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  • 1. Figueiredo, I. N.
    et al.
    Leal, C.
    Pinto, L.
    Figueiredo, P. N.
    Tsai, R.
    KTH. Department of Mathematics and the Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, United States.
    Hybrid multiscale affine and elastic image registration approach towards wireless capsule endoscope localization2018In: Biomedical Signal Processing and Control, ISSN 1746-8094, E-ISSN 1746-8108, Vol. 39, p. 486-502Article in journal (Refereed)
    Abstract [en]

    Wireless capsule endoscope (WCE) enables the visualization of the interior of the gastrointestinal (GI) tract. In particular it is very important for the examination of regions in the small bowel that cannot be reached by conventional endoscopy techniques. However, when an abnormality is found in WCE images of the small bowel, it is unknown how far is this abnormality from an anatomical reference point. The primary objective of the present paper is to give a contribution to WCE localization, using image-based methods. The main focus of this work is on the description of a hybrid multiscale affine and elastic image registration approach, its experimental application on WCE videos, and comparison with a multiscale affine registration. The proposed approach intends to track the WCE motion, by using the successive WCE frames that image the walls of the elastic small intestine. It includes registrations that capture both rigid-like and non-rigid deformations, due respectively to the rigid-like WCE movement and the elastic deformation of the small intestine originated by the GI peristaltic movement. Furthermore, the proposed approach enables the extraction of two parameters (scale and rotation) from which the relative displacement and orientation of the WCE inside the GI tract can be derived, via projective geometry. Under this approach an indicator of the WCE speed can be inferred, which can be clinically useful for video interpretation. The results of the experimental tests with real WCE video frames show the good performance of the proposed approach, when elastic deformations of the small intestine are involved in successive frames, and its superiority with respect to a multiscale affine image registration, which accounts for rigid-like deformations only and discards elastic deformations. 

  • 2.
    Figueiredo, Isabel N.
    et al.
    Univ Coimbra, CMUC, Dept Math, Fac Sci & Technol, Coimbra, Portugal..
    Pinto, Luis
    Univ Coimbra, CMUC, Dept Math, Fac Sci & Technol, Coimbra, Portugal..
    Figueiredo, Pedro N.
    Univ Coimbra, Fac Med, Coimbra, Portugal.;CHUC, Dept Gastroenterol, Coimbra, Portugal.;Ctr Cirurg Coimbra, Coimbra, Portugal..
    Tsai, Yen-Hsi Richard
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Numerical Analysis, NA. Univ Texas Austin, Dept Math, Austin, TX 78712 USA.;Univ Texas Austin, Oden Inst Computat Engn & Sci, Austin, TX 78712 USA..
    Unsupervised segmentation of colonic polyps in narrow-band imaging data based on manifold representation of images and Wasserstein distance2019In: Biomedical Signal Processing and Control, ISSN 1746-8094, E-ISSN 1746-8108, Vol. 53, article id UNSP 101577Article in journal (Refereed)
    Abstract [en]

    Colorectal cancer (CRC) is one of the most common cancers worldwide and after a certain age (>= 50) regular colonoscopy examination for CRC screening is highly recommended. One of the most prominent precursors of CRC are abnormal growths known as polyps. If a polyp is detected during colonoscopy examination the endoscopist needs to decide whether the polyp should be discarded, removed, or biopsied for further examination. However, the last two options involve some risks for the patient, while not all the polyps are precancerous. On the other hand, discarding a polyp has the risk of failing to detect CRC. We propose an automatic and unsupervised method for the segmentation of colonic polyps for in vivo Narrow-Band-Imaging (NBI) data. Polyp segmentation is a crucial step towards an automatic real-time polyp classification system, that could help the endoscopist in the diagnosis of CRC. The proposed method is a histogram based two-phase segmentation model, involving the Wasserstein distance. These histograms incorporate fused information about suitable image descriptors, namely semi-local texture, geometry and color. To test the proposed segmentation methodology we use a dataset consisting of 86 NBI polyp frames: the 83% sensitivity, 95% specificity, and 93% accuracy suggest a better performance compared to the results obtained with other methods.

  • 3.
    Händel, Peter
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Wahlström, J.
    Digital contraceptives based on basal body temperature measurements2019In: Biomedical Signal Processing and Control, ISSN 1746-8094, E-ISSN 1746-8108, Vol. 52, p. 141-151Article in journal (Refereed)
    Abstract [en]

    Digital contraceptives and fertility awareness products are currently offered as convenient smartphone applications. The first legitimate contraceptive smartphone app was recently introduced on the European market, with the digital processing based on measurements of the female user's basal body temperature (BBT). According to recent pilot market data, at some Swedish hospitals, up to 5–10% of women seeking abortion had become involuntarily pregnant while using the product. This fact motivates a review of the research on fertility determination based on BBT measurements. This paper provides the first estimation theoretical review and evaluation of BBT-based ovulation detection. From an engineering perspective, it is concluded that the available detection algorithms have similar performance and that the performance is rather insensitive to a one- or two-decimal resolution of the employed thermometer. Further, we highlight that when using the output from proposed ovulation detection algorithms, one must consider not only the uncertainty in the relative time difference of the detected temperature shift and the ovulation, but also the statistical uncertainty of the detection methods due to noisy measurements.

  • 4.
    Selamtzis, Andreas
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH.
    Castellana, Antonella
    Department of Electronics and Telecommunications, Politecnico di Torino, Italy.
    Salvi, Giampiero
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH.
    Carullo, Alessio
    Department of Electronics and Telecommunications, Politecnico di Torino, Italy.
    Astolfi, Arianna
    Department of Electronics and Telecommunications, Politecnico di Torino, Italy.
    Effect of vowel context in cepstral and entropy analysis of pathological voices2019In: Biomedical Signal Processing and Control, ISSN 1746-8094, E-ISSN 1746-8108, Vol. 47, p. 350-357Article in journal (Refereed)
    Abstract [en]

    This study investigates the effect of vowel context (excerpted from speech versus sustained) on two voice quality measures: the cepstral peak prominence smoothed (CPPS) and sample entropy (SampEn). Thirty-one dysphonic subjects with different types of organic dysphonia and thirty-one controls read a phonetically balanced text and phonated sustained [a:] vowels in comfortable pitch and loudness. All the [a:] vowels of the read text were excerpted by automatic speech recognition and phonetic (forced) alignment. CPPS and SampEn were calculated for all excerpted vowels of each subject, forming one distribution of CPPS and SampEn values per subject. The sustained vowels were analyzed using a 41 ms window, forming another distribution of CPPS and SampEn values per subject. Two speech-language pathologists performed a perceptual evaluation of the dysphonic subjects’ voice quality from the recorded text. The power of discriminating the dysphonic group from the controls for SampEn and CPPS was assessed for the excerpted and sustained vowels with the Receiver-Operator Characteristic (ROC) analysis. The best discrimination in terms of Area Under Curve (AUC) for CPPS occurred using the mean of the excerpted vowel distributions (AUC=0.85) and for SampEn using the 95th percentile of the sustained vowel distributions (AUC=0.84). CPPS and SampEn were found to be negatively correlated, and the largest correlation was found between the corresponding 95th percentiles of their distributions (Pearson, r=−0.83, p < 10−3). A strong correlation was also found between the 95th percentile of SampEn distributions and the perceptual quality of breathiness (Pearson, r=0.83, p < 10−3). The results suggest that depending on the acoustic voice quality measure, sustained vowels can be more effective than excerpted vowels for detecting dysphonia. Additionally, when using CPPS or SampEn there is an advantage of using the measures’ distributions rather than their average values.

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