Biomedical subjects

T Schöpf

Publications and source records attributed to T Schöpf.

3 recordsLinked to original sources

PubMed1996

[The smart-scan procedure of spiral computed tomography. A new method for dose reduction].

PURPOSE: In this article a new method - the Smart-Scan-Technique - for dose reduction during spiral computed tomography is described. This technique allows a dynamical adaptation of the tube current according to the measured local density structure form and absorption values of the object of interest. Its clinical applicability for dose reduction is investigated. In addition, changes in image quality are evaluated. METHODS: Specially designed, water filled plexiglas-phantoms, an Alderson-Rando phantom, and 20 patients were used to simulate possible measures of patients within the thoracic and abdominal region. For those two regions the dose reduction, the modulation transfer function, and the pixel noise were measured. RESULTS: Depending on patient geometry dose reduction up to 20% could be achieved with the Smart-Scan-Technique. This technique also enabled a decrease of the modulation transfer function and an increase of the pixel noise by 8%. CONCLUSION: Relevant dose reductions can be achieved by applying the Smart-Scan-Technique in spiral computed tomography.

Absorption↗

PubMed1996

[Dose reduction in computerized tomography with a new scan procedure].

A new investigation technique in computed tomography--the Smart Scan process--and the associated reduction in tube current are discussed. In addition, the reduced dosage values resulting from the reduced current values are compared with those of a standard measurement and image characteristics such as picture unit noise are evaluated. By means of three special water phantoms with dimensions corresponding to those of actual patient geometries and a pool of 183 patients, the Smart Scan process was tested by the control algorithm implemented on a spiral computer tomograph. The dosage values with and without the Smart Scan being activated were determined. Dosage reductions of up to 18% can be realized with this new examination technique. In particular, patients with transverse oval head profiles will benefit from this modality.

Adolescent↗

PubMed1994

Spectral transmission of the optical media of the human eye with respect to keratitis and cataract formation.

The spectral transmissions of cornea, aqueous humour, lens and vitreous humour of human eyes were measured in the range from 250 nm to 800 nm in 1 nm steps using a high resolution double monochromator. Cornea and lens are good cut off filters; 1% transmission was measured in various cornea samples between 291 and 298 nm, and in different lenses between 389 and 414 nm. Aqueous humour and vitreous humour showed high transparency (80%) at lambda > 320 nm. The wavelength range of keratitis effective irradiance was found to be completely within the wavelength range of absorption of the cornea, that of cataract effective irradiance was found to be at the short wavelength end partly outside the wavelength range of absorption of the lens. It may therefore be supposed that the action spectrum of cataract obtained by animal experiments is applicable to the human eye only with certain reservations.

Absorption↗