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Biomedical subjects

M Bergström

Publications and source records attributed to M Bergström.

At least 199 records · Page 11Linked to original sources
PubMed1980

CT localization of stereotactic surgery.

A stereotactic system is described. It is built around a baseplate which is fastened to the head of the patient and to various diagnostic and therapeutic modalities. In principle this system can function as an interface between most diagnostic (CT scanners, PET scanners, conventional X-ray instrumentation for angiograms and pneumoencephalograms) and therapeutic (stereotactic instruments, linear accelerators) instruments. It has been in practical use since 1976 and used in a number of 'diagnostic-therapeutic' combinations.

Biopsy↗
PubMed1980

Stereotaxic computerized tomography with a GE 8800 scanner.

A stereotaxic system is described that uses computerized tomography scanning for target localization. This system is unique in that the sterotaxic localization may be carried out using the scanner computer without the addition of any extra software. The hardware of the system is built up around a base plate which is fastened to the scanner's patient table. The head is positioned and fixed to the base plate with aluminum bars, which are fixed to the calvaria with screws. Various stereotaxic devices may be fastened to the base plate. The system has been in clinical use for 4 months at the time of writing. Its main application has been in tumor biopsies, but it has also been used for functional operations.

Humans↗
PubMed1979

Diagnosis of sellar and parasellar lesions by computed tomography.

Suspected lesions in and around the sella were examined by CT in 129 cases. The diagnostic accuracy and various technical aspects of the method are described. The mean attenuation and enhancement after administration of contrast material are evaluated in craniopharyngiomas, chromophobe adenomas, meningiomas, aneurysms, dermoid cysts, an arachnoid cyst and a glioma. the choice of collimator and its use in relation to sellar dimensions, particularly the sellar depths, are emphasized.

Diagnosis, Differential↗
PubMed1979

Compartment analysis of contrast enhancement in brain infarctions.

Contrast enhancement has been studied with computed tomography in 18 patients with brain infarction. Four patients were examined on more than one occasion. A mode of contrast medium administration has been used that results in constant blood iodine concentration during the investigation. The enhancement pattern was analyzed using a compartment model. A fast and a slow component of contrast enhancement was quantified for different parts of the infarct. Correlation with the age of the infarct confirms earlier studies, indicating a maximum enhancement at 2 to 4 weeks after the incidence of the infarct.

Brain↗
PubMed1979

Incidence of basal ganglia calcifications on computed tomography.

In a group of 3,800 computed tomography examinations, 14 patients (0.4%) were found to have high attenuating lesions suggesting calcifications within the basal ganglia. The lesions were bilateral in all patients. A majority of the patients had psychic symptoms and convulsions. Electroencephalographic changes were frequent and extrapyramidal symptoms occurred. Until now only three patients have been endocrinologically examined. One of them had hypoparathyroidism. Since parathyroid dysfunction frequently is associated with calcifications of the basal ganglia, these patients should be referred for endocrinological evaluation.

Adult↗
PubMed1979

Computer tomography of the head in children. Technical aspects.

A modified routine for computer tomography of children, avoiding general anesthesia is discussed. The patients were sedated and examined in a supporting plastic cradle. Radiation doses to various parts of the body were measured during the scanning and the results confirm that the dose levels are within generally accepted limits.

Adolescent↗
PubMed1978

Early contrast enhancement of acoustic neuroma.

The changes of the enhancement of the lesion with time after intravenous administration of contrast medium were measured with computed tomography (CT) in 23 cases of acoustic neuroma. The pattern of high initial enhancement followed by a fairly rapid decrease is confirmed. A more rigorous study of the enhancement pattern using a mathematical description of the enhancement curve of the tumor as well as a measurement of the individual blood enhancement curve is discussed.

Adult↗
PubMed1978

Transformation and action of metrifonate.

Chemical formation of dichlorvos (2, 2-dichlorovinyl dimethyl phosphate) was found to occur in mouse brain after i.p. injection of metrifonate (2, 2, 2-trichloro-1-hydroxyethyl dimethyl phosphonate). A mass fragmentographic technique was used. Different isotopic variants were used both as internal standards and to compensate for dichlorvos formed during the workup procedure. The dichlorvos formed in vivo was found to have its maximal concentration a few minutes after the maximum of the metrifonate itself. The effect of metrifonate and dichlorvos on acetylcholine levels, acetylcholinesterase activity and synthesis rate of acetylcholine in mouse brain was also studied. In all three cases the effect of metrifonate was found to be prolonged and delayed as compared to the effect of dichlorvos. It is concluded that metrifonate acts as a slow release formulation in the body giving rise to dichlorvos nonenzymatically. This circumstance at least partly explains its efficacy in the treatment of schistosomiasis.

Acetylcholine↗
PubMed1978

Attenuation values of the cerebrospinal fluid (CSF).

The attenuation value of CSF, obtained by lumbar puncture, was determined with computed tomography in 25 patients. Measurement of the protein content in the same samples showed no correlation with the attenuation value. It is concluded that in the normal range of protein concentrations, the effect on the attenuation is insignificant and that the attenuation value of the CSF might be used to check large deviations in the CT numbers due to artifacts.

Brain↗
PubMed1978

Attenuation changes of the ventricular CSF after intravenous injection of contrast material.

The CT attenuation change of the intraventricular CSF after i. v. administration of contrast material has been studied in 20 patients. A very small increase of attenuation was observed in the entire material. The method does not seem to be appropriate at present for the study of small attenuation changes in the CSF reflecting the passage of contrast material.

Adolescent↗
PubMed1978

A ring detector positron camera system: its merits: clinical experience.

A ring detector positron camera system for CT of the brain is described. The system uses 95 NaI (Tl) detectors, arranged with cylindrical geometry, for the simultaneous detection of coincidences from 1,900 detector combinations. With a new sampling technique an experimental system resolution of 7 mm FWHM has been obtained. The sensitivity was found to be 5,300 c/s with a 100-keV energy threshold and using a 19.2-cm-diameter cylindrical phantom with a homogeneous specific activity of 1 muCi/cm3. A clinical study of blood-brain barrier damage using 68Ga-EDTA is reported.

Brain↗
PubMed1978

A method for determining bone mineral content using Fourier image reconstruction and dual source technique.

The basic principles of a quantitative tomographic technique for bone mineral determination are considered. The bone mineral content could be evaluated from a single reconstruction using projection data from two different energies. Beam hardening effects and photon counting statistics are studied by computer simulation and found to be the limiting factors in precision and accuracy.

Bone and Bones↗
PubMed1978

Contrast enhancement of cranial lesions in computed tomography.

The time course of enhancement in apparently normal brain tissue, edema and focal lesions during 30 to 60 min after intravenous injection of vascular contrast medium was evaluated in a series of 41 patients with different intracranial lesions. The attenuation of apparently normal unenhanced brain tissue varied with the level of the scan, mainly an effect of beam hardening. Different types of enhancement response are discussed in terms of a 3-compartment model. The differential diagnostic potential of contrast enhancement in the early phase needs further evaluation using instruments with short scanning time, while the late phase of enhancement must be recorded with the use of a reliable head fixation to provide reproducibility of repeat measurements.

Adolescent↗
PubMed1978

Stereotactic computer tomography for biopsy of gliomas.

A technique is introduced enabling automatic transfer of coordinates obtained at computer tomography into a stereotactic system previously applied in biopsies of brain lesions. Four to five biopsies from different parts of gliomas were taken to compare the structures demonstrated on computer tomography with the microscopic appearances. Of 45 biopsies in 13 patients, 36 were predicted correctly. This also served as an attempt to classify gliomas on the basis of their appearance in the CT image.

Adolescent↗
PubMed1978

Radiation dose related to collimator geometry in the first generation EMI scanner.

The radiation dose from the first generation EMI scanner has been analysed, including the variation of the dose perpendicular to the section, the dose dependence of the size and collimation of the beam, and the fraction of radiation passing the patient and utilized for information. The possible dose in case of malfunctions of the scanner was also measured.

Adult↗