Introduction
Capsule endoscopy (CE) is a mainstay for endoscopic examination of small bowel diseases,
such as obscure gastrointestinal bleeding (OGIB), Crohn’s disease, and polyposis syndromes
[1]
[2]. The diagnostic superiority of CE has been proven by studies comparing CE with other
methods for evaluating the small bowel, such as push enteroscopy and radiologic procedures
[3]
[4]. CE has been suggested as the first-line modality for diagnosis of OGIB. However,
the overall positive diagnostic yield of CE in OGIB is only around 60 % [1]. Recently, to improve diagnostic capability, virtual chromoendoscopy techniques
have been proposed to enhance the contrast of microvessels, resolution of superficial
mucosal patterns, and color differences [5]. One such modality, the flexible spectral imaging color enhancement (FICE) system,
was developed and introduced in 2005 as a new image processing tool for video endoscopy.
FICE is a system that estimates the spectral reflectivity of the target tissue, reconstructs
flexible spectral images with different wavelengths calculated from conventional white
light (WL) images, and develops new flexible spectral images by selecting and reconstructing
RGB wavelengths that emphasize the target [5]
[6]
[7]
[8]. FICE is a digital imaging technology that utilizes RAPID software and allows processing
of ordinary images captured using standard video capsule devices. Blue mode (BM),
an additional image-enhanced modality setting available with the RAPID software package,
entails a color coefficient shift of light in the short wavelength range (490 – 430 nm)
superimposed onto a white light image. The addition of these technologies to CE is
expected to improve the diagnostic yield. Imagawa and colleagues reported that FICE
can improve the visibility of small bowel lesions detected under WL by CE [9]. However, Gupta and associates reported that FICE did not improve the detection
of small bowel lesions in comparison with WL [10]. Moreover, Krystallis and coworkers reported that BM offers better image enhancement
in CE compared with FICE [11]. Thus, data on the use of FICE and BM in CE are limited and the results are controversial.
Therefore, the clinical value of FICE-enhanced CE remains unknown. Studies conducted
to date have been limited by the lack of qualitative methods to assess visibility.
In this study, we aimed to qualitatively evaluate FICE and BM enhancement in CE, using
a RAPID6 Access image diagnostic system, in images of lesions obtained during small
bowel CE, and to compare the results with corresponding images obtained using WL.
Therefore, to evaluate visibility, we first quantified the color contrast of small
bowel lesions using the color space CIELAB method, [12] which associates color perception with colorimetric values, and we used a visual
analogue scale (VAS) to assess visibility [13]. We also assessed whether FICE-CE could improve the detection of small-bowel lesions.
Methods
CE procedure
A PillCam SB or SB2 (Given Imaging Ltd, Yoqneam, Israel) was used for CE. All patients
included had received 500 ml of polyethylene glycol-based bowel preparation before
the examination and were given dimethicone before swallowing the capsule after an
overnight fast. A RAPID6 Access CE diagnostic system (Given Imaging Ltd) equipped
with the FICE system and BM was used for the analysis. The principle of FICE estimation
technology is described elsewhere [5]. FICE set 1 (R, 595 nm; G, 540 nm; and B, 535 nm), FICE set 2 (R, 420 nm; G, 520 nm;
and B, 530 nm), and FICE set 3 (R, 595 nm; G, 570 nm; and B, 415 nm), which are the
default FICE settings, and BM (wavelength 490 – 430 nm) were used in this study.
Image interpretation
To evaluate the visualization of CE images, we retrospectively assessed all images
of lesions obtained from 189 patients (123 male, 66 female; median age 53 years) who
underwent CE for small-bowel lesions at Sapporo Medical University Hospital between
January 2009 and April 2012. CE was performed for the following reasons: obscure gastrointestinal
bleeding (OGIB) (n = 129), examination of the extent of tumor spread (n = 43), chronic
abdominal pain or diarrhea (n = 13), and miscellaneous (n = 4). The 261 lesions in
which the final diagnoses were confirmed by balloon enteroscopy, surgery, or periodical
observation were chosen on the basis of their overall acceptability as CE images by
one of the authors (YS) who has extensive experience with CE. Lesions classified as
P0 (no potential for bleeding) were not taken into account [14]. This author did not participate in further evaluation of the images. CE images
were categorized according to 3 different lesion categories: i. e., angioectasia (n = 152),
erosion/ulceration (n = 88), or tumor (n = 21).
Representative CE images are shown in [Fig. 1]; the color difference (ΔE) was examined between each lesion and corresponding background
mucosa in WL images, FICE set 1 – 3, and BM images. ΔE was calculated using the CIE
1976 (L*a*b*) color space (CIELAB) method.[12] CIE L*a*b* (CIELAB) is a 3-dimensional color space consisting of a black – white axis (L*), a red – green axis (a*), and a yellow – blue axis (b*) ([Fig. 2 a]). L* is defined as lightness, a* as the red – green component, and b* as the yellow – blue component. All endoscopic images were stored in JPEG format.
ΔE obtained from the WL image, the FICE set 1, set 2, and set 3 images, and BM images
was determined. ΔE was measured by a single computer operator (TS) who was able to
recognize small bowel lesions and background mucosa in the endoscopic images but had
no knowledge of the patients’ histories. The operator was initially asked to select
1 sample point at random from a lesion, such as an area of rubefaction, in each WL
image, as shown in [Fig. 2 b,] and subsequently to select 1 sample point from background mucosa close to the sample
points for the small bowel lesion. The corresponding regions were then selected on
the FICE and BM images and the color difference was calculated using the method described
for WL images ([Fig. 2 c]). One sample point consisted of 81 pixels (9 × 9 pixels) and the median RGB value
determined using Adobe Photoshop Elements 2.0. L*a*b* was then calculated based on
the median RGB value. The Photoshop RGB value (sRGB value; designated as R’, G’, and
B’) indicates “the color dependent on the device.” Therefore, an sRGB value does not
express an absolute color value and, consequently, it is necessary to convert the
sRGB value to the XYZ color system independent of a device. After determining the
sRGB values, we calculated ΔE and compared differences in ΔE among FICE, BM, and WL
images.
Fig. 1 Capsule endoscopy (CE) images of small intestinal diseases obtained using flexible
spectral imaging color enhancement (FICE) and blue mode (BM). Representative images
of white light (WL), FICE and BM-CE of a small-bowel angioectasia (a – e), ulcer (f – j), and tumor (k – o), respectively. WL-CE image (a, f, k). BM image (b, g, l). FICE-CE images derived from the 3 different wavelength settings (set 1 [c, h, m], set 2 [d, l, n], set 3 [e, j, o]).
Fig. 2 Colorimetric evaluation of conventional capsule endoscopy (CE) images and flexible
spectral imaging color enhancement (FICE) and blue mode (BM) images. (a) 1976 CIE L*a*b* Space. CIE L*a*b* (CIELAB) is the color space specified by the International Commission on Illumination
(Commission Internationale d'Eclairage). The color of images is expressed in terms of 3 coordinate values (L*, a*, b*), located in a 3-dimensional color space. The 3 coordinates of CIELAB represent
the lightness of the color (L* = 0 yields black and L* = 100 indicates diffuse white; specular white may be higher), its position between
red and green (a*, negative values indicate green while positive values indicate red), and its position
between yellow and blue (b*, negative values indicate blue and positive values indicate yellow). The color difference
(ΔE) shows the distance between 2 sample regions in the color space. (b) Representative vascular lesion images for calculating color differences. In the
area of the yellow square in the conventional image (left), 1 sample point is selected
from a vascular lesion and 1 sample point is selected from the background mucosa close
to the vascular lesion sample point. The sample points in the corresponding region
of FICE setting 2 image (right) were selected using the same method. (c) Protocol for calculating color differences (ΔE) between small bowel lesions and
background mucosa.
The VAS was used to score the visibility of small bowel lesions in the images, which
were evaluated by 5 expert endoscopists (MH, HO, TO, YO, FT) who had not been informed
about the study design. All images were incorporated into a slideshow (Microsoft Office
PowerPoint 2008, Microsoft Inc, USA) and displayed on a black background with a 15-inch
screen. For slides containing either WL; FICE set 1, 2, 3 images; or BM images, the
assessors were asked to grade the following items on a 100-mm VAS (0 = low quality;
100 = high quality) [13].
To evaluate the detectability of small bowel lesions in images from each FICE setting
or BM compared with the WL image, a total of 50 patients (27 males/23 females; median
age, 62.5 years) who underwent CE between May 2012 and April 2013 were examined at
Sapporo Medical University Hospital. CE was performed for the following reasons: OGIB
(n = 34), examination of the extent of tumor spread (n = 8), chronic abdominal pain
or diarrhea (n = 4), and miscellaneous (n = 4). Three certified endoscopists (YS,
TS, MH) who had similar levels of experience in CE image analysis (i. e., more than
100 cases) read the videos in a blinded fashion. In practice, one endoscopist (YS)
read videos 1 to 20 with WL, videos 21 to 40 with FICE at settings 1 – 3, and videos
41 to 50 with BM. A second reader (TS) read the same sequences of videos using FICE,
BM and WL, in that order, and a third reader (MH) read the videos sequentially using
BM, WL, and FICE. The FICE reader read each FICE setting on another day and was blinded
to the results. The most relevant findings obtained from CE were documented and classified
by each endoscopist as: vascular lesion, erosion/ulceration, tumor, or no abnormality.
The numbers of lesions detected and reading times were compared between WL and FICE
setting 1 – 3, or BM. The final diagnoses, which were made by several modalities including
CE, balloon enteroscopy, surgery and periodical observation, were used as the gold
standard for the analyses. This study was approved by our institutional review board.
All patients provided written informed consent for participation in the study.
Statistical analysis
All statistical analyses were performed using StatView version 5.0 software (SAS Institute,
Inc., Cary, NC, USA). Parametric data were expressed as mean ± standard deviation
(SD). In all analyses, the mean values were compared by paired Student’s t-test. A P-value less than 0.05 was considered statistically significant.
Results
Comparison of color differences in WL, FICE, and BM images quantified using the CIERAB
method for each lesion Type
To evaluate the color contrast between 261 small bowel lesion images from 189 patients
and their respective background normal mucosa, we determined ∆E in WL, FICE set 1 – 3,
and BM images. The protocols for calculating ∆E are shown in [Fig. 2 b, c], and the results for each FICE setting and BM are shown for each lesion type in
[
Table 1
]. For vascular lesion (152 images), the ∆E values were as follows: WL images = 24.3 ± 9.4,
FICE set 1 = 76.1 ± 17.4, FICE set 2 = 78.2 ± 20.6, FICE set 3 = 56.3 ± 26.2 and BM
set = 67.3 ± 16.6. The ∆E of the FICE set 1 and 2, and BM images was significantly
higher than ∆E of the WL images (P < 0.01). There was no significant difference in ∆E between FICE set 1 and 2, BM and
FICE set 1, and BM and FICE set 2. For erosion/ulceration (88 images), the ∆E values
were as follows: WL images = 18.5 ± 7.3, FICE set 1 = 43.2 ± 14.9, FICE set 2 = 46.9 ± 17.6,
FICE set 3 = 31.8 ± 15.6, and BM = 37.2 ± 14.2. The ∆E of FICE set 1 and 2 images
was significantly higher than that of WL images (P < 0.01). There was no significant difference in ∆E between FICE setting 1 and 2. For
tumors (21 images), the ∆E values were as follows: WL images = 20.2 ± 7.6, FICE set
1 = 21.5 ± 11.2, FICE set 2 = 21.2 ± 8.4, FICE set 3 = 23.1 ± 9.2 and BM = 23.3 ± 8.8.
There was no significant difference in ∆E among settings. Regarding specific types
of tumor, there were 4 lymphangioma, 5 follicular lymphoma, 3 gastrointestinal stromal
tumor (GIST), 6 adenomatous polyp, and 3 Peutz-Jeghers polyp cases, and there was
no significant difference among settings in the ∆E values relative to WL images for
the different tumor type settings.
Table 1
Comparison of visibility in WL, FICE, and BM images quantified using the CIERAB (∆E)
and VAS method for each lesion type.
|
Vascular lesion
|
Erosion/ulceration
|
Tumor
|
|
CE
setting
|
ΔE
|
VAS
|
ΔE
|
VAS
|
ΔE
|
VAS
|
|
WL
|
24.3 ± 9.4
|
50.2 ± 1.2
|
18.5 ± 7.3
|
50.2 ± 3.0
|
20.2 ± 7.6
|
50.1 ± 1.0
|
|
FICE 1
|
76.1 ± 17.4[*]
|
72.7 ± 5.2[*]
|
43.2 ± 14.9[*]
|
72.9 ± 5.4[*]
|
21.5 ± 11.2
|
50.7 ± 4.4
|
|
FICE 2
|
78.2 ± 20.6[*]
|
74.0 ± 14.9[*]
|
46.9 ± 17.6[*]
|
67.9 ± 5.7[*]
|
21.2 ± 8.4
|
54.0 ± 3.8
|
|
FICE 3
|
56.3 ± 26.2
|
58.7 ± 14.9
|
31.8 ± 15.6
|
53.5 ± 6.5
|
23.1 ± 9.2
|
50.1 ± 9.8
|
|
BM
|
67.3 ± 16.6[*]
|
64.8 ± 4.6[*]
|
37.2 ± 14.2
|
59.5 ± 6.5
|
23.3 ± 8.8
|
54.1 ± 5.0
|
Abbreviations: BM, blue mode; CE, capsule endoscopy; FICE, flexible spectral imaging
color enhancement; VAS, visual analogue scale; WL, white light.
*
P < 0.01 versus White light CE
Evaluation of visibility quantified by lesion type using a VAS with WL, FICE, and
BM images
We also assessed visibility scores for each of the imaging methods ([Table 1]). For vascular lesion (152 images), the VAS scores were as follows: WL images = 50.2 ± 1.2,
FICE set 1 = 72.7 ± 5.2, FICE set 2 = 74.0 ± 14.9, FICE set 3 = 58.7 ± 14.9, and BM = 64.8 ± 4.6.
The VAS scores for FICE set 1 and set 2 and BM images were significantly higher than
the score for WL images (P < 0.01). However, the score for FICE set 3 was not improved as much as the score
for FICE set 1 and set 2, and BM. For erosion/ulceration (88 images), the VAS scores
were: WL images = 50.2 ± 3.0, FICE set 1 = 72.9 ± 5.4, FICE set 2 = 67.9 ± 5.7, FICE
set 3 = 53.5 ± 6.5, and BM = 59.5 ± 6.5. The VAS scores for FICE set 1 and set 2 were
significantly higher than the score for WL images (P < 0.01). However, the score for FICE set 3 and BM was not improved as much as the
score for FICE set 1 and set 2. For imaging tumors (30 images), the VAS scores were:
WL images = 50.1 ± 1.0, FICE set 1 = 50.7 ± 4.4, FICE set 2 = 54.0 ± 3.8, FICE set
3 = 50.1 ± 9.8, and BM = 54.1 ± 5.0. There was no significant improvement with any
of the settings relative to WL images. However, the score for FICE and BM was not
decreased relative to the score for WL images.
Sensitivity and specificity of CE for each type of small intestinal disease on a per-patient
basis
A complete examination of the entire small bowel was achieved in 88 % (44 /50) of
cases, with median small bowel transit time being 250 min (range 71 – 522). The final
diagnosis indicated that there were 40 vascular lesions in 12 patients, 42 erosion/ulcerative
lesions in 13 patients, and 26 tumors or polyps (follicular lymphoma [n = 6]; gastrointestinal
stromal tumor [n = 2]; Peutz-Jeghers polyps [n = 2]; familial adenomatous polyposis
[n = 16]) in 11 patients. The remaining 14 individuals without any significant lesions
were also confirmed. The per-patient sensitivity and specificity of CE for the detection
of small intestinal diseases are shown in [Table 2]. With respect to vascular lesions, FICE setting 1 and 2 had the highest sensitivity
(100 %), and specificity (97.3 – 100 %). As for erosive/ulcerative lesions, FICE setting
2 had the highest sensitivity (100 %) and specificity (97.2 %). In terms of tumors
or polyps, WL had the highest sensitivity (90.9 %) and specificity (87.1 %).
Table 2
Per-patient sensitivity and specificity of CE for detecting small intestinal lesions.
|
% Sensitivity (95 % CI)
|
% Specificity (95 % CI)
|
|
WL
|
FICE 1
|
FICE 2
|
FICE 3
|
BM
|
WL
|
FICE 1
|
FICE 2
|
FICE 3
|
BM
|
|
Vascular
|
83.3
(50.8 – 97.0)
|
100
(69.8 – 100)
|
100
(69.8 – 100)
|
75.0
(42.8 – 93.3)
|
83.3
(50.8 – 97.0)
|
92.1
(77.5 – 97.9)
|
100
(88.5 – 100)
|
97.3
(84.5 – 99.8)
|
94.7
(80.9 – 99.0)
|
92.1
(77.5 – 97.9)
|
|
Erosion/Ulceration
|
84.6
(53.6 – 97.2)
|
92.3
(62.0 – 99.5)
|
100
(71.6 – 100)
|
76.9
(45.9 – 93.8)
|
84.6
(53.6 – 97.2)
|
89.2
(73.6 – 96.4)
|
94.6
(80.4 – 99.0)
|
97.2
(84.1 – 99.8)
|
91.9
(76.9 – 97.8)
|
89.2
(73.6 – 96.4)
|
|
Tumor
|
90.9
(57.1 – 99.5)
|
81.8
(47.7 – 96.7)
|
81.8
(47.7 – 96.7)
|
72.7
(39.3 – 92.6)
|
81.8
(47.7 – 96.7)
|
87.1
(71.7 – 95.1)
|
84.6
(68.7 – 93.5)
|
84.6
(68.7 – 93.5)
|
84.6
(68.7 – 93.5)
|
84.6
(68.7 – 93.5)
|
BM, blue mode; CE, capsule endoscopy; CI, confidence interval; FICE, flexible spectral
imaging color enhancement; WL, white light.
Detection of the number of lesions using FICE or BM imaging enhancement
The results of WL, FICE, and BM are shown per lesion type in [Table 3]. In these 50 patients, a total of 17 angioectasias were identified by WL; 24 were
detected by FICE at setting 1, 33 at setting 2, and 18 at setting 3; and 20 were detected
with BM. There were statistically significant differences between WL and FICE setting
1 and 2 (P = 0.02 and P = 0.003, respectively). A total of 28 erosive/ulcerative lesions were detected by
WL; 33 by FICE setting 1, 41 FICE setting 2, 24 at FICE setting 3, and 28 with BM.
Only FICE setting 2 showed significantly superior detection ability over WL (P = 0.007). For tumors, a total of 13 lesions were detected by WL; 13 were detected
by FICE setting 1, 14 at FICE setting 2, and 10 at FICE setting 3; and 14 were detected
by BM. Detection did not differ significantly among groups. With respect to tumor
type, 6 adenomatous polyps were detected by WL, and the same adenomatous polyps were
detected by FICE setting 1 – 3 and BM. Two Peutz-Jeghers polyps were detected by WL
and FICE setting 1, 2, and BM, but only 1 was detected by FICE setting 3. Three follicular
lymphoma were detected by WL and by FICE setting 1; four were detected by FICE setting
2 and by BM, and 1 was detected by FICE at setting 3. With each of the imaging settings,
2 GISTs were detected. The analysis times with WL (36 ± 3.9 min) and FICE at the various
settings (setting 1, 35 ± 2.9 min; setting 2, 37 ± 3.7 min; setting 3, 35 ± 5.3 min),
and BM (37 ± 5.6 min) did not differ significantly.
Table 3
Number of significant lesions detected by FICE or blue mode imaging enhancement.
|
CE
setting
|
|
Lesion type
|
|
|
Vascular
lesion (n = 40)
|
Erosion/
ulceration (n = 42)
|
Tumor
(n = 26)
|
|
WL
|
17
|
28
|
13
|
|
FICE 1
|
24[1]
|
33
|
13
|
|
FICE 2
|
33[2]
|
41[3]
|
14
|
|
FICE 3
|
18
|
24
|
10
|
|
BM
|
20
|
28
|
14
|
Abbreviations: BM, blue mode; CE, capsule endoscopy; FICE, flexible spectral imaging
color enhancement; WL, white light.
1
P = 0.02 versus WL-CE
2
P = 0.003 versus WL-CE
3
P = 0.007 versus WL-CE.
Positives of FICE imaging and negatives of WL-CE imaging
There were 2 of 50 patients (4 %) whose angioectasias were missed with WL-CE imaging
and only detected with FICE settings 1 and 2. In these lesions, visualization of the
mucosa was impaired by the presence of air bubbles and bile pigments. Representative
images are shown in [Fig. 3 a – c]. There were 2 of 50 patients (4 %) whose aspirin-induced erosions were missed with
WL-CE imaging and only detected with FICE settings 1 and 2. With FICE imaging, it
was easier to observe demarcation of the lesion compared with WL-CE imaging. Representative
images are shown in [Fig. 3d – f].
Fig. 3 Two representative cases in which flexible spectral imaging color enhancement (FICE)
detected small bowel lesions that were missed with conventional capsule endoscopy
imaging. White light (WL) and FICE images of a small-bowel angioectasia with air bubbles
and bile pigments (a – c) and a faint erosion with white spot surrounded by a red halo (d – f). WL-CE image (a, d). FICE-CE setting 1 (b, e), setting 2 (c, f).
Discussion
The diagnostic yield of CE remains unsatisfactory, partly because faint or minute
small-bowel lesions can be easily missed. Thus, there is a need for image-enhancement
technology to enable visualization of such lesions. However, it remains to be verified
which of the available image enhancement modes, such as FICE or BM, is most appropriate
for improving the ability to diagnose small-bowel lesions. In fact, conflicting results
have been reported to date ([Table 4]). This uncertainty is due in part to the fact that studies conducted so far have
been limited by the lack of qualitative methods to assess visibility.
Table 4
Literature on comparison of detectability between WL and each FICE setting.
|
Reference
|
Indication
(number of patients)
|
Detectability
|
|
|
Vascular lesion
|
Erosion/ulcer
|
Tumor
|
Note
|
|
FICE 1
|
FICE 2
|
FICE 3
|
FICE 1
|
FICE 2
|
FICE 3
|
FICE 1
|
FICE 2
|
FICE 3
|
|
Kobayashi et al.[19]
|
OGIB/IDA/suspected tumor/pain
(24)
|
↑
|
→
|
→
|
↑
|
→
|
→
|
↓
|
→
|
→
|
FICE set 1 missed more tumors than the WL-CE
|
|
Matsumura et al.[20]
|
OGIB
(81)
|
→
|
↑
|
→
|
Diagnostic yield for OGIB is not improved by FICE
|
|
Sakai et al.[15]
|
OGIB
(12)
|
↑
|
↑
|
→
|
↑
|
↑
|
↑
|
NA
|
Detectability of FICE set 2 was reduced by the presence of bile-pigments, but not
FICE set 1
|
|
Nakamura et al.[16]
|
Angiodysplasia
(50)
|
|
↑
|
|
|
NA
|
|
|
NA
|
|
FICE enables accurate detection of angiodysplasia in the preview of CE
|
|
Duque et al.[17]
|
OGIB
(20)
|
NA
|
↑
|
NA
|
NA
|
↑
|
NA
|
NA
|
→
|
NA
|
FICE set 2 seems to increase its diagnostic accuracy of erosions and angiodysplasias
|
|
Imagawa et al.[18]
|
OGIB/IDA/
suspected tumor/pain/others
(55)
|
↑
|
↑
|
→
|
→
|
→
|
→
|
→
|
→
|
→
|
FICE set 1 and 2 are particularly useful for detecting angioectasias
|
|
Gupta et al.[10]
|
OGIB
(60)
|
→
|
NA
|
NA
|
→
|
NA
|
NA
|
|
NA
|
|
Some vascular lesions could be more accurately characterized with FICE compared with
WL-CE
|
Abbreviations: ↑, significantly improved; →, no significant change; ↓, significantly
decreased; FICE, flexible spectral imaging color enhancement; IDA, iron deficiency
anemia; NA, not applicable; OGIB, obscure gastrointestinal bleeding; WL, white light.
In this study, we demonstrated that FICE-CE provided useful information for the diagnosis
of small bowel lesions by enhancing the contrast between lesions and background mucosa.
This is the first report to objectively evaluate the quantitative detection capacity
of small bowel lesions using the CIELAB method (ΔE). We found that FICE significantly
improved the visibility and detection of small bowel vascular and erosion/ulceration
lesions better than the other settings that were evaluated.
FICE uses computerized processing to convert standard RGB signals from the endoscope’s
charge-coupled device, which represents a type of electronic image-enhanced endoscopy
(IEE) [5]
[6]
[7]
[8]. Recent advances in image processing technology have enabled isolation of RGB signals
as “image information according to the light at a specific wavelength” [6]. An endoscopic image obtained using light of a specific wavelength is known as a
spectral image; such images are obtained by the application of spectral estimation
technology. Although spectral images are monochromatic, they are displayed in pseudo-colors
by allocating RGB signals in FICE. It is possible to analyze images using a combination
of light at different wavelengths in FICE. Therefore, the same degree of brightness
can be maintained as in conventional endoscopy, and distant-view observations are
possible while maintaining adequate viewing. Obtaining bright images is extremely
important in small bowel CE, in which the distance from a lesion cannot arbitrarily
be controlled. As a result, FICE-CE would be expected to improve the detection of
lesions and their characterization, and as a consequence, may improve the diagnostic
yield.
In terms of quantitative contrast enhancement, the color difference (ΔE) between small
bowel vascular or erosion/ulceration lesions and background mucosa was significantly
larger with FICE set 1 and 2 images than with WL-CE images; a similar tendency was
observed with respect to VAS visibility scores. These results indicate that ΔE reflects
the results of VAS, and thus, that the measurement of ΔE would be useful for objectively
assessing the visibility of small intestine lesions. The results of the present study
are comparable to those of a recent study by Imagawa and colleagues [9], which showed improved visibility for 87.0 % of vascular images analyzed with FICE
setting 1 or 2, and for 53.3 % and 25.5 % of erosion/ulceration images with FICE settings
1 and 2, respectively.
In our study, there were no significant visibility differences between FICE settings
1 and 2; however, in particular lesions, such as minute small or faint bowel vascular/erosive
lesions, the color difference and VAS score were greatest with FICE set 2 (data not
shown), which was assumed to be because the image of background mucosa of FICE set
2 is blue. It was therefore possible to emphasize the redness of angioectasia or the
border of the surrounding reddened area of an erosion/ulceration with inflammatory
change more clearly and demarcation of the lesion would be distinct. In contrast,
in environments with relatively high amounts of bile juice such as the terminal ileum,
FICE set 1 images produced the largest ΔE and showed better detectability than FICE
set 2 images in cases of vascular or erosion/ulceration lesions (data not shown).
This is presumably because bile juice is visualized with almost no color with FICE
set 1, since wavelengths at this setting (500 nm or longer) are not absorbed by bile
juice. In fact, Sakai et al. reported that FICE set 1 may reduce the bile-pigment
effect and improve the detectability of small-bowel lesions [15]. Additional research is needed to determine which of these settings is most appropriate
depending on the condition of the small intestine.
As shown in [Table 4], there have been conflicting findings to date from studies comparing detectability
with WL and each FICE setting, [10]
[15]
[16]
[17]
[18]
[19]
[20] or instance, Gupta and colleagues reported that FICE did not improve the detection
of significant small bowel lesions in comparison with WL [10]. Interestingly, they found that FICE setting 1 provided slightly better characterization
of vascular lesions compared with WL. However, in addition to not quantifying visibility,
the study did not examine the validity of each FICE settings. It has also been reported
that discrepancies in detectability results may be attributable to the lesion location
[19], pigment effect [15], conditions of preparation, and experience level of the reader [20]; however, in most of these reports, including our study, FICE settings 1 and/or
2 showed significantly superior ability compared with WL for the detection of vascular
and/or erosive/ulcerative lesions. In fact, our main diagnoses were changed by FICE
reading versus WL reading in 4 patients (8 %) with minute vascular lesions and faint
erosive lesions. In these cases, FICE can avoid interference from bile juice or residues
and enhance the color contrast of the lesions.
Our data showed that FICE-CE is not particularly useful for improving the detection
of tumors such as follicular lymphoma, Peutz-Jeghers polyp, and adenomatous polyp,
which is consistent with other reports [9]
[11]. In general, it is difficult to demonstrate the usefulness of CE for identifying
tumor lesions, since lesions typically vary with respect to morphology, size, surface
patterns, hypervascularity, and vascular morphology. In fact, Kobayashi and coworkers
[19] reported that FICE set 1 is worse at detecting tumors or polyps than is the WL mode
([Table 4]). This does not necessarily negate the utility of FICE compared with WL, but suggests
that there is a risk of overlooking critical lesions by spectral modifications, in
particular, in the exploration of tumor lesions. Therefore, further studies will be
needed to assess the ability of FICE-CE to detect specific types of tumor.
BM, which can be obtained by simply enhancing the blue color range of WL images, has
been reported to offer better image enhancement in CE compared with FICE, in contrast
with the results of our study [11]. However, in that study, FICE was better than BM in image enhancement for vascular
lesions such as arteriovenous malformation (AVM). In fact, we found that the detection
rate and the sensitivity and specificity for angioectasia cases at FICE settings 1
and 2 were greater than those with BM. In that respect, especially for vascular lesions,
it appears that visibility is improved more with FICE than with BM.
Taken together, the data from the present study indicate that FICE setting 1 or 2
was most useful for improving visibility in cases of angioectasia and erosion/ulceration
of the small intestine. We believe that the enhanced visibility with FICE is responsible
for the improved sensitivity, specificity and detection of angioectasias and erosion/ulceration
documented in the present study.
In particular, vascular lesions such as angiodysplasias and other vascular abnormalities
account for ~ 80 % of the major source of bleeding from the small bowel [21]; thus, improved detection of angioectasia with FICE would be clinically meaningful
for OGIB.
The present study has potential limitations. It was conducted at a single center and
the data were analyzed retrospectively. Prospectively assessing the diagnostic yield
of CE-FICE and comparison with a comprehensive examination including double-balloon
endoscopy would be worth investigating in a future study.
In conclusion, our data show that FICE imaging adds valuable information to conventional
CE imaging and provides better diagnostic ability for small bowel lesions such as
angioectasia and erosion/ulceration, especially with the use of FICE setting 1 and/or
2. A multicenter trial to screen diseases of the small intestine by FICE is warranted
to clarify the clinical indications for FICE.
