."
Virtually any type of file can be attached to an e-mail message and forwarded to any number of recipients. Word processor documents, spreadsheets, voice files, video clips and digital images are among the types of data commonly sent attached to standard e-mail messages.
Does my software support attachments?
Most likely, the e-mail software you're already using is equipped to handle file attachments. America Online's e-mail editor does an excellent job with file attachments. When you are creating an e-mail message, simply look at the row of buttons to the left of the text-editing area and you'll see one that reads "attach." If you click on this button, you'll be presented with a standard Windows dialog box with which you can find and then specify the file you want to send with your e-mail message.
The only drawback to America Online e-mail editor's file-attach function is that you can send only one file along with an individual message. Most standard e-mail clients, such as Pegasus and Eudora, allow you to attach several files to a single e-mail message, if needed.
With America Online, you'll see a status box pop up on the screen showing that a file is being transmitted, along with the e-mail message. A gauge will show just how much of the file has been transmitted and how much longer the transmission will take. With standard e-mail clients, you'll often just see a message showing the percentage of the e-mail message (with attachment) that's been transmitted.
When the file is received
Let's suppose that someone sent you an e-mail message with a file attached. What will you see on your computer? With America Online, when you view the message headers that are displayed from your mailbox, you'll notice that the header has a small graphic of a diskette displayed on the left. When you open the message, you'll see two buttons at the bottom of the screen. One will read "download file" and the other will read "download later."
By clicking the first one, you'll be given the opportunity to specify where you want the file to go, then you'll see a status bar come up showing you the progress of the download.
If you do not specify a destination for the file before you begin the download, the file will automatically be written into the C:\aol30\download folder or directory. Many optometrists become confused after they've downloaded a file-attachment because they didn't pay attention to where it went.
Other mailers behave similarly, except that by the time you see the e-mail's header, you will have already downloaded the file in an encrypted format. When you open the e-mail message, you'll be given the opportunity to save the file wherever you wish using the same sort of Windows dialog box mentioned earlier. Simply specify the desired drive, folder and file name.
Choose smallest file size
The technology supporting file attachments described above works with any type of data file. There is one primary concern, though, when transmitting files, regardless of their type. You want to make sure you're using the smallest possible file size necessary to transfer. This will keep the transmission time both on the sending and receiving ends to a minimum.
For most data files, this requires compressing the files using the standard zip protocol. Check out the shareware program Winzip on file exchange (www.optcom.com). Winzip makes the compression and decompression of .zip files easy.
Luckily, graphic files don't need to be compressed because the two most popular image formats are already compressed. It's important to use one of the two formats when sending your images off into the Internet. The current standard for medical images is the JPEG format. These files usually have the .jpg extension. For example, a digital image of a retinal detachment might read "retina.jpg."
JPEG images are compressed but maintain a 24-bit palette comprised of millions of colors. This is termed "color depth" and is important in maintaining clinical accuracy. JPEG also supports "variable compression." Many graphics utilities ask you how much compression you want to apply to the image before converting to JPEG. The more compressed you make the image, the lower the end quality. Resolution suffers greatly at the highest compression ratios. A good rule of thumb is to keep compression levels at about 75% unless you notice significant degradation of quality at that level.
GIF files are mainstay
Engineers at CompuServe created GIF, or the graphics interchange format, several years ago in an effort to provide users with a compressed, efficient graphics standard. GIF files are terrific in many ways. They are compressed and easily readable by dozens of graphics utilities. GIF files are a mainstay of the World Wide Web.
GIF files have some real drawbacks, however, for moving clinical images around. GIF files support a variety of palettes, but only with a maximum of 256 colors instead of the 16 million that JPEG supports. While retinal images might be acceptable at 256 colors, anterior segment shots usually suffer.
The general rule of thumb is to stick with the JPEG format when moving files from one Internet user to another. Try to avoid GIF simply because of the color depth. Avoid all other formats due to size considerations or the difficulty your recipient might have in reading the file.
It's also important to keep the pixel dimensions of your image reasonable in size. Most image capture systems only capture in 640 x 480 or smaller, so this is usually not a problem. If your particular system can save at higher resolutions, such as 800 x 600, 1024 x 768 or 1280 x 1024, consider using the lower formats, because these large images take up considerably more time to transmit and fill up your hard drive a lot faster as well.
Efficiently manage images
One final hurdle lies in efficiently managing these graphic images. Your image capture system may not have the editing and conversion capabilities you want if you plan to send or receive more than a file or two; adding a quality graphics editor enhances any digital imaging system. The industry standard is PhotoShop, a $595 application. All but the most serious graphic artists would do better to stick with Paint Shop Pro, a wonderful image editor that can be downloaded at www.jasc.com.
All of this may sound a bit daunting, but it's really not difficult. If you need help getting started, call a few of your colleagues who are using the Internet effectively. Joining the optcomlist is another great way to set you racing along the learning curve. This electronic discussion group currently has more than 1,100 optometrists from 35 countries involved. See www.optcom.com to subscribe.
For Your Information:
- Walter A. Mayo, OD, is founder of the Optometric Computing home page (http://www.optcom.com/) and a charter member of the Editorial Advisory Board of Primary Care Optometry News. He can be reached at Coastal Eye Group, 400 Marina Drive, PO Drawer L, Georgetown, SC 29442; (803) 546-8421; fax: (803) 546-1173; e-mail: waltmayo@aol.com. Dr. Mayo has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any company mentioned.