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 19 March 2018

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View all the figures for this chapter.

Endoscopy Practice and Safety

Peter B. Cotton ed.

5. Digital documentation in endoscopy

Lars Aabakken

Top of page Synopsis  Next section

Gastrointestinal endoscopy is a visual clinical discipline. All examinations, findings, descriptions, and recommendations are based on the images that are created during the endoscopy. In interventional work, the images are our sole guiding material for correct procedures.

Fiberoptic imaging  Previous section Next section

Fiberoptic imaging was introduced into endoscopes in the 1960s. The mere view into the intestine was a revolution. However, the revolution was a very private one, conveyed through the eyepiece of the endoscope, without dissemination, sharing, or storing options. Endoscopic teaching and clinical practice was somewhat anecdotal and inconsistent, simply because the endoscopists had little or no means of communicating what they saw, apart from the written endoscopy report—already an interpretation of the images.

Teaching attachments and photography  Previous section Next section

Twin eyepieces and mountable cameras (still and video) were steps in the right direction, allowing exchange and discussion of image information, but these were cumbersome gadgets with limited dissemination, and archiving solutions were mostly non-existent.

Videoscopes  Previous section Next section

The introduction of video-based imaging systems created a host of new opportunities. The eyepiece was replaced with the greatly enhanced viewing experience of a large monitor screen. The endoscopic examination became a shared experience with colleagues and assistants, and, in some cases, even with the patients themselves. Important findings could be recorded in print form.

Image capture  Previous section Next section

The video signals that are received and processed in the endoscopy rack can be utilized further: they can be stored electronically—as captured electronic images, or as digital video. In combination with other existing technologies, this enables access and utilization of our endoscopic images far beyond what was previously feasible (Fig. 1).

The increasing availability of electronic image-capturing systems opens up new ways for documenting our procedures. Where we were previously confined to the endoscopist's concept of a 'large ulcer', 'profuse bleeding', or 'moderate inflammation' in a text report, the addition of images allows the reader of the endoscopy report to get a better understanding of what is actually found, sometimes even take part in the interpretation. This is a development completely parallel to what our radiologists have been doing for a long time, i.e. relating their diagnostic considerations directly to demonstrations of their image material. There is no compelling reason why the endoscopist should not now be doing the same thing.

Standardized image terminology  Previous section Next section

This enhanced information flux has a very interesting side-effect: we are beginning to understand what our colleagues are talking about. The exposure of how we label our findings with medical terms has brought to attention the need for language standardization; the same words should have the same meaning. The content of a written report will be of value only if the 'image-to-word' coding algorithm is the same. The task of establishing a common language for gastrointestinal endoscopy has been taken on by the OMED, and later by the European and US Endoscopy Societies.

Structured reporting  Previous section Next section

Once the lexicon is agreed upon, the collected information needs also to be structured. The endoscopy report should be composed in a standardized way, similar to what we have come to expect for other encounters, e.g. the medical history and physical findings of a patient on admission. The introduction of computerized reporting systems for endoscopy likewise calls for this type of structuring. The use of these systems for cumulative reporting and statistics requires rigorous coding. Even more standardization is required if our endoscopy reports and images are to be implemented in a complete electronic medical record.

The opportunities and challenges of the digital revolution  Previous section Next section

The digital revolution in endoscopy has the potential to change the way we work and communicate, offering great improvement in the service we can give our patients and referring doctors. However, this pay-off requires a significant investment of money, time, and thought on the part of the endoscopist. This paper deals with some of these issues.

Top of page Digital imaging  Previous section Next section

Imaging the gastrointestinal tract using a videoendoscope requires several steps  Previous section Next section

  • Illumination by fiberoptic light transmission
  • Surface reflectance
  • Magnification
  • CCD conversion of the reflected light to an electrical signal
  • Reconstruction of the signals to an image
  • Projection onto a monitor

PCs with image capture cards and network capabilities permit these images to be captured, stored, printed, and transmitted.

Color models  Previous section Next section

The physical quantities of the colors that represent an image are defined chromatically by wavelength, and the luminance is defined by the amount of light. The colors detected by a videoendoscope are continuous values. In the digital domain, color must be converted from this continuous or analog value to a discrete digital value.

The representation of color can be based on one of three color models:

RGB  Previous section Next section

Most of the visible color spectrum can be represented by mixing the three primary colors, Red, Green and Blue, known as the RGB color model. This model is the one used by most computer monitors, TV screens, graphics cards, and lighting effects. Color mixing is analogous to illumination of an area with red, green, and blue bulbs of different intensity. Mixing different amounts of the red, green, or blue creates different colors, and each can be measured on a scale ranging from 0 to 255. If red, green, and blue are all set to 0, the color is black; if all are set to 255, the color is white (Fig. 2).

CMYK  Previous section Next section

The CMYK color model is based on printing ink being absorbed into paper. It gives the greatest number of printable colors from the fewest number of inks. By using varying amounts of cyan, magenta, yellow, and black, a great number of colors can be printed. Most full-color printed materials, including magazines, posters, and packaging, are printed using just the four CMYK inks. Here the level of ink is measured from 0% to 100%. As an example, orange would be represented by 0% cyan, 50% magenta, 100% yellow, and 0% black.

HSB  Previous section Next section

With the HSB model all colors are described in terms of three fundamental characteristics, hue, saturation, and brightness. This is a useful model for image processing, because calculations need be applied only to one HSB axis as opposed to three RGB axes. Therefore, it is often used in imaging software in computers.

Hue is the wavelength of light reflected or transmitted from an object, although more commonly, hue is known as the actual color, such as red, yellow, or blue. Hue is measured as a position on the standard color wheel, and is described as an angle in degrees, between 0 and 360.

Saturation is the amount or strength of the color (or hue). It is measured as a percentage. At 0% the color would contain no hue, and would be gray; at 100%, the color is fully saturated.

  • Brightness is the lightness or darkness of the color, again measured as a percentage. If any hue has a brightness of 0%, it becomes black; with 100% it becomes fully light (Fig. 3).

Each of these three models has advantages and shortcomings, but there is good reason to know they exist, in particular to understand the pitfalls in converting computer screen images to printed images. To accurately match a color print with what you see on screen, special expertise from a print-shop is usually recommended. Practical experience and trial-and-error exercises make a good alternative approach.

Top of page Digitization of color  Previous section Next section

The number of unique colors that can be represented by the coordinate system depends on the length of each axis. Because the digital world is binary, the number of possible values is represented by an exponential exponent of 2 or 2x. If a color is represented in RGB space by 8 unique binary digits (bits), then there are only 28 = 256 colors to choose from. Increasing the number of digits representing a color increases the color range, i.e. 16 or 24 bits define 216 = 65 536 and 224 = 16 777 216 colors, respectively. Computer screens are typically able to display 224 colors ('millions of colors'), but the color range still has an impact on file size.

An image is presented as a continuous signal, which is converted or transduced by an analog-to-digital device. To create a digital image, a specific device in the computer called a frame grabber or capture board converts the video signal into a digital form. The resulting digital values are mapped to specific locations and stored as a two-dimensional array of numbers.

The frame grabber performs two functions: sampling and quantification.

  • Sampling captures evenly spaced data points that represent the image.
  • Quantification assigns each data point a binary value. The evenly spaced data points for an image represents specific two-dimensional locations called picture elements or pixels. The pixel is the basic unit of a digital image and each pixel stores the value produced by the quantification described above.

Top of page Color depth  Previous section Next section

The number of discrete colors available to present an image is the color depth or color resolution. A grayscale image digitized by an 8-bit image capture card is represented by assigning values to each pixel making black = 0 and white = 256, because 28 = 256. Color is more complex. The range of colors depends on the number of bits that can be stored at the pixel location. Thus, an 8-bit frame grabber can capture 8 bits/pixel or 256 colors/pixel. Most frame grabbers today capture 24 bits per pixel (i.e. 8 bits for each of the three colors red, green, and blue). This allows a total of 224 combinations, 'millions of colors'. It is important to recognize that the actual color range (number of discrete colors) of an endoscopic image is small. This is the reason why the appreciable difference between 16 and 24 bits/pixel images is minimal. The limited range of colors present in an endoscopic image also affects how such an image can be compressed.

Top of page Pixel density  Previous section Next section

Pixel density (sampling density) is the number of pixels into which an image is divided by the frame grabber. The greater the number of pixels/unit area the higher the resolution of the image (Fig. 4). For an image of a given size, sampling density can be defined by the dimension of the image in pixels. For example, 640 × 480 represents an image that is 640 pixels wide and 480 pixels high (VGA resolution). If this same image is sampled at 1024 × 768 (XGA resolution) then the number of pixels/unit area is higher and the resolution is greater (Fig. 5). Sampling becomes important when images are enlarged because there is a discrete separation between adjacent points in the image. Thus, zooming an image which has been sampled at a low density quickly reveals the individual pixels, a phenomenon called pixelation. On the other hand, pixel resolution beyond that of your viewing mechanism (e.g. an 800 × 600 computer screen (SVGA)) requires extra storage space without any utility.

Top of page File size  Previous section Next section

The final size of an uncompressed image is calculated simply by the formula width (in pixels) by height by color depth. A VGA resolution 24-bit image (typical for an endoscopic image) would be 640 × 480 × 8 × 3 = 7 372 800 bits, approximately 900 kilobyte (1 byte = 8 bits).

File size affects storage requirements, display delays, and transfer times, and so becomes important in the everyday use of the images. Transferring a 900 kbyte image with a 28.8 kbyte modem requires 4.3 min, and a 1 gigabyte disk drive would be filled with 1100 such images [2].

Thus, all the factors determining the file size should be considered to optimize the composition of endoscopic images.

What detail is needed?  Previous section Next section

In some clinical situations resolution is not important, e.g. a large mass or a pedunculated polyp may be easily identified as such even at low resolution. On the other hand, subtle findings such as the granularity of the mucosa or disruption of the vascular pattern may require a higher pixel ratio. It is also of interest how the image will be utilized. To show the image on a computer screen, the resolution of the screen determines the optimal resolution (e.g. SVGA), but for printing with a high-quality printer (e.g. glossy prints for a journal manuscript), a higher resolution is needed, typically 2–3 times the screen requirements.

At the present time, there is definitely an upper limit to the resolution that is feasible for endoscopic images. The CCD chip in the tip of the endoscope has a pixel resolution in the SVGA range. Thus, even if we had capture cards with higher resolution, the image quality would be but marginally better. However, high-resolution endoscopes are being developed that may change this situation.

File compression  Previous section Next section

For practical purposes, uncompressed images are almost theoretical relics of the past. With the increasing utility of network-based and internet-based computer applications, the need for smaller files is indisputable.

File compression is a computational processing technique that effectively reduces the size of a file by removing redundancies in large binary data sets. Full motion video requires a display rate of 30 frames/s. If each frame is 0.5 megabytes then one second of digital video contains 15 megabytes of data. Disk storage would be rapidly exceeded and image transmission even on high-speed networks would be slow. Compression is measured as a ratio of the size of the original data divided by the compressed data.

Compression techniques  Previous section Next section

There are two general categories of compression techniques: lossless and lossy.

Lossless compression  Previous section Next section

  • Lossless compression techniques preserve all the information in the compression/decompression process. This may be vital for compressing documents or computer program files, but these techniques can only achieve moderate compression ratios, which may not be sufficient for medical images, especially for radiological grayscale images. However, when images are used as a means of primary diagnosis, they require lossless compression, storage, and transmission. Most PACS systems utilize lossless compression, but require high-end hardware and dedicated high-speed networks.

Lossy compression  Previous section Next section

For the purpose of practical archival storage and transmission of medical images, compression ratios of 20 : 1 or higher are required. In order to achieve this amount of file size reduction, lossy compression techniques need to be employed. Lossy compression implies that some information is lost in the compression/decompression process, but algorithms can be designed to minimize the effect of data loss on the diagnostic features of the images.

Image file formats  Previous section Next section

JPEG (Joint Photographic Experts Group) compression is one of the three file formats used for graphical images on the World Wide Web (the others being GIF (Graphical Interchange Format) and PNG (Portable Network Graphics)). JPEG files have the advantage of retaining 24-bit true color files during compression, while GIF files are limited to 8-bit color (256 colors). The PNG file format shows promise as a lossless compression method for the Web, but has not yet gained acceptance. The issue of standard Web formats is an important one, because an increasing number of relevant software solutions rely on browser technology for screen display (Figs 6, 7).

Color and black and white compression  Previous section Next section

While color images using JPEG can typically achieve 10 : 1 to 20 : 1 compression ratios without visible loss and can compress to 30 : 1 to 50 : 1 with small to moderate defects, black and white (grayscale) images do not compress so well by such large factors. Because the human eye is much more sensitive to brightness variations than to hue variations, JPEG can compress hue (color) data more heavily than brightness (grayscale) data. A grayscale JPEG file is generally only about 10–25% smaller than a full-color JPEG file of similar visual quality. But the uncompressed grayscale data is only 8 bits/pixel, or 1/3 the size of the color data, so the calculated compression ratio is much lower. The threshold of visible loss is often around 5 : 1 compression for grayscale images, substantially different from color images [1].

JPEG 2000 and beyond  Previous section Next section

The importance of image handling and compression for Internet applications creates a huge momentum for development. The JPEG working group has developed a new standard which is only just becoming available (accepted as an ISO standard December 2000). This standard is called JPEG 2000, with the file extension .jp2. This standard offers a host of advantages over the existing JPEG standard, the most significant being lack of pixelation at high compression rates, and significantly more effective compression (Fig. 8).

Although the file sizes of individual endoscopic images are not a major issue at this point, we should keep in mind that when the display and transfer of large numbers of images and videos becomes a significant part of our daily workflow, even minute delays for every picture will have an impact. Further developments for more efficient file compression will be of major significance for medical imaging. PACS development currently suffers from the heavy cost of high-end workstations and networks to handle huge image data sets.

Top of page DICOM standard  Previous section Next section

DICOM (Digital Imaging and Communications in Medicine) is a standard for imaging that contains very specific information about the images, as well as the images themselves. DICOM relies on explicit and detailed models of how the features (patients, images, reports, etc.) of an imaging operation are described, how they are related, and what should be done with them. This model is used to create Information Object Definitions (IODs) for all of the imaging modalities covered by DICOM.

Information Objects  Previous section Next section

An Information Object is a combination of Information Entities and each Entity consists of specific modules. A Service Class defines the service that can take place on an Information Object, e.g. print, store, retrieve. In DICOM a Service is combined with an Information Object to form a Service/Object Pair, or SOP. For example, storing a CT scan or printing an ultrasound is an SOP. A device that conforms to the DICOM standard can perform this function. Thus, in a DICOM-conforming network the devices must be capable of executing one or more of the operations the SOP definition prescribes. Each imaging modality has an IOD. The result is that different imaging modalities such as CT, MRI, digital angiography, ultrasound, endoscopy, pathology; imaging workstations; picture archiving systems; and printing devices can be networked and execute a high level of cooperation. In addition, these imaging networks can be connected to other networks found in a hospital or facility.

The modules that comprise an Information Entity (IE) are precisely defined and may be common to multiple entities. The Patient Entity is common to all IODs. However, the Image Entity must be capable of supporting different imaging modalities. An IOD that supports endoscopy will of necessity include modules unique to endoscopy and be distinct from a CT IOD. The Patient IE defines the characteristics of a Patient who is the imaging subject of one or more procedures that produce images. The Patient IE is modality independent, i.e. it is common to all imaging modalities. The Patient IE consists of only one module, which is illustrated in Fig. 9. Each module is a table consisting of four attribute elements:

  • Name
  • Tag
  • Type
  • Description.

The attribute name and description define the attribute precisely.

The attribute tag uniquely identifies that attribute among all of the many other attributes present. The tag (0010,0010) always identifies the fact that this is the patient name. The attribute type specifies whether this attribute is mandatory or optional. For example, it is not necessary for an image to be transmitted with the patient's name. In fact, DICOM requires only a few mandatory attributes that give the study a unique identifier, define the modality, e.g. CT, MRI, ultrasound, and provide information about the image, e.g. pixel data, number of rows and columns. DICOM also provides a dictionary that specifies the form in which the value of each attribute must be presented.

Patient name attributes  Previous section Next section

The patient name attribute (0010,0010) uses Person Name (PN) as its value representation. PN contains five components in the following order: family name, given name, middle name, name prefix, and name suffix. Thus, any system that complies with DICOM knows that (0010,0010) is a person name and that the format of the information transmitted is defined by the DICOM standard.

DICOM conformance  Previous section Next section

It is not sufficient simply to define a standard. It is also necessary to develop a mechanism to enable vendors and purchasers to understand whether a particular system conforms to the standard. DICOM defines a conformance statement that must be associated with a specific implementation of the DICOM standard. It specifies the Service Classes, Information Objects, Communication Protocols, and Media Storage supported by the implementation.

DICOM in endoscopy  Previous section Next section

The American Society for Gastroeintestinal Endoscopy (ASGE), in collaboration with other medical and surgical societies such as the European Society for Gastrointestinal Endoscopy (ESGE), American College of Radiology, the College of American Pathologists, the American Academy of Ophthalmology, and the American Dental Association, has defined a new Supplement to the DICOM standard [2]. This specifies a DICOM Image Information Object Definition (IOD) for Visible Light (VL) images. This standard enables specialists to exchange color images between different imaging systems using direct network connections, telecommunications, and portable media such as CD-ROM and magneto-optical disk.

The DICOM standard for endoscopy is part of a larger standard for color images in medicine which has been provisionally approved by the DICOM Committee. The current version will go through a process of public comment and testing. This period ensures that any interested party may review the document and suggest changes to a committee that is responsible for creating the final version. This process is time-consuming but it ensures that the standard is comprehensive and meets the needs of a broad group of users.

Expanding the scope of DICOM  Previous section Next section

The endoscopy community, through the ASGE and ESGE, has also suggested that the DICOM standard be expanded to incorporate other information associated with the imaging study. These expanded standards would include image labels and overlays, sound, and waveform. The goal of a true multimedia report will be achieved only when these standards have been thoroughly tested and implemented as part of the daily clinical activities of endoscopists throughout the world. The cooperation of endoscopists, professional societies, and industry is absolutely necessary for improved endoscopic information systems and will result in improved patient care.

Top of page How much compression is clinically acceptable?  Previous section Next section

Because of the specific nature of endoscopic images, the amount of compression that can be employed without compromising important information must be determined by the endoscopist. The acceptable compression rate when we are looking at a polyp would likely differ substantially from that for a case of mild gastritis. These issues have major impact on the utility of digital images. We have to be involved in deciding what imaging is required to be useful for clinical purposes.

Studies of compression acceptability  Previous section Next section

The topic was excellently reviewed by Kim [1], but very few relevant studies have been published.

Vakil and Bourgeois  Previous section Next section

Vakil and Bourgeois [3] conducted a trial to determine the amount of color information required for a diagnosis from an endoscopy image. The least amount of color information in an endoscopic image that carries sufficient diagnostic information was unknown. Ten lesions of upper gastrointestinal lesions were presented in an 8-bit format, 16-bit format, and a 24-bit format blindly side-by-side on a Macintosh II system with a 19 inch monitor that could display 24-bit color. Eleven observers (6 nurses and 5 endoscopists) were asked to rank each format for each lesion (i.e. which of the two was the higher quality one). There were a total of 330 observations, and for each format and total the results were similar: the observers could not tell a difference on 41% of the images; identified the best image correctly in 22%; and identified incorrectly in 37% of the images. All the lesions were correctly diagnosed from both images. From this study for endoscopic images, the color resolution does not appear to affect an endoscopist's ability to make a diagnosis.

Kim (personal communication)  Previous section Next section

Kim presented a set of six images to 10 expert gastroenterologists using software that allowed them to determine their personal cut-off level of acceptable compression for each of the images. Different types of lesions were studied. The acceptable compression ratio varied markedly, as expected, but in general, a compression ratio of between 1:40 and 1:80 was deemed acceptable (Fig. 10).

This type of study gives us important information concerning the order of magnitude of acceptable compression. However, the clinical context is of interest as well—the arterial bleed in the above study was probably identified easily as such at a high rate of compression, but a therapeutic endoscopist would likely need additional details as to the exact location, structures next to the vessel, etc.

Developments in compression  Previous section Next section

Compression schemes are evolving quickly and, at the same time, the requirements for minute files are becoming less crucial. Storage space is rapidly becoming cheaper, and networks faster. The 28.8 kbyte modem is no longer a reasonable yardstick for download time. The virtue of compressing our images remains, but there is no reason to compromise the quality of our images to achieve the tiny file sizes that yesterday's technology urged us to aim at. The endoscope manufacturers have been struggling hard to offer us high-resolution endoscopes, structure enhancement, and magnification, and it would be counterproductive to take that advantage away for a few kilobytes of file size reduction.

As for clinical utility, we will need to establish a general standard for compression and formats that will work across diagnoses. This will have to aim at a quality sufficient for our most difficult diagnoses, e.g. subtle, diffuse lesions like mild gastritis or tiny erosions, or delineation of the vascular pattern in colitis.

Top of page Still pictures or live video?  Previous section Next section

Digital video is increasingly becoming an option for endoscopic documentation. Many capture cards have the capability of storing video as well as still images, and in certain situations, video may definitely offer an advantage. This is particularly true for teaching purposes, but even clinical documentation can be enhanced by live footage in certain situations. Obvious examples are documentation of distensibility or propagating waves of the stomach, spasticity of the colon, or imaging in difficult areas (the cardia).

However, video clips come at a cost in terms of processing, storing, and even presentation. While still images can be vividly reproduced in our printed endoscopy report together with our recommendations, a video clip is forever tied to the computer or network. Down the road—when electronic medical records become mainstream and wide area networks (WANs) a tool for medical purposes—these concerns may vanish, but for now a paper-based report is a prerequisite in most endoscopy labs.

Then there is the issue of storage and transfer. Studio quality video shows at 25 or 30 frames per second (fps). Although we can get reasonable quality video at 10–15 fps, this still produces enormous files quickly, and we need to determine if and when the value of digital video justifies the cost.

Video storage developments  Previous section Next section

Again, fortunately, things are moving rapidly in the right direction. Compression algorithms allow significant compression of digital video file size with acceptable results. Best known to date are probably the Quick Time and MPEG-1 formats, but this is a field of continuous development, MPEG-4 being the one of the most promising option at the moment.

Most of the compression algorithms utilize similar techniques to those discussed above for still images. For example: if a segment of the movie image is unchanged for a period of time (the sky, or the black portion to the left of the endoscopic picture), all the information that needs to be stored is the boundaries of the area, the color value, and the start and stop timecodes.

With this type of compression, a video, for example, of a news reader can be reduced to a still picture with a small moving segment representing the mouth. This technique, in addition to a multitude of others, allows for increasing compression of video clips, offering efficient storage, as well as network-based distribution, with no or minimal depreciation of the diagnostic value.

Top of page What images should be recorded in practice?  Previous section Next section

In parallel to the technological developments in digital imaging and video, there are important decisions that need to be made by the endoscopic community. A crucial one is: What pictures are needed?

Lesion documentation  Previous section Next section

If we want to report a polyp in the sigmoid colon, a single picture might be sufficient if it is a good one—showing the size and shape, stalk, amount of luminal obstruction, surface texture, etc. But what about a distal rectal lesion? Maybe an extra picture of the relation to the anal verge would be important, not least if a surgeon is to remove it. A retroflexed view, as well as a standard forward-viewing depiction, would be reasonable for that. For diffuse pathology, typically more than one image might be preferable, and maybe high resolution becomes an issue for minimal changes.

Recording negative examinations  Previous section Next section

More complex still are the issues raised by 'negative' examinations. Which images are needed to rule out a lesion, e.g. to document a normal colonoscopy? We obviously cannot picture every single fold, let alone behind them, but there may still be reasons to document normality, e.g. to show what kind of view, cleansing, and distension was available to the endoscopist and to confirm that the examination was complete (e.g. by digital images of the ileocecal value).

The virtue of this becomes even more obvious in the context of referrals and second-opinion cases. When we are asked to evaluate a patient who has had a procedure at another hospital, too often we distrust the results because the images that we receive are inadequate for independent assessment, or even lacking. Standardization of documentation will reduce the need to repeat many procedures. In addition, the availability of relevant images from a prior examination will make follow-up studies much more meaningful (e.g. in the assessment of the activity of colitis or esophagitis).

Structured image documentation  Previous section Next section

The ESGE has made an attempt to establish guidelines for image recording, proposing fixed sets of images for various procedures [4]. Figure 11 illustrates the standard set of images for upper endoscopy, and a similar set has been prepared for colonoscopy. The requirements are similar for ERCP and EUS, but may be slightly more complex to describe. This is obviously a process that will continue, but the importance of initiating this work in parallel with the implementation of digital documentation systems in the endoscopy lab cannot be over-emphasized.

Costs of image documentation  Previous section Next section

Previously, the cost of color reproduction of a large number of pictures for every procedure was a concern. However, with electronic storage and display, this concern is diminishing, and picture documentation should be the rule now rather than the exception. Having these images in a readily searchable management system is essential.

Top of page Image enhancement  Previous section Next section

The impact of video endoscopes has been substantial, but the images produced are still just natural light images showing the gastrointestinal mucosa in a life-like manner. Novel technologies are now emerging, offering modification of the original images that may increase the diagnostic output of the endoscopic procedure. These technologies do not relate to the digital imaging as such, but they all rely on such imaging as the core technology for endoscopy.

Color manipulation  Previous section Next section

Color manipulation methods deal primarily with the color characteristics of the pixels representing the image. This is a simple way of enhancing the contrast features of the image, but sometimes at the cost of resolution. These methods are so far available only for manipulation of still images, and a live version of the technology would be needed to make this applicable clinically (Fig. 12).

Narrow band imaging and spectroscopy  Previous section Next section

Narrow band imaging and spectroscopy are just two examples of a host of other technologies that will enhance our diagnostic yield. In these technologies, parallel 'imaging' is utilized to extract information about the imaged tissue, and the regular digital images are used primarily to guide the process of advanced tissue characterization.

Top of page Terminology standardization  Previous section Next section

Endoscopic findings are conveyed with words, although the findings themselves are images. Thus, the coupling between what we see and how it is described becomes crucial, and standardization of our endoscopic language is an integral part of this concept.

Endoscopic teaching includes descriptions of what is found, but the definitions of terms used have been weak or non-existent. If the conclusion of the endoscopy report is the only item of value then the specifics of the findings are of less importance. However, if the findings themselves are important, then the descriptive language becomes interesting too. For research purposes, in particular collaborative research, the utility of this is obvious, but even for general clinical purposes the objective description of lesions may be of interest, e.g. in the situation of a second-opinion referral of a case where the referral center needs to decide whether a repeat endoscopy is needed. Likewise, follow-up endoscopy in a patient with a known lesion will profit from an unequivocal initial description of what was seen, at least when no image documentation is available.

OMED standardized terminology  Previous section Next section

The world organization of digestive endoscopy (OMED) initiated the efforts to standardize our language based on the pioneer work of Professor Zdenek Maratka who developed the first 'Terminology, definitions and diagnostic criteria in digestive endoscopy.' This terminology is a codified list of terms with explicit definitions that allow endoscopic findings to be fitted into a hierarchical nomenclature and assigned a code, thus enabling international collaboration. This terminology has since been supplemented with images to exemplify the various terms. Despite deficiencies, this remains the de facto standard for describing the various findings of digestive endoscopy.

Minimal standard terminology—MST  Previous section Next section

The OMED terminology, while defining the framework for the terminology efforts within digestive endoscopy, proved too complex for practical utilization in everyday endoscopy. A simplification was needed, and the European Society for Digestive Endoscopy (ESGE) teamed up with its US counterpart (ASGE) to develop minimal standard terminology (MST) for endoscopy [5]. This terminology is completely based on the OMED terminology, but the term lists are limited, aimed at covering 95% of the terms needed for typical endoscopic practice, and omitting the definitions, which are available when needed in the OMED terminology book. The MST is meant to be a standardizing prerequisite for software companies developing reporting software for digestive endoscopy, ensuring that a joint language is used in the various available software solutions. The MST work has been endorsed and supported by all the major vendors of such systems (Figs 13, 14).

The initial version of the MST was thoroughly tested within the GASTER project [6] and this experience led to a number of adjustments as to the selection and definition of terms. Version 2.0 of the MST has been released, and is presently undergoing a similar clinical evaluation.

In addition, term definitions are now being included, and an image library is being developed through a joint European effort, to help illustrate the various terms of the MST by high-quality sample pictures.

Problems with MST  Previous section Next section

The principles of the MST work have been endorsed almost universally, and the utility of a joint standardized language of endoscopy is readily acknowledged. Still, the knowledge, dissemination, and implementation of the MST is at the present time insufficient, even disappointing. Why is this?

One issue is that the MST term lists are still not perfect. They are designed to be 'minimal lists', and this means you may not find the precise term that you need. This is partly a software issue, because the lists were never meant to be all-inclusive, and individual additions will be needed in most centers. Still, incomplete choice lists are difficult to accept.

More fundamental, though, is the whole concept of structuring the language of the endoscopist. We are used to formulating our findings and recommendations in natural language, and any superimposed structure may take extra time, be considered cumbersome and limiting, and even as something that yields less informative reports.

The solution to this has not yet been found, and the MST is at present primarily only an excellent initiative. The utility of standardized terms is indisputable, but the challenge is to embed them in software that allows their use to be sufficiently transparent. Also, it is probably unnecessary that the endoscopy report be produced exclusively by 'point-and-click'. Certain segments should probably remain free text blocks with natural language.

Top of page Outstanding issues and future trends  Previous section Next section

Endoscopic recording has come a long way since Rudolph Schindler employed an artist to paint watercolor pictures of the images he saw with his semiflexible gastroscope. We are now on the threshold of easy and comprehensive digital (still and video) documentation of all of our procedures. This should provide enormous enhancement of the clinical value of our examinations, and of our ability to both teach and communicate with colleagues. Tele-endoscopy (distance diagnosis) has been tested, and could have substantial clinical and educational benefits.

Image manipulation and automated analysis eventually will add another dimension to our practice. Image data, when collected, stored, annotated, and validated, will provide a memory bank far greater than the human brain can handle, or perhaps even contemplate. Our endoscopes will soon start to recognize pathology ('optical biopsy'), and will provide instant differential diagnoses, along with access to examples of similar conditions (and a comprehensive knowledge base about them).

It will be some time before the brain of the endoscopic processor replaces the brain of the endoscopist, but the potential for development is enormous. Neural networks and artificial intelligence will facilitate and optimize our effectiveness. Initially these developments will have greatest impact in diagnostic endoscopy. Already the video capsule maximizes the digital information whilst minimizing endoscopic expertise. Eventually these concepts will be applied to therapeutic procedures; endoscopes may recognize lesions (and even their depth), and apply therapy automatically. The future is as exciting as it is unpredictable.

Top of page Acknowledgments  Previous section Next section

I would like to thank Doctors Louis Korman and Chris Kim for valuable input to specific segments of this manuscript, and for their efforts in the field in general.

Top of page References  Previous section

1 Kim, CY. Compression of color medical images in gastrointestinal endoscopy: a review. Medinfo 1998; 9 Part 2: 1046–50.

2 Korman, LY & Bidgood, WD Jr Representation of the Gastrointestinal Endoscopy Minimal Standard Terminology in the SNOMED DICOM microglossary. Proceedings of the AMIA Annu Fall Symp, 1997: 434–8.

3 Vakil, N & Bourgeois, K. A prospective, controlled trial of eight-bit, 16-bit, and 24-bit digital color images in electronic endoscopy. Endoscopy 1995; 27 (8): 589–92. PubMed

4 Rey, JF & Lambert, R. ESGE recommendations for quality control in gastrointestinal endoscopy: guidelines for image documentation in upper and lower GI endoscopy. Endoscopy 2001; 33 (10): 901–3. PubMed

5 Delvaux, M, Korman, LY, Armengol-Miro, JR, Crespi, M, Cass, O & Hagenmuller, F et al. The minimal standard terminology for digestive endoscopy: introduction to structured reporting. Int J Med Inf 1998; 48 (1–3): 217–25. PubMed

6 Delvaux, M, Crespi, M, Armengol-Miro, JR, Hagenmuller, F, Teuffel, W & Spencer, KB et al. Minimal standard terminology for digestive endoscopy: results of prospective testing and validation in the GASTER project. Endoscopy 2000; 32 (4): 345–55. PubMed

Copyright © Blackwell Publishing, 2004

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  A (very) brief history of endoscopy
  Professionalism and quality
Unit design
  Space planning
   Daily room volumes
   Procedure room size
   Preparation and recovery ratios
   Separate entrances
   Common space problems
  Physical infrastructure
  Intake and recovery areas
   Intake areas
   Managing clothes and valuables
   Recovery facilities
  Procedure room reprocessing and storage
   Standard procedure rooms
   Scope reprocessing and storage
   Patient flow issues
   Complex procedure rooms
   Storage of supplies and medications
   Travel carts for emergencies
Unit management
  Major areas of responsibility
  Staffing design
   Staffing emergencies
  Procedure schedules
   Relative time requirements
   Barriers to efficiency
   How many endoscopes?
   Endoscope repair costs
  Endoscope reprocessing
  Coding and billing
Outstanding issues and future trends
  Capsule endoscopy
  Colon screening technologies
  Endoscopy by non-specialists
  Growth of advanced endoscopy
  Moderate sedation
  Deep sedation/analgesia
Advances in monitoring during sedation
  Standard pulse oximetry
  CO2 monitoring
   Transcutaneous CO2 monitoring
  BIS monitoring
Topical anesthetics: are they worth the effort?
Titration vs. bolus administration of sedation and analgesia
  Problems with propofol
  Specific training for use of propofol
  Contraindications of propofol
  Clinical trials of propofol
   Propofol or midazolam?
   Upper endoscopy
   Upper endoscopy and colonoscopy
   Propofol with or without midazolam
   Patient-controlled administration of propofol
   Nurse-administered propofol
   Gastroenterologist-administered propofol
Outstanding issues and future trends
Gastrointestinal endoscopes
  Endoscope design
   Control section
   Insertion tube
   Connector section
   Light source/processors
  Endoscope equipment compatibility
  Endoscope categories
   Esophagogastroduodenoscope (gastroscope)
   Wireless capsule endoscopy
Gastrointestinal endoscopic accessories
  Tissue sampling
   Biopsy forceps
   Single-bite cold-biopsy forceps
   Biopsy cup jaws
   Multi-bite forceps
   Other specialty forceps
   Monopolar hot biopsy forceps
   Reusable vs. disposable biopsy
   Cytology brushes
   Needle aspiration
  Polypectomy snares
  Retrieval devices
  Injection devices
   Injection needles
   Spray catheters
   ERCP catheters
  Hemostatic and ablation devices
   Contact and non-contact thermal devices
   Heater probe
   Laser fibers
   Argon plasma beam coagulator
   Mechanical hemostatic devices
   Band ligation
   Metallic clip application via flexible endoscopes
   Marking with clips
   Detachable loops
  Transparent cap
  Dilation devices
   Push-type fixed-diameter dilators
   Hurst and Maloney dilators
   Savary-type dilators
   American Dilation System dilators
   TTS fixed diameter dilators
   Threaded-tip stent retrievers
   Radial expanding balloon dilators
   TTS dilators
  Achalasia balloon dilators
Outstanding issues and future trends
  Fiberoptic imaging
   Teaching attachments and photography
   Image capture
   Standardized image terminology
   Structured reporting
   The opportunities and challenges of the digital revolution
Digital imaging
  Imaging the gastrointestinal tract using a videoendoscope requires several steps
  Color models
Digitization of color
Color depth
Pixel density
File size
  What detail is needed?
  File compression
  Compression techniques
   Lossless compression
   Lossy compression
  Image file formats
  Color and black and white compression
  JPEG 2000 and beyond
DICOM standard
  Information Objects
   Patient name attributes
  DICOM conformance
  DICOM in endoscopy
  Expanding the scope of DICOM
How much compression is clinically acceptable?
  Studies of compression acceptability
   Vakil and Bourgeois
   Kim (personal communication)
  Developments in compression
Still pictures or live video?
  Video storage developments
What images should be recorded in practice?
  Lesion documentation
  Recording negative examinations
  Structured image documentation
  Costs of image documentation
Image enhancement
  Color manipulation
  Narrow band imaging and spectroscopy
Terminology standardization
  OMED standardized terminology
  Minimal standard terminology—MST
   Problems with MST
Outstanding issues and future trends
Editor's note
Relevant thermal effects in biological tissues
  Thermal devitalization
  Thermal coagulation
  Thermal desiccation
  Thermal carbonization
  Thermal vaporization
Generation of temperature in thermal tissue
  Heater probe
  High-frequency surgery
   General principles of high-frequency electric devices
   Electric arcs
Principles of high-frequency surgical coagulation
  Monopolar coagulation instruments
  Electro-hydro-thermo probes
  Bipolar coagulation instruments
Principles of high-frequency surgical cutting with particular regard to polypectomy
Technical aspects of polypectomy
  Polypectomy snares
  The polypectomy snare handle
  Polypectomy snare catheters
Safety aspects of high-frequency surgery
Argon plasma coagulation
  The principle of argon plasma coagulation
  Equipment for argon plasma coagulation
  Safety aspects of argon plasma coagulation
  Principle of Nd:YAG laser
  Specific characteristics of Nd:YAG lasers in flexible endoscopy
Safety aspects of Nd:YAG laser in flexible endoscopy
Sterilization and disinfection
  High-level disinfection
  What level of disinfection is required?
   Critical items
   Semi-critical items
  The practical problem
  The organisms
  The critical points in reprocessing
Risks of infections associated with endoscopic procedures
  Mechanisms of infection
  Clinical infections
   Infecting organisms
   Vegetative bacteria
   Clostridium difficile
   Mycobacterium tuberculosis
   Atypical mycobacteria
   Serratia marcescens
   Helicobacter pylori
   Human immunodeficiency virus (HIV)
   Hepatitis B
   Hepatitis C (HCV)
   What to do in practice about CJD?
   New variant CJD (vCJD)
   Other infections
  The endoscopic procedures
   Upper gastrointestinal endoscopy
   Lower gastrointestinal endoscopy
   Endoscopic retrograde cholangiopancreatography
   Percutaneous endoscopic gastrostomy
   Endoscopic ultrasound
  Host factors
   Immune competence
   The degree of tissue damage
   Intrinsic sources of infection
   Damaged valves and implants
Antibiotic prophylaxis for endoscopic procedures
  Principles of prevention of bacterial endocarditis
  High risk cardiovascular conditions [43]
  Moderate risk cardiovascular conditions [43]
  Recommendations for antibiotic prophylaxis
   Who should receive antibiotics?
   Clinical problems where opinions diverge
   What antibiotic regimen?
Antibiotic prophylaxis for ERCP
  Prophylactic antibiotic regimens for ERCP
Principles of effective decontamination protocols
  Cleaning is essential
  Effectiveness of recommended protocols
  Endoscope structure
   Common features
   External features
   Common internal features
   Special internal features
   Cleaning equipment
   Cleaning fluids
   Soaking time
   General maintenance
   Work areas
Reprocessing regimens
  Disinfect before and after procedures
  Manual cleaning
  Manual disinfection
  At the end of the list
  Endoscopic accessory equipment
   Cleaning accessories
   Special accessory items
   Sclerotherapy needles
   Water bottles and connectors
Problem areas in endoscope reprocessing
  Rinsing water
   Poor quality water
   Infections from rinsing water
   Bacteria free water
   Water testing
   Recommendations for rinsing water
Variation in cleaning and disinfection regimens depending upon the supposed infective status of the patient
Compliance with cleaning and disinfection protocols
The investigation of possible endoscopy infection transmission incidents
  Common causes
  Golden rules for investigating potential infection incidents
  The investigation process
  Transmission of viral disease
Automatic flexible endoscope reprocessors (AFERs)
  Machine design and principles
   Water supply
   Alarm function
   Fume containment
   Disinfectant supply
   Reprocessing time
   AFERs cannot guarantee to sterilize endoscopes
   Plumbing pathway
   Rinse and dry cycle
   Regular bacteriological surveillance
Quality control in endoscope reprocessing
  Quality control measures
Microbiological surveillance in endoscopy
  Testing procedures
  Interpretation of cultures
  Microbiological surveillance of AFERs
Outstanding issues and future trends
The contract with the patient; informed consent
  Educational materials
What are 'risks' and 'complications'?
  Threshold for 'a complication'
  Timing of unplanned events
  Direct and indirect events
  Data set for unplanned events
General issues of causation and management
  Technical and cognitive performance
  Fitness for procedures
   ASA score
   Other risk indices
  Prompt recognition and management
   Act promptly
  Specific unplanned events
   Failure to diagnose
   Risk factors
   Risk factors
   Cardiopulmonary and sedation complications
   Allergic reactions
   IV site issues
   Miscellaneous and rare events
Preventing unplanned events
Outstanding issues and future trends
Gastroenterologist–pathologist communication
  Endoscopist communication responsibility
  Pathologist communication responsibility
  Question-orientated approach
  Common terminology
Endoscopic biopsy specimens
  Specimen handling and interpretation issues
   Number of biopsies per container
   Tissue processing
   Prep-induced artifact
   Endoscopy-induced artifacts
   Biopsy-induced artifacts
   Crush artifact
   Burn/cautery artifact
   Endoscopic mucosal resection
   Core biopsy
  Regular stains
Exfoliative and fine-needle cytology
  Specimen handling; staining and fixation
   Cytological diagnosis
  Fine-needle aspiration
Organ system overview
   Where and when to biopsy
   Gastroesophageal reflux disease
   Barrett's esophagus
   Infective esophagitis
   Herpes simplex virus
   Adenocarcinoma and squamous cell carcinoma
   Where and when to biopsy
   Inflammatory conditions; gastritis
   H.pylori gastritis
   Hypertrophic folds
   Mass lesions
  Small bowel
   Celiac sprue
   Infective enteropathies
   Whipple's disease
   Mycobacterium avium–intracellulare
   Giardia lamblia
   Mass lesions
   Defining 'normal'
   Inflammatory colitides
   Normal colonoscopy
   Abnormal colonoscopy
   Inflammatory bowel disease
   Pseudomembranous colitis
   Ischemic colitis
   Mass lesions
Special stains
  Histochemical stains
  Immunohistochemical stains
  In situ hybridization
  Flow cytometry
  Electron microscopy
  Molecular pathology
Outstanding issues and future trends
The endoscopy facility and personnel
  Endoscopy facility
   Endoscopy instruments
   Ancillary equipment
   The endoscopist
   Nursing and ancillary personnel
The pediatric patient and procedural preparation
  Patient preparation
   Psychological preparation
   Medical preparation
   Recommendations for fasting
   Bowel preparation
   Antibiotic prophylaxis
  Informed consent
Endoscopic procedures currently performed in pediatric patients
  Indications and limitations
  Patient sedation
  Endoscopic technique
   Therapeutic endoscopy
   Other endoscopic modalities
   Small bowel enteroscopy
   Wireless capsule endoscopy
   Endoscopic ultrasonography
   Endoscopic retrograde cholangiopancreatography (ERCP)
Selected gastrointestinal pathologies in pediatric patients
  Eosinophilic esophagitis
  Food allergic enteropathy and colitis
  Foreign body ingestion
  Helicobacter pylori gastritis
  Polyps in the pediatric patient
  Lymphonodular hyperplasia
Outstanding issues and future directions
General principles of endoscopy training
  Traditional standard means of instruction
   Is self-teaching still acceptable?
  What to teach and how to teach it
  Defining competency and how to access it
   Linking diagnosis and therapy
   How competent?
   Varying rates of learning
   Learning beyond the training period
Training and competency in specific endoscopic procedures
  Esophagogastroduodenoscopy (EGD)
   Published guidelines for training in EGD
   Defining competence for EGD
   Data on acquisition of competency in diagnostic EGD
   Competency and EGD outcome
  Therapeutic EGD techniques
   Standard upper GI endoscopy techniques
   Hemostasis techniques
   Bleeding team
   Retaining competence
   Other specialized therapeutic upper GI endoscopy techniques
  Flexible sigmoidoscopy
   Published guidelines for training in flexible sigmoidoscopy
   Published guidelines for training in colonoscopy
   Defining competence for colonoscopy
   Technical components
   Cognitive objectives
   Minimum training requirements to achieve competency for colonoscopy
   The Cass study
   Competency and colonoscopy outcome
   Acceptable outcomes
   Rate of skills acquisition for colonoscopy
   Cases per week
   Too many cases?
  Therapeutic colonoscopy (biopsy, polypectomy, hemostasis techniques, stricture dilation, stent deployment)
   Standard therapeutic techniques (integral to performance of diagnostic colonoscopy)
   Advanced therapeutic colonoscopy techniques
  Diagnostic and therapeutic ERCP
   Published guidelines for training in ERCP
   Non-technical training
   Defining competence for ERCP
   Technical success
   Varying case difficulty
   Minimum training requirements to achieve competency for ERCP
   Case numbers
   What is a case?
   Competency and ERCP outcome
   Improving after training
   Annual volume
   Competence affects complication rates
   Rate of acquisition of ERCP skills
   Therapeutic ERCP
   Rate of acquisition of therapeutic skills
  Diagnostic and therapeutic EUS
   Defining competency in EUS
   Learning curve for EUS
   Therapeutic EUS
   EUS training opportunities
Complementary methods for instructions in GI endoscopy
  Advances in didactic methods
   Group instruction
   Laboratory demonstrations
  Endoscopy simulators
   Static models
   Courses with static models
   Ex vivo artificial tissue models: the 'phantom' Tübingen models
   Ex vivo animal tissue simulators: EASIE and Erlangen models
   Live animals
   Computer simulation
   GI Mentor™
   Current status of simulators
   Costs of simulators
   EUS models and simulators
  Use of training resources: summary
Endoscopy training 2010—a glimpse into the future
Credentialing and granting of privileges
   ASGE guidelines
Renewal of privileges and privileging in new procedures
  New procedures
Privileging for non-gastroenterologists and non-physician providers
The future of credentialing and privileging
  The use of new technology for credentialing
The role of endoscopic societies in training and credentialing
  Society courses
  Hands-on courses
  Research in training
  Influencing credentialing
Outstanding issues and future trends
Achieving competence—the goal of training
What experience is necessary in training? The fallacy of numbers
Beyond numbers: tools to measure competence
What level of competence is good enough? How is it recognized?
Endoscopic performance beyond training
Issues in measuring endoscopic performance
The report card agenda
The quality of endoscopy units
Outstanding issues and future trends
Most endoscopists are not interested
Is the problem declining?
Newly recognized infections
Compliance with guidelines
What can be done to remedy this sorry state of affairs?
  Infection control staff
  Microbiological surveillance
   British practice
The role of industry
Manual cleaning is key

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