Frequently Asked Questions on TelePathology
- What is Telepathology?
- What is static TelePathology?
- What is "Dynamic" TelePathology?
- What equipment do I need for telepathology?
- What are analog and digital cameras?
- How to choose a camera for TelePathology?
- How to choose a microscope for TelePathology?
- Can I use the Internet for Telemedicine purposes?
- How are images networked internally and/or to remote locations?
- Which Telecommunications medium can be used for Telepathology?
- What are different acquisition devices?
- What is "Virtual glass slide"?
- What are advantages of Web Based System?
- What is FlashPix?
- Why is Gross Imaging important?
- What is DICOM?
- What is Frame Buffer Memory?
- What is Refresh Rate?
- What is DPI?
- What are different types of Video Signals?
- What is System Resolution?
- What is meant by BIT size?
- What is Image Management
- How are images archived and stored?
- How do you calculate image transmission time?
- What are different formats for image files?
- What is the relationship between Resolution and speed?
- What does image compression mean?
- Why File compression is important?
- What is Color Depth?
Telepathology is the practice of pathology (consultation, education and research) using telecommunications to transmit data and images between two or more sites remotely located from each other. Telepathology allows a pathologist practicing in a geographically distant site to consult another pathologist for a second opinion, or other pathologists who are experts on particular disease processes. Telepathology has been proven to be an accurate and cost effective way to support such an exchange between pathologists. Time consuming, labor and cost intensive exchanges of specimens by post or other means of transportation can be avoided.
2. What is static telepathology?Static telepathology consists of the capture and digitalization of a group of macroscopic and/or microscopic images selected by a pathologist or pathologist assistant, which are then transmitted through electronic means to a telepathologist. This transmission is usually done by electronic mail (e-mail) or by a file transfer protocol (FTP). With e-mail, the image files are sent as attached files in a message containing the basic information about the case. The FTP is used to send files directly into a web server from which the telepathologist can download them. To include both the images and the information about the case in a web page and give simultaneous access to several pathologists in different parts of the world is another alternative method.
Store and forward systems are simple and therefore inexpensive, and they can be used without any special telecom equipment other than a standard PC modem and Internet account. Because of the limited field of view of the microscope's objective, a typical specimen can provide tens of thousands of distinct images. For this reason, many consultant diagnosticians may not be willing to offer a definite diagnosis.
Still image acquisition allows for higher resolution than dynamic real-time methods, because the need for real-time makes not possible to adopt very high resolution images, which occupy a large amount of memory. Very high-resolution devices could be used for acquiring low magnification images of whole biopsies, making thus selection of the fields from them unnecessary.
Static systems are inexpensive to set-up and operate which can be used with low bandwidth communication. Although it has been reported that the static system is not suitable for remote diagnosis such as performing frozen section diagnosis remotely, it is a powerful and effective tool for consultation and the exchange of opinions among pathologists.
3. What is "Dynamic" telepathology?Dynamic systems are used to support online, interactive sessions where images are transmitted continually as the specimen is moved on the microscope stage during the process of examination. For this, the microscope that sends the images may be equipped with a telerobotic system that is remotely operated by the telepathologist who makes the diagnosis. This robotic system may include one or more of the following elements: movement of the microscopic plate, changing objectives, and focusing and light adjustment. Some of these systems provide the telepathologist with an overview image of the specimen at low resolution, including the coordinates of the slide. This is accompanied by images at medium resolution, which show the constantly changing microscopic fields according to the movement of the plate. A live videophone link is normally provided to allow continuous two-way communication between the participants. A modality of dynamic telepathology, in the absence of a telerobotic system, is to use a telepathologist assistant who operates the microscope in the remote location and moves the plate following telephone instructions from the telepathologist.
Dynamic telepathology has limitations, since it has to be accomplished between centers using the same operating system (software). Dynamic telepathology requires more than 128 kbit/s bandwidth. The cost of the equipment and the computer programs fluctuate between $20,000 and $100,000 US and they are affordable only by large hospital and/or academic institutions. The actual cost of a good high-resolution digital camera is between $5,000 and $10,000 US.
4. What equipment do I need for telepathology?
The basic telepathology setup consists of a microscope, a high resolution camera (750 x 500 resolution is the minimum, 1K x 750 ideal), an image capture board or card in a computer (Windows or Macintosh), software to manage the images and a telecommunication system to transmit images.
(1) Hardware : Camera (NTSC or high resolution), Computer (PC or Mac) and Storage
(2) Software : image acquisition, database (file storage and retrieval), image manipulation
(3) Basic components: Microscope, Adapter, Camera, Cable, Video Cards, Bus, Processor, Storage, Monitor, Table,
Software, NIC, CARD
- Microscope: any high quality microscope will generally work. The scope will need a camera mount for the specific scope and camera chosen.
- Connection to a telemedicine system with composite video.
- Camera: The choice of the camera will depend on other desired uses (image capture, conferencing, etc.).
- Monitor: A regular TV could be used with significant resolution loss, or one can purchase a true high resolution RGB monitor. Typically these are 600 line, RGB monitors. Both Olympus and Sony make good ones. Price depends on screen size. Sony PVM-1353 MD is $1400; the 19 inch is $2500.
The system must have a mechanism for transfer of images. For web-based service, you'll need a web browser, e.g. Netscape Navigator /Communicator or Microsoft Internet Explorer, and Internet access. One can use a local-area network to transmit cases across the Internet or a modem and telephone service to send images directly. Commercial telepathology systems are also available. Since these systems are proprietary, both parties have to have the same system to send and receive consultation cases.
5. What are analog and digital cameras?There are two ways of acquiring images from the microscope:
1. Analogue camera: This needs a frame grabber card into the computer, which converts the analog signal coming from the camera into digital values; the usually available devices are based either on a single input chip (mono CCD) or on three separated chips for red, green and blue color components (3CCD), which are preferable for pathology due to the higher quality. Spatial resolution is up to 600 lines with color resolution of 24 bits, and images are acquired at up to 30 frames per second.
2. Digital cameras: These devices have a digital output, and are usually connected to the computer through a direct connection to the SCSI bus or other high speed connection; digital cameras and photo scanners reach an higher spatial and color resolution (up to 5000x5000 pixels), in spite of acquisition speed, making its adoption adequate mainly for store-and-forward telepathology.
6. How to choose a camera for telepathology?The choice of camera is important for quality results in telepathology. Not many CCD cameras are capable of capturing the fine detail at the low power magnification. A critical test of any microscopy camera is to compare image quality and field of view when using the low-magnification objectives. The problem comes from the relation between the objectives' resolving power, which is set by numerical aperture (NA), and the limit to resolution set by the camera's CCD element size. This problem cannot be overcome by the use of magnifying lenses in the microscope trinocular because the field of view then becomes too small to be useful and may no longer be flat. For general use in telepathology, a digital camera having at least a million [<10micron] square CCD elements is required. This in turn imposes a limit on speed and interactivity since such cameras readout more slowly than the more familiar analog cameras. However, they are definitely worth it in terms of image quality.
7. How to choose a microscope for telepathology?
The image quality and level of interactivity is set by the quality of the camera and its acquisition hardware, by the processor speed of the host computer, and by the telecommunication protocol. The optical quality of even a modest laboratory microscope is likely to be degraded by one or more of these. Thus the purchaser of a telepathology system should first pay particular attention to the quality of the image capture and transmission system.
8. Can I use the Internet for Telemedicine purposes?A quick answer is yes but there are concerns to address. The usual store and forward software uses Internet protocols for image transfer buy using a 56K modem. This can only be accomplished if the hospital has a dedicated Internet connection with at least ISDN bandwidth.
9. How are images networked internally and/or to remote locations?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 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,ADSL, or T3 connections.
10. Which Telecommunications medium can be used for Telepathology?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.
Over the next several years, ISDN lines which offer high speed and better line quality than standard dial-up phone lines will become popular. Other high-speed lines including ADSL, T1, and T3, will also become more popular as prices continue to fall and accessibility increases.
11. What are different acquisition devices?
They are Scanners (kodachrome scanners ) or Cameras (Analog Video , "Digital" video and Digital still).
12. What is "Virtual glass slide" ?A bird's eye view of the entire glass slide can be captured by the Modified 35mm film scanner On the monitor, a scanned image has almost as much diagnostic information as a microscopic image captured by a 2x objective lens and a NTSC camera.
13. What are advantages of Web Based System?The World Wide Web provides a flexible, economical, ubiquitous, user friendly and intrinsically multimedia environment in which to display and distribute image enhanced reports to remote clients. Hypertext Markup Language (HTML) is the ideal, standardized tool through which to craft reports composed of images linked to text.
14. What is FlashPix?FlashPix is a format for storing digital images, especially digital photographs, developed by Eastman Kodak Company. FlashPix offers a number of unique features, including:
Currently, FlashPix is not supported by most imaging software.
15. Why is Gross Imaging important?Gross imaging is the only documentation on the gross specimen. It is easier than microscopic image capture. It is very useful for sign out and section diagrams. Clinicians can relate to the gross images.
16. What is DICOM?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. 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. DICOM provides standardized formats for images, a common information model, application service definitions, and protocols for communication.
17. What is Frame Buffer Memory?
The frame buffer is the video memory that is used to hold the video image displayed on the screen. The amount of memory required to hold the image depends primarily on the resolution of the screen image and also the color depth used per pixel.
The formula to calculate how much video memory is required at a given resolution and bit depth is:
Memory in MB = (X-Resolution * Y-Resolution * Bits-Per-Pixel) / 8
18. What is Refresh Rate?Refresh rate is measured in Hertz (Hz), a unit of frequency.
Support for a given refresh rate requires two things:
1) a video card capable of producing the video images that many times per second2) a monitor capable of handling and displaying that many signals per second.
The refresh rates are standardized; common values are 56, 60, 65, 70, 72, 75, 80, 85, 90, 95, 100, 110 and 120 Hz. This is for compatibility between video cards and monitors. Most individuals notice flicker at refresh rates below 60 Hz. Many individuals have a problem with flicker at 60 Hz. Some individuals see flicker at refresh rates above 60 but below 72 Hz. A small percentage of individuals notice flicker at 72 Hz. Very few people notice flicker at refresh rates above 72 Hz.
19. What is DPI?DPI: is most often used to describe monitors, printers, and bit-mapped graphic images. In the case of dot matrix and laser printers, the resolution indicates the number of dots per inch.
Example 1 : a 300-dpi printer is one that is capable of printing 300 distinct dots in a line 1 inch long. This means it can print 90,000 dots per square inch. For graphics monitors, the screen resolution signifies the number of dots (pixels) on the entire screen. Example 2: a 640 x 480 pixel screen is capable of displaying 640 distinct dots on each of 480 lines, or about 300,000 pixels. This translates into different dpi measurements depending on the size of the screen. Example 3: a 15-inch VGA monitor (640x480) displays about 50 dpi. (dots per inch)
20. What are different types of Video Signals?
Component RGB: 1 channel for each color , red, green, blue, and sync.
Component YCrCb: It is a three wire signal format. The Y(luminance) information is separate from the color information. Cr for Red and Cb for Blue values. The green information is produced by subtracting the red and blue values from the total signal. S-Video Y/C: 2 channels are used with two separate wires, 1) for chrominance(C) and another for 2) luminance (Y). This level is suitable for industrial videos and pro-consumers such as pathologists. Composite: Compound signal. Color(chrominance) and Brightness (luminance) and the required synchronizing pulses are modulated into one single signal. It is the most commonly used. 21. What is System Resolution?As a general rule, the resolution of a specific system composed of multiple pieces of equipment is limited by the weakest link, which determines the maximum obtainable resolution of all components in the system. At present, video cameras are the weakest link in most systems since high resolution color video cameras are very expensive. Video camera capable of higher resolutions can be used at the expense of more memory requirements and video display limitations.
22. What is meant by BIT size?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.
23. What is Image Management?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.
24. How are images archived and stored?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.
25. How do you calculate image transmission time?
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.
26. What are different formats for image files?
With increasing resolution, the file size increases so the time required to move that file increases.
Although images should be permanently archived as raw data or with only lossless data compression, hardware and software technology exists that allows telepathology systems to compress digital images into smaller file size so that the images can be transmitted faster.
29. Why File compression is important?
An image with 640x480 pixels and 24 bits color (e.g., coming from a 3CCD camera) needs 900 Kbytes of storage space; for a 3000x2000 image (typical size of a high-end digital camera), the value grows up to 17.6 Mbytes.
Being transmission time dependent on image file size, methods for reducing the amount of memory needed for storage are highly recommended. The main way to obtain this is to apply some compression algorithm, which may be of two kinds: lossless (i.e. completely reversible) and lossy (i.e., with a loss of information such that a compressed and decompressed image is different from the original one). Former methods allow for compression ratios up to 1:3, depending on the image features, while the latter ones are more efficient, with a selectable level of quality and thus compression (which could be up to 100-200:1). The most known lossy algorithm is JPEG (Joint Photographic Expert Group), developed to exploit eye and camera limitations for discharging apparently less useful visual information from images; in store-and-forward static telepathology, JPEG has been widely applied at compression ratios up to 30:1.
Another way of reducing storage size is the color reduction from 24 to 8 bits, which means that the number of available different colors decreases from millions to 256, while the file size becomes one third of the original one; on such files, a lossless compression method could be further applied.
Another important issue is that of file formats: in order to allow the effective interchange of images, they should be stored using some standard. Currently, the GIF format is being used for 8 bits, lossless compressed images; TIFF is adequate for 24 bit lossless compressed images, and the JFIF format (usually called JPEG) hosts JPEG compressed images.
30. What is Color Depth?Refers to number of gradations for each of three primary colors (red, green and blue).
Since 8 bits equals a byte, then for 24-bit color, you need 3 bytes of data for each pixel.
