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Radiation Detectors for Area (Ambient) Monitoring
Published in K. N. Govinda Rajan, Radiation Safety in Radiation Oncology, 2017
The above two designs are the most popular designs for a neutron survey meter. The cylindrical design, with CH2 moderator and a perforated 10B loaded layer, is by Andersson and Braun. It has a central BF3 PC. The spherical design, with CH2 moderator and perforated Cd layer, by Leake, is of spherical design with a centrally placed spherical 3He gas PC (or thermal neutron detector). The design overresponds to the intermediate energy response, so a thermal neutron absorber with perforations to limit the thermal fluence to the required extent is placed at an intermediate depth in the moderator. The highest neutron energy that can be thermalized depends on the dimensions of the moderator. The commercially available survey meters have a radius of 8 to 10 inches which is adequate for surveying linac rooms for neutron levels.
Contact lenses
Published in Pablo Artal, Handbook of Visual Optics, 2017
The original corneal, or hard, contact lenses were made from PMMA, a relatively stiff material that would not warp or distort from the eyelid and tear film pressures inherent in contact lens wear. However, as manufacturers developed new oxygen permeable rigid lens materials, particularly those containing silicone, the stiffness of the materials decreased to the point that clinicians were noticing changes in the astigmatic correction of patients over time (Stevenson 1991, Carney et al. 1997). Patients whose corneal and refractive astigmatism was corrected using a spherical design RGP lens found that their vision were degrading over time, and clinicians were finding that the silicone-containing rigid lenses were deforming to partially match the astigmatic corneal shape, losing their ability to “mask” the corneal and refractive astigmatism of the patient’s eye. Clinicians found that increasing the thickness of the lens provided a solution for some patients, but this often reduced the true benefit of silicon containing rigid lens materials—increased oxygen permeability and better physiology. Fortunately, manufacturers were able to improve their formulations and include fluorine in their formulations, which improved the stiffness and the wettability of the materials while also improving the oxygen permeability. The vast majority of material used in RGP (corneal) and scleral lenses today is fluorosilicone acrylate. This has essentially eliminated the problem of lens flexure for the majority of patients.
Recent advances in stent-assisted coiling of cerebral aneurysms
Published in Expert Review of Medical Devices, 2020
Soliman Oushy, Lorenzo Rinaldo, Waleed Brinjikji, Harry Cloft, Giuseppe Lanzino
The Contour device (Cerus Endovascular Inc, Fremont, CA, USA) is a self-expanding, intrasaccular flow diverter specifically targeting the neck of intracranial aneurysms. The Contour is constructed from braided nitinol and platinum memory mesh. In contrast to the spherical design of the WEB, the Contour’s hemispheric shape targets the aneurysm neck only, minimizing intrasaccular manipulation of the dome, and facilitating treatment of aneurysms with complex morphology not amenable to WEB placement. Furthermore, dual antiplatelet therapy is not required for treatment. The device is compatible with a 0.027” inner diameter microcatheter and comes in four sizes for treatment of aneurysms measuring 2 mm – 8.5 mm in diameter. The device is not approved by the FDA for clinical use in the United States.
Similar polyethylene wear between cemented and cementless Oxford medial UKA: a 5-year follow-up randomized controlled trial on 79 patients using radiostereometry
Published in Acta Orthopaedica, 2019
Kristian Horsager, Frank Madsen, Anders Odgaard, Claus Fink Jepsen, Lone Rømer, Per Wagner Kristensen, Bart L Kaptein, Kjeld Søballe, Maiken Stilling
Bearing overhang and impingement against the vertical wall were approximated using the femorotibial contact point, as the bearing is not visible on the stereoradiographs. The femorotibial contact point was defined from the projected mJSW line and reflects the center position of the bearing (Figure 3). This is allowed because of the spherical design of the femoral component and the fully congruent bearing. Overhang was noted when the distance between the femorotibial contact point and the most medial, anterior, or posterior edge of the tibial component was less than the corresponding dimensions of the bearing. Impingement against the vertical wall was noted when the mediolateral distance between the femorotibial contact point and the vertical wall was less than half the width of the bearing (Horsager et al. 2018).
Twenty years of silicone hydrogel contact lenses: a personal perspective
Published in Clinical and Experimental Optometry, 2020
After more than a decade of intensive research and development, two spherical‐design silicone hydrogel contact lenses were introduced into the market around the dawn of the millennium – Focus Night & Day (CIBA Vision) and PureVision (Bausch & Lomb).2018 Actually, this was a phased release; these lenses were made available to select practitioners on a limited basis in 1998 in some countries, followed by release in the USA in 2001 (after Food and Drug Administration approval in October that year), culminating in world‐wide availability in 2002. This year (2020) can therefore be considered to be approximately the 20th anniversary of the introduction of silicone hydrogel contact lenses.