ABSTRACT
The dosimetric response of a multi guard ring structure (MGR) diode has been studied with clinical electron beam energies from 5â¯MeV to 15â¯MeV. The results showed that the MGR dose response is linear in the range of 5-320â¯cGy and presents reproducibility with variation coefficients less than 0.4%. The field output factors measured with the MGR agreed within 2% with those measured with an ionization chamber. This study evidences that this diode can be used for clinical electron beam dosimetry.
ABSTRACT
OBJECTIVES: Infection caused by Helicobacter pylori (H. pylori) is one of the most common causes of chronic infection in the world. The presence of the infection is strongly associated with the neoplasia of the gastrointestinal tract, and its diagnosis is easily made by means of invasive or non-invasive methods. Among such methods, the H. pylori antigen detection in stool through ELISA technique is easily performed and it is an alternative to endoscopy in children, since this exam is not usually indicated in this age group. The aim of the current study is to establish the standardization of the ELISA method for the detection of H. pylori in stool specimens in Brazil. DESIGN AND METHODS: Patients between 18 and 70 years of age were randomly selected in the gastroenterology ambulatory center at Faculdade de Medicina do ABC between 2007 and 2009. They all answered a questionnaire to investigate possible dyspeptic symptoms and then underwent endoscopy and detection of H. pylori through no more than 4 methods. Besides the gastric biopsy, established as the gold standard test, the urease test, the stool ELISA test and serology were also methods applied. RESULTS: The sensitivity and specificity of the exams in this sample were respectively 87.2% and 44% for the stool ELISA test, 41.9% and 64% for serology, 65.6% and 58.8% for the urease test and 100% and 80.8% for the clinical analysis. CONCLUSIONS: The ROC curve showed a good correlation between the compared methods. In Brazil the standardization of the ELISA test for the detection of H. pylori in stool specimens constitutes a non-invasive diagnostic alternative.
Subject(s)
Enzyme-Linked Immunosorbent Assay/standards , Feces/microbiology , Helicobacter Infections/diagnosis , Helicobacter pylori/isolation & purification , Adolescent , Adult , Antigens, Bacterial/blood , Bacterial Proteins/analysis , Biopsy , Brazil , Enzyme-Linked Immunosorbent Assay/methods , Female , Helicobacter Infections/microbiology , Helicobacter pylori/immunology , Humans , Male , Middle Aged , Sensitivity and Specificity , Urease/analysisABSTRACT
In this work we have studied the direct detection and spectrometric capabilities of low-cost commercial silicon photodiodes for X- and gamma-rays (energies from 10 up to 80 keV) envisaging their use in characterization of porous microstructures by X-ray microtomography. The best values of the energy resolution for the 59.5 keV 241Am gamma-ray line, measured at room temperature, were found to be 2.1 and 1.8 keV for SFH00206K (Siemens) and S2506-04 (Hamamatsu) PIN diodes, respectively.
