1,721,001 research outputs found
[Ultrasound and the bone: a difficult relationship].
No full textThe principles of US physics and technology hampering both the production of US images of the bone and the assessment of the soft tissue structures underlying it are discussed. In theory, two US parameters play a role in this field: the different transmission velocity of the US beam through soft tissues and bone, and the marked attenuation of the US beam when crossing the bone. The former parameter, due to higher density and lower compressibility of the bone with respect to soft tissues, causes both intense reflection (and thus beam weakening) and refraction (and thus lateral resolution and US image distortions) at the soft tissue/bone interfaces. Moreover, US transmission velocity in the bone differs significantly from the reference velocity of the US scanners on the market based on that of soft tissues. As a consequence, during the reconstruction of a bone US image, artifacts resulting in the axial compression of bone structures should, at least in theory, occur. The latter parameter, due to both conversion into heat (absorption) and local dispersion (scattering), is likely to be main factor causing the loss of US energy when the US beam passes through the bone. Although the amount of matter (bone mass or density) undoubtedly accounts for some attenuation, local bone architecture (bulk and shear moduli of bone and marrow, bone and marrow density, marrow viscosity and porosity, permeability and tortuosity of cancellous bone structure) seems nevertheless also responsible for some attenuation through both absorption and scattering. Other consequences of attenuation reflecting on US imaging of the bone are: marked lowering of central transducer frequency and US beam widening preventing the correct identification of the interfaces originating echoes by relating them to the structures on the transducer axis. In conclusion, based on the above parameters, echoencephalography and transcranial Doppler US can be expected to improve, in the near future, their bone-crossing capabilities, even though no true gray-scale bone sonogram will ever be feasible
[Evaluation of the post-traumatic course of injuries of the Achilles tendon using computerized telethermography].
No full textFollow-up of Achilles tendon injuries was carried out by means of computerized telethermography. The thermographic examination was performed at definite time intervals (a few hours, 15 days, 1 month, 3 months after acute traumatism) on 15 young patients subdivided into two different groups according to the tenonic injured site: proximal (6 cases) or insertional (9 cases). The study showed a satisfying correlation between hyperthermal level and clinical symptoms, thus allowing to define accurately the resolution or persistence (3 cases) of inflammatory process. In conclusion, the authors recommend the combined use of computerized telethermography and diagnostic US for a complete evaluation of Achilles tendon disorders according to their different evolutive phases
Magnetic resonance imaging of the penis: normal anatomy.
No full textThis study was undertaken to investigate the magnetic resonance anatomy of the normal penis, by means of the use of a new designed surface coil specific for the study of male external genital organs. The combined evaluation of T1- and T2-weighted images obtained by choosing different repetition and echo time values together with an appropriate selection of scanning planes oriented according to various angles of incidence strongly contributed to perform a complete morphological analysis of the penis and constantly revealed fine anatomical details of diagnostic and clinical significance. Among these, the magnetic resonance examination (data referred to a 0.5 T apparatus) allowed a precise morphological differentiation of the penile covering tissues, such as outer skin, dartos tunica and hypodermal connective; the vascular characterization of cavernous tissue, belonging to corpora cavernosa and spongiosum urethrae, of deep arteries and superficial dorsal vein(s); the resolution of the albuginea and the identification of the urethral lumen. Such a capability of magnetic resonance imaging in providing accurate demonstration of penile structures without technical artifacts and use of ionizing radiations makes the actual technology able to cooperate efficaciously with computerized tomography and diagnostic sonography for an efficient clinical assessment of penis diseases
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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