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W Angerstein

Publications and source records attributed to W Angerstein.

27 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↗
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↗
PubMed1975

[Observer error in interpretation of chest-radiophotographs (author's transl)].

A series of 434 radiophotographs (70 X 70 mm) containing 40 patients with known abnormal symptoms and 15 resp. 21 pictures with suspected abnormalities were interpreted by 85 chest physicians. 84% (average of 77 readers) of the known symptoms were found in the right localisation. The mean value of 8 diagnosticians with only little routine in reading radiophotographs, was 65%. The number of correct findings with respect of the 40 plus 15 resp. 21 abnormalities lies near 80%. Nearly 10% of the true negative cases were described as positive by the diagnosticians. The number of false positives varies considerably (between 0% and 50%) for different interpreters. The number of true positive findings when the films are read by two observers independently increases only when we combine two readers with poor results in finding true positive cases. But dual reading means nearly twice as much false positive findings. The repetition of reading the films by the same interpreter gives nearly the same results as the first reading.

Diagnostic Errors↗
PubMedDate not supplied

Evaluation of functional positions of tongue and soft palate with MR imaging: initial clinical results.

Magnetic resonance imaging was used to analyze functional positions of the tongue and soft palate in 10 patients and 10 healthy volunteers. The patients had velopharyngeal insufficiency and/or dysfunction of the tongue. With snapshot FLASH (fast low-angle shot) sequences (data acquisition time, less than 1 second), malpositions of the articulatory apparatus were imaged and recorded for follow-up documentation.

Adult↗