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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Computed tomography of cranial subdural and epidural hematomas: variation of attenuation related to time and clinical events such as rebleeding

Forty-one cases of subdural and nine of epidural hematomas were studied with regard to attenuation and the time between trauma and computed tomography scanning. The attenuation of the hematomas showed a consistent decrease with time during the first 4 weeks. High attenuation of chronic subdural hematomas is explained by a sudden or continuous rebleeding. No correlation was found between the attenuation of the hematoma and the attenuation of venous blood from the same patient.

Titanium clips in neurosurgery for elimination of artefacts in computer tomography (ct) a technical note

To eliminate the occurrence of artefacts produced by clips on the CT images, the use of titranium clips is suggested. Tests in vitro and in vivo indicate that clips manufactured from 0.2 mm thick 99.9 per cent titanium do not cause artefacts. They are resistant to corrosion, nontoxic, effective, easy to handle, relatively cheap, and are visible on plain X-ray films.

Diagnosis of intrasellar cisternal herniation (empty sella) by computer assisted tomography

Twenty-six cases of empty sella were studied using computer assisted tomography (CAT). Emphasis was placed on the technical factors controlling the pictures. The diagnosis seems to be feasible in a large number of cases provided movement artifacts are reduced and the angulation, thickness, and level of the cut are carefully chosen.

Variation with time of the attenuation values of intracranial hematomas

Fourteen cases of subdural, epidural, and intracerebral hematoma, in which the time of the trauma or bleeding was known, were selected. Attenuation of samples taken at surgery showed good correlation with attenuation values determined by computed tomography (CT). The decrease in the attenuation of the hematoma from the time of trauma or bleeding was studied.

Stereotaxic computed tomography

A method for stereotaxic computed tomography is described. A head fixation system has been devised enabling the exact transfer of information fromthe diagnostic coordinate system of the scanner to other therapeutic or diagnostic coordinate systems.

Picture processing in computed tomography

Using the EMI scanner system computer, picture processing of various kinds can be performed. Computer programs enabling analysis of regions of interest, subtraction, smoothing, and reconstruction in three dimensions have been designed; they are easy enough to be handled by the regular staff. The potential of the methods is illustrated.

Airway closure during mechanical ventilation

A nitrogen-dilution technique for measurement of airway closing volumes (CV) and functional residual capacity (FRC) not requiring subject cooperation was tested in five healthy, awake, spontaneously breathing subjects and subsequently used in 20 patients during anesthesia with mechanical ventilation. Incomplete exhalation before inhalation of oxygen did not significantly alter CV. Inspiration of a volume of oxygen equal to 75 per cent of vital capacity (VC) did not affect CV, whereas inspiration to 50 percent VC resulted in a 20 per cent decrease in CV. Expiratory resistance tended to reduce CV. By means of this technique, the validity of which had been thus demonstrated, airway closure could be shown to occur at lung volumes larger than FRC (and thus within a normal tidal volume) in six patients prior to anesthesia, and in a further 11 (total 17 of 20) during anesthesia with mechanical ventilation. FRC decreased by an average of 0.5 liters during anesthesia with mechanical ventilation and was only 0.2 liters above residual volume. Significant hypoxemia was observed in association with airway closure.

The limitations of definition of blood vessels with computer intravenous angiography

Using a polystyrene phantom and various concentrations of iodine contrast material, the discrimination of blood vessels by the EMI scanner was studied. Although a 2 mm tube can be delineated using high concentrations of iodine, smaller tubes are not seen due to noise inherent in the system.

Computer intravenous angiography

Computer tomography could be useful in demonstrating lesions of intracranial vascular structures. Experimental methods aimed at achieving this are presented and clinical examples using intravenous angiography are given. The factors involved by the demonstration of intracranial vessels are discussed.