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Radiometry
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
One of the earliest types of detectors is photographic film, which is an example of a chemical detector. The active material of the film consists of grains of silver bromide (AgBr) embedded in a thin emulsion. This emulsion is placed on a transparent base and covered with a protective coating. Upon irradiation with ionizing radiation (or light, as in conventional photography), a latent image is created. This latent image is then made visible by exposing the film to a chemical (developing) that reduces the exposed silver halides to metallic Ag. In order to make the film insensitive to further exposure, the image is fixed by a chemical that produces soluble salts with Ag ions in the remaining silver halide crystals. These salts are then removed when the film is rinsed.
Two-dimensional and Three-dimensional Dosimetry
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
Mark Oldham, Devon Godfrey, Titania Juang, Andrew Thomas
The primary strengths of silver halide radiographic film include high contrast (image quality), high spatial resolution and high sensitivity. The basic physical mechanisms of image formation and development are the same for both radiographic and photographic film. The active component of film consists of a gelatin emulsion, which suspends small radiation sensitive silver halide crystals* (e.g. silver bromide [AgBr]). The emulsion is evenly coated onto both sides of a polyester base, which provides the stiffness and mechanical stability of the film. Details of film manufacture and the active chemical ingredients can be found in Carlton and Adler (1996). Film can be used to measure dose distributions, but the accuracy is dependent on the performance and stability of the processor and the consistency between different films in the same batch. Absolute dose error may exceed 10% unless strict controls are imposed on the developing solutions.
Film Dosimetry
Published in Arash Darafsheh, Radiation Therapy Dosimetry: A Practical Handbook, 2021
Sina Mossahebi, Nazanin Hoshyar, Rao Khan, Arash Darafsheh
Interaction with radiation, ionizes the microscopic grains containing silver bromide; effectively converting ionic silver (Ag+) into silver (Ag) atoms. According to Gurney and Mott model of latent image formation [25], this happens in grains containing sensitive centers or ‘speck’. Electrons, which produced due to absorption of radiation in or around grain, make a sensitivity center negatively charged. Mobile silver Ag+ rushes to the sensitivity centers to neutralize and form an aggregate of metallic silver and hence the latent image on the film. Only a few metallic silvers primarily along the surface of the grain (containing around ten billion silver bromide) are enough to record the radiation signature.
Development of antibacterial composite resin containing chitosan/fluoride microparticles as pit and fissure sealant to prevent caries
Published in Journal of Oral Microbiology, 2022
Chun-Cheng Lai, Chun-Pin Lin, Yin-Lin Wang
Antibacterial substances have been considered as additions to fissure sealants to avoid secondary caries, such as bioglasses [8], nanoamorphous calcium phosphate [9], chlorhexidine-encapsulated nanotubes [10] or cationic nanocomposite containing silver bromide [11]. A systematic review assessed the antimicrobial effects of different antibacterial agents incorporated in resin-based dental sealants and revealed that those based on quaternary ammonium compounds stand out [12]. Therefore, Huang added dimethylaminododecyl methacrylate (DMADDM) to pit and fissure sealants and tried to achieve sustainable antibacterial effects [13]. Another antibacterial material frequently considered was that composed of fluoride [14–16]. The action of fluoride includes inhibition of demineralization, enhancement of remineralization, and bactericidal activity [17–20]. Most scientists have affirmative opinions on effects of decreased demineralization and increased remineralization. However, the bactericidal action is controversial. According to a hypothesis proposed by Li and Bowden [21], the bactericidal activity is due to the formation of hydrofluoric acid (HF) in the oral cavity and transported into cells. The pH value is altered, killing the bacteria. This explanation is paradoxical because the acid dissociation constant of HF is 3.14, and only 1% of fluoride converts to HF in the oral cavity, where the pH is 5. At present, a more convincing hypothesis is that fluoride has a repressive action on bacteria due to influence on enolase during glycolysis [22].
Inferior and Central Mound Pedicle Breast Reduction in Gigantomastia: A Safe Alternative?
Published in Journal of Investigative Surgery, 2021
Fatma Bilgen, Alper Ural, Mehmet Bekerecioğlu
Preoperative skin drawings were performed using a flexible keyhole pattern (made of silver bromide film) similar to the Wise and McKissock models while the patient was standing. First, the midline was determined by a straight line from sternal notch to the umbilicus. The clavicular point was then adjusted to 7.0–7.5 cm laterally from the midline. The mid-breast meridian was marked from the clavicular point to the NAC. The new nipple was placed 19–22 cm inferior from the clavicular point and the new areola was marked at this point with a diameter of 4–4.5 cm. The vertical length of the flap edges (vertical pillars) was planned as 7–8 cm. The divergence angle between the medial margins of the lateral flaps was generally determined to be 90° (Figure 1).