Computertomographie最新文献

Digital radiography is a generally accepted term comprising all x-ray image systems producing a projected image which resembles the conventional x-ray film image, and which are linked to any type of digital image processing. Fundamental criteria of differentiation are based on the production and detection method of the x-ray image. Various systems are employed, viz. the single-detector, line-detector or fanbeam detector and the area-beam or area-detector image converters, which differ from one another mainly in the manner of conversion of the radiation produced by the x-ray tube. The article also deals with the pros and cons of the various principles, the multitude of systems employed, and the varying frequency of their use in x-ray diagnosis work.

In Real-time Sonography slice-thickness artifacts may lead to misinterpretation, mainly in cystic organs. With in vitro studies it was possible to show the mechanism of this artifact, which is based on beam thickness.

The contribution made by computed tomography to the diagnostics of the skeletal system was studied in the basis of 53 examinations in patients with space-occupying growths and malformations. With reference to clinical final diagnoses the CT findings were graded into I. Correct diagnosis or diagnosis by exclusion, II. Contribution to determining the growth of the process, III. No additional information obtained via CT. The distribution of these grades was as follows: Grade I = 34%, II = 49%, III = 17%. Indications for CT of the skeletal system were based on the following problems: primary malignant bone tumours; bone metastases in the region on the vertebral column; benign and potentially malignant bone tumours and abscesses in the region of the skeleton itself and of the skull; suspected diastematomyelia; assessment of the vertebral canal in case of suspected inflammatory or tumorous changes of the adjacent areas as well as exclusion of osseous changes in the region of the vertebral canal with peripheral neurological symptoms. CT serves to determine the exact dimension of the growth; to prove infiltration of organs and structures; for the planning of operations; for controlling the course; and for diagnosing relapses.

The article points to the possibility of producing a topogram with the gantry in oblique position. Although this yields a distorted image, it enables accurate planning of the section and also a localization of objects in slanted position, for example, the intervertebral disks of the lower lumbar vertebral column, thus saving the patient time, material and radiation exposure.

CT enables the identification and localization of foreign bodies which cannot be visualised at all or only slightly so via conventional x-ray film, iatrogenic foreign bodies not recognisable by the usual methods were identified by us by means of CT in two cases direct and in one case indirect as a "soft part finding". Basing on these three cases the article discusses the validity of CT when searching for foreign bodies.

Hardening of the beam is a major disturbing effect in densitometry close to the calotte. This phenomenon is demonstrated in a phantom, and its theoretical base is discussed. If possible sources of error are considered and reduced by means of appropriate measuring conditions, measurement of density will furnish useful additional data in CT examination. The value of CT densitometry is demonstrated via follow-up observations; after an operation of a glioma of the optic nerve, a child developed hygromas complicated by superinfection which subsequently became horny or calcified.

Software windows are a flexible and general method for defining arbitrary functions for the mapping of Hounsfield-numbers of CT-scans on to the grey levels of the display image. The method which is illustrated with the aid of a few examples has been implemented on an EMI viewing console.

The importance of the myelography in comparison to CT (CT-myelography) is demonstrated in a patient with an intradural neurinoma.

Ependymal and meningeal metastases of brain tumors may frequently be demonstrated by computerized tomography. The mode of metastasis formation and appearance of some CT findings are described. Essential criteria in the differential diagnosis of neoplastic, metastatic, inflammatory and vascular changes are discussed.

Ct assessment of the lymphatic system in the area of the retroperitoneum and the lower mediastinum had so far been limited to pathologically enlarged lymphatic nodes of more than 2 cm diameter. Improvements in apparatus construction and increased clinical experience have made it possible to include lymphatic nodes of smaller size, although it is often difficult to distinguish them clearly from the other formations in those regions. The following article deals with the structures recognisable via CT, such as arteries, veins, lymphatic chains and crura of the diaphragm, systematically and by means of relevant illustrations. The possibilities of identifying these structures by means of a suitable examination technique are discussed.