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Measurements of the attenuation and velocity of ultrasound from 0.3 to 0.8 MHz have been performed on a number of bovine cancellous bone samples. The influence of bone mineral content has been isolated by measuring the acoustic properties of the samples at various stages of demineralization resulting from controlled nitric acid attack. The correlation(More)
PURPOSE The goal of this work was to implement a recently proposed small field dosimetry formalism [Alfonso et al., Med. Phys. 35(12), 5179-5186 (2008)] for a comprehensive set of diode detectors and provide the required Monte Carlo generated factors to correct measurement. METHODS Jaw collimated square small field sizes of side 0.5, 0.6, 0.7, 0.8, 0.9,(More)
The goal of this work was to examine the use of simplified diode detector models within a recently proposed Monte Carlo (MC) based small field dosimetry formalism and to investigate the influence of electron source parameterization has on MC calculated correction factors. BEAMnrc was used to model Varian 6 MV jaw-collimated square field sizes down to 0.5(More)
The propagation mechanisms of ultrasound in trabecular bone are poorly understood and have been the subject of extended debate; also, the reproducibility of ultrasonic measurements on bone in vivo using commercial ultrasound heel-scanning devices is such that the interpretation of the obtained data is difficult. In this paper we describe recent developments(More)
The measurement of attenuation and velocity of ultrasound in cancellous bovine femora has been studied. The dependence of both attenuation between 0.2 and 0.8 MHZ and velocity on the bone density has been measured. The results show a correlation coefficient of around 0.5 for attenuation and density, and a value of roughly 0.85 for velocity and density. The(More)
Three methods were used to investigate the role of infection in sudden unexpected infant death (SUD): (i) microbiological comparison of SUD victims and matched, live, community controls; (ii) postmortem classification of the contribution of infection to death; and (iii) case-control analysis of the relative risk associated with both infection and heavy(More)
The relationship between the structure of bovine cancellous bone, and its ultrasonic propagation parameters is investigated by means of a novel technique involving the application of large static loads, thereby changing the porosity in a controlled manner. The results show that for frequencies in the range 0.4 to 1 MHz, porosity decreases up to 35% are(More)
Ultrasonic velocities were measured in three orthogonal directions for 17 cubes (2 x 2 x 2 cm approximately) of defatted calcaneal trabecular bone using a novel pulse transmission method with 37 kHz transducers. Since the wavelength was greater than the cross-sectional dimensions of the specimens, it was assumed that bar wave propagation was occurring and(More)
This paper describes a method of effectively electroporating mammalian cell membranes with pulsed alternating-current (ac) electric fields at field strengths of 30-160 kV m(-1). Although many in vivo electroporation protocols entail applying square wave or monotonically decreasing pulses via needles or electrode plates, relatively few have explored the use(More)
The velocity of ultrasound in a series of 10 fixed os calces was measured using both short pulses and 750 kHz tonebursts. The values obtained from the pulse measurements differed from the toneburst values by up to 16% depending on the selection of the zero-crossing point used as a reference in the pulse measurements. It is demonstrated that the discrepancy(More)