An overview of doses to patients and irradiation conditions of diagnostic chest x ray examinations carried out in hospitals of the City of São Paulo, Brazil.
Recently the Brazilian health organisation published information conceming the number of hospitals, details of radiological equipment and frequency of medical examinations in the country. The information concerning the city of São Paulo is compiled here, complemented by a survey of absorbed doses to patients undergoing the most frequent examination: chest radiographs (postero-anterior (PA) and lateral (LAT) projections), as well as the physical parameters employed (tube voltage, current-time product, focus-film distance, field size). To collect the data, a sample of 12 hospitals (a representative sample of the 199 located in the city) was chosen, totalling 27 X ray machines. An anthropomorphic phantom was irradiated to simulate the patient. Absorbed doses were determined with thermoluminescence dosemeters placed in the phantom, externally and internally. Mean values of entrance surface dose (ESD) for PA and LAT projections were 0.22 mGy (from 0.07 to 0.61 mGy) and 0.98 mGy (from (1.30 to 4.01 mGy), respectively. The average organ doses per complete examination (PA and LAT) were 0.15 and 0.24 mGy to thyroid and lung, respectively. The thyroid was thus in the primary beam in many cases. The large variation in the ESD and organ doses indicates that much can be done in order to reduce the patient doses by adequate changes of physical parameters, without loss of image quality.
Freitas
M B
MB
Laboratório de Dosimetria, Departamento de Física Nuclear, Instituto de Física da Universidade de São Paulo, PO Box 66318, 05315-970 São Paulo, SP, Brazil. marcelo.freitas@dfn.if.usp.br
Yoshimura
E M
EM
D001938:Brazil; D005260:Female; D006306:Health Surveys; D006801:Humans; D008168:Lung / Q000528:radiation effects; D008297:Male; D009928:Organ Specificity; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011859:Radiography / Q000706:statistics & numerical data; D013902:Radiography, Thoracic / Q000295:instrumentation / Q000706:statistics & numerical data*; D011874:Radiometry / Q000295:instrumentation; D012189:Retrospective Studies; D013819:Thermoluminescent Dosimetry; D013961:Thyroid Gland / Q000528:radiation effects; D014505:Urban Population