Studies of contrast bolus geometry and dynamics were carried out by means of a chronogram - a digital serial radiographic method. Four situations were considered - contrast volume, speed of injections, subsequent saline injections and rapidly repeated contrast boli. Peak values, maximum duration and half-life of the bolus and maximum contrast enhancement were recorded. The results have shown that a larger volume of contrast with reduced injection speed leads to a lengthening of the peak period. More rapid injection speed up to 8 ml/sec leads to a higher peak and increased contrast enhancement. Further increases of injection speed beyond 8 ml/sec does not further increase contrast enhancement. The subsequent injection of saline has no recognisable effect on bolus geometry or dynamics.
To improve the diagnosis of fistulas in CT by using a new method. 68 CT examination of fistulas from 1990 to 1995 were evaluated retrospectively. The examinations were performed in two phases: The regions of interest were scanned as usual, in the case of abdominal fistulas after filling the bowels with contrast medium. In the second phase, the fistulas were filled with highly concentrated contrast medium and re-examined. The presentation of this examination was carried out in a wide window and a high centre. In 59 of the 68 cases the fistula and a communication with an organ or an abscess was found, in 9 cases only the fistulous tract. The fistula and its surrounding structures can be well defined each with a different and individual density. By means of the chosen method the different density readings are visualised. Therefore, the 2-phase contrast method can improve fistula diagnosis by using CT.
The causes and types of artefacts produced by a translation-rotation scanner were studies by model experiments. Aids for recognising these are described, which would prevent errors of interpretation. Means for reducing artefacts are indicated.
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