Table 1.Reproduction of colors by Kodak Ektachrome infraredfilm
Mucosal vessels, which were less distinctly or notat all visible in usual gastroscopic photographs,showed up in infrared photography. The left half ofFigure 1 shows two infrared pictures of an early gastriccancer type lIe. The upper photograph was takenbefore the injection of ICG and the lower one, after-wards. In the right half of Figure 1 a comparableconventional color photograph of the same lesion canbe seen. Some vessels at the lower pole of the cancer,which cannot be perceived in the conventional pho-tograph, are clearly distinguishable in the infraredphotographs.
In some cases it was possible to improve the depic-tion of mucosal vessels even more decisively by theintravenous application of ICG. In the right handphotograph of Figure 2 ICG makes some varicose veinscrossing a fold in the right half of the photographdistinguishable. These veins cannot be recognized inthe left-hand picture of Figure 2, which was madebefore ICG was injected.
with Kodak color-compensating filters. During the tests allfilters were placed between the flashbulb and the bulb coverglass of the gastrocamera. This made it possible to changefilters easily. However, the filters could only be used for ashort time because they were exposed to the heat of thebulb, and we could not use more than three filters at thesame time. As soon as the best filter combination had beendetermined, the Olympus Corporation fixed two filters infront of the photo-lens. As before, one other filter was placedbehind the bulb cover glass so that minor variations of thefiltering still could be made. We used only Kodak gelatinefilters.
The most promising filtering was the combination of oneKodak Wratten filter no. 8 and two color-compensatingCyan 2 filters with a density of 50 (8 + 2 x CG 50 Cyan 2).Using these filters we took intragastric infrared photographsof 20 patients with pathological gastroscopic findings. ICG(2 mg/kg of body weight) in 10 ml of solvent was injected asa bolus into the cubital veins of 12 of these patients. Im-mediately afterwards 10 ml of a 0.9% sodium chloride solu-tion was injected to guarantee a quickly rising high concen-tration of ICG in the central blood vessels. The appearanceof the contrast dye in the gastric mucosa was registered bya series of infrared photographs of a specific mucosal area,made at intervals of 1 to 2 seconds. Some infrared pictureswere taken before the application of ICG. The appearanceof ICG cannot be observed with the naked eye.
Intragastric infrared photography inconjunction with infrared absorptionangiography
J. Franke, MDG. Lux,MD
L. Demling, MD
Infrared photography is used for visualization ofskin vessels in dermatology because infrared radiationcan penetrate deeper into cellular tissue than visiblelight. In combination with indocyanine green (lCG)infrared absorption angiography of the chorioid isperformed in ophthalmology. The aim of the presentstudy was to visualize gastric mucosal vessels by in-tragastric infrared photography under normal condi-tions and after intravenous infusion of ICG.
MATERIALS AND METHODS
Kodak Ectachrome infrared film IE 135-20, which iscalled false color film because it reproduces objects in colorsdifferent from the visible colors, was employed. It is notsensitive to blue, green, and red, as usual color films are, butto green, red and infrared (Table 1). The Kodak infraredfilm is available in 20-exposure 35-mm rolls. For its appli-cation in the gastrocamera a special technique for cuttingand processing the film had to be developed.
To avoid possible impairment of infrared radiation byglass fiber transmission a gastrocamera type GTF-C (Olym-pus Corporation) was chosen for intragastric photography.
Two different kinds of filters are necessary to take pho-tographs with false color film. The first kind is a yellowfilter, which absorbs short-wave, blue light and transmitslight of longer wavelengths. For a yellow filter the KodakCompany recommends the Kodak Wratten filter no. 12 forregular applications of infrared photography. This filtertransmits wavelengths longer than 500 nm. Both the KodakCompany and Fritz1 claim that the use of filters havingslightly different transmission characteristics may be effi-cient in certain cases. The other kind of filters are color-compensating filters, which are able to increase the infor-mation content of infrared photography by shifting the colorbalance.1- 4 They accentuate or reduce certain parts of thespectrum. These filters are available in different densities.
The best filtering for intragastric infrared photographywas determined by two series of tests on an anesthetizeddog, which underwent a total of 41 gastroscopies. Three daysbefore the examinations a few biopsies of the dog's stomachwere made by means of a hot snare, thus making it possibleto photograph normal and injured mucosa. In planning thefilter tests we paid special attention to the fact that the colorbalance was shifted in every direction as far as it was possible
From the Department of Medicine, University of Erlangen-Num-berg, Erlangen, West Germany. Reprint requests: Dr. G. Lux, De-partment of Medicine, University of Erlangen-Numberg, Erlangen,West Germany.
VOLUME 31, NO.2, 1985
Original color of theobject
Reproduction of thecolor by the falsecolor film
Blue Green Red Infrared
Blue Green Red
Visible light is defined as that part of the electro-magnetic spectrum between 400 and 700 nm, whichthe human eye is able to perceive. The segment of theelectromagnetic spectrum bordering on the visible partat the long wavelength side is called infrared. Medicalinfrared photography employs films sensitive to a partof the invisible infrared light-the so-called actinicband of infrared radiation-between 700 and 900 nm.
Actinic infrared radiation is reflected and/or ab-sorbed by photographed objects in the same way asvisible colors, which also correspond to certain seg-ments of the electromagnetic spectrum. It is possiblefor objects having the same visible color to be distin-guished by means of their differing infrared reflectioncharacteristics. Medical infrared photography doesnot register heat radiation.
Infrared light is able to penetrate deeper than visiblelight into cellular tissue because its waves are longerthan those of visible light. The penetration qualitiesof actinic infrared radiation into skin can be of usefor medical photography up to a depth of 3 mm.5 Inthis way it is possible to get a picture of cutaneousareas covered by scab or to photograph vessels lyingdeeper under the skin.67 Furthermore, infrared helpsin the depiction of veins because deoxygenated venousblood absorbs infrared very well, whereas neighboringtissue and oxygenated blood reflect more of the in-frared.
In 1975 Polak8 was able to improve the depiction oflymph vessels on the surface of the liver by employinglaparascopic infrared photography. Zagoren andPecora9 found clearer and more distinct delineation ofupper gastrointestinal tract by infrared photography.In 1981 Mimura et al. lO published a study of gastro-scopic infrared photography without using a contrastsubstance.
For further improvement of vasovisualization ICGwas used as an intravascular contrast substance tocarry out an infrared absorption angiography of thechoroid.11. 12 After intravenous application a high per-centage of ICG is bound to serum proteins13 andtherefore does not leave the blood vessel to an appre-
VOLUME 31, NO.2, 1985
ciable degree. ICG absorbs infrared light extremelywell. The doses of ICG necessary for that kind ofangiography are practically nontoxic.14
The present research shows that intragastric in-frared photography, especially in conjunction withICG, is able to supply information about intragastriclesions that cannot be obtained by conventional en-doscopic methods. It cannot yet be judged whetherthis additional information will become important forclinical diagnosis. However, this new method can cer-tainly be helpful in expanding our knowledge of thepathology of gastric mucosal lesions, especially withregard to mucosal blood circulation.
REFERENCES1. Fritz NL. Filters: an aid in color-infrared photography. Photo-
gram Eng 1977;43:67.2. Worsfold RD. A qualitative study of Kodak aerochrome infrared
film, type 2443 and the effect produced by Kodak colour com-pensating filter at high altitudes. First Canadian Symposiumon Remote Sensing, 1972:417.
3. Worsfold RD. Colour