Effects on the accelerating electron bunches due to the presence of sulfur hexafluoride or air in the linac waveguide.

Sulfur hexafluoride gas (SF6) is used as a dielectric insulator in the acceleration process of certain medical linear accelerator waveguides. Nevertheless, some innovative development and investigation cases require intervention in the linear accelerator or, specifically, on the waveguide, which could affect the sealing of the device. In this regard, vacuum sealing systems can be compromised, affecting the properties of the radiation beams produced. The presence of sulfur hexafluoride or air inside the VARIAN 6/100 waveguide was investigated under different pressure conditions and non-uniform electric fields, adapting Monte Carlo simulation techniques for modeling radiation transport coupled with electric fields. Obtained results indicated the suitability of the proposed approach, while comparisons with theoretical approaches and experimental evidence supported the model's consistency.

Dosimetry of tumor targeting imaging by convergent X-ray beam as compared with nuclear medicine.

During decades nuclear medicine procedures, based on radiolabeled agents, have proved to be efficient for diseases diagnosis and treatment. Radiation emerging from patient is detected aimed at localizing radiotracer distribution that is further correlated with biochemical/metabolic physiological processes. However, a significant drawback associated with current nuclear medicine procedures implementing radionuclide infusion regards to the inherent absorbed dose as well as radiopharmaceuticals' production, storage and elimination from patient body, thus representing a risk at patient and public health level. In the recent years, alternative methods have been proposed to reduce/eliminate radionuclides in some nuclear medicine procedures. The combination of high atomic number nanoparticles infused within patient body with incident X-ray beam, like tumor targeting and treatment, appears as a potential alternative method capable of theranostics. The process is based on inducing X-ray fluorescence and secondary electrons emission in high atomic number nanoparticles by means of excitation with an external X-ray beam, avoiding employing radioactive substances. The present work reports on the dosimetry performance of both methods, comparing whenever the external convergent X-ray beam alternative may involve less or larger radiation dose levels, according to comparable signal/image quality during the procedure. To this aim, a simplified theoretical model is proposed and associated Monte Carlo simulations are performed in order to compare typical case of nuclear medicine imaging with potential performance of an innovative method, called OXIRIS (Orthovoltage X-ray Induced Radiation and Integrated System), based on convergent X-ray beam exciting high atomic number nanoparticles infused in patient. The obtained results support the proposed alternative method's feasibility, once demonstrated that patient absorbed dose levels are relative similar to those currently used by nuclear medicine procedures, whereas dose to targeted region (tumor) are significantly higher, which may be useful for treatment purposes.

[The direct costs of epilepsy in a Chilean population]. / Costes directos de la epilepsia en una población chilena.

INTRODUCTION: Epilepsy Chilean prevalence is 17-21/1,000 inhabitants. In past years, there is concern for the high costs involved in its handling. AIM. To estimate the direct costs of treatment and handling in specific population with epilepsy. PATIENTS AND METHODS: It is a retrospective study, in 6 groups of people with epilepsy: recent diagnosis (RD), remission (R), occasional seizures (OS), active without resistance to drugs (AWRD), resistance to pharmacological treatment (RPT), and epilepsy surgery (S). Data and characteristics tabulation and economical study of each group were made, considering 1 year of treatment. A comparison was made between them and their average in relation to international data. RESULTS: 293 patients. 52% male. 76% adults. 25% students. 55% focal seizures. Costs per group: (USD/patient/year): RD, 443; R, 316; OS, 430; AWRD, 711; RPT, 946; S, 4,262. Direct average cost of treatment for epilepsy in this population: 615 USD/patient/year. CONCLUSIONS: When differentiating in groups of individuals with epilepsy, the highest average annual cost is in surgery and the lowest in remission. In all the groups, except for surgery one, the highest expense is in drugs (average 81%). In relation to other countries, our direct costs are 5 times lower than in some developed countries and 3.5 times higher than in other developing countries. This data is of interest to governmental and financial spheres, so to provide a better quality of life for people with epilepsy, lowering costs and fees for their treatment and contributing to epilepsy and surgery national programs.

Costes directos de la epilepsia en una población chilena / The direct costs of epilepsy in a chilean population

Introducción. La prevalencia de la epilepsia en Chile es de 17-21/1.000 habitantes. Últimamente ha habido preocupación por los costes en su diagnóstico y tratamiento. Objetivo. Calcular los costes directos del tratamiento de una determinada población chilena con epilepsia. Pacientes y métodos. Estudio retrospectivo en seis grupos de pacientes: diagnóstico reciente (DR), remisión (R), crisis ocasionales (CO), activos sin resistencia a fármacos (ASRF), resistencia al tratamiento con fármacos (RTF) y cirugía de la epilepsia (C). Se tabularon datos clínicos y económicos por grupo, considerando un año de tratamiento, además de su comparación entre ellos y su promedio respecto a datos internacionales. Resultados. Hubo 293 pacientes, 52% masculinos, 76% adultos, 25% estudiantes; 16% con trabajo estable; 55% con crisis focales. Los costes promedios por grupos, calculados en dólares estadounidenses (USD)/paciente/año, fueron los siguientes: DR, 443; R, 316; CO, 430; ASRF, 711; RTF, 946; C, 4.262. Conclusiones. El coste más elevado en cada grupo, excepto el quirúrgico, fueron fármacos, con un promedio de 81%. El coste directo promedio grupal fue de 615 USD/paciente/año. En los costes promedios anuales por grupos, el mayor es el de cirugía, y el menor, el de remisión, debido al menor uso de medicamentos, exámenes y consultas. Nuestros costes directos son 5 veces menores que algunos países desarrollados y 3,5 veces superiores que otras naciones en vía de desarrollo. Estos datos pueden contribuir a mejorar la calidad de vida de personas con epilepsias, optimizando costes y tarifas, ayudando a programas nacionales de epilepsia y cirugía de la epilepsia

Introduction. Epilepsy Chilean prevalence is 17-21/1,000 inhabitants. In past years, there is concern for the high costs involved in its handling. Aim. To estimate the direct costs of treatment and handling in specific population with epilepsy. Patients and methods. It is a retrospective study, in 6 groups of people with epilepsy: recent diagnosis (RD), remission (R), occasional seizures (OS), active without resistance to drugs (AWRD), resistance to pharmacological treatment (RPT), and epilepsy surgery (S). Data and characteristics tabulation and economical study of each group were made, considering 1 year of treatment. A comparison was made between them and their average in relation to international data. Results. 293 patients. 52% male. 76% adults. 25% students. 55% focal seizures. Costs per group: (USD/patient/year): RD, 443; R, 316; OS, 430; AWRD, 711; RPT, 946; S, 4,262. Direct average cost of treatment for epilepsy in this population: 615 USD/patient/year. Conclusions. When differentiating in groups of individuals with epilepsy, the highest average annual cost is in surgery and the lowest in remission. In all the groups, except for surgery one, the highest expense is in drugs (average 81%). In relation to other countries, our direct costs are 5 times lower than in some developed countries and 3.5 times higher than in other developing countries. This data is of interest to governmental and financial spheres, so to provide a better quality of life for people with epilepsy, lowering costs and fees for their treatment and contributing to epilepsy and surgery national programs

The epidemiology of malaria in an epidemic area of the Peruvian Amazon.

A longitudinal study of malariometric indicators and their association with potential risk factors was conducted during August 1997-July 1998 at Padre Cocha, a village of 1,400 residents in the Peruvian Amazon. The incidence of Plasmodium falciparum infections during the study year was 166/1,000 persons; that of P. vivax was 826/1,000 persons. The mean duration of symptoms prior to diagnosis was 2 days; presenting geometric mean parasite densities were 3,976 parasites/microl for P. falciparum infections and 2,282 parasites/microl for P. vivax. There were no malaria-associated deaths. Consistent with the epidemic nature of malaria in the area, the incidence of both parasite species increased with age and there were no age-specific differences in mean parasite densities. No specific occupational risks for malaria were identified. Activities significantly associated with malaria risk reflected local vector behavior and included strolling outdoors after 6:00 PM and arising before 6:00 AM for adults, and attending evening church services for children.

Malaria reemergence in the Peruvian Amazon region.

Epidemic malaria has rapidly emerged in Loreto Department, in the Peruvian Amazon region. Peru reports the second highest number of malaria cases in South America (after Brazil), most from Loreto. From 1992 to 1997, malaria increased 50-fold in Loreto but only fourfold in Peru. Plasmodium falciparum infection, which has increased at a faster rate than P. vivax infection in the last 3 years, became the dominant Plasmodium infection in the highest transmission areas in the 1997 rainy season. The vector Anopheles darlingi has also increased during this epidemic in Loreto. Moreover, chloroquine and pyrimethamine-sulfadoxine drug-resistant P. falciparum strains have emerged, which require development of efficacious focal drug treatment schemes.