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Biomedical subjects

G Rockstroh

Publications and source records attributed to G Rockstroh.

11 recordsLinked to original sources
PubMed1998

[Spiral CT. Better resolution by increased pitch?].

The longitudinal resolution of spiral CT has been investigated in dependence on table increment and beam collimation by use of a phantom. The results show clearly that the pitch (ratio of table increment per tube rotation to beam collimation) alone does not allow one to draw any conclusions about the resolution. Thus, a large pitch can yield a better resolution than the pitch of 1. The individual parameters table increment and beam collimation are more relevant with regard to the resolution than the rate of pitch. An alteration of the pitch can be achieved in two different ways. An increase of the pitch by a decreased beam collimation improves the resolution. In contrast, an increase of the pitch by an increased table increment decreases the resolution. A good spatial resolution of objects with high contrast (bone, lung, enhanced vessels) needs a narrow beam collimation, even if a pitch as high as 2 is necessary for a given scanning coverage. A large pitch does not cause gaps in the data set. Moreover, the patient's radiation dose decreases.

Humans↗
PubMed1990

Imaging techniques: state and future.

Technical progress has produced a variety of novel imaging techniques (digital projection radiography, X-ray-transmission computed tomography, sonography, single photon emission computed tomography, positron emission tomography, magnetic resonance imaging), and has enormously extended the diagnostic possibilities in industrialized countries. Further technological developments will be considered under three aspects: --Improvement of current imaging procedures and opening-up of new applications --introduction of new imaging techniques --progressive use of computer technology in imaging diagnostics [digital image generation, image processing, image archiving and communication systems (PACS)] Finally, several consequences emerging from these aspects will be discussed.

Computer Systems↗
PubMed1989

[Quality control in computed tomography].

In comparison to the constancy checks in conventional roentgenography, quality control in computed tomography (CT) should be limited to a few simple but essential checks for image quality and radiation burden. These requirements, however, can only be fulfilled in part, because of the complexity of CT systems. Possible parameters are: water and air values, pixel noise/contrast resolution, spatial resolution, artifacts, homogeneity, contrast scale/tube voltage, slice thickness, positioning accuracy, image quality of the topogram, radiation dose and film imaging. With a simple test program, comprising 4 CT-scans and a camera test image that is presently being tested, most of the mentioned quantities can be checked.

Quality Control↗
PubMed1987

[Evaluation of computerized tomograms using a black and white and a color monitor: an ROC (receiver operation characteristic) comparison].

Different views about the value of a colour monitor for the evaluation of computer tomograms have prompted us to carry out this ROC (Receiver Operation Characteristic) examination. The latter was based on patient computer tomograms in which lesions of the liver were simulated by image manipulation. 5 radiologists analysed the image material (a) on a black-and-white monitor, (b) on a colour monitor, and (c) simultaneously on a black-and-white and a colour monitor. The study shows that the use of a colour monitor gives no essentially different result than evaluation with a black-and-white monitor. The slightly better result of 2% more true positive findings with simultaneous representation of black-and-white and colour image relative to the sole use of black-and-white display is within error limits. The colour representation gives no advantage for the evaluation of usual computer tomograms because the window technique enables a contrast representation in black-and-white too.

Color↗
PubMed1985

[ROC (receiver operating characteristic) study for the recognition of liver lesions on the computer tomogram].

ROC examination was based on patient computer tomograms, in which lesions of the liver were simulated by image manipulation. The window width for optimal recognition of the lesions was found to be 128 Hounsfield units (HU). Evaluation of Receiver Operating Characteristics (ROC) by diameters and contrasts of the lesions yielded a contrast detail diagram largely reflecting conditions in clinical practice. The detectability--measured via the smallest visible diameter of the lesions--is inferior by the factor 3 to 60 to the results obtained with hole pattern phantoms. For example, in computer tomograms lesions of the liver of 24 mm and 4 HU or also 11 mm and 10 HU yield 70% true positive and 10% false positive findings.

False Positive Reactions↗