T. Whittingham

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In the first part of the review, recent developments in medical imaging technology are described. Developments in transducer materials and matching, leading to improvements in band-width and sensitivity are discussed. Improvements in dynamic range due to increased transducer sensitivity, lower electronic noise levels and more efficient filtering are then(More)
Tissue harmonic imaging (THI) is an increasingly common option for B-mode scanning [1]. It improves image quality in many situations, particularly those involving large, difficult-to-scan patients, where conventional Bmode images may be poor [2]. For good ultrasound subjects, however, THI commonly produces a poorer image than conventional B-mode. However,(More)
Ultrasound transducers are only efficient over a limited range of frequencies. This frequency range is described by the frequency response curve of the transducer, which is a plot of transducer efficiency vs frequency (Fig. 1). The transducer bandwidth is defined as the width of the frequency response curve, at some specified fraction of maximum. Typically(More)
The ways in which ultrasound is used in medical diagnosis are reviewed, with particular emphasis on the ultrasound source (probe) and implications for acoustic exposure. A brief discussion of the choice of optimum frequency for various target depths is followed by a description of the general features of diagnostic ultrasound probes, including endo-probes.(More)
The factors limiting the resolution achievable with array-based imaging methods are considered. The limitations on beamwidth and field of view for beam scanning systems are first examined using plane wave diffraction theory, treating focusing and any array curvature as separable to the plane wave analysis. It is found that in all cases the number of(More)
1. We have tested the hypothesis that the fall in hepatic mass with age influences the age related increase in sensitivity to warfarin. In 39 otherwise healthy outpatients, aged 50-87 years, stabilised on warfarin for prophylaxis of thromboembolism, age, mean International Normalised Ratio (INR), and mean warfarin dosage were recorded. Liver volume was(More)
Impotence may be caused by arterial disease affecting the vessels supplying the corpora cavernosa. Color duplex ultrasound was used to measure the peak systolic velocity and systolic rise time in the deep penile arteries in 22 impotent men following papaverine stimulation. The results were compared with the findings of selective internal pudendal(More)