Transducers and beam forming
Peter R Hoskins, Kevin Martin, Abigail Thrush in Diagnostic Ultrasound, 2019
The scanning technique described so far is commonly referred to as ‘line-by-line’ scanning, since, for each image line, the transmit pulse must travel to the deepest part of the image and the echo return to the transducer before the next pulse is transmitted. The go and return time for each image line is determined by the speed of sound in the tissue and this leads to compromises between three competing qualities: Temporal resolutionSize of the field of viewImage quality (e.g. lateral resolution, contrast resolution, dynamic range)
Introduction to Multi-Atlas Auto-Segmentation
Jinzhong Yang, Gregory C. Sharp, Mark J. Gooding in Auto-Segmentation for Radiation Oncology, 2021
There is little research on the effect of image quality on atlas-base segmentation, but it is widely believed that atlas image quality should match the quality of the query images. There are many aspects to image quality: slice thickness, longitudinal and transaxial field of view, presence of contrast, immobilization, truncation, metal artifacts, and more. There is a similar lack of research on the effect of segmentation quality within the database. However, there are community guidelines for maximizing the quality of the segmentation: adherence to professional standards, consensus results from multiple observers, and quality assurance. Furthermore, it is possible to perform statistical analysis of segmentation results to detect outliers [7]. Unfortunately, the database designer must also consider the thorny questions of missing segmentations, segmentations that abut or intersect anatomic abnormalities, and segmentations that lie near the image boundary. Opinions are mixed as to whether these should be included as a means of database enrichment or should be excluded to prevent them from being selected inappropriately. Chapter 14 discusses additional concerns for data curation, albeit with a focus on deep learning methods
Gastrointestinal and hepatobiliary
Dave Maudgil, Anthony Watkinson in The Essential Guide to the New FRCR Part 2A and Radiology Boards, 2017
Are the following statements regarding MRI of the abdomen and pelvis true or false? Out of phase T1-weighted imaging is useful in the diagnosis of fatty liver.HASTE is typically a T1-weighted sequence.Fat suppression is superior without gadolinium enhancement for the detection of pathology.Motion artefact is more pronounced in the phase-encoding direction.Reduction of the field of view improves spatial resolution.
Immersive Virtual Reality and Persons with Dementia: A Literature Review
Published in Journal of Gerontological Social Work, 2020
As new VR systems are released, the tendency is toward increased field of view over previous efforts. The field of view is an important consideration in this technology because it affects the extent to which the human binocular visual field is filled by the video. Field of view is commonly defined as the extent to which binocular vision extends, horizontally and vertically, at a fixed moment in time – i.e. without eye or head movement. Field of reference is a related term and is concerned with the extent of binocular vision with head and eye movement; it has important implications in VR, but is not discussed at length here because all modern VR headset systems are capable of omnidirectional output. The human binocular field of view, as determined by Traquair (1949), is roughly oval in shape, extending to approximately 200° across the horizontal, and approximately 130° along the vertical. Field of view in VR systems that approach natural human binocular vision increases the fidelity of the system, or the extent to which a virtual environment mimics a real space (Dahai, Machiarella, & Vincenzi, 2009). The more completely the human field of vision is occupied by the VR environment, the more immersive the technology, ultimately leading to a greater sense of presence for the user.
Roughness effects of diatomaceous slime fouling on turbulent boundary layer hydrodynamics
Published in Biofouling, 2018
Elizabeth A. K. Murphy, Julio M. Barros, Michael P. Schultz, Karen A. Flack, Cecily N. Steppe, Matthew A. Reidenbach
Particle image velocimetry (PIV) was used to capture the flow field in the streamwise - wall-normal dt, between the image-pairs was 250 μs. The time-delayed images were interrogated using a recursive two-frame cross-correlation methodology, with a final pass of 322 pixels with 50% overlap to satisfy the Nyquist sampling criterion (Insight 4G version 11). Statistical validation tools were employed to identify and replace erroneous vectors, including the replacement with displacement assessed from secondary peaks from the correlation map identified during the interrogation process. All instantaneous fields were then low-pass filtered with a narrow Gaussian filter to remove high-frequency noise. On average, between 1% and 2% of the velocity vectors were erroneous and therefore removed and interpolated across. A total of 4,000 statistically independent instantaneous velocity fields were acquired. The field-of-view (FOV) was
Arterial Stiffness and Cardiorespiratory Fitness Are Associated With Cognitive Function in Older Adults
Published in Behavioral Medicine, 2022
Justin R. Mason, Gershon Tenenbaum, Salvador Jaime, Nelson Roque, Arun Maharaj, Arturo Figueroa
The neuropsychological tests were performed on a 15-inch touchscreen monitor with a display refresh rate of 60 Hz positioned at ≈60 cm distance from the participant’s eyes. Simple and choice reaction time were recorded via the Deary-Liewald task.38 The mental rotation test and Stroop test were run using E-Prime (Psychology Software Tools, Inc.) and Psychology Experiment Building Language,39 respectively. The cognitive battery took approximately 2 hours to complete and tests were provided in the following order: (a) simple reaction time, evaluating processing speed; (b) choice reaction time, evaluating psychomotor speed; (c) Useful Field of View®, evaluating processing speed, divided attention, and selective attention; (d) Trail Making Test part A, evaluating visual scanning and psychomotor speed; (e) Trail Making Test part B, evaluating cognitive flexibility of executive function; (f) mental rotation test, evaluating figural spatial skill; and (g) Stroop test, evaluating inhibition control and selective attention (see Supplementary File 1 for description of cognitive assessments and screening measures).38,40–44
Related Knowledge Centers
- Color Vision
- Eye
- Stereopsis
- Visual Perception
- Binocular Vision
- Depth Perception
- Optical Instrument
- Angle of View
- Visual Field
- Species