Computertomographie最新文献

The absorption values of cancellous bone of the third lumbar vertebral body were measured in 80 patients by CT. It was possible to demonstrate a statistically significant linear correlation between absorption values and patient age. The older the patient, the lower the average absorption values of cancellous bone. The average absorption values in patients between 20 and 30 Jrs. were found to be about 200 HU, between 30 and 50 Jrs. 180, between 60 and 70 Jrs. 120 and between 70 and 80 Jrs. 100 HU. Although correlation between calcium salt content and absorption of bone under CT are well known, there are other factors (mainly fatty involution of bone marrow) who influences the absorption behaviour of cancellous bone.

The article gives the organ doses for whole body CT examinations of the thoracic region, the upper abdomen, the mesogastric and pelvic regions as well as of the lumbar vertebral column and for CT scanning of the skull. The examinations were performed using an Alderson-Rando phantom with the whole body computer tomograph Somatom DR2 supplied by Siemens and with the skull computer tomograph Siretom 2000, also supplied by Siemens. It was found that the magnitude of radiation exposure of the patient depends not only on instrument-specific properties, but also to a very large measure on the examination parameters and techniques which can vary considerably from one clinic to another.

The article presents two methods for the theoretical determination of CT values. These methods involve relatively little work and cost and enable at least an estimation of the CT value of any object to be examined. The results are compared with the experimental data, and possible sources of errors are shown. The article concludes with a discussion of a few examples from actual practice.

Bow-shaped artifacts can often be seen in B-mode-ultrasound examinations. In order to find out the origin of these artifacts, water tank experiments were carried out and compared with in vivo observations. The studies showed that bow-shaped artifacts are caused by beam breadth, and that their shape is influenced by the type of the B-mode-instrument, the adjustment of the machine, and by the shape of the reflector. In vitro and in vivo, bow-shaped artifacts arise at strong reflectors and are visible in regions of low echogeneity. In vivo bow-shaped artifacts may imitate pathological findings such as septa or sludge.

In long time or serial operation metal anode discs with blackened layer can be loaded much higher than graphite anode discs, because the distance between thermal source and temperature sensitive spot in metal discs is larger than in graphite discs and the maximum permissible temperature for metal discs is much higher than that for graphite discs.

The article discusses initial experiences of NMR examinations of carcinoma of the uterus and cervix uteri (resistive magnet, NMR prototype of Siemens). All examined carcinomas show prolonged relaxation times. Variation of measurement parameters results in good optical presentation of carcinoma tissue in the resonance scans. The results are compared with those of CT-scans and in one case with the site of the operation.

To estimate risks involved in x-ray diagnosis, it is useful to employ the concepts of organ dose and integral dose, whereas the surface dose should be considered as unsuitable. Although the methods of measurement differ from each other, they can lead to comparable results, as is demonstrated in this article, eg, for computerised tomography of the skull.

The article reports on the CT image of a venous thrombosis of the liver with severe parenchymal damage (Budd-Chiari's syndrome) in a young woman, resulting in her death. The x-ray morphology image showed a liver pattern of reduced density in spot form with hepatomegaly and ascites. The hypodense areas were both circumscribed and disseminated over both lobes with density values between +15 and +30 HE. Enlargement of the lobus caudatus is considered as typical of the disease (4, 7).

The authors report on an orbital complication in a child of 14 years of age with an abscess on the upper eyelid and pansinusitis on the left side. The clinical suspicion of involvement of the orbita could be definitely clarified with computed tomography only. The article describes the regression of this finding.

Four cases are presented, in whom conventional radiography of the abdomen including tomography and ultrasound raised high suspicion of a left suprarenal tumor. Abdominal CT explained the finding in each case as being produced by a normal anatomic variation of the pancreatic tail, which was found in a paraspinal and suprarenal location. The statistical incidence of such a variation is discussed.