Mr. Diego Bravo Higuera Profile

Diego Bravo Higuera

at Univ Nacional de Colombia Bogota

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Publications (3)

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Proceedings Article | 16 March 2020 Paper

Automatic polyp detection and localization during colonoscopy using convolutional neural networks

Diego Bravo, Josue Ruano, Martín Gómez, Eduardo Romero

Proceedings Volume 11314, 113143A (2020) https://doi.org/10.1117/12.2549736

KEYWORDS: Video, Databases, Image segmentation, Convolutional neural networks, Colon

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A computer-aided detection (CAD) second reader of colorectal polyps can decrease the rate of missed polyps in actual colonoscopy procedures. Currently, regular screening of colorectal cancer (CRC) demands a colonoscopy procedure during which polyps are located and removed. Unfortunately, different investigations have reported 22%-28% of polyps and 20%-24% of adenomatous polyps are missed. The adenoma detection rate (ADR) is a colonoscopy quality indicator highly dependent on expert training, spent time, device withdrawal technique, colon preparation and procedure-dependent factors. Several approaches have improved ADR, namely image enhancement, advancements in endoscope design and developments of accessories. Recently, artificial intelligence (AI) has shown potential to aid the task of polyp detection. This paper introduces an automatic detection of polyps that localize hyperplastic and adenomatous colorectal polyps in colonoscopy images and full video sequences. The proposed pipeline is achieved by two sequentially encoder-decoder Convolutional Neural Networks: The first detects frames with high probability of having polyps and the second estimates the actual location of the polyp. Detection of polyps showed an Annotated Area Covered AAC = 0.889 and IoU = 0.816 in actual colonoscopy images containing at least a polyp. In addition, in colonoscopy videos achieved a 0.63, 0.85, 0.65 of precision, specificity, and F1-score respectively for the ASU-Mayo database.

Proceedings Article | 3 January 2020 Paper

Automatic polyp localization by low level superpixel features

Diego Bravo, Josué Ruano, Martín Gómez, Eduardo Romero

Proceedings Volume 11330, 1133017 (2020) https://doi.org/10.1117/12.2542583

KEYWORDS: Image segmentation, Modulation, Colorectal cancer, Error control coding, Colon

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Colorectal cancer (CRC) is a major public health issue by its high incidence and mortality rate. CRC appears as premalignant lesions growing in the endoluminal wall, called polyps. Currently, a regular screening of CRC during a colonoscopy is the standard procedure to localize and treat polyps. However, evidence suggests 20% - 24% of adenomatous polyps may be missed during a routine colonoscopy. A limited adenoma detection (ADRs) is obtained because colon exploration is a very challenging task: it is highly dependent on the expert training and colon preparation. Hence, a second reader is required to support CRC screening. This paper presents a novel automatic computer-aided method to localize polyps in colonoscopy images. The method starts by segmenting an input frame into a set of superpixels, each of them characterized by concatenating color, texture, and shape features computed either locally, i.e., basic local statistics, or regionally, i.e., any measure is modulated by information in neighboring superpixels. Afterward, this representation feeds a classifier which sets a probability and a polyp is a group of superpixels with high assigned probability. Finally, the resultant groups were enclosed by a bounding box which corresponds to the colorectal polyp localization. The proposed approach was trained with 200 polyps (350 images) and tested with 86 polyps (236 images) of different size. Performance of our method was compared with a baseline based on deep CNN obtaining an average of Annotated Area Covered of 0.90 vs 0.89 and a precision of 0.96 vs 0.95 respectively.

Proceedings Article | 21 December 2018 Paper

Automatic detection of colorectal polyps larger than 5 mm during colonoscopy procedures using visual descriptors

Diego Bravo, Josué Ruano, Martín Gómez, Eduardo Romero

Proceedings Volume 10975, 109750E (2018) https://doi.org/10.1117/12.2511577

KEYWORDS: Video, Visualization, Databases, RGB color model, Specular reflections, Image processing, Error control coding, Tissues, Convolutional neural networks, Binary data

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New evidence suggests 25% - 26% of colon polyps may be missed during a routine colonoscopy[1, 2, 3, 4, 5]. These polyps or hyperplastic lesions are currently considered as pre-neoplastic lesions that must be detected. In this context, automatic strategies are appealing as second readers or diagnostic supporting tools. However, this task is challenging because of the huge variability and multiple sources of noise. This paper introduces a strategy for automatic detection of polyps larger than 5 mm. The underlying idea is that polyps in a sequence of frames are those locations with smaller frame-to-frame variance. The method starts by segmenting an input frame into a set of superpixels, i.e., clusters of neighbor pixels with minimal luminance variance. Each of these superpixels in characterized by a concatenated vector of 57 features collecting texture, shape, and color. A Support Vector Machine with a linear and Radial Basis Function (RBF) kernel was used as a supervised learning model. The evaluation was carried out using a set of 39 cases belonging to two datasets (6.594 frames: 3.123 with polyps and 3.471 without polyps) under a Leave-One-Out Cross Validation scheme and obtaining a 0.73 of accuracy. In addition, the data set was split into 70%-30% between train and test respectively and obtaining a 0.87 of accuracy.

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