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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 traditional instrument used to measure the optical density of a film is called a densitometer. More complex scanning densitometers or flatbed scanners are now commonly used and will be described later.
Radiographic Absorptiometry (Photodensitometry)
Published in Stanton H. Cohn, Non-Invasive Measurements of Bone Mass and Their Clinical Application, 2020
Charles Colbert, Richard S. Bachtell
Radiographic absorptiometry,1-3 or photodensitometry, is one of several sensitive, noninvasive, quantitative methods used to assess bone mineral changes. In the system developed at the Radiological Research Laboratory (RRL) of Greene Memorial Hospital, the X-ray image is divided into an array of cells (pixels), each of which has a distinctive optical density (grey level). A computer-controlled densitometer scans the X-ray image with a light beam, and the data are analyzed by computer for the determination of bone mineral density. The term mineral concentration, used by Doyle,4 is preferred to bone mineral density, as it avoids confusion with gravimetric density (wt/vol); however, as the term bone mineral density is so widely used, it will also be used in this chapter. In other systems, the image is probed with a fixed pencil-beam, rather than scanned.
The presentation and management of physical disease in older people
Published in David Beales, Michael Denham, Alistair Tulloch, Community Care of Older People, 2018
Early in the disease, formal assessment of bone mass using a densitometer is the only reliable current method. Later, plain X-rays, especially of the spine and hips can provide semi-quantitative evidence (especially examining the trabecular lines in the hips). Finally, in the late stages, vertebral collapse with kyphosis (the dowager’s hump) become obvious.
Enabling faster subcutaneous delivery of larger volume, high viscosity fluids
Published in Expert Opinion on Drug Delivery, 2022
Christopher J. Rini, Bruce C. Roberts, Aishwarya Vaidyanathan, Aojun Li, Rick Klug, Douglas B. Sherman, Ronald J. Pettis
Commercial radiographic contrast media without formulation modification were used to investigate lower range viscosity solutions at nominal viscosities of 2.3 cP, 5.8 cP, 11.8 cP, and 20.4 cP at 20°C (Omnipaque™ 140 mg, 240 mg, 300 mg, and 350 mg iodine/mL, respectively; GE Healthcare, Oslo, Norway). Custom contrast injection solutions were formulated to examine higher injectate viscosities (30 cP, 40 cP, and 50 cP) using iohexol contrast (reagent grade, Sigma-Aldrich Histodenz™) with dextran (Dextran 40 MW 40,000, pharmaceutical grade, Pharmacosmos, Holbaek, Denmark) as a viscosity modifier. Rheological characterization of solution viscosity across shear rates was completed by Brookfield LVDV III+ rheometer (AMATEK Brookfield, Middleborough, MA, USA) at 20°C using a CPE-40 spindle; actual measured viscosities reported (Table 2). Solution density measurements were completed using a DMA 4500 M densitometer (Anton Paar, Graz, Austria) at 20°C. Syringes were manually filled with 2.0-mL contrast solution by positive displacement pipette, vacuum stoppered, and evaluated using a visual gauge to confirm a ± 5% fill accuracy.
Supplementation with macular carotenoids reduces psychological stress, serum cortisol, and sub-optimal symptoms of physical and emotional health in young adults
Published in Nutritional Neuroscience, 2018
Nicole Tressa Stringham, Philip V. Holmes, James M. Stringham
The concentration of MCs in the central retina (MPOD) was assessed with a non-invasive, perceptual task called heterochromatic flicker photometry (HFP). A densitometer (Macular Metrics Corp., Rehoboth, MA) described by Wooten et al.40 was used for this purpose. The densitometer, detailed measurement procedures, and the principle of HFP have been fully described in earlier publications.41,42 Briefly, subjects are presented with two superimposed lights that are temporally alternated in square-wave counterphase. This gives the subject an impression on a flickering disc of light. The peak (550 nm) of the spectral composition of one of the lights is chosen to bypass the absorption of MP, and the other (460 nm) is strongly absorbed by MP. The subject's task is to adjust the relative radiance of the two lights until a percept of no flicker is achieved. All other factors being equal, a subject that requires more short-wave (i.e. 460 nm) relative to middle-wave (i.e. 550 nm) light to achieve null flicker has higher MPOD. This task is performed for the locations of interest within the fovea, which presumably contain MP, and for a reference location in the parafovea that does not (about 7° eccentricity). To obtain a measure of MPOD at a given test locus, the logarithmic ratio of short- to middle-wave radiance (for null flicker) at the reference location is subtracted from the corresponding logarithmic ratio found at the test locus.
Optimization and development of antidiabetic phytosomes by the Box–Behnken design
Published in Journal of Liposome Research, 2018
The experiments were performed at a temperature of 22 °C and 55% humidity in controlled conditions. Precoated silica gel HPTLC plates (E-Merck, Darmstadt, Germany) were used for chromatographic separation. Five microliters of extract was spotted with the help of the auto sampler. The chromatogram was run using solvent system of ethyl acetate:formic acid:glacial acetic acid:water (100:11:11:26). The resulted plates were air dried and scanned. A spectro-densitometer (Scanner 3, CAMAG) was employed for the densitometry measurements, spectra recording and data processing. The chromatograms were recorded at the wavelength of 254 and 366 nm. The retention factor (Rf) value of each compound separated on plate and data of peak area of each band were documented.