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Publications

2018

3D mapping of choroidal thickness from OCT B-scans

Authors
Faria, SP; Penas, S; Mendonca, L; Silva, JA; Mendonca, AM;

Publication
Lecture Notes in Computational Vision and Biomechanics

Abstract
The choroid is the middle layer of the eye globe located between the retina and the sclera. It is proven that choroidal thickness is a sign of multiple eye diseases. Optical Coherence Tomography (OCT) is an imaging technique that allows the visualization of tomographic images of near surface tissues like those in the eye globe. The automatic calculation of the choroidal thickness reduces the subjectivity of manual image analysis as well as the time of large scale measurements. In this paper, a method for the automatic estimation of the choroidal thickness from OCT images is presented. The pre-processing of the images is focused on noise reduction, shadow removal and contrast adjustment. The inner and outer boundaries of the choroid are delineated sequentially, resorting to a minimum path algorithm supported by new dedicated cost matrices. The choroidal thickness is given by the distance between the two boundaries. The data are then interpolated and mapped to an infrared image of the eye fundus. The method was evaluated by calculating the error as the distance from the automatically estimated boundaries to the boundaries delineated by an ophthalmologist. The error of the automatic segmentation was low and comparable to the differences between manual segmentations from different ophthalmologists. © 2018, Springer International Publishing AG.

2018

Calculation and mapping of choroidal thickness in OCT images

Authors
Mendonca, L; Faria, S; Penas, S; Silva, J; Mendonca, AM;

Publication
INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE

Abstract

2015

Rehab@home: A tool for home-based motor function rehabilitation

Authors
Faria, C; Silva, J; Campilho, A;

Publication
Disability and Rehabilitation: Assistive Technology

Abstract
Purpose: This paper presents the Rehab@home system, a tool specifically developed for helping neurological patients performing rehabilitation exercises at home, without the presence of a physiotherapist. It is centred on the rehabilitation of balance and on the sit-to-stand (STS) movement. Method: Rehab@home is composed of two Wii balance boards, a webcam and a computer, and it has two main software applications: one for patients to perform rehabilitation exercises and another one for therapists to visualize the data of the exercises. During the exercises, data from the boards and the webcam are processed in order to automatically assess the correctness of movements. Results: Rehab@home provides exercises for the rehabilitation of balance (in sitting and in standing positions), and for the execution of the STS movement. It gives automatic feedback to the patient and data are saved for future analysis. The therapist is able to adapt the difficulty of the exercises to match with each patient's needs. A preliminary study with seven patients was conducted for evaluating their feedback. They appreciated using the system and felt the exercises more engaging than conventional therapy. Conclusions: Feedback from patients gives the hope that Rehab@home can become a great tool for complementing their rehabilitation process.Implications for RehabilitationRehab@home can be used at home by patients with motor deficits, without the presence of a therapist, as a complement to conventional therapy for accelerating the rehabilitation process.The system provides exercises for improving the balance and the STS movement capabilities of patients, gives automatic feedback, and saves video and load information from the movements for future analysis by the therapist.Its most important feature is adaptability: the therapist is able to tune the difficulty of the exercises for adapting them to the needs of each patient.Patients get more engaged for this type of exercises and think they can take profit from using it.

2014

Automatic detection of the carotid lumen axis in B-mode ultrasound images

Authors
Rocha, R; Silva, J; Campilho, A;

Publication
COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE

Abstract
A new approach is introduced for the automatic detection of the lumen axis of the common carotid artery in B-mode ultrasound images. The image is smoothed using a Gaussian filter and then a dynamic programming scheme extracts the dominant paths of local minima of the intensity and the dominant paths of local maxima of the gradient magnitude with the gradient pointing downwards. Since these paths are possible estimates of the lumen axis and the far wall of a blood vessel, respectively, they are grouped together into pairs. Then, a pattern of two features is computed from each pair of paths and used as input to a linear discriminant classifier in order to select the pair of paths that correspond to the common carotid artery. The estimated lumen axis is the path of local minima of the intensity that belongs to the selected pair of paths. The proposed method is suited to real time processing, no user interaction is required and the number of parameters is minimal and easy to determine. The validation was performed using two datasets, with a total of 199 images, and has shown a success rate of 99.5% (100% if only the carotid regions for which a ground truth is available are considered). The datasets have a large diversity of images, including cases of arteries with plaque and images with heavy noise, text or other graphical markings inside the artery region.

2014

Segmentation of carotid ultrasound images

Authors
Rocha, R; Silva, J; Campilho, A;

Publication
Multi-Modality Atherosclerosis Imaging and Diagnosis

Abstract
This chapter surveys methodologies for the segmentation of carotid ultrasound images and describes a method for the semiautomatic detection of the lumen-intima and the media-adventitia interfaces of the near and far common carotid wall. The approach is based on feature extraction, fitting of cubic splines, dynamic programming, smooth intensity thresholding surfaces, and geometric snakes. A set of 47 B-mode images of the common carotid were used to assess the performance of the method. The detection errors are similar to the ones observed in manual segmentations for 95% of the far wall interfaces and 73% of the near wall interfaces. © 2014 Springer Science+Business Media, LLC. All rights are reserved.

Supervised
thesis

2017

Quantitative assessment of Central Serous Chorioretinopathy in Angiographic sequences of retinal images

Author
Carlos Alexandre Nunes Ferreira

Institution
UP-FEUP

2016

Estimation of choroidal thickness in OCT images

Author
Simão Pedro Marques Pinto de Faria

Institution
UP-FEUP

2015

3D reconstruction from multiple RGB-D images with different perspectives

Author
Mário André Pinto Ferraz de Aguiar

Institution
UP-FEUP