Torgny Greitz

A COMPUTERIZED BRAIN ATLAS : CONSTRUCTION, ANATOMICAL CONTENT, AND SOME APPLICATIONS

An adjustable computerized atlas of the human brain has been developed, which can be adapted to fit individual anatomy. It is primarily intended for positron emission tomography (PET) but may also be used for single photon emission CT, transmission CT, magnetic resonance imaging, and neuroimaging-based procedures, such as stereotactic surgery and radiotherapy. The atlas is based on anatomical information obtained from brains fixed in situ soon after death. All structures have been drawn in on digitized photos of slices from one cryosectioned brain. The definition and classification of the anatomical structures and divisions are in agreement with the standard textbooks of anatomy, and the nomenclature is that of the Nomina Anatomica of 1965. The boundaries of the cortical cytoarchitectonic areas (Brodmann areas) have been determined using information from several sources, since three-dimensional literature data on their distribution are incomplete, scarce, and partly contradictory. However, no analysis of the cytoarchitectonics of the atlas brain itself has been undertaken. At present the data base contains three-dimensional representations of the brain surface, the ventricular system, the cortical gyri and sulci, as well as the Brodmann cytoarchitectonic areas. The major basal ganglia, the brain stem nuclei, the lobuli of the vermis, and the cerebellar hemispheres are also included. The computerized atlas can be used to improve the quantification and evaluation of PET data in several ways. For instance, it can serve as a guide in selecting regions of interest. It may also facilitate comparisons of data from different individuals or groups of individuals, by applying the inverse atlas transformation to PET data volume, thus relating the PET information to the anatomy of the reference atlas rather than to the patients anatomy. Reformatted PET data from individuals can thus be averaged, and averages from different categories or different functional states of patients can be compared.

Head Fixation Device for Reproducible Position Alignment in Transmission CT and Positron Emission Tomography

A head-positioning device allowing accurate position transference between computed tomography and positron emission tomography is described. A base plate is fixed to the patients head through either an individual mold or screws into the calvarium. This base plate fits onto the headholders of the two devices, thus ensuring that scans are taken at the same level. Using the regular software, the coordinates of an anatomic structure may be determined and transferred between the two images.

Discrepancies in Brain Tumor Extent as Shown by Computed Tomography and Positron Emission Tomography Using [68Ga]EDTA, [11C]Glucose, and [11C]Methionine

A patient with an anaplastic (malignant) astrocytoma was examined with computed tomography (CT) and with positron emission tomography (PET), in the latter case using [68Ga]EDTA, [11C]glucose, and [11C]methionine. The CT examination as well as the [68Ga]EDTA study showed a small tumor located in the region of the head of the left caudate nucleus. The [11C]glucose examination showed increased uptake on the same region, as did the [11C]methionine examination, but the latter also showed a considerable uptake in the entire left thalamic region. The patient died 15 days after the [11C]methionine study and a histologic evaluation of thin sections obtained at autopsy showed excellent agreement between tumor extent and activity distribution after [11C]methionine administration. The tumor tissue seen only with [11C]methionine was histologically different from that part of the tumor observed with the other tracers. Although cytologically similar, the latter showed large necrotic areas and an ability to induce marked endothelial proliferation, whereas in the former neither necroses nor notable endothelial proliferation was seen. In this case more than 50% of the tumor would have remained radiologically imperceptible without the [11C]methionine PET examination.

Preparation of 11C-labelled raclopride, a new potent dopamine receptor antagonist: Preliminary PET studies of cerebral dopamine receptors in the monkey

A new dopamine receptor antagonist, Raclopride (S-(-)-3,5-dichloro-N-[(1-ethyl-2-pyrrolidinyl)]methyl-2-hydroxy- 6-methoxybenzamide, FLA 870) (1), has been labelled using [11C]ethyl iodide for alkylation of the nitrogen of the pyrrolidine ring in the corresponding secondary amine (5). The synthesis of 5 and an efficient method for the preparation of [11C]ethyl iodide are described. The 11C-labelled FLA 870 (1) was purified by HPLC and then used in positron emission tomography to visualize the dopamine receptor-rich areas of the monkey brain. The images obtained show selective accumulation of FLA 870 in striatum and a 10-fold separation between the binding to caudate vs cerebellum.

Normal Size of the Internal Carotid, Middle Cerebral and Anterior Cerebral Arteries

The size of the internal carotid, middle cerebral and anterior cerebral arteries have been investigated by WOLLSCHLAEGER & WOLLSCHLAEGER (1966) in unselected cadaver brains as well as with carotid angiography performed during life. However, neither the angiographic nor the clinical diagnoses were given for the living subjects. The present investigation has been made in an attempt to determine the normal size of the internal carotid, middle cerebral and anterior cerebral arteries.

Computer assisted tomography of intracranial CSF circulation using a water-soluble contrast medium.

By the introduction of isotope cisternography (DI CHIRO 1964) a new tool was provided for the investigation of the circulation of the cerebrospinal fluid (CSF). To-day this method is regarded as indispensable in the examination of patients with disturbances of CSF dynamics, especially those with communicating hydrocephalus. However, isotope cisternography is hampered by certain drawbacks. Passage of the tracer material to the ventricular system is an important sign of pathology, but may be difficult to ascertain especially in patients with small ventricles due to the low resolution of isotope scanning methods. Furthermore, the ventricles in the lateral view are superimposed on the sylvian fissures and in the a.p. and axial views on the interhemispheric fissure; these fissures being main CSF pathways usually contain large amounts of the isotope which may render evaluation of ventricular filling difficult. Another disadvantage of the method is the relatively high radiation doses to the spinal cord (HILDITCH 1968, WAGNER et coll. 1970) which significantly restricts the number of examinations that can be made in one and the same patient. Computer assisted axial tomography (HOUNSFIELD 1973, AMBROSE 1973), in the following referred to as

Stereotactic radiosurgery in intracranial arterio-venous malformations.

Stereotactic radiosurgery has been used to treat five arteriovenous malformations, in which surgical excision could not be carried out, using the “Co Gamma Unit.

HYDROCEPHALUS DUE TO ELONGATED BASILAR ARTERY: A New Clinicoradiological Syndrome

Abstract In 3 patients a typical clinical picture of chronic adult hydrocephalus was apparently caused by an elongated basilar artery. The disorder should be recognised as a treatable cause of presenile dementia.

Hydrocephalus due to ectasia of the basilar artery

Abstract Nine patients, aged 46–68 years, showed typical clinical features, usually characterized by three stages: (1) a latent stage with essential hypertension; (2) the appearance of disturbances of gait and balance, as well as bilateral pyramidal tract symptoms; the disturbance of gait was of the “spastic ataxia” or “apraxia of gait” type; (3) the appearance of progressive presenile dementia. Four patients had epilepsy. Neuroradiological investigation showed, in every case, a characteristic deformation of the third ventricle, caused by elongation and ectasia of the basilar artery, and symmetrical dilatation of the lateral ventricles. Air did not pass up on to the convexity of the brain. RIHSA cisternography was performed in 6 cases, and disclosed a characteristic picture of delayed resorption of CSF over the convexity. The cerebral blood flow was determined in 7 cases; reduced values were noted in all of them. It is concluded that, in these cases, the ectatic basilar artery had caused a functional form of obstructive hydrocephalus, in which the obstruction lay anterior to the aqueduct of Sylvius, and resulted from deformation of the third ventricle. Probably, the strong vascular pulsations can be transmitted to the ventricular system, and cause or contribute to the appearance of hydrocephalus. A ventriculo-atrial shunt according to Pudenz et al. (1957) was made in 6 patients. Definite improvement was observed in 2 patients, moderate in 1, and slight improvement in another 1. In 2 cases, no improvement could be observed after operation. In 3 of the patients who improved, the cerebral blood flow was also determined post-operatively. In all 3 cases, the flow had increased, and this increase was correlated with the degree of clinical improvement. It is suggested that this forms the basis of the clinical improvement that can be achieved by a shunt operation.

EFFECT OF BRAIN DISTENSION ON CEREBRAL CIRCULATION

Abstract It is contended that distension of the brain secondary to regressive changes—e.g., brain atrophy— is common in the higher age-groups. The distension may be, and often is, the cause of diminished blood-flow in the ageing brain. This hypothesis is supported by recent investigations, initiated by the discovery of a pathological condition termed normal-pressure hydrocephalus. With this type of hydrocephalus the cerebrospinal-fluid (C.S.F.) pressure is normal or not pathologically increased, but the cerebral blood-flow is reduced. This reduction in flow is correlated with the degree of ventricular dilatation. The condition of those affected improves after drainage of the C.S.F. by shunt procedures which cause a concomitant increase in cerebral blood-flow. The brain can be said to form an elastic container around the ventricular system, and the tensile strength of this container is diminished by atrophic processes due to ageing. These processes allow the ventricular system to expand even without an increase in the intraventricular pressure. Pneumoencephalographic investigations confirm that such distension is the rule rather than the exception at higher ages. This distension reduces the cerebral blood-flow by compressing the cerebral vessels. Probably there is a complex interaction between, on the one hand, morphological changes due to ageing in the brain tissue, in the C.S.F. valves, and in the cerebral blood-vessels, and, on the other hand, physiological disturbances in the cerebral blood circulation and in the C.S.F. circulation.