Local Diagnostic Reference Levels in Digital Radiography Examinations Based On Patient Thickness and Age
Presentations
TH-C-201-5 (Thursday, 7/14/2022) 10:00 AM - 11:00 AM [Eastern Time (GMT-4)]
Room 201
Purpose: Given the stochastic radiation risk in medical imaging, accurate dose estimation is necessary, especially for pediatric patients with increased radiosensitivity and longer lifespan. Current x-ray systems have automatic exposure control (AEC) systems that regulate dose to the image receptor based on thickness and attenuation. Several dose-thickness-correlation studies have been done using estimated patient thickness. This study estimates the entrance skin dose (ESD) for different radiography exams and evaluates its dependence on measured patient thickness and age. Age-based local diagnostic reference levels (LDRLs) are also generated and compared with established DRLs.
Methods: Radiographic exam data were collected from an Agfa DR600 system, which has patient thickness measuring capability. 2452 patient studies were performed including 323 Abdomen, 1058 Chest AP/PA, 899 Chest LAT, 112 Pelvis AP, 43 skull and 15 neck exams and categorized into five age groups (0-1.5, 1.6-5, 6-12, 13-16 and 17+). Correlation between patient thickness and age was evaluated using Pearson Correlation. ESD was estimated from the recorded air kerma at the reference level by incorporating the necessary correction factors.
Results: Measured patient thickness had a positive and significant correlation with age groups for all exams (R: 0.28 – 0.67; P-value <0.05). The entrance skin dose (ESD) showed strong correlation with increasing patient thickness for all age groups. The mean ESD for Abdomen AP is 0.34±0.57, 1.01±1.26, 2.02±2.25 and 2.26±2.07 mGy for age groups 1.6-5, 6-12, 13-16 and 17+ years, respectively; while for Chest AP/PA, it is 0.08±0.03, 0.06±0.03, 0.09±0.05, 0.11±0.09 and 0.12±0.26 mGy respectively. Facility ESDs LDRLs were established.
Conclusion: Measured patient thickness permits accurate estimation of ESD for various radiographic exams and patient ages. Age-based LDRLs were below many international DRLs and image receptor dose, was largely within acceptable limits with DI ±3, suggesting that image quality was preserved with low patient doses.
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