[Dosimetry and bone densitometry: examples of LUNAR IQ and HOLOGIC 4500A]. / Doses et ostéodensitométries: exemple du LUNAR IQ et de l'HOLOGIC 4500 A.

Patient dosimetry related to two bone densitometer units from different manufacturers (LUNAR IQ and HOLOGIC 4500A) were evaluated using the parallel beam technique and thermoluminescence from Ca (SO4)/Dy. The radiation dose measured for a phantom of 18 cm in thickness was 0,11 mGy (+/- 0,004) at a maximum current of 3 mA for the LUNAR IQ unit in the high-resolution mode. The radiation dose is 0,28 mGy (+/- 0,011) for the HOLOGIC 4500A unit used at 2,5 mA in the high resolution-mode. These results obtained by thermoluminescence of the Ca (SO4)/Dy are in favor of the LUNAR IQ unit. However, dosimetry must be weighted against image quality.

Onchocerciasis in West Africa after 2002: a challenge to take up.

Initially planned for a 20 year life time, the Onchocerciasis Control Programme in West Africa (OCP) will have finally continued its activities for nearly three decades (vector control alone from 1975 to 1989, then vector control and/or therapeutic treatment until 2002). Although onchocerciasis is no longer a problem of public health importance nor an obstacle to socio-economic development in the OCP area, the control of this filariasis is not over because OCP never aimed at eradication, neither of the parasite (Onchocerca volvulus), nor of its vector (Simulium damnosum s.l.). In 2003, the eleven Participating countries of OCP will take over the responsibility of carrying out the residual activities of monitoring and the control of this disease. This mission is of great importance because any recrudescence of the transmission could lead in the long run to the reappearance of the clinical signs of onchocerciasis, if not its most serious manifestations. For epidemiological and operational reasons, and given the disparity in national health policies and infrastructures, the capacities of the countries to take over the residual activities of monitoring and control of onchocerciasis are very unequal. Indeed, the interventions to be carried out are very different from one country to another and the process of integrating the residual activities into the national health systems is not taking place at the same pace. This inequality among the countries vis-a-vis the challenges to be met does not, however, prejudge the epidemiological situation after 2002 whose evolution will also depend on the effectiveness of the provisions made before that date by OCP, then after 2002, by the Regional Office for Africa of the World Health Organization which is currently setting up a sub-regional multidisease surveillance centre.

Assessment of cerebrovascular reactivity by dynamic susceptibility contrast-enhanced MR imaging.

In patients with cerebrovascular disease the acetazolamide (ACZ) test is performed to evaluate the decrease in cerebral perfusion pressure (CPP) through the investigation of the vasomotor reactivity (VMR). This latter is currently assessed with ACZ with several methods. Recently, magnetic resonance imaging (MRI) techniques have been developed that are sensitive to stimulus-induced changes in blood flow. Dynamic susceptibility contrast material-enhanced gradient-echo MRI techniques (DSC-MRI) might be an attractive tool to assess VMR. We aimed to test the ability of DSC-MRI in the assessment of VMR. Relative hemodynamic parameters rCBV, MTT, and rCBF were evaluated at baseline after the first injection of gadopentetate dimeglumine and 10 min after the intravenous administration of ACZ (1 g) with a second bolus of contrast agent. Assessment of hemodynamic parameters was performed over the whole hemisphere and also within regions of interest. The significances of the mean differences, before and after ACZ, were assessed with repeated-measures ANOVA with two within factors: laterality (right-left) and ACZ. DSC-MRI with ACZ test was performed in ten healthy controls (aged 51.4+/-16.2 years). The cerebral hemispheric ratio for the three parameters (cerebral blood volume (CBV), mean transit time (MTT), and cerebral blood flow (CBF)) ranged between 1.01 and 1.03. The mean gray matter-to-white matter ratio for CBV, CBF and MTT were 2.44, 2.41 and 1.05, respectively. As the laterality effect was not significant, left and right hemispheric values were averaged. A significant increase of all hemodynamic parameters was observed after ACZ (P<0.01-0.001). The same changes for CBV, CBF and MTT were observed after ACZ according to the regions of interest (P<0.006-0.015). DSC-MRI is a non-invasive method which enables the assessment of VMR. This technique may be added to any conventional MRI in order to detect a hemodynamic impact of an ICA stenosis. Therefore, it might be useful in determining the appropriate management when the indication for surgical versus medical therapy is in question.

Hemodynamic parameter assessment with dynamic susceptibility contrast magnetic resonance imaging in unilateral symptomatic internal carotid artery occlusion.

BACKGROUND AND PURPOSE: Hemodynamic parameters such as regional cerebral blood volume (rCBV), mean transit time (MTT), and regional cerebral blood flow (rCBF) can be assessed by dynamic susceptibility contrast MRI. The aim of the present study was to apply this method in patients who had symptomatic unilateral internal carotid artery occlusion. METHODS: Relative hemodynamic parameters (rCBV, MTT, and rCBF) were evaluated on the occluded side and thus compared with contralateral hemispheric values. We also attempted to detect any relationship between collateral flow and the hemodynamic parameters. RESULTS: Although rCBV was clearly increased in five patients over the whole hemisphere, we did not observe a statistically significant difference regarding the whole sample between sides (mean rCBV, 14.1 +/- 4.58 on the occluded side versus 11.8 +/- 2.99 on the contralateral side, P>.10). MTT was clearly increased on the occluded side (mean MTT, 4.29 +/- 0.83 on the lesion side versus 3.14 +/- 0.81 on the contralateral side, P<.010). A statistically significant decrease of rCBF on the occluded side was observed (mean rCBF, 3.27 +/- 0.73 versus 3.93 +/- 1.03 on the contralateral side; P<.01). CONCLUSIONS: A significant hemodynamic compromise in patients who had unilateral symptomatic carotid occlusion was observed according to CBF and MTT values. This approach might be promising in the understanding of cerebral hemodynamics in patients with vascular disorders.

Cerebral blood flow reserve assessment in symptomatic versus asymptomatic high-grade internal carotid artery stenosis.

BACKGROUND AND PURPOSE: Thromboembolic stroke is likely to occur in patients with a restricted cerebral blood flow reserve. Our aims were to determine (1) whether symptomatic patients had any significant hemodynamic restriction ipsilateral to carotid occlusive disease compared with patients whose carotid stenosis is asymptomatic and (2) whether patients with carotid occlusive disease have impaired cerebral perfusion reserve compared with control subjects. METHODS: We compared cerebral blood flow and collateral capacity using the 133Xe inhalation method and acetazolamide test in symptomatic (n = 10) and asymptomatic (n = 10) patients who had a high-grade internal carotid artery stenosis (range, 70% to 99%). Results were compared with those from 10 healthy control subjects. RESULTS: Mean baseline cerebral blood flow was 40.29 +/- 1.38 mL/100 g per minute on the symptomatic side in symptomatic patients versus 45.20 +/- 2.53 mL/100 g per minute on the lesion side in asymptomatic patients (control subjects, 46.91 +/- 2.11 mL/100 g per minute in the right hemisphere versus 46.17 +/- 1.93 mL/100 g per minute in the left). There was no statistical difference between patients in symptomatic and asymptomatic groups versus control subjects (P > .10). Mean cerebral blood flow increase after acetazolamide was in the same range in symptomatic (52.89 +/- 2.54 mL/100 g per minute) and asymptomatic (56.22 +/- 3.35 mL/100 g per minute) patients (P > .10), and no difference was observed regarding control subjects (54.25 +/- 2.94 mL/100 g per minute; P > .10). Three asymptomatic and two symptomatic patients and three control subjects had no significant cerebral blood flow increase after acetazolamide. CONCLUSIONS: An additional hemodynamic factor in thromboembolic ischemia related to severe unilateral carotid stenosis might be an unusual finding in patients without apparent hemodynamic induction of symptoms. The lack of significant variation in postacetazolamide cerebral blood flow in some patients and control subjects implies that this procedure may be inconsistent in assessing the cerebral perfusion reserve in the individual case.

[National entomological teams of the western extension zone of the Onchocerciasis Control Program (OCP) in west Africa from 1986 to 1990]. / Equipes nationales entomologiques de la zone d'extension ouest du programme de lutte contre l'onchocercose en Afrique de l'ouest (OCP) de 1986 à 1990.

The western extension area of the Onchocerciasis Control Programme in West Africa (OCP) covers five countries: Guinea, Guinea-Bissau, Mali (western part), Senegal and Sierra Leone. From 1986 to 1990, national teams employed by the respective governments have been regularly collecting entomological data on the vectors of onchocerciasis in these countries. As in the initial programme area of the OCP, the entomological surveillance network was composed of entomological sectors and subsectors (the latter are called "operational bases" in the western extension). In 1990, 308 staff in 47 capture teams were employed for the entomological surveillance activities in seven sectors and twenty-five operational bases. They included a national coordinator as head of the teams for each country, a wide range of technicians, and administrative support staff to assist the national coordinator in the overall management of available resources. The national teams worked under the technical responsibility and supervision of WHO/OCP but with no employee/employer relationship between them and WHO, since they were employed and their salaries were paid by their governments. The OCP, however, paid additional lump sum allowances to each worker, as well as daily subsistence allowances when away from their duty station. Vehicles, entomological equipment, office supplies and furniture, fuel and lubricants were provided by WHO/OCP. Despite the difficulties encountered in the field, which were often great, and their lower salaries (compared with colleagues paid by WHO/OCP), the technical workers in the national teams performed well by OCP standards, with results as satisfactory as those obtained by the WHO/OCP teams in the rest of the programme area. The main reasons for the efficiency and dynamism of the national entomological teams are described. The future of these teams after OCP has ceased its activities is also discussed.

Functional neuroimaging strategy in temporal lobe epilepsy: a comparative study of 18FDG-PET and 99mTc-HMPAO-SPECT.

We performed 99mTc-hexamethylpropyleneamineoxime-single-photon emission computed tomography (SPECT) and 18F-fluorodeoxyglucose-positron emission tomography (PET) in 20 epileptic patients with well-lateralized temporal electroencephalographic focus, normal computed tomographic scan, and brain magnetic resonance imaging (MRI) either normal (n = 10) or showing nonspecific changes in the epileptogenic temporal lobe (n = 10). In patients with a normal MRI, PET exhibited focal hypometabolism in 80%, whereas SPECT showed corresponding hypoperfusion in only 20%. In patients with an abnormal MRI, PET and SPECT yielded 100% and 90% sensitivity, respectively. The metabolic and regional cerebral blood flow disturbances were topographically concordant with electroencephalographic and MRI findings in all these patients. Only patients with a large and pronounced hypometabolism on PET images exhibited hypoperfusion on SPECT. Spatial resolution appeared to be the critical factor responsible for the higher sensitivity of PET. However, this superiority of PET did not prove clinically useful in patients whose SPECT was abnormal, particularly when brain MRI showed nonspecific changes in the epileptogenic temporal lobe.

High signal intensity on T2-weighted MRI correlates with hypoperfusion in temporal lobe epilepsy.

Single-photon emission computed tomography (SPECT) and [99mTc]HMPAO were used to assess the functional significance of nonspecific magnetic resonance imaging (MRI) abnormalities observed in patients with temporal lobe epilepsy and no focal lesion on CT scan. We studied 18 patients whose MRI was normal or showed high signal intensity on T2-weighted images (T2WIs) at the site of the EEG focus in 11 and 7 cases, respectively. EEG was monitored during regional cerebral blood flow (rCBF) study. Lateralized hypoperfusion was present in 7 of 17 interictal (41%) and in one postictal cases; it was located in the temporal lobe on the side of the EEG focus in all, and was significantly more frequent in patients with high signal intensity on T2WI (86%) than in patients with a normal MRI (18%). The degree of temporal perfusion asymmetry measured in each individual was higher in patients whose MRI was abnormal.

Nuclear hemodynamic vertebrobasilar insufficiency. A new approach with the xenon Xe 133 method.

Vertebrobasilar insufficiency is a well-known syndrome, but no corresponding hemodynamic deficit has yet been established. We propose to define nuclear hemodynamic vertebrobasilar insufficiency on the basis of an oligemia lower than 35 mL/100 g per minute in the brain stem-cerebellar region with use of the xenon Xe 133 inhalation method. Fifteen patients fulfilling this criterion underwent four-vessel angiography, computed tomography, and a standardized neurologic examination. An acetazolamide test showed poor reactivity in more than half of the patients, sometimes specifically in the vertebrobasilar area. With use of single-photon emission computed tomography and intravenous technetium Tc 99m-labeled hexamethylpropyleneamineoxime in two cases, the considerable decrease of regional cerebral blood flow in the brain stem-cerebellar region was confirmed. An excellent correlation was observed between the existence of nuclear hemodynamic vertebrobasilar insufficiency and angiographically proved arterial occlusions. The dominant nuclear oligemic zone was regularly on the side of the anatomic arterial chief lesion. Clinical manifestations included rare transient ischemic attacks (in one of 15 patients), intermittent basilar symptoms (in 15 of 15 patients), and a subacute vertebrobasilar "threatening" syndrome. Thus, imaging of a nuclear hemodynamic vertebrobasilar deficit provides an objective basis to the diagnosis of vertebrobasilar insufficiency and useful objective data for revascularization surgery.

The WHO Onchocerciasis Control Programme: retrospect and prospects.

The history of onchocerciasis control in Africa and the genesis of the WHO Onchocerciasis Control Programme in West Africa (OCP) are briefly reviewed. The importance of experience gained in anti-locust campaigns in helping to plan the OCP is stressed. Members of the Simulium damnosum species complex are the vectors of onchocerciasis, which OCP is controlling with insecticide treatments on the stretches of rivers where the Simulium breed. Migrations of flies have been responsible for reinfestations of controlled areas and the spread of insecticide resistance. The management of these problems and related research are described, but it is emphasized that despite setbacks OCP is achieving its aims. A strategy for the future is outlined: vector control supplemented by chemotherapy is expected to continue until the year 2004.

[Value of cerebral blood flow study with nimodipine test in intracranial aneurysm]. / Intérêt de l'étude des débits sanguins cérébraux avec test à la nimodipine dans les anévrismes intracraniens.

The study of cerebral blood flow (DSC) in 29 patients with intracranial aneurysm is interesting to diagnose cerebral ischemia without clinical and radiological effect. A test with nimodipine sensitize this exam, confirm the efficacy of this drug in located ischemias. But may reveal a decrease of cerebral blood flow after nimodipine: it is probably an interesting therapeutic test.

[Effects of an intravenous injection of nicardipine on cerebral blood flow in subarachnoid hemorrhage caused by intracranial aneurysm]. / Effets d'une injection intraveineuse de nicardipine sur le débit sanguin cérébral au cours des hémorragies méningées par anévrisme intracrânien.

Fifteen patients with ruptured intracranial aneurysm have been operated before undergoing post surgery xenon inhalation for cerebral blood flow valuation: first measurement has been performed as CBF reference; 2nd measurement has been done after 0.1 mg.kg-1 I.V. bolus of nicardipine; sides effects are mainly due to BP fall 2/15 and some consequent neurological distress have been noticed (2/15); results should be carefully interpreted. Significant CBF increase have been measured after nicardipine injection, specially in brain area correlated to low CBF before injection (the lower the CBF, the higher the increase of local flow). The study prompt us to check the effect of nicardipine on patient (with CBF measurement after nicardipine test) before giving the treatment. Problems remain to be solved with further studies and not yet established: correlation between hemodynamics changes and clinical status and also which time of disease evolution is the best to be treated.

[Hemodynamic vertebrobasilar insufficiency demonstrated by chronic oligemic cerebral flow and cerebellar ataxia: two new concepts]. / Insuffisance vertébro-basilaire hémodynamique démontrée par les débits cérébraux et ataxie cérébelleuse oligémique chronique: deux nouveaux concepts.

We propose in the paper of the concept of nuclear hemodynamic vertebrobasilar insufficiency, defined as an oligemic blood flow lower than 35 ml/100 g/min. in the brain stem-cerebellum zone, when using the method of inhalation of 133Xe. In 15 patients, the neurophysiologic manifestations included intermittent symptoms. We describe here permanent neurophysiologic motor disturbances: extrapyramidal Dopa sensitive syndrome (2/15), chronic cerebellar ataxia (12/15), often associated with cerebellar atrophy (8/12). The concept of chronic oligemic cerebellar ataxia, corresponding to selective neuronal death and/or neurochemical failure, is proposed.

A controlled study of Dextran 40: effect on cerebral blood flow and metabolic rates in acute head trauma.

A controlled double-blind evaluation of the effects of Dextran 40 at different concentrations on cerebral blood flow (CBF), cerebral oxygen consumption (CMRO2) and cerebral lactate production (CMRLact) was carried out. We studied 40 patients in coma due to recent head injury. Concentrations of Dextran solution were not significantly related to variations in CBF and metabolic rate over the period of infusion. The lack of effect of the Dextran infusion may be explained by the absence of global brain ischemia in these patients at the time of the study. The very low initial CBF values were a consequence of brain metabolic depression and not a sign of global ischaemia. The rheological benefits of treatment with Dextran 40 in head injured patients should preferably be investigated using techniques which permit detection of local changes in CBF and metabolism.

rCBF landscapes during motor performance and motor ideation of a graphic gesture.

The regional cerebral blood flow (rCBF) distribution was measured by 133xenon inhalation using a gamma camera in 18 right-handed volunteers, 6 subjects performing a graphic task (writing numbers in letters) with the right hand, 6 subjects imagining the same task, and 6 subjects were assessed during two rest periods to determine the reproducibility of the technique. The mean rCBF increased between 10% and 25% (P less than 0.01) during both motor performance and motor ideation. However, there were regional differences. While motor performance activated mainly the rolandic regions bilaterally, motor ideation gave prefrontal and premotor rCBF augmentations. In both situations there was significant bilateral increase in regions corresponding to the cerebellum.