Biomedical subjects
Publications and source records attributed to M Bergström.
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.
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.
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.
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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.
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.
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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.
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.
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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.
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Sixteen patients with supratentorial tumors were examined with positron emission tomography (PET) using [( 11C]methyl)-L-methionine, [11C]D-glucose, and [68Ga]EDTA as well as CT. There were nine astrocytomas (grade II), three oligoastrocytomas (grade II), two anaplastic astrocytomas (grade III), and two meningiomas. Six patients with low-grade astrocytomas and all three patients with oligoastrocytomas had an accumulation of [11C]methionine varying from slightly to intensely increased as compared with normal brain tissue. There was a markedly increased uptake of methionine in the anaplastic astrocytomas. Three of the low-grade astrocytomas had a decreased uptake of [11C]methionine in at least part of the tumor as compared with normal brain tissue. Contrast enhancement on CT or uptake of [68Ga]EDTA was not a prerequisite for increased accumulation of methionine. Uptake of [11C]glucose was lower than or equal to that of normal brain tissue in the low-grade tumors and also in one of the two anaplastic astrocytomas and in the bulk of the other. In each individual case the methionine uptake tended to be higher--or less decreased--than the glucose uptake. In the low-grade tumors the uptake of methionine and that of glucose were often different, occasionally markedly different, as far as the tumoral-peritumoral areas involved. These differences were even more remarkable in the two anaplastic astrocytomas. An increased uptake of methionine was often seen in areas appearing normal on CT. It appears that PET with [11C]glucose has limitations with regard to delineation of the low-grade astrocytomas, whereas PET with [11C]methionine usually better reflects the extent of these tumors and, to a lesser degree, the extent of the high-grade neoplasms. The results of PET with [68Ga]EDTA were similar to those with postcontrast CT in most patients. The two meningiomas exhibited a high uptake of all tracers used for PET as well as a marked contrast enhancement on CT. The extent of the meningiomas judged by PET with the various tracers correlated well with the extent assessed by postcontrast CT.
Five patients with unilateral acoustic neuromas were studied with CT before and after treatment with dexamethasone. Rather small effects, in the order of 10-20%, were observed on the parameters evaluated, including the size of the tumor, size of the peritumoral edema, and the contrast enhancement. Hence, the acoustic neuromas, which ultrastructurally and with their extraaxial location bear great resemblances to meningiomas, also show a similarity in their minimal response to steroid treatment.
This is a preliminary investigation of the cerebrospinal fluid (CSF) spaces using cardiac gated magnetic resonance imaging. A variation of intensity of the signal from the cerebral aqueduct is demonstrated during the cardiac cycle. The pattern of this variation suggests pulsatile CSF flow. Calculations that have been verified by phantom measurements show that CSF flow rates less than 1 mm/s may be detectable. Magnetic resonance may therefore offer a new method for the demonstration and measurement of CSF flow.
Two patients with pituitary tumors were examined with positron emission tomography (PET) after intravenous administration of 11C-N-methylspiperone. In repeat studies the patients were given 1 mg of intravenous haloperidol prior to the administration of the radioligand to block the dopamine receptors. High uptakes of the radiolabeled ligand were seen in one of the tumors. With haloperidol pretreatment the uptake was lower, probably mainly showing the remaining unspecific binding. The most marked uptake and the largest effect of haloperidol pretreatment was seen in a patient with a hormonally active prolactinoma. Dopamine receptor binding in pituitary tumors can be demonstrated in vivo with PET, and quantification of this binding is possible using a compartmental model. This technique may be useful in improving our understanding of the variable response to medical treatment of prolactinomas with dopamine agonists as well as in the prediction of the effect of such treatment.
The distribution of scattered radiation was measured for transmission scans in positron emission tomography by adding the scattered radiation distributions in different projections from line source experiments. It is shown that in a 20 cm diameter water-filled phantom the scattered radiation effects contribute approximately one-third of the events centrally in the field of view. This may lead to systematic errors of the order of 15-25% in reconstructed images. A scheme for correction for scattered radiation effects in the transmission scans is described and tested in phantom experiments.