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Thin-Layer Chromatography in Parasitology
Published in Bernard Fried, Joseph Sherma, Practical Thin-Layer Chromatography, 2017
The second above–cited quantification method, in situ densitometry, is of increasing current interest in TLC and has a large body of literature.65 A number of recent studies in parasitology have employed this method of quantification.26’29−44 Many compounds that can be detected in visible or ultraviolet light can be subjected to densitometric analysis. Suitable standards are required and should match the compounds of interest. TLC methods for in situ densitometry are similar to those of conventional TLC; however, greater care is needed in sample preparation and application, and choice of development system, detection reagents, and standards. The range of weights of standards used should bracket as closely as possible the weights of the compounds of interest in the applied samples. Densitometry is usually accomplished in the transmittance or reflection mode with a particular commercial densitometer. Considerable choice exists in the selection of densitometers, from simple models to automated instruments coupled to computer systems.66 Detailed descriptions of quantification by in situ densitometry are available elsewhere.40
Human studies
Published in C M Langton, C F Njeh, The Physical Measurement of Bone, 2016
Christopher F Njeh, John Shepherd, Harry K Genant
Although conventional radiographs are readily available and fairly inexpensive, estimation of bone mineral density (BMD) from appearance is insensitive and inaccurate, since the subjective assessment is influenced by radiographic exposure factors, patient size and film processing techniques [1, 2]. BMD must decline by as much as 40% before it can be detected reliably on radiographs [3]. These factors have supported the need for objective, non-invasive methods of bone density measurements. These methods should be accurate, precise (reproducible), sensitive, inexpensive and involve minimal exposure to ionizing radiation. Current techniques include radiographic absorptiometry (RA), single X-ray absorptiometry (SXA), dual X-ray absorptiometry (DXA), quantitative computed tomography (QCT) and quantitative ultrasound. These techniques have been extensively described in chapters 8–14, varying in precision, accuracy, fracture discrimination and fundamental methodology, along with their clinical and research utility (table 17.1). This chapter discusses the clinical utility of bone densitometry in evaluating bone status. Although primary osteoporosis is the main use of bone densitometry, it is also used to assess bone status in paediatrics, subjects with secondary osteoporosis and arthritis.
Densitometry Measurement
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
As the name indicates, densitometry is the measurement of optical density (OD). OD, in turn, can be broadly defined as a measure of the attenuation of radiant flux by some sort of optical element that can be transmitting, reflecting, or both. Densitometry is most widely applied in photographic science, and measurements in this field are covered by a four-part ANSI/ISO standard [1]. The treatment here follows that document. The measurement of transmission and reflection from the standpoint of optics has been discussed by Palmer [2]. This chapter uses the single word density, without the adjective, and uses the words “light” and “flux” interchangeably (although density can be measured in the UV and infrared [IR] also, of course).
Low-dose single-energy material decomposition in radiography using a sparse-view computed tomography scan
Published in Instrumentation Science & Technology, 2019
G. Kim, Y. Lim, J. Park, H. Cho, C. Park, K. Kim, S. Kang, D. Lee, S. Park, H. Lim, H. Lee, D. Jeon, W. Kim, C. Seo, M. Lee
Dual-energy material decomposition (DEMD) is a well-established theoretical x-ray technique that uses low- and high-kilovoltage radiographs to separate soft tissue and bone in radiography and computed tomography (CT).[1–4] This technique, which was first described by Alvarez and Macovski in 1976,[5] is based on the assumption that the attenuation of materials in the diagnostic x-ray energy range can be represented as a linear combination of two governing physical functions (the energy dependencies of the photoelectric absorption attenuation and Compton scattering attenuation) or the attenuation of two basis materials.[6,7] As a result, images of the two basis material coefficients are obtained (i.e., the equivalent thicknesses of soft tissue and bone). The technique’s use in bone densitometry is particularly useful because it improves bone mineral density measurements on the vertebral body and hip (or femoral head) by eliminating the so-called fat error.[8,9]
A Survey on Osteoporosis Detection Methods with a Focus on X-ray and DEXA Images
Published in IETE Journal of Research, 2022
S.M. Nazia Fathima, R. Tamilselvi, M. Parisa Beham
Bone densitometry is a non-intrusive method to quantify the bone density quickly and accurately. There are various techniques developed to evaluate the density of the bone and thereby evaluate the condition of osteoporosis. There are morphometric methods and photon absorptiometric methods. Morphometric methods give either qualitative or quantitative analysis of skeletal structure from the plain radiographs. Initially, visual interpretation of plain radiographs was used to diagnosis osteoporosis that gave a qualitative analysis.