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Toward Clinically Viable Ultrasound-Augmented Laparoscopic Visualization
Published in Terry M. Peters, Cristian A. Linte, Ziv Yaniv, Jacqueline Williams, Mixed and Augmented Reality in Medicine, 2018
The system involved a conventional 2D laparoscopic camera with a 0º, 5-mm scope, and an EM tracking system as described in Section 13.3.2. An EM sensor was mounted on the laparoscope similarly to that shown in Figure 13.3. Perceive3D’s (Coimbra, Portugal) API based on the single-image calibration (SIC) method (Melo et al. 2012; Barreto et al. 2009) was used. The API features automatic corner detection and calibration of camera intrinsic parameters and lens distortion from a single image of an arbitrary portion of a special calibration pattern. Compared to using the conventional checkerboard pattern, more corners, especially on image periphery, can be detected. This helps better estimate lens distortion. Based on the SIC calibration results, hand-eye calibration was obtained using OpenCV.
3D liquid scintillation dosimetry for photons and protons
Published in Sam Beddar, Luc Beaulieu, Scintillation Dosimetry, 2018
In addition to perspective and image blurring, the lens introduces distortions and vignetting to the image. Lens distortion is a nonlinear mapping between object space and image space. It is primarily radial because of the radial symmetry of the lens system. However, it can include tangential components. The most common forms of lens distortion are barrel distortion, in which the image magnification decreases with distance from the image center (Figure 15.8a), and pincushion distortion, in which the magnification increases with distance from the image center (Figure 15.8b).
Methodological considerations for kinematic analysis of upper limbs in healthy and poststroke adults Part II: a systematic review of motion capture systems and kinematic metrics
Published in Topics in Stroke Rehabilitation, 2019
Inês Albuquerque Mesquita, Pedro Filipe Pereira da Fonseca, Ana Rita Vieira Pinheiro, Miguel Fernando Paiva Velhote Correia, Cláudia Isabel Costa da Silva
First, most of the articles used optoelectronic systems (with passive markers), possibly because this type of system is more widespread, is accurate, and presents the best relation between the advantages and the limitations regarding its use, when comparing with other systems14,17 However, the laboratory and task-specific error assessments to guarantee the control of whole measurement process34 are missing in most of the reviewed studies, which can compromise their validity and comparison between them. Actually, the data of optoelectronic systems could suffer from a number of inaccuracy sources, collectively termed instrumental errors,16 due to the use of a camera-based approach which has been found to be dependent on: the number and position of the cameras,35,36 their lens distortion,37 the dimension of the capture volume,38 and the algorithms used for the reconstruction of a marker’s 3D position.39 The number of cameras was the only referred factor to be mentioned by most authors, with the exception of the study of Chen et al.21 Position of the cameras was only referred in the study of Murphy et al.11 Eichelberger et al.34 advocated that instrumental errors should also be determined and documented relative to various task-specific movement protocols to guarantee a high-quality research. Therefore, according to these recommendations,34,35,38 future research should evaluate the system-specific error in the laboratory and for the task performed, presenting that data.
Advances in technologies for cervical cancer detection in low-resource settings
Published in Expert Review of Molecular Diagnostics, 2019
Kathryn A. Kundrod, Chelsey A. Smith, Brady Hunt, Richard A. Schwarz, Kathleen Schmeler, Rebecca Richards-Kortum
In initial studies, the POCkeT Colposcope showed comparable performance to commercially available colposcopes in terms of resolving power, color reproduction accuracy, lens distortion, and illumination [120]. Earliest designs of the POCkeT Colposcope faced challenges with specular reflection, illumination uniformity, and fogging effects; however, subsequent designs have improved each of these areas [121]. A small-scale clinical evaluation of the POCkeT colposcope demonstrated fair agreement in physician interpretation of images acquired with both standard and POCkeT colposcopes [118].