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A method for absolute measurements of the 225Ac activity in equilibrium with its progeny was developed. Measurements were performed using the triple-to-double coincidence ratio (TDCR) method in two different TDCR counters. The activity concentration of an 225Ac solution was determined and the solution was sent to the SIR system for a comparison. The half-life of 225Ac was determined by one of the TDCR counters and found to be 9.9150(63) days.

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STUDY DESIGN: Preoperative magnetic resonance imaging was performed on 45 consecutive patients diagnosed with adolescent idiopathic scoliosis to evaluate the brain and spinal cord. OBJECTIVES: To investigate the prevalence of spinal cord abnormalities in patients undergoing surgery for adolescent scoliosis. SUMMARY OF BACKGROUND DATA: A review of the literature indicates that the number of abnormalities of the brain stem and spinal cord reported with magnetic resonance imaging in patients with idiopathic scoliosis is increasing. METHODS: Forty-five consecutive patients with idiopathic adolescent scoliosis were examined with magnetic resonance imaging to rule out underlying pathologic abnormalities of the brain stem or spinal cord. RESULTS: Two of 45 patients had abnormal findings on magnetic resonance imaging. One patient had a cervical cord syrinx from C4-T2 with an Arnold-Chiari malformation; the other patient had a syrinx from C6-C7. CONCLUSIONS: This study reports a higher than expected frequency of spinal cord abnormalities in patients with the preoperative diagnosis of adolescent idiopathic scoliosis. The indications for preoperative magnetic resonance imaging before spinal fusion vary among physicians; however, strict adherence to previously published recommendations as listed in this report is advisable. It appears from the results of this study that by following these guidelines, small syrinxes may remain undetected, but the clinical significance of this is unknown.

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Five ultrasound laboratories from Obstetrics and Gynecology departments of Belgian university hospitals or affiliated institutions conducted a prospective study from 1984 to 1992 in which the results of prenatal ultrasound examinations were compared to examination reports of the neonates. The results of the period 1984-89 (PI) have been published previously, and those of the period 1990-92 (PII) are presented here. Some very minor congenital anomalies, as listed and defined in the EUROCAT Register, were excluded. Of 26,147 pregnant women at normal risk for congenital anomalies, 25,046 had at least one ultrasound scan (96%). A total of 616 fetuses were structurally abnormal (prevalence 2.42%), and 685 abnormalities were recorded. The sensitivity of the ultrasound test was 40.4% in PI and 51.1% in PII for abnormal fetuses (p < 0.05), and 45% (PI) and 64% (PII) for abnormalities (p < 0.01). The specificity was 99.9% and the positive and negative predictive values were 94.2% and 98.6%, respectively; these values did not differ significantly between the two periods. The sensitivity for the detection of anomalies before 23 weeks increased from 21% in PI to 41% in PII, indicating an improvement in the early detection of fetal abnormalities.

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United States and European consensus views differ on the place of routine ultrasound scans during pregnancy and the validity of such scans as screening tests for fetal malformations in the general population is still under debate. Four ultrasound laboratories from Obstetric and Gynecology departments of Belgian University hospitals and affiliated hospitals have conducted a prospective study from 1984 to 1989 to compare the anomalies discovered in ultrasonic screening of the fetus with the anomalies of the neonates. Of 16,370 pregnant women at normal risk for congenital anomalies attending the antenatal clinics of these hospitals, 16,072 have had at least one ultrasound screening for congenital anomalies (98.5%). Congenital anomalies, single or multiple and 'minor' or 'major', were clearly defined in order to allow comparisons. The excluded congenital anomalies were listed as defined in the Eurocat Register. A total of 381 fetuses (2.3%) were structurally abnormal. Of the 381, 154 were correctly detected by ultrasound (sensitivity 40.4%). Altogether 15,972 fetuses were true negatives (specificity 99.9%). Eight (0.05%) were false positive for congenital anomalies. The positive predictive value was 95.1% and the negative predictive value was 98.6%. Ultrasound diagnoses were correctly achieved before 23 weeks of gestation for 21% of the anomalies. The gestational age, operator and technical dependence of ultrasound screening for congenital anomalies is discussed.

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We report a case of pneumocephalus following a water jet injury to the nose incurred during a water-skiing fall. Pneumocephalus due to this type of injury has not been previously reported, to our knowledge. Since this unusual injury may be associated with serious complications, it must be promptly recognized and treated.

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This article presents a methodology based on two complementary approaches, thus allowing a selection of maximal concentration in foodstuffs for determining appropriate countermeasures. The first approach is based on a minimal and maximal per capita intervention level and takes into account the annual intake of each product. The second one is based on a cost-benefit analysis, comparing the advantages of a countermeasure concerning those products presenting a contamination higher than a given maximal concentration (in terms of reduction of cost of the detriment associated with the risk), with its drawbacks (in terms of cost of the products) in order to select the "ALARA" maximal concentration. This second approach is used as a complement to the first one. The results obtained through these two approaches are given for four products (milk, meat, fresh vegetables, and corn) and two nuclides (Cs-137 and I-131). These are presented for various scenarios: one or various products contaminated by one or various radionuclides. It is concluded that these two approaches are complementary, the first one being related to individual risk and the second to collective risk. Therefore, these approaches are both of interest in the context of the elaboration of modalities for the radiological control of foodstuffs following an accidental release and both methods may be useful for determining appropriate countermeasures.

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High-resolution real-time ultrasound scanning of 54 patients was performed with a sector scanner during a variety of neurological procedures. Scans obtained at the time of craniotomy were successful in characterizing and localizing tumors, abscesses, arteriovenous malformations, and hematomas within the brain of 15 of 16 adult patients. One attempt to visualize a brain cyst through a 15-mm burr hole was unsuccessful. Scanning of 37 infants and young children was performed through the anterior fontanelle during placement of ventricular shunts. This allowed for the accurate placement of shunts in all patients and resulted in fewer short-term and long-term complications. Intraoperative ultrasound is a practical and highly effective means of providing intraoperative localization of intracranial anatomy and disease.

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An intra-axial epidermoid cyst of the brain stem is presented. X-ray studies revealed a mass within the brain stem; computerized tomography showed the mass to be cystic. The epidermoid cyst was successfully removed surgically. Six months after operation the patient is stable with sixth and seventh nerve palsies but resolution of right spastic hemiparesis.

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43 cases of intracranial ependymomas in children 0-13 years of age have been reviewed with attention given to various clinical aspects, including location, age, duration of history, signs and symptoms, and plain skull film abnormalities. 39 of the patients were treated by intracranial surgical procedures and 30 of these also had radiation therapy. Three patients had needle biopsy only and one died without treatment. The survival rate was below that anticipated and in part felt to be related to the frequent occurrence of malignant tumors in this series.

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A short review is made of the general characteristics of electromagnetic and corpuscular radiations to which man can be exposed. Following some considerations on the action of ionizing radiations and the radiobiological factors governing their effects on health, the overall characteristics of pathological effects differentiating stochastic from non-stochastic effects are summarized. The uncertainties remaining as to low-level exposures are stated as well as the cautious assumptions usually madein this field. The various sources of exposure to which the population is submitted are considered, i.e. exposures from natural, medical, domestic, industrial sources or from fallout from nuclear weapon tests; the present or predictable levels of exposure and their variations are given for each source. But for medical irradiation, all the exposures connected to human activities are much lower than natural exposure variations; such exposures should modify the incidence of certain affections but quite insignificantly as compared with the regional or local variations observed.

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