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DOI: 10.1055/s-2004-826102
A Novel Diagnostic Method for Evaluation of Vascular Lesions in the Digestive Tract Using Infrared Fluorescence Endoscopy
N. Muguruma, M. D.
Department of Digestive and Cardiovascular Medicine, The University of Tokushima Graduate
School
3-18-15 Kuramoto-cho · Tokushima City · Tokushima 770-8503 · Japan ·
Fax: + 81-88-633-9235
Email: muguruma@clin.med.tokushima-u.ac.jp
Publication History
Submitted 12 April 2004
Accepted after Revision 1 September 2004
Publication Date:
19 January 2005 (online)
Background and Study Aims: We have developed an infrared fluorescence endoscope to evaluate gastrointestinal
vascular lesions. Infrared endoscopy (IRE) after intravenous administration of indocyanine
green (ICG) is used at present to examine vascular lesions such as esophageal varices.
However, no previous study has compared the sensitivity of infrared fluorescence endoscopy
(IRFE) with that of IRE. In this study, we compared the usefulness of IRFE and IRE.
Patients and Methods: For IRFE we used an infrared endoscope equipped with excitation and barrier filters
and an intensified charge-coupled device camera. In preliminary experiments, the observable
tissue depth was assessed by wrapping increasing numbers of layers of commercially
available pork around a syringe containing a uniform concentration of ICG or by changing
the concentration of ICG in a syringe covered by a piece of pork of uniform thickness.
In the clinial part of the study, ICG was administered intravenously at different
concentrations to patients with esophageal varices and the resulting infrared fluorescent
images were evaluated.
Results: The preliminary experiments revealed that the depth of tissue that could be visualized
was significantly greater in IRFE than it was in IRE (11.2 mm in IRFE vs. approximately
3.2 mm in IRE). Clear infrared fluorescence was obtained by IRFE at lower concentrations
of ICG than the concentrations required to obtain clear images using IRE. In the clinical
part of the study, clear infrared fluorescence was observed in a region where esophageal
varices had been detected by conventional endoscopy when ICG was administered in doses
of 0.005 mg/kg to 0.01 mg/kg, which was lower than the doses used in IRE.
Conclusions: Compared with conventional IRE, IRFE facilitated the observation of deeper layers,
and esophageal varices were observed by IRFE following the intravenous administration
of a markedly reduced dose of ICG. IRFE, in combining the characteristics of reflected
infrared light and fluorescence, may be a useful novel procedure in the diagnosis
of vascular lesions in the gastrointestinal tract.
Introduction
We developed a technique of infrared fluorescence endoscopy (IRFE) as a novel method in the diagnosis of gastrointestinal cancer [1] [2] [3]. Currently, infrared endoscopy (IRE) is widely used in the clinic because it is useful for examining vascular lesions, including esophageal varices [4] [5], and for assessing the depth of gastric cancer invasion [6], but the results of IRE have been unsatisfactory due to its insufficient resolving power. In the field of ophthalmology, an infrared fluorescent fundus camera using indocyanine green (ICG) has been used in the clinical setting for a long time, and useful findings relating to a variety of vascular lesions have been obtained to date [7]. We would therefore expect that if vascular structures in the gastrointestinal tract are observed by IRFE after intravenous administration of ICG, findings that have not been observed by IRE would be observed by IRFE [8]. In this study, we compared the level of mucosal permeability of IRFE and conventional IRE experimentally using pork meat.
To date, several studies have reported the results of IRE after intravenous ICG administration [5] [6] [9] [10]. Regarding ICG toxicity, Speich et al. [11] reported that ICG exhibited side effects in a dose-dependent manner, and that side effects were more common when doses of 0.5 mg/kg or more were administered. We therefore compared the results of IRE and IRFE at different concentrations of ICG. In addition, we also performed IRFE after intravenous administration of ICG in 20 patients with esophageal varices in order to evaluate its clinical usefulness.
#Patients and Methods
IRFE was performed using an infrared endoscope (XGIF-Q40IR; Olympus Optical Co. Ltd., Tokyo, Japan) equipped with an excitation filter, a barrier filter, and an intensified charge-coupled device camera (Hamamatsu Photonics Co. Ltd., Hamamatsu, Japan). The Olympus CLV-U20D was used as the light source. IRE was performed using an Olympus GIF-Q200IR endoscope equipped with an Olympus CLV-U40D light source. The light source was also equipped with an excitation filter and a conventional light filter that allowed observation by either conventional endoscopy or by IRFE following a switch-over of filters. Band pass filters were used as excitation and barrier filters, based on the characteristics of ICG’s absorption and fluorescence spectrum: the excitation filter used in this study allowed the transmission of light at wavelengths between 710 nm and 790 nm; and the barrier filter allowed the transmission of light at wavelengths between 810 nm and 920 nm.
#Preliminary Experimental Study
Evaluation of tissue permeability. An increasing number of layers of commercially available pork (each slice approximately 1.6 mm thick) were wrapped over a 7-mm diameter syringe containing a specified concentration of ICG (0.5 mg/ml), and the depth through which the syringe was observable by IRFE and IRE was compared.
Evaluation using different concentrations of ICG. IRFE and IRE were compared with respect to their depth of observation using different concentrations of ICG in the syringe (2.0 mg/ml, 1.0 mg/ml, 0.5 mg/ml, 0.1 mg/ml, 0.05 mg/ml, 0.01 mg/ml, and 0.001 mg/ml) while keeping the thickness of pork covering the syringe constant.
#Clinical Study
IRFE was performed in 19 patients with esophageal and one patient with esophagogastric varices, changing the concentration of ICG administered intravenously (2.0 mg/kg, 0.1 mg/kg, 0.01 mg/kg, 0.005 mg/kg, or 0.001 mg/kg) in order to compare the quality of infrared fluorescent images obtained. Written informed consent was obtained from all patients before their participation in this study, which was approved by the Ethics Committee of the Tokushima University Hospital. The study population consisted of 19 patients with class B or class C liver cirrhosis, in whom esophageal varices had been detected by upper gastrointestinal endoscopy during the course of their disease between June 1999 and July 2003 in our department, and one patient with esophageal varices caused by primary biliary cirrhosis. The mean age of these patients (12 men, eight women) was 65 years. Two patients also had hepatocellular carcinoma. Before this study started, the esophageal varices had been treated by endoscopic injection sclerotherapy and endoscopic variceal ligation in 18 patients; in one patient gastric varices had been treated by balloon-occluded retrograde transvenous obliteration; and one patient had not been treated (Table [1]).
| Patient no. | Age, sex | Underlying disease | Previous treatment | ICG dose, mg/kg |
| 1 | 51 (M) | LC (HBV+, HCV+) | EVL, EIS | 2.0 |
| 2 | 58 (M) | LC (HCV+) | EVL, EIS | 2.0 |
| 3 | 61 (F) | LC (HCV+), AP shunt | EVL, EIS | 0.1 |
| 4 | 71 (F) | LC (HCV+) | EVL, EIS | 0.1 |
| 5 | 72 (M) | LC (HCV+) | EVL, EIS | 0.1 |
| 6 | 74 (F) | LC (HCV+) | EVL, EIS | 0.01 |
| 7 | 60 (F) | LC (HCV+) | EVL, EIS | 0.01 |
| 8 | 51 (F) | LC (HCV+), HCC | B-RTO | 0.01 |
| 9 | 51 (M) | LC (HBV+, HCV+) | EVL, EIS | 0.01 |
| 10 | 71 (F) | LC (HCV+) | EVL, EIS | 0.01 |
| 11 | 70 (M) | LC (HCV+) | EVL, EIS | 0.01 |
| 12 | 69 (M) | LC (HCV+) | None | 0.01 |
| 13 | 69 (M) | LC (HCV+) | EVL, EIS | 0.01 |
| 14 | 71 (M) | LC (HCV+) | EVL, EIS | 0.005 |
| 15 | 68 (M) | LC (HCV+), HCC | EVL, EIS | 0.005 |
| 16 | 68 (F) | LC (HCV+) | EVL, EIS | 0.005 |
| 17 | 73 (M) | LC (HCV+) | EVL, EIS | 0.005 |
| 18 | 58 (F) | PBC | EVL, EIS | 0.001 |
| 19 | 66 (M) | LC (HCV+) | EVL, EIS | 0.001 |
| 20 | 69 (M) | LC (HCV+) | EVL, EIS | 0.001 |
| LC, liver cirrhosis; HBV, hepatitis B virus; HCV, hepatitis C virus; EVL, endoscopic variceal ligation; EIS, endoscopic injection sclerotherapy; AP arterioportal; HCC hepatocellular carcinoma; B-RTO, balloon-occluded transvenous obliteration; PBC, primary biliary cirrhosis. | ||||
The intensity of macroscopically observed fluorescence was classified as - (negative), + (mild), ++ (moderate), +++ (strong), or ++++ (very strong).
#Results
#Preliminary Experimental Study
Evaluation of tissue permeability. The tissue depth observable by IRFE (approximately 11.2 mm) was significantly greater than that observable by IRE (approximately 3.2 mm) (Table [2]). Figure [1 a] shows an infrared image and Figure [1 b] an infrared fluorescent image, obtained after wrapping two slices of pork (total thickness approximately 3.2 mm) over a syringe containing 0.5 mg/ml of ICG. The infrared image showed only weak contrast of the syringe, compared with the infrared fluorescent image, in which the syringe was identifiable by clear contrast.
| No. of slices | IRE image intensity | IRFE image intensity |
| 0 | ++ | +++ |
| 1 | ++ | ++ |
| 2 | + | ++ |
| 3 | - | + |
| 4 | - | + |
| 5 | - | + |
| 6 | - | + |
| 7 | - | + |
| 8 | - | - |
| 9 | - | - |
| 10 | - | - |
| 11 | - | - |
| 12 | - | - |
Figure 1 Images obtained by infrared endoscopy (IRE) and by infrared fluorescent endoscopy (IRFE) of a syringe containing 0.5 mg/ml indocyanine green (ICG), through two slices of pork (total thickness approximately 3.2 mm). The infrared image (a) showed only weak contrast of the syringe compared with the infrared fluorescent image (b), which facilitated identification of the syringe with clear contrast.
Evaluation using different concentrations of ICG. Clear infrared fluorescenct images were obtained by IRFE at the lower concentrations of ICG. In contrast, clear images were observed by IRE only at the higher concentrations of ICG (Table [3]). Figure [2 a] shows an infrared image and Figure [2 b] an infrared fluorescent image, obtained after wrapping two slices of pork (total thickness approximately 3.2 mm) over a syringe containing 0.5 mg/ml of ICG. Figure [2 c] and [2 d] show an infrared image and an infrared fluorescent image respectively, obtained after wrapping two slices of pork over a syringe containing 0.01 mg/ml of ICG. Looking at the infrared images, it was easier to identify the syringe containing 0.5 mg/ml of ICG (Figure [2 a]) than it was to identify the syringe containing 0.01 mg/ml of ICG (Figure [2 c]). However, when infrared fluorescent images were compared, the syringe containing 0.01 mg/ml of ICG (Figure [2 d]) was more clearly identified by IRFE than the syringe containing 0.5 mg/ml of ICG (Figure [2 b]). When the concentration of ICG in the syringe was 0.001 mg/ml, no clear image was obtained by IRE and only moderate fluorescence by IRFE.
| Concentration of ICG, mg/ml | IRE image intensity | IRFE image intensity |
| 2.0 | +++ | ++ |
| 1.0 | +++ | +++ |
| 0.5 | +++ | ++++ |
| 0.1 | +++ | ++++ |
| 0.05 | ++ | ++++ |
| 0.01 | + | ++++ |
| 0.001 | - | ++ |
Figure 2 Comparison of images obtained by IRE and IRFE of syringes containing different concentrations of ICG, through two slices of pork (total thickness approximately 3.2 mm). a IRE image of a syringe containing 0.5 mg/ml of ICG. b IRFE image of a syringe containing 0.5 mg/ml of ICG. c IRE image of a syringe containing 0.01 mg/ml of ICG. d IRFE image of a syringe containing 0.01 mg/ml of ICG. Using IRE, the identification of the syringe containing 0.5 mg/ml of ICG (a) was easier than identification of the syringe containing 0.01 mg/ml of ICG (c). However, when IRFE images were compared, the syringe containing 0.01 mg/ml of ICG (d) was more clearly identified than the syringe containing 0.5 mg/ml of ICG (b).
Clinical Study
When esophageal varices were observed by IRFE after the administration of ICG at a dose of 2.0 mg/kg or 0.1 mg/kg, the entire esophageal mucosa was represented by strong white fluorescence, and it was difficult to differentiate normal mucosa from esophageal varices.
The differentiation of the esophageal varices was difficult in the patients who received ICG at a dose of 2.0 mg/kg. When ICG was administered at a dose of 0.01 mg/kg, however, clear infrared fluorescence corresponding to the esophageal varices detected by conventional light endoscopy was obtained. Figure [3 a] shows the conventional endoscopic image and Figure [3 b], [c] show infrared fluorescent images obtained after intravenous administration of ICG (0.01 mg/kg) in patient 12. Clear infrared fluorescence corresponding to the esophageal varices was also obtained in this patient. Clear infrared fluorescence corresponding to the esophageal varices was also obtained when ICG was administered at a dose of 0.005 mg/kg. Figure [4 a] shows the conventional endoscopic image and Figure [4 b] [c] show infrared fluorescent images obtained after intravenous administration of ICG (0.005 mg/kg) in patient 15. Clear fluorescence corresponding to the esophageal varices was also obtained in this patient. When ICG was administered at a dose of 0.001 mg/kg, however, the intensity of infrared fluorescence was markedly reduced and the differentiation of the normal mucosa from esophageal varices was difficult. These findings suggest that the optimal dose range of ICG for IRFE lies between 0.005 mg/kg and 0.01 mg/kg.
Figure 3 Conventional endoscopic image of patient 12 (a) and IRFE images after administration of ICG (0.01 mg/kg) (b and c). Clear infrared fluorescence corresponding to the esophageal varices was also obtained in this patient.
Figure 4 Conventional endoscopic image of patient 15 (a) and IRFE images after administration of ICG (0.005 mg/kg) (b and c). Clear infrared fluorescence corresponding to the esophageal varices was also obtained in this patient.
Discussion
Many previous studies have reported the usefulness of infrared fluorescence endoscopy, with and without intravenous ICG administration [4] [5] [6] [9] [10] [12]. Because infrared rays demonstrate better mucosal permeability than visible rays, more visual information about the deeper mucosal regions can be obtained by IRE than by conventional endoscopy [13] [14]. IRE is therefore reported to be especially useful for examining vascular lesions such as esophagogastric varices, angiodysplasia, Dieulafoy’s lesion, or vascular tumors. Esophageal varices are vascular lesions in which there are structural changes in the vascular wall caused by the portal hemodynamic changes brought about by portal hypertension. Information about the vascular structures and hemodynamics is very important in planning the treatment of esophageal varices: Ohta et al. [4] reported that such information was useful for the early detection of esophageal varices; for evaluating the therapeutic value of endoscopic injection sclerotherapy; and in the identification of regions at risk of further rupture.
Kohso et al. [9] reported that IRE principally provided information about the region up to an approximate depth of 3 mm from the mucosal surface. In our study using porcine tissue, IRE allowed observation of a region up to a tissue depth of approximately 3.2 mm, a finding almost identical to that reported previously. Using the same concentration of ICG and the same slices of pork, the technique of IRFE that we have developed allowed observation of a region up to a tissue depth of approximately 11.2 mm, the thickness of which was over three times greater than that achieved by IRFE. IRFE may therefore facilitate the observation of blood vessels in the esophageal wall in patients with esophageal varices (varices in the submucosal and propria layers) more clearly than IRE. In addition, information about deeper blood vessels outside the esophageal wall and about the entry and re-entry of blood vessels penetrating the esophageal muscle layer may also be obtained by IRFE.
Previous studies have reported various types of ICG toxicity. Benya et al. [15] reported some cases of ICG toxicity observed in 17 patients after intravenous administration of ICG (5 mg total dose or 0.5 mg/kg), including urticaria, itching, headache, shortness of breath, asthma, hypotension, tachycardia, nausea, peripheral vasodilatation, and death caused by pharyngeal spasm. When Iseki et al. [16] administered a total dose of 5 mg of ICG in 43 hemodialysis patients, four patients went into shock (9.3 %). In our preliminary study using different concentrations of ICG, clearer infrared fluorescence was obtained by IRFE at lower concentrations of ICG. In the clinical study IRFE allowed the observation of fluorescence using a concentration of ICG lower than that required for IRE and so the frequency of side effects may be markedly lower in IRFE than in IRE. Notably, none of our 20 patients developed complications related to IRFE.
However, when ICG was administered at doses of 0.001 mg/kg or 0.1 mg/kg and over, clear infrared fluorescence was not obtained by IRFE. This probably occurred because the administration of ICG at a dose below or above the optimal concentration prevented the acquisition of clear infrared fluorescence by decreasing the fluorescence intensity. This phenomenon is known as ”concentration fluorescence quenching”, in which the fluorescence intensity in the solution increases with the concentration of the fluorescent substances, but decreases when the concentration of fluorescent substance exceeds a specified level [17]. The concentration of ICG immediately before the concentration at which fluorescence quenching occurs may therefore be the optimal concentration of ICG. More clinical data and an objective evaluation system for fluorescence intensity would be required before decisions can be made on the optimum concentration of ICG for clinical use.
For the time being, IRFE using fiberoscopy and an external charge-coupled device system produces somewhat fuzzy images. However, although images of IRFE are relatively difficult to interpret compared with those of IRE, we consider that IRFE is equivalent to IRE for the early detection of esophageal varices, for the evaluation of the therapeutic value of endoscopic injection sclerotherapy, and for identification of areas at risk of future rupture. Because IRFE may be useful in the evaluation of changes in deeper hemodynamic features in individual patients with esophageal varices, it may also be useful in determining the therapeutic strategy and in predicting the prognosis after treatment. The true usefulness of IRFE compared with IRE remains to be elucidated by future studies, but the use of fluorescent characteristics in the field of infrared rays may greatly contribute to the development of a novel method for the diagnosis and evaluation of vascular lesions in the gastrointestinal tract.
#References
- 1 Ito S, Muguruma N, Hayashi S. et al . Development of an imaging system using fluorescent labeling substances excited by infrared rays. Dig Endosc. 1997; 9 278-282
- 2 Taoka S, Ito S, Muguruma N. et al . Reflected illumination-type imaging system for the development of infrared fluorescence endoscopy. Dig Endosc. 1999; 11 321-326
- 3 Ito S, Muguruma N, Kusaka Y. et al . Detection of human gastric cancer in resected specimens using a novel infrared fluorescent anti-human carcinoembryonic antigen antibody with an infrared fluorescence endoscope in vitro. Endoscopy. 2001; 33 849-853
- 4 Ohta H, Kohgo Y, Goto Y. et al . The near-infrared electronic endoscope for diagnosis of esophageal varices. Gastrointest Endosc. 1992; 38 330-335
- 5 Franke J, Lux G, Demling L. Intragastric infrared photography in conjunction with infrared absorption angiography. Gastrointest Endosc. 1985; 31 87-89
- 6 Iseki K, Tatsuta M, Lishi H. et al . Effectiveness of the near-infrared electronic endoscope for diagnosis of the depth of involvement of gastric cancers. Gastrointest Endosc. 2000; 52 755-762
- 7 Flower R W, Hochheimer B F. A clinical technique and apparatus for simultaneous angiography of the separate retinal and choroidal circulations. Invest Ophthalmol Vis Sci. 1973; 12 248-261
- 8 Borotto E, Englender J, Pourny C J. et al . Detection of the fluorescence of gastrointestinal vessels in rats using a CCD camera or a near-infrared video endoscope. Gastrointest Endosc. 1999; 50 684-688
- 9 Kohso H, Tatsumi Y, Fujino H. et al . An investigation of an infrared-ray electronic endoscope with a laser diode light source. Endoscopy. 1990; 22 217-220
- 10 Hayashi N, Kawano S, Tsuji S. et al . Identification and diameter assessment of gastric submucosal vessels using infrared electronic endoscopy. Endoscopy. 1994; 26 686-689
- 11 Speich R, Saesseli B, Hoffmann U, Neftel K A. Anaphylactoid reactions after indocyanine-green administration [letter]. Ann Intern Med. 1988; 109 345-346
- 12 Ohta H, Kohgo Y, Takahashi Y. et al . Computer-assisted data processing of images of mucosal and submucosal blood vessels of the stomach obtained by visible and infrared endoscopy using a directional-contrast filter. Gastrointest Endosc. 1994; 40 621-628
- 13 Gibson H L, Buckley W R, Whitmore K E. New vistas in infrared photography for biological surveys. J Biol Photogr Assoc. 1965; 33 1-33
- 14 Cartwright C H. Infrared transmission of the flesh. J Opt Soc Am. 1930; 20 81-84
- 15 Benya R, Quintana J, Brundage B. Adverse reactions to indocyanine green: a case report and a review of the literature. Cathet Cardiovasc Diagn. 1989; 17 231-233
- 16 Iseki K, Onoyama K, Fujimi S, Omae T. Shock caused by indocyanine green dye in chronic hemodialysis patients [letter]. Clin Nephrol. 1980; 14 210
- 17 Flower R W, Hochheimer B F. Quantification of indicator dye concentration in blood vessels. Exp Eye Res. 1977; 25 103-111
N. Muguruma, M. D.
Department of Digestive and Cardiovascular Medicine, The University of Tokushima Graduate
School
3-18-15 Kuramoto-cho · Tokushima City · Tokushima 770-8503 · Japan ·
Fax: + 81-88-633-9235
Email: muguruma@clin.med.tokushima-u.ac.jp
References
- 1 Ito S, Muguruma N, Hayashi S. et al . Development of an imaging system using fluorescent labeling substances excited by infrared rays. Dig Endosc. 1997; 9 278-282
- 2 Taoka S, Ito S, Muguruma N. et al . Reflected illumination-type imaging system for the development of infrared fluorescence endoscopy. Dig Endosc. 1999; 11 321-326
- 3 Ito S, Muguruma N, Kusaka Y. et al . Detection of human gastric cancer in resected specimens using a novel infrared fluorescent anti-human carcinoembryonic antigen antibody with an infrared fluorescence endoscope in vitro. Endoscopy. 2001; 33 849-853
- 4 Ohta H, Kohgo Y, Goto Y. et al . The near-infrared electronic endoscope for diagnosis of esophageal varices. Gastrointest Endosc. 1992; 38 330-335
- 5 Franke J, Lux G, Demling L. Intragastric infrared photography in conjunction with infrared absorption angiography. Gastrointest Endosc. 1985; 31 87-89
- 6 Iseki K, Tatsuta M, Lishi H. et al . Effectiveness of the near-infrared electronic endoscope for diagnosis of the depth of involvement of gastric cancers. Gastrointest Endosc. 2000; 52 755-762
- 7 Flower R W, Hochheimer B F. A clinical technique and apparatus for simultaneous angiography of the separate retinal and choroidal circulations. Invest Ophthalmol Vis Sci. 1973; 12 248-261
- 8 Borotto E, Englender J, Pourny C J. et al . Detection of the fluorescence of gastrointestinal vessels in rats using a CCD camera or a near-infrared video endoscope. Gastrointest Endosc. 1999; 50 684-688
- 9 Kohso H, Tatsumi Y, Fujino H. et al . An investigation of an infrared-ray electronic endoscope with a laser diode light source. Endoscopy. 1990; 22 217-220
- 10 Hayashi N, Kawano S, Tsuji S. et al . Identification and diameter assessment of gastric submucosal vessels using infrared electronic endoscopy. Endoscopy. 1994; 26 686-689
- 11 Speich R, Saesseli B, Hoffmann U, Neftel K A. Anaphylactoid reactions after indocyanine-green administration [letter]. Ann Intern Med. 1988; 109 345-346
- 12 Ohta H, Kohgo Y, Takahashi Y. et al . Computer-assisted data processing of images of mucosal and submucosal blood vessels of the stomach obtained by visible and infrared endoscopy using a directional-contrast filter. Gastrointest Endosc. 1994; 40 621-628
- 13 Gibson H L, Buckley W R, Whitmore K E. New vistas in infrared photography for biological surveys. J Biol Photogr Assoc. 1965; 33 1-33
- 14 Cartwright C H. Infrared transmission of the flesh. J Opt Soc Am. 1930; 20 81-84
- 15 Benya R, Quintana J, Brundage B. Adverse reactions to indocyanine green: a case report and a review of the literature. Cathet Cardiovasc Diagn. 1989; 17 231-233
- 16 Iseki K, Onoyama K, Fujimi S, Omae T. Shock caused by indocyanine green dye in chronic hemodialysis patients [letter]. Clin Nephrol. 1980; 14 210
- 17 Flower R W, Hochheimer B F. Quantification of indicator dye concentration in blood vessels. Exp Eye Res. 1977; 25 103-111
N. Muguruma, M. D.
Department of Digestive and Cardiovascular Medicine, The University of Tokushima Graduate
School
3-18-15 Kuramoto-cho · Tokushima City · Tokushima 770-8503 · Japan ·
Fax: + 81-88-633-9235
Email: muguruma@clin.med.tokushima-u.ac.jp
Figure 1 Images obtained by infrared endoscopy (IRE) and by infrared fluorescent endoscopy (IRFE) of a syringe containing 0.5 mg/ml indocyanine green (ICG), through two slices of pork (total thickness approximately 3.2 mm). The infrared image (a) showed only weak contrast of the syringe compared with the infrared fluorescent image (b), which facilitated identification of the syringe with clear contrast.
Figure 2 Comparison of images obtained by IRE and IRFE of syringes containing different concentrations of ICG, through two slices of pork (total thickness approximately 3.2 mm). a IRE image of a syringe containing 0.5 mg/ml of ICG. b IRFE image of a syringe containing 0.5 mg/ml of ICG. c IRE image of a syringe containing 0.01 mg/ml of ICG. d IRFE image of a syringe containing 0.01 mg/ml of ICG. Using IRE, the identification of the syringe containing 0.5 mg/ml of ICG (a) was easier than identification of the syringe containing 0.01 mg/ml of ICG (c). However, when IRFE images were compared, the syringe containing 0.01 mg/ml of ICG (d) was more clearly identified than the syringe containing 0.5 mg/ml of ICG (b).
Figure 3 Conventional endoscopic image of patient 12 (a) and IRFE images after administration of ICG (0.01 mg/kg) (b and c). Clear infrared fluorescence corresponding to the esophageal varices was also obtained in this patient.
Figure 4 Conventional endoscopic image of patient 15 (a) and IRFE images after administration of ICG (0.005 mg/kg) (b and c). Clear infrared fluorescence corresponding to the esophageal varices was also obtained in this patient.