High Resolution White Light Research Articles

Endoscopic Trimodality Imaging (ETMI) for the Detection and Classification of Colonic Polyps

Background and Aim: Endoscopic detection and removal of colonic adenomas prevents the development of colorectal cancer (CRC). During standard colonoscopy 13-26% of small adenomas are missed and 17-40% of detected polyps are non-adenomatous. A new endoscopic trimodality imaging (ETMI) system has been developed, incorporating high resolution white light endoscopy (WLE), autofluorescence imaging (AFI) and narrow band imaging (NBI). In this ongoing randomized cross-over study we are assessing the value of ETMI for the detection and classification of colonic polyps in patients at increased risk for adenomas.

Endoscopic Trimodality Imaging (ETMI) for Detection and Classification of Neoplasia in Patients with Longstanding Ulcerative Colitis

Background and Aims: Patients with longstanding ulcerative colitis (UC) are recommended to undergo regular colonoscopic surveillance with targeted and random biopsies for the detection of neoplasia. However, the sensitivity of this method is low. Recently, Endoscopic TriModality Imaging (ETMI) has been developed, incorporating high resolution White Light Endoscopy (WLE), AutoFluorescence Imaging (AFI) and Narrow Band Imaging (NBI). We performed a pilot study, in which we assessed the feasibility and accuracy of ETMI and compared AFI with WLE for the detection of neoplasia in patients with longstanding UC. Methods: Consecutive UC patients, scheduled for surveillance colonoscopy, were invited to participate in this study. During withdrawal, each colonic segment was inspected twice; once with WLE and once with AFI, in randomized order. All detected lesions were subsequently inspected by NBI for assessing Kudo classification. Hereafter, targeted as well as random biopsies were taken. The histology of the biopsies was used as the gold standard. Results: Informed consent was obtained from 58 patients. Three patients had to be excluded because of insufficient colon preparation and 5 because of active inflammation despite a low disease activity index. Among 25 patients randomized to start with AFI, 8 neoplastic lesions were found with AFI (in 4 patients). Second inspection with WLE revealed 1 extra neoplastic lesion (1 additional patient). Among 25 patients examined with WLE first, 4 neoplastic lesions were found with WLE (2 patients). Subsequent AFI yielded 3 additional neoplastic lesions (2 extra patients). A mean number of 40 (SD 7) random biopsies was taken per patient, revealing neoplasia in 4 biopsies (one additional patient with neoplasia in whom WLE and subsequent AFI were both normal). The sensitivity of AFI and WLE for the detection of patients with neoplasia was 75% and 50% respectively (p = 0.580). The positive predictive values were 21% and 12% respectively (p = 0.470). The Kudo classification based on NBI for predicting histological outcome of detected lesions had a sensitivity of 75%, specificity of 80%, positive predictive value of 43% and negative predictive value (NPV) of 94%. A detected lesion which was green with AFI never revealed neoplasia. Conclusion: The use of ETMI in patients with UC is feasible, provided that the colon is properly prepared and the mucosa is not actively inflamed. In this pilot study, the sensitivity of AFI seems to be better than WLE for the detection of neoplasia, but the small sample size of our study prevents drawing any firm conclusion. Once a lesion has been detected, ETMI has a high NPV for histology.

Evolution and motions of small-scale photospheric structures near a large solar pore

The analysis of an 11-hour series of high resolution white light observations of a large pore in the sunspot group NOAA 7519, observed on 5 June 1993 at the áSwedish Vacuum Solar Telescope, La Palma, Canary Islands, is described. We used a total of 1782 frames, with average time interval of 22 s. Special attention was paid to the áevolution of a filamentary region attached to the pore, to horizontal motions around the pore, and to small-scale morphological changes. The filamentary region was observed to change its structure back and forth between penumbra-like filaments and elongated granules. A clockwise rotation of this region around the center of the pore was detected during the whole observing period. This rotation had angular velocities decreasing with time from 7.6° h-1 to 2.7° h-1. Motions inside the filamentary region and around the pore, including penetrations of photospheric granules into the pore, were studied in detail using local correlation and feature tracking algorithms. It was found that the observed filamentary region, although having some typical penumbral features, was different from a normal penumbra.

Center to limb variation of solar granulation

From high resolution white light photographs it is determined that the surface density of solar granulation decreases towards limb. A schematic model is proposed to interpret both decrease of surface density and size of granules in the upper photosphere.