Effect of arm position, presence of medical devices, and off-centering during acquisition of scout image on automatic tube voltage selection and current modulation in pediatric chest CT

• Published in: PloS one Vol. 13; no. 4; p. e0195807
• Main Authors: Ryu, Young Jin, Choi, Young Hun, Cheon, Jung-Eun, Park, Ji Eun, Kim, Woo Sun, Kim, In-One
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 17.04.2018; Public Library of Science (PLoS)
• Subjects: Age; Age groups; Biology and Life Sciences; Body mass; Body mass index; Body size; Chest; Computed tomography; Current modulation; Diagnostic systems; Dosimetry; Drug dosages; Electric potential; Emergency medical care; Image acquisition; Medical devices; Medical electronics; Medical equipment; Medical imaging; Medical research; Medicine; Medicine and Health Sciences; Multivariate analysis; Patients; Pediatrics; People and Places; Radiation; Radiation dosage; Radiation therapy; Research and Analysis Methods; Studies; Subgroups; Tomography; Voltage
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0195807

To evaluate the patients' morphologic factors affecting radiation dose in pediatric chest CT. From November 2013 to May 2015, 315 pediatric chest CT scans were obtained using a CT scanner, and classified into 5 groups according to the patients' age. For each age group, the chest CT scans were divided into two subgroups. A cut-off value used was the 75th percentile of size-specific dose estimates (SSDE), age-specific diagnostic reference level (DRL): less than the 75th percentile of SSDE (Group A, n = 238) and greater than the 75th percentile of SSDE (Group B, n = 77). All CT scans were performed with the same protocol using automatic tube voltage selection and current modulation techniques. The morphologic factors of the patients including body mass index (BMI), arm angles, presence of medical devices in the scan field, and degree of off-centering within the CT gantry were compared between groups A and B. Group B showed narrower arm angles on scout and coronal reformatted images, higher frequency of the presence of devices and higher BMI than group A (P < 0.001, P < 0.001; P = 0.018, and P < 0.001, respectively). In multivariate analysis, narrower arm angles, the presence of devices on the scout images and higher BMI were independently associated with higher SSDE (P = 0.001, P = 0.037, and P < 0.001, respectively). During acquisition of the scout images, arms-down position and the presence of medical devices were associated with a high radiation dose above age-specific DRLs in pediatric chest CT, regardless of repositioning before the actual scanning. In addition, off-centering had no clinical impact on radiation dose in the routine practice.