China
Africa
Explore chapters and articles related to this topic
Machines and Instrumentation
Published in Pradeep Venkatesh, Handbook of Vitreoretinal Surgery, 2023
Non-contact lenses are a little more complex and need to be integrated into the operating microscope or surgical field using separate supporting elements. The field of view is slightly narrower, and resolution is lesser [for fine macular surgery such as internal limiting membrane peeling]. Also, corneal dryness needs to be prevented by intermittent fluid jets. The major advantages with these lenses are the lack of dependency on an assistant and the ability to indent the retinal periphery more freely. Non-contact lenses can be manually or automatically swiveled into the viewing axis or moved away. Usually, two types of lenses are available, one for macular or posterior retinal surgery and one for the periphery. Some of the widely used non-contact inverter systems include Resight, AVI, Merlin, EBIOS, and BIOM. Resight has two versions based on the method used for operating these lenses, manual [RESIGHT 500] and electric [RESIGHT 700].
The Scintillation Camera
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
The imaging couch is constructed from a material with low attenuating properties, such as carbon fibre, to ensure its presence does not adversely affect the scintigraphic image. The couch should be sufficiently strong to avoid sagging when fully extended. For hybrid systems containing both SPECT and CT imaging modalities, a sub-pallet is often required to ensure sufficient support is available to further extend the imaging couch beyond the gamma camera field of view and into the CT gantry. The sub-pallet does not have the same low-attenuation properties of the imaging couch, and care should be taken to ensure it is not present within the imaging field of view during an acquisition.
3D Printing
Published in Takahiro Shiota, 3D Echocardiography, 2020
In general, image quality has the largest effect on model accuracy. Issues such as signal dropout, partial volume effects, and inadequate field of view affect anatomical accuracy. This means that an accurate model requires meticulous echocardiography image acquisition. Improved automatic multimodality imaging fusion will definitively allow the creation of whole heart models including leaflets and subvalvular apparatus.
Reliability of radiographic findings in large FOV CBCTs of mandibular third molars as basis for pre-operative patient information
Published in Acta Odontologica Scandinavica, 2022
Louise Hauge Matzen, Lars Schropp, Louise Hermann, Janne Ingerslev, Ann Wenzel
In the SEDENTEXCT guidelines published in 2012 [10], it was recommended to perform a CBCT of mandibular third molars to be removed when in doubt of the relation between the tooth and the mandibular canal. Because of an increased radiation dose to the patient, when using CBCT compared to merely a 2 D radiographic examination, it was furthermore recommended to use a small FOV for this purpose [10]. With a smaller FOV, the spatial resolution of the images is higher and therefore supposed to display more details. Based on recent years’ research, the European Academy of Dentomaxillofacial Radiology in 2019 published an updated guideline for CBCT examination of mandibular third molars [11] concluding that CBCT in general should not be the method of choice to assess the relationship between the tooth and the mandibular canal before removal of a third molar. In the updated guideline, size of FOV was not discussed, but the included studies in the paper had been conducted using small FOV CBCT exams [11]. In the present study, a large FOV CBCT examination was performed for 3 D treatment planning before orthognathic surgery and evaluated for the third molars as well. To obtain knowledge on diagnostic accuracy of large FOV CBCTs, these cases were selected for the present study, which had merely a radiographic focus.
Non-contact infrared assessment of human body temperature: The journal Temperature toolbox
Published in Temperature, 2021
Josh Foster, Alex Bruce Lloyd, George Havenith
Assuming a camera resolution of 640 by 480 pixels, a thermogram like that in Figure 1, with a field of view estimated at 300 mm wide, roughly has a size of 0.5 mm per pixel (2 pixels/mm). This meets the criteria set in IEC 80601-2-59 (2019) which suggests that for optimal analysis there should be at least 1 pixel per mm. This implies that several pixels will cover the inner(medial) canthus, as required, providing a reliable measurement for this area. However, when considering situations observed, e.g., at airports, cameras are often aimed at a stream of people rather than an individual’s face and cover a field of view with a width of several meters. Taking an example of 3 meters with the same camera and lens, each pixel covers around 4.5 mm (0.22 pixels/mm). Thus, no individual pixel will be representing only the inner eye-canthus, making the measurement more error prone. Budzan and Wyzgolik [23] observed a reduction of 1.6°C in their assessment of inner canthus temperature going from 1 to 3 meters distance (384 × 288-pixel uncooled FPA microbolometer camera). Lens angle is not provided, but field of view is estimated at 70 cm at 1 m (0.55 pixels/mm) to 140 cm at 2 m (0.28 pixels/mm). Note that neither of the conditions in this experiment meets the IEC advised 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.