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Results for “Radiographic Magnification”

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At least 37 records · Page 2Linked to original sources
PubMed1975

[Optimal distances for direct radiographic magnification].

This paper deals with the theoretical basis for radiographic magnification. In particular, the relationship between focal size and optimal magnification for various systems is discussed. Maximal resolution was chosen as the criterion for best results. It has been shown that resolution (Lp-mm) can be improved by the reciprocal of the focal spot and for optimal magnification (see article) where f is focal spot size and AVBW is resolution of the imaging system.

Humans↗
PubMedDate not supplied

Optical versus radiographic magnification for fine-detail skeletal radiography.

Fine-detail radiographic techniques for peripheral skeletal imaging have gained wide clinical acceptance. In this study, the imaging properties and clinical applications of the optical magnification technique, which employs fine-grain industrial film and a large focal spot, are compared quantitatively and qualitatively with those of three slow screen-film techniques, namely, contact exposure with a large focal spot, 2 times radiographic magnification with a 0.3 mm focal spot, and 4 times radiographic magnification with a 50 mu focal spot. The modulation transfer functions (MTF's) of the recording systems and focal spots are obtained and film sensitometry performed. Clinical comparisons are made for patients with metabolic, arthritic, and neoplastic skeletal disorders. The results illustrate the superiority of the optical magnification technique over contact or 2 times magnification techniques using slow screen-film systems. If a microfocus tube is used, however, direct radiographic magnification may provide images comparable in resolution, noise and contrast to those made with the optical magnification technique, and at lower radiation exposure to the patient.

Arthritis, Rheumatoid↗
PubMed1991

[Direct radiographic magnification in bone infections].

An experimental model of bacterial osteomyelitis was used to investigate the correlation of direct radiographic magnification and histopathologic changes in the femora of rabbits. The histopathologic changes demonstrated a severe chronic state of osteomyelitis. The extent of radiographic changes was more clearly recognizable with direct radiological enlargement (up to 15-fold) than on normal radiographs: this applied to destruction of marrow and cortical bone, formation of sequestra, and (frequently) extraosseous extension. Histopathologic findings were in agreement with the changes revealed by direct radiographic enlargement.

Animals↗
PubMed1977

Noise reduction by radiographic magnification.

Effective noise in the rare-earth system can be substantially reduced by use of radiographic magnification technique. The basic imaging properties of the rare-earth system (Alpha 8-XM) and the medium-speed system (Par-RP) were evaluated by the Wiener spectra, modulation transfer functions, and H&D curves. The visibility of radiographic details was determined with simple test objects. Results indicate that, as the magnification increases, the effective noise in the rare-earth system is reduced, and that the visibility of small structures can be improved.

Models, Anatomic↗
PubMed1998

Radiographic magnification in the diagnosis of traumatic lesions of the hyoid-larynx complex.

This paper proposes the use of radiographic magnification to detect the effects of neck traumas. This technique, both fast and economical, has proved to be particularly useful in all those cases where post mortem examinations failed to detect valid evidence of lesions of the hyoid-larynx complex. This is the case with corpses in an advanced stage of putrefaction where death occurred as a result of pressure or when a soft object is placed between the victim's neck and the assailant's hands. The radiological study was performed "on site" on four cases of medicolegal interest and its potential was confirmed.

Adult↗
PubMed1982

Application of direct magnification radiographic technique to the jaws.

Direct magnification radiography is widely applicable to situations in which enhanced definition and enlarged images are desirable. This technique is capable of providing high subject resolution when conventional radiography is not definitive. It serves as a variable supplementary radiograph for the diagnosis of conditions in the oral and maxillofacial region. The general mechanics of the technique as well as its possible use as a supplementary high detail film are discussed. Three cases are reported in which this technique was applied in the diagnosis of oral and maxillofacial surgery patients.

Aged↗
PubMedDate not supplied

Dose efficiency and the effects of resolution and noise on detail perceptibility in radiographic magnification.

The detail signal-to-noise ratio model of radiographic imaging is quantitatively analyzed in terms of its accuracy in describing observer threshold perceptibility of radiographic detail. The model is found to adequately describe the effects of magnification, scatter radiation, and system resolution on observer threshold perceptibility. However, it is shown that the model does not apply in screen/film radiography for very low contrasts and high scatter conditions due to insufficient optical density contrast. The dose-to-information conversion efficiency of a radiographic imaging system is defined and the effects of magnification, scatter, resolution, image processing, detector efficiency, grids, patient table support, field size, and geometry on the dose efficiency of the imaging system are investigated.

Models, Theoretical↗
PubMed1975

[Reduction in radiation scatter during radiographic magnification techniques (author's transl)].

The reduction in scatter during magnification techniques is compared with the effect of grids. The results of extensive measurements concerning scatter and distance in a water phantom are shown in 24 diagrams. The various factors were altered as follows: distance 0-1.5 m., phantom thickness 0-27.5 cm., area 5 cm. x 5 cm. - 30 cm. x 30 cm. and kilovoltage 50-150 kv. The amount of scatter immediately behind the phantom is compared with that through a grid by observing image quality for given amounts of scatter. This "grid-equivalent" image quality can be used to determine the circumstances under which a magnification technique can be employed without using a grid.

Radiation Dosage↗