[Radiation burden of patients in conventional diagnostic radiology: analysis of radiologic practice in Serbia].

X-rays are by far most significant contributor to total population dose from man-made sources of radiation. Diagnostic reference levels provide frameworks to reduce variability. The aim of this study is to establish, for the first time, a baseline for national diagnostic reference levels in Serbia for the most common X-ray examination types. Dose estimates are based on measurements of kerma-area product and Entrance surface air kerma for at least ten patients for each examination type, in each of 16 randomly selected hospitals in Serbia. Mean, median and third quartile values of patient doses are reported. Results have shown wide variation of mean hospital doses. Entrance surface doses were compared with previously published diagnostic reference levels. Doses for all studied examination types except chest radiography were within European DRL. The reasons for dose variation are discussed. The findings emphasize the importance of regular patient dose measurement to ensure that patient doses are kept as low as reasonable achievable.

Influence of bending on power distribution in step-index plastic optical fibers and the calculation of bending loss.

A means of calculating optical power distribution in bent multimode optical fibers is proposed. It employs the power-flow equation approximated by the Fokker-Planck equation that is solved by the explicit finite-difference method. Conceptually important steps of this procedure include (i) dividing the full length of the bent optical fiber into a finite number of short, straight segments; (ii) solving the power equation for each segment sequentially to find its output distribution; and (iii) expressing that output distribution in rotated coordinates of the subsequent segment along the curved fiber to determine the input distribution for that subsequent segment and thus enable the calculation of the power flow and output distribution for it. The segment length and bend-induced perturbation of output angles are determined by geometric optics. The resulting power distributions are given at different cross sections along the curved fiber axis. They vary with the radius of fiber curvature and launch conditions. Results are compared to those for straight fiber. Bending loss is calculated as well.

[Vertebrobasilar flow: clinical manifestations and diagnostic approaches]. / Vertebrobazilarni sliv: klinicke manifestacije i dijagnosticki postupci.

INTRODUCTION: The role of the damaged function of the brain and brain stem of vascular origin is very important in human pathology, especially today when these lesions are frequent, and prevention and elimination of consequences are complex. In practice vertebrobasilar insufficiency is a very important diagnostic problem. The aim of the paper is to point to the most frequent symptoms of vertebrobasilar dysfunction and to evaluate some diagnostic (electrophysiologic and neuroradiologic) procedures for the detection of a lesion. PATIENTS AND METHODS: The examination concerned the patients with symptoms and signs of the damaged vertebrobasilar torcular, hospitalized at the Department of Urgent Neurologu of the Clinical Centre of Serbia in Belgrade, from January 1 to December 31, 1990. The diagnosis was made on the basis of the clinical picture and electrophysiologic and neuroradiologic findings. On the basis of these findings the patients were divide in groups 1-5. According to the duration of symptoms and signs of the disease the following damages were observed: transitory ischaemic attack, reversible ischaemic neurologic dificiency and total ischaemic cerebral stroke. RESULTS: Fifty patients (36 men and 14 women), aged from 18 to 74 years, were examined. According to the localization of the lesion 20 patients belonged to group 2 (vascular area of a cerebelli inferior anterior). Definite infarct lesion was diagnosed in 32 patients (Table 1). The results of electrophysiologic examinations (auditive evoked potentials, somatosensorial evoked potentials, blink reflex, electroencephalographic screenint) were positive in 27-50% of examined patients (Tables 2, 3). The results of neuroradiologic examinations (vertebral angiography-19 patients and computed tomography-40 patients) were statistically significant in comparison to electrophysiologic results. DISCUSSION: In everyday practice the diagnosis of vertebrobasilar dysfunctions, and especially of transitory attacks of vertebrobasilar insufficiency, may be an important problem because of a large number of symptoms and signs with frequent alterations. The symptoms of this torcular are diverse and they reflect many structures in a limited area which, if minimaly damaged, cause important neurologic deficiency. Instead of a conclusion, we wish to emphasize that, in addition to the clinical picture, the use of different electrophysiologic methods in the diagnosis of vertebrobasilar failure is needed, as with these methods the preservation of function of different nuclei and ways, can be secured. A far as the neuroradiologic methods are concerned, computed tomography of the head must be obligatory when cerebellar or supratentorial elsions of vertebrobasifar torcular are suspected, or when the aetiology of the disease is not clear. Vertebral angiography should only be carried out when all non-invasive methods are exhausted.

[Diagnosis of cerebrovascular diseases in the elderly]. / Dijagnostika cerebrovascularnih bolesti kod starnih osoba.

Modern diagnostical methods and treatment of geriatric patients depend on the course and nature of cerebrovascular diseases. They require special individual therapy. The incidence of stroke increases with the age of a patient. This fact can be explained by the effect of risk factors associated with the statistically significant frequency of cardiac arrhythmias and heart decompensation. The loss of consciousness, convulsions and metabolic disorders predominate in the clinical picture of old people. The evolution of flexion contractions on paretic and non-paretic sides is usually faster and easier in this population. Taking into account the general condition of old people and frequent existence of other diseases in them, the diagnostic procedure should give priority to the treatment with non-invasive methods.

[Transient global amnesia--possible aetiopathogenetic mechanisms]. / Tranzitorna globalna amnezija--moguci etipatogenetski mehanizmi.

Transient global amnesia is a clinically well defined syndrome, characterized by transient isolated epizodes of confusion with inability to acquire new data, repetitive quieries, retrograde amnesia and absence of other neurologic symptoms or signs. Eighteen patients who presented at admission the clinical picture of transient global amnesia were, after the examination, classified in three groups: patients with symptoms or signs of transitory focal ischemia, migraine group, and miscellaneous group. The transitory global amnesia in patients suffering from atherosclerotic changes of the vascular system is usually the first manifestation of transitory ischaemic attack pointing to the vascular insufficiency of the posterior cerebral regions as the cause of attack. The typical transient global amnesia is not a rare phenomenon, but it supposes the existence of the precipitating factors. Although its "pure" form is usually benign, the appearance of other factors such as cerebral neoplasms, involved in the aetiology of transient global amnesia, requires the complete clinical examination of each individual with these symptoms.

[Cerebellar ataxia and acute cerebellar insult]. / Cerebelarna ataksija i akutni cerebelarni insult.

Ataxia, loss of muscle coordination during complex movement, is the most important sign of cerebellar lesion. Acute cerebellar attack of ischaemic and/or haemorrhagic nature is a focal disorder of cerebellar function which occurs rarely considering the prominent collateral net of blood vessels conveying blood to the cerebellum and the brain stem. We examined 12 patients with acute cerebellar attack (9 with ischaemic and 3 with haemorrhagic attack) of 300 patients with symptoms and signs of acute cerebrovascular attacks. We used all available diagnostic methods (EEG, neuro-ophthalmological examination, computed tomography as well as brain scintigraphy and angiography) in the management of these patients.

[Vascular headache and cerebral edema]. / Vaskulne glabovolje i edem mozga.

Headache is one of the commonest symptoms in neurology. It can be present among many other somatic illnesses. There are many aetiological factors. Pathogenetic mechanisms are unknown. There is a significant number of patients with headache, especially with vascular headache, (about 15%), and vascular headache associated with cerebrovascular ischaemic stroke. Therefore the new investigations of neurobiochemical and neurophysiological problems are necessary. A group of patients involved in our study with diagnosis of vascular headache was tested. The result of the study (especially neuroradiological results) show that many patients, prevalently young women, had cerebral oedema during the attack of vascular headache.

["One and a half syndrome" caused by lateral pontine haemorrhage]. / "Sindrom jedan i po" prouzrokovan lateralnom pontinom hemoragijom.

"One and a half syndrome" is an internuclear ophthalmoplegia combined with lateral gaze palsy on the same side. It is caused by ipsilateral lesion of the caudal part of pontine dorsal tegmentum - medial longitudinal fasciculus and paramedian pontine reticular formation or/and abducens nucleus. Usually it is of vascular origin and it can be a sign of lateral pontine haemorrhage. We described a patient with "one and a half syndrome" caused by spontaneous hypertensive hemorrhage in the lateral pontine legmentum which was visualised by brain CT scanning.

[Treatment of status epilepticus with intravenous lidocaine (Xylocaine)]. / Lecenje epilepticnog statusa intravenskim likokainom (Xylocain).

A case history of a 19-year old epileptic woman with diffuse encephalopathy of unknown aetiology and frequent attacks of status, epilepticus, whose last episode of the status epilepticus was successfully treated with intravenous lidocaine, after several first-line antiepileptic drugs failed to control, it, is presented. Although highly effective in treating refractory status epilepticus this treatment received little attention in clinical practice. We observed no un desired side effects of such treatment. The authors shortly reviewed current knowledge about several widely used treatment protocols. Some specific pharmacokinetic and pharmacodynamic properties of lidocaine during convulsions were also mentioned. A warning was drawn to toxic fide effects of lidocaine which were precipitated by increasing brain-blood pH gradient during convulsions, which in high doses included seizures caused by lidocaine per se. The effects of high dose lidocaine on the latencies and the amplitudes of the BAER and possible ways for mechanism of drug action were also reviewed.

Distribution of the occipital branches of the posterior cerebral artery. Correlation with occipital lobe infarcts.

The occipital branches of the posterior cerebral artery were examined in 31 human brains. The authors determined the origin, course, and region of supply of each occipital branch: the parieto-occipital, calcarine, posterior temporal, and common temporal arteries, as well as the lingual gyrus artery. These vessels were found in all the brains examined except the lingual gyrus artery, which was present in only 8.3%. The occipital branches were noted to supply variable cortical regions. In addition, they sometimes took part in irrigation of deep forebrain structures. It was concluded that occlusion of a certain occipital artery may cause varying clinical signs and symptoms in different patients. The neurologic deficits that may occur following the isolated occlusion of individual occipital branches of the posterior cerebral artery are discussed.

Anastomoses among the thalamoperforating branches of the posterior cerebral artery.

Thirty-three injected human brains were examined, and anastomotic vessels were found in 26 (79%) of them. Anastomoses varied in number from one to six. The mean diameter was 148 microns, and the mean length was 3.3 mm. Anastomoses were observed among the following: the branches of the single thalamoperforating vessel of the posterior cerebral artery (PCA), the individual thalamoperforating arteries of the same PCA, the thalamoperforating vessels and branches of the basilar and superior cerebellar arteries on the same side, the peduncular branches of the PCA and ipsilateral branches of the basilar and superior cerebellar arteries, and the thalamoperforating arteries on one side and various contralateral vessels. Anastomoses could be important components of collateral circulation in occlusive cerebrovascular diseases.

Perforating branches of the middle cerebral artery. Microanatomy and clinical significance of their intracerebral segments.

Perforating branches of the middle cerebral arteries (MCA) were examined on the forebrain hemispheres of fourteen human brains. It was noticed that their intracerebral segments arose from the MCA main trunk, and its terminal and collateral (cortical) branches. They terminated in certain parts of the basal ganglia and internal capsule. The course, direction, shape, diameters and branches of these segments were examined in detail. Classification of all the vessels was made according to caliber. It was concluded that the size of lacunar infarcts depends on the caliber and ramification zone extent of the occluded perforating vessels. Diameters of the intracerebral segments of vessels ranged from 80 to 840 microns, of their terminal branches from 80 to 780 microns, and of the collateral branches from 50 to 400 microns. The average size of the ramification zone was: 41.6 X 15.5 mm for the entire perforating artery; 37.9 X 15.5 mm for the intracerebral segment; 23 X 13 mm for the terminal branches; 8.9 X 5.5 mm for larger collateral branches; and 2.6 X 1.4 mm for the smallest branches.

Perforating branches of the middle cerebral artery. Microsurgical anatomy of their extracerebral segments.

Perforating branches of the middle cerebral artery (MCA) were examined under magnification in 50 formalin-fixed brain hemispheres. Perforating vessels varied in number from three to 18, with an average of nine. The greater the number of vessels, the smaller was their diameter. In this study, the perforating arteries were divided into medial, middle, and lateral groupings. Those in the medial group usually arose directly from the MCA main trunk close to the carotid bifurcation. There were usually three vessels in the middle group, which originated not only from the MCA trunk, but also from the MCA collateral (cortical) branches. Common stems, when present, gave rise to individual perforating vessels and occasionally to thin olfactory and insular rami. Perforating arteries in the lateral group varied from one to nine in number. In addition to an origin from the MCA trunk, they also arose from cortical branches supplying the frontal and temporal lobes. The fact that lateral perforating vessels often originated from division sites and from terminal branches of the MCA is of clinical significance, because aneurysms are more commonly located at the MCA bifurcation. Anastomoses were not found among the perforating arteries. In two specimens, a fusion between a perforating artery and the MCA trunk was noted. Since the perforating vessels are obviously end arteries, injury to them must be avoided during operations for MCA aneurysms.