All about FAX: a Female Adult voXel phantom for Monte Carlo calculation in radiation protection dosimetry.

The International Commission on Radiological Protection (ICRP) has created a task group on dose calculations, which, among other objectives, should replace the currently used mathematical MIRD phantoms by voxel phantoms. Voxel phantoms are based on digital images recorded from scanning of real persons by computed tomography or magnetic resonance imaging (MRI). Compared to the mathematical MIRD phantoms, voxel phantoms are true to the natural representations of a human body. Connected to a radiation transport code, voxel phantoms serve as virtual humans for which equivalent dose to organs and tissues from exposure to ionizing radiation can be calculated. The principal database for the construction of the FAX (Female Adult voXel) phantom consisted of 151 CT images recorded from scanning of trunk and head of a female patient, whose body weight and height were close to the corresponding data recommended by the ICRP in Publication 89. All 22 organs and tissues at risk, except for the red bone marrow and the osteogenic cells on the endosteal surface of bone ('bone surface'), have been segmented manually with a technique recently developed at the Departamento de Energia Nuclear of the UFPE in Recife, Brazil. After segmentation the volumes of the organs and tissues have been adjusted to agree with the organ and tissue masses recommended by ICRP for the Reference Adult Female in Publication 89. Comparisons have been made with the organ and tissue masses of the mathematical EVA phantom, as well as with the corresponding data for other female voxel phantoms. The three-dimensional matrix of the segmented images has eventually been connected to the EGS4 Monte Carlo code. Effective dose conversion coefficients have been calculated for exposures to photons, and compared to data determined for the mathematical MIRD-type phantoms, as well as for other voxel phantoms.

A contribution to the establishment of reference values for total mercury levels in hair and fish in amazonia.

Studies on mercury levels in the Amazonian Region have typically lacked background or reference parameters. A sectional study on Hg concentration in hair and fish was conducted, together with an assessment of the prevalence of signs and symptoms related to Hg poisoning, in four communities in the Amazon Basin not impacted by gold mining, located either by a river course (Santana do Ituqui and Caxiuanã) or by a lake (Aldeia do Lago Grande and Vila do Tabatinga). Mercury determinations in hair and fish were made by flameless atomic absorption spectrophotometry. Mean total Hg in hair was 4.33 microg/g (0.40-11.60 microg/g) in 321 individuals from Santana do Ituqui, 3.98 microg/g (0.40-11.76 microg/g) for 316 persons in Aldeia do Lago Grande, 5.46 microg/g (0.37-49.85 microg/g) for 504 individuals from Vila do Tabatinga and 8.58 microg/g (0.61-45.59 microg/g) for 203 inhabitants from Caxiuanã. Fish consumption was very high in all those communities but no signs or symptoms associated with Hg poisoning were found. Mean Hg concentration in fish varied from 0.006 to 2.529 microg/g for carnivores and from 0.008 to 0.871 microg/g for noncarnivores. These values suggest that further studies including a larger number of communities would eventually lead to values of "normal" Hg concentration in the Amazonian Region quite above the limits suggested by the World Health Organization.

A voxel-based head-and-neck phantom built from tomographic colored images.

Recent progress in computer speed and medical imaging has made possible the development of a new family of anthropomorphic models, based on a volume elements (voxels) approach to phantom design. Such phantoms can represent details of the anatomical structures of the human body more realistically. Tomographic images (CT or MRI) contain the basic information for the construction of voxel-based phantoms. Use of voxel-based phantoms has its most significant application in the planning of individual patients therapy. To be implemented, results must be obtained in a reasonably short period of time. The segmentation of organs and tissues is a critical step in this process. This article presents a new approach in the construction of voxel-based phantoms that was implemented to simplify the segmentation process of organs and tissues, reducing the time used in this procedure. A voxel-based head and neck phantom, called MCvoxEL, was built using this new approach. The volumes and masses of the segmented organs and tissues were compared with data published by other investigators.

Mercury exposures in riverside Amazon communities in Pará, Brazil.

Cross-sectional studies were conducted in three riverside communities in the state of Pará in the Amazon Region of Brazil. Two of these communities, Brasília Legal and São Luís do Tapajós, are located in a watershed exposed to mercury pollution from artisanal gold mining, and the third, Santana do Ituqui, is outside this area. The studies were based upon a community census and included all persons volunteering for participation in each community. All participants were surveyed by questionnaire for health history, occupation, residence, and diet. Clinical evaluations were also done on each subject, along with collection of blood, urine, feces, and hair. Fish samples were collected to represent the most frequently consumed species. Mercury was measured in hair and fish. Although no signs or symptoms of overt mercury intoxication were observed, persons in Brasília Legal and São Luís do Tapajós had higher levels of mercury in hair than residents of Santana de Ituqui, located out of the risk area. Levels of mercury in fish were below Brazilian health guidance limits, but the high rates of fish consumption among these populations raise concerns for the possible effects of chronic exposure, especially among young children and women of childbearing age.

[Diagnosis of health conditions in a pan-mining community in the Tapajós River Basin, Itaituba, Par , Brazil, 1992]. / Diagnóstico das condições de saúde de uma comunidade garimpeira na regiõ o do Rio Tapajós, Itaituba, Pará, Brasil, 1992.

The purpose of this article is to describe health conditions in a pan-mining community, in particular the interaction of mercury contamination with other health problems. This study was carried out in a panning mine located on Rato Creek, a tributary of the Tapajó s River Basin in the municipality of Itaituba, State of Par The study population consisted of 223 individuals. An epidemiological questionnaire was applied, medical treatment was given, and biological specimens were collected. Testing of fecal samples showed that 96.1% of the individuals had parasites and 66.4% were anemic. Prevalence of hepatitis B virus was 85.0%, and 11 individuals (6.0%) were virus carriers (HBsAg positive). Of 186 patients tested for malaria, 65 individuals (35.0%) had the infection, of whom 34 (52.3%) were asymptomatic. Prevalence of syphillis was 41.6%. Urine mercury levels were measured in 173 individuals. Some 16 (9.2%) of those tested had mercury levels between 10 and 19 ug/l, while 9 patients (5.2%) had levels above 20 ug/l. An overview of general health conditions showed a combination of problems in individuals, who lacked adequate diagnosis, in addition to a high level of self-medication, given the absence of health facilities. In addition, these individuals are threatened by critical levels of mercury contamination. In conclusion, this article gives a general overview of health conditions in these pan-mining communities, demonstrating the multicausal nature of health conditions in the Amazon region, a fact which should be considered when planning appropriate strategies for clinical treatment.

Longitudinal study of rotavirus infections among children from Belém, Brazil.

From December 1982 to March 1986 a group of 80 children between 0 and 3 years old who lived in the peripheral area of Belém, Brazil, were followed up for episodes of diarrhoea. A total of 441 diarrhoeal episodes were recorded and 36 (8.2%) were associated with rotavirus. This agent was the only pathogen in 50% of rotavirus-related episodes of acute diarrhoea, and strains were characterized by analysis of RNA in polyacrylamide gels. Forty-one belonged to subgroup II (long pattern) and five to subgroup I. Reinfections by rotavirus were noted in 12 children involving either the same or different subgroups. Ten distinct electrophoretypes were detected in the study period and the predominant one had the '1N2L' profile. The cumulative age-specific attack rate for diarrhoea reached 2.8 by the end of the first year of life; a frequency of 2.3 episodes of diarrhoea per child per year was observed throughout the complete investigation. In comparing the age-specific attack rates for diarrhoea between breast-fed and bottle-fed children, a peak at 6 months of age was noted in the former, and at 1 month in the latter. A comparison by Fischer's exact test (P = 0.21) provided no evidence for protection against clinical rotavirus disease by maternal milk. By the same test, however (P = 0.021), we found significant evidence that early rotavirus infections were more likely to be asymptomatic and that infections after 4 months were more likely to be symptomatic. The clinical picture in children with rotavirus-related diarrhoea was more severe than in those suffering from acute diarrhoea due to another agent.

[Cryptosporidiosis in children from 1 to 2 years of age, with acute diarrhea in Belém, Pará, Brazil]. / Criptosporidiose em crianças de 1 a 2 anos de idade, com diarréia aguda em Belém, Pará, Brasil.

Two hundred and one samples obtained from 61 children were examined for Cryptosporidium infection during a period of 12 months. One hundred fifteen specimens were collected during diarrhoea episodes and the remaining 86 obtained out of diarrhoea period, as controls. All samples were examined by a modified Ziehl-Neelsen staining method. Cryptosporidium was detected in 6 (5.2%) of 115 samples from diarrhoeic children. All non-diarrhoeic control patients were negative for Cryptosporidium. The present study suggests that Cryptosporidium is an agent of self-limited diarrhoea among immunocompetent children from Belém, Pará.

Acute diarrhoea associated with rotavirus among children living in Belém, Brazil.

Between January 1979 and December 1980, rotaviruses were detected in faecal samples from 122 (33.1%) of 369 diarrhoeic children less than six years old, living in Belém, Brazil. In 55 (45.1%) of the 122 rotavirus-positive specimens, no bacteria or parasite associated with gastro-enteritis was found. Salmonella typhimurium, Shigella and Escherichia coli were found in 92 (35%) of the 263 faecal specimens examined for bacterial pathogens. Rotaviruses were readily detected throughout the year, which may indicate no seasonal pattern of incidence in the Belém region. A comparison of the excretion of rotavirus was made between children of two socio-economic groups. Of 144 children from the higher level group, 63 (47.3%) excreted rotavirus, whereas only 12 (16.7%) of those from the lower level did so. Vomiting (68.0%) and fever (65.6%) were the main symptoms, other than diarrhoea, exhibited by the 122 rotavirus-positive children.

Escherichia coli enterotoxigenicas e rotavirus detectados em criancas com gastroenterite aguda em Belem, Para. / Enterotoxigenic Escherichia coli isolated from children with acute gastroenteritis, Belem, Para

Procurou-se pesquisar, em Belem do Para, a presenca de Escherichia coli enterotoxigenica e outros enteropatogenos, incluindo agentes virais, nas fezes de 44 criancas de 0 a 5 anos de idade, com quadro diarreico agudo. A presenca de bacterias enteropatogenicas foi investigada pela coprocultura e a pesquisa de rotavirus atraves das tecnicas de ELISA e contra-imunoeletroosmoforese. O isolamento de enterovirus foi feito em cultura de celulas (Vero e HEp 2) e camundongo recem-nascido. Helmintos e protozoarios intestinais foram procurados pelo metodo direto. Trinta e tres (75%) dos casos foram positivos para um ou mais enteropatogenos, sendo 30,3% de etiologia bacteriana, 39,4% de origem viral e 30,3% de infeccao mista. A procura de enterotoxina LT e ST em 153 cepas de E.coli isoladas dos pacientes, foi feita, pelos testes de imuno-hemolise passiva (PIH) e camundongo recem-nascido (Teste de Dean), respectivamente. Cepas enterotoxigenicas de E. coli, em numero de 17 foram isoladas de sete dos 44 pacientes estudados. Em nenhuma amostra ocorreu producao simultanea de duas enterotoxinas

Observacoes sobre o isolamento de Campylobacter jejuni de criancas com gastroenterite aguda em Belem do Para (Nota previa). / Isolation of Campylobacter jejuni from children with acute gastroenteritis in Belem, Para (Preliminary report)

Amostras de Campylobacter jejuni foram isoladas das fezes de tres criancas com gastroenterite aguda em Belem do Para, tendo sido observada, em um dos casos, uma associacao desse agente bacteriano com Rotavirus. O relato desses isolamentos, constitui-se o primeiro a ser feito sobre o assunto na regiao Amazonica do Brasil