Evaluation of entrance skin air kerma in digital and conventional pediatric chest examinations performed in Parana-Brazil

Full text: In pediatric radiology it is important to evaluate patient exposure due to the high sensitivity of his/her tissue and his/her relatively longer life expectancy, which may increase the chance of radiogenic cancer development. Special attention is necessary when digital systems are used since a high dosage level for the patient may go unnoticed because the resulting image is not overexposed. The purpose of this work is to evaluate the Entrance Skin Air Kerma (ESAK) in pediatric patients submitted to digital and conventional chest examinations performed in the State of Parana, located in the Southern region of Brazil. The survey was performed in two hospitals, one located in Curitiba, the Capital of the State (A) and the other in the city of Cascavel (B). Hospital A uses a conventional image system and Hospital B uses a CR digital system. The study group consisted of 50 patients (from 2 days to six years of age) undergoing chest PA/AP examinations. At the time of the examination, the exposure parameters (kV, mAs, focal-film distance, etc) and the gender, height, weight and age of the patient were recorded. To evaluate the Entrance Skin Air Kerma (ESAK), two TLD-100 dosimeters were packaged in a polyethylene case, heat sealed and placed on the surface of each patient. The TLDs were calibrated the Metrology Laboratory of Ionizing Radiation of the Federal University of Pernambuco. The TLDs were processed on a Victoreen readout system model 2800M. The results showed that the kilovoltage values used in Hospital A are in the range of 46 to 65 kV with the average value of 51,7 kV, while the ones in Hospital B are in the range of 65 to 80 kV. On the other hand, even though hospital B uses the CR system, the mAs used for the chest exams are 4 times higher than the ones used in Hospital A. For Hospital A, the mean ESAK value was 0.044 mGy (min: 0.08 and max 0.146 mGy), and for Hospital B the mean ESAK value was 0.368 mGy (min: 0.021 and max 1.21mGy). The results made it clear that the pediatric chest images produced with the digital system are not optimized and the doses are very high when compared with the film system. It is possible to conclude that the introduction of advanced technologies in the radiographic clinics not necessary represents a reduction of the patient dose. Reduction of patient dose requires optimization of the whole imaging chain, and this includes the information for the technicians. (author)