AbstractsMedical & Health Science

Purpose: This study aimed to propose Diagnostic Reference Levels (DRLs) in paediatric plain radiography and to optimise the most frequent paediatric plain radiography examinations in Portugal following an analysis and evaluation of current practice. Methods and materials: Anthropometric data (weight, patient height and thickness of the irradiated anatomy) was collected from 9,935 patients referred for a radiography procedure to one of the three dedicated paediatric hospitals in Portugal. National DRLs were calculated for the three most frequent X-ray procedures at the three hospitals: chest AP/PA projection; abdomen AP projection; pelvis AP projection. Exposure factors and patient dose were collected prospectively at the clinical sites. In order to analyse the relationship between exposure factors, the use of technical features and dose, experimental tests were made using two anthropomorphic phantoms: a) CIRSTM ATOM model 705®; height: 110cm, weight: 19kg and b) Kyoto kagakuTM model PBU-60®; height: 165cm, weight: 50kg. After phantom data collection, an objective image analysis was performed by analysing the variation of the mean value of the standard deviation, measured with OsiriX® software (Pixmeo, Switzerland). After proposing new exposure criteria, a Visual Grading Characteristic image quality evaluation was performed blindly by four paediatric radiologists, each with a minimum of 10 years of professional experience, using anatomical criteria scoring. Results: A high heterogeneity of practice was found and the established Portuguese DRL values (Kerma Air Product percentile 75, KAPP75 and Entrance Surface Air kerma percentile 75, ESAKP75) were higher than the most recent published data. The national DRLs established for Portugal are: CHEST: KAPP75, 13mGy.cm2, 19mGy.cm2, 60mGy.cm2, 134mGy.cm2, 94mGy.cm2, respectively for age groups <1, 1-<5, 5-<10, 10-<16, 16-≤18. ABDOMEN: KAPP75, 25mGy.cm2, 84mGy.cm2, 140mGy.cm2, 442mGy.cm2, 1401 mGy.cm2, respectively for age groups <1, 1-<5, 5-<10, 10-<16, 16-≤18. PELVIS: KAPP75, 29mGy.cm2, 75mGy.cm2, 143mGy.cm2, 585mGy.cm2, 839mGy.cm2, respectively for age groups <1, 1-<5, 5-<10, 10-<16, 16-≤18. DRLs by patient weight groups have been established for the first time. The post optimisation DRLs by patient weight groups are: CHEST: KAPP75, 9mGy.cm2, 10mGy.cm2, 15mGy.cm2, 32mGy.cm2, 57mGy.cm2, respectively for weight groups <5kg; 5-<15kg; 15-<30kg; 30-<50kg; ≥50kg. ABDOMEN: KAPP75, 10mGy.cm2, 20mGy.cm2, 61mGy.cm2, 203mGy.cm2, 225mGy.cm2, respectively for weight groups <5kg; 5-<15kg; 15-<30kg; 30-<50kg; ≥50kg. PELVIS: KAPP75, 15mGy.cm2, 18mGy.cm2, 45mGy.cm2, 75mGy.cm2, 79mGy.cm2, respectively for weight groups <5kg; 5-<15kg; 15-<30kg; 30-<50kg; ≥50kg. ESAKP75 DRLs for both patient age and weight groups were also obtained and are described in the thesis. Significant dose reduction was achieved through the implementation of an optimisation programme: an average reduction of 41% and 18% on KAPP75 and ESAKP75, respectively for chest plain radiography; an average reduction of 58% and 53%… Advisors/Committee Members: Vaño, Eliseo (advisor), Rodrigues, Adriano (advisor).