6.1 Proyectos de investigación científica

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https://hdl.handle.net/20.500.12390/383

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Examinando 6.1 Proyectos de investigación científica por Autor "rp00075"
  • Publicación
    Attenuation coefficient estimation of the healthy human thyroid in vivo
    (Elsevier, 2015)
    Rouyer J.
    ;
    Cueva T.
    ;
    Portal A.
    ;
    Yamamoto T.
    ;
    Lavarello R.
    Previous studies have demonstrated that attenuation coefficients can be useful towards characterizing thyroid tissues. In this work, ultrasonic attenuation coefficients were estimated from healthy human thyroids in vivo using a clinical scanner. The selected subjects were five young, healthy volunteers (age: 26 ± 6 years old, gender: three females, two males) with no reported history of thyroid diseases, no palpable thyroid nodules, no smoking habits, and body mass index less than 30 kg/m2. Echographic examinations were conducted by a trained sonographer using a SonixTouch system (Ultrasonix Medical Corporation, Richmond, BC) equipped with an L14-5 linear transducer array (nominal center frequency of 10 MHz, transducer footprint of 3.8 cm). Radiofrequency data corresponding to the collected echographic images in both transverse and longitudinal views were digitized at a sampling rate of 40 MHz and processed with Matlab codes (MathWorks, Natick, MA) to estimate attenuation coefficients using the spectral log difference method. The estimation was performed using an analysis bandwidth spanning from 4.0 to 9.0 MHz. The average value of the estimated ultrasonic attenuation coefficients was equal to 1.34 ± 0.15 dB/(cm.MHz). The standard deviation of the estimated average attenuation coefficient across different volunteers suggests a non-negligible inter-subject variability in the ultrasonic attenuation coefficient of the human thyroid.
  • Publicación
    In Vivo Estimation of Attenuation and Backscatter Coefficients From Human Thyroids
    (Institute of Electrical and Electronics Engineers, 2016)
    Rouyer, J
    ;
    Cueva, T
    ;
    Yamamoto, T
    ;
    Portal, A
    ;
    Lavarello, RJ
    Fine-needle aspiration (FNA) remains the gold standard for the diagnosis of thyroid cancer. However, currently, a large number of FNA biopsies result in negative or undetermined diagnosis, which suggests that better noninvasive tools are needed for the clinical management of thyroid cancer. Spectral-based quantitative ultrasound (QUS) characterizations may offer a better diagnostic management as previously demonstrated in mouse cancer models ex vivo. As a first step toward understanding the potential of QUS markers for thyroid disease management, this paper deals with the spectral-based QUS estimation of healthy human thyroids in vivo. Twenty volunteers were inspected by a trained radiologist using two ultrasonic imaging systems, which allowed them to acquire radio-frequency data spanning the 3-16-MHz frequency range. Estimates of attenuation coefficient slope (ACS) using the spectral logarithmic difference method had an average value of 1.69 dB/(cm·MHz) with a standard deviation of 0.28 dB/cm·MHz. Estimates of backscatter coefficient (BSC) using the reference-phantom method had an average value of 0.18 sr -1 · cm -1 over the useful frequency range. The intersubject variability when estimating BSCs was less than 1.5 dB over the analysis frequency range. Further, the effectiveness of three scattering models (i.e., fluid sphere, Gaussian, and exponential form factors) when fitting the experimentally estimated BSCs was assessed. The exponential form factor was found to provide the best overall goodness of fit (R 2 = 0.917), followed by the Gaussian (R 2 = 0.807) and the fluid-sphere models (R 2 = 0.752). For all scattering models used in this study, average estimates of the effective scatterer diameter were between 44 and 56 μm. Overall, an excellent agreement in the estimated attenuation and BSCs with both scanners was exhibited.