Purpose or Case Report: Pectus excavatum (PEx) is a chest wall deformity that leads to sternal depression and can impair cardiopulmonary function. CT imaging is used for surgical planning but exposes children to a significant radiation dose. Ultra-low dose CT enables PEx assessment in children with radiation exposure comparable to plain radiographs. The purpose of this study is to evaluate image quality and detection of thoracic pathology on ultra-low dose CT in children with PEx.
Methods & Materials: A HIPAA-compliant, IRB-approved retrospective query of a single institution clinical database identified children who underwent a CT scan for PEx from 2010 to 2019. Scans were either performed using conventional chest CT protocol or using the ultra-low dose pectus protocol. The ultra-low dose protocol consisted of low kV (80-100kv) and low mA (25-50mA) settings. Image quality was determined objectively by signal to noise ratio (SNR) and subjectively by two radiologists scoring on a five-point Likert scale. Any additional findings were noted (e.g. nodules), and follow-up imaging were reviewed to evaluate for potential pathology missed on CT. Student’s t test was used to assess significance in differences between continuous variables.
Results: 161 children and 195 chest CTs for PEx were identified during the study period, including 102 ultra-low dose (mean age: 14.0±2.2) and 93 conventional scans (mean age: 14.6±2.5). The mean effective dose was 0.2±0.1mSv for ultra-low dose CT and 1.1±0.8mSv for conventional CT (p<0.01). The average SNR on ultra-low dose CT was 22.8±10.8 and on conventional CT was 37.7±12.3 (p<0.01). The subjective image quality for ultra-low dose and convetional scans of bones were scored at 4.2±0.6 and 5.0±0.1 and lungs were scored at 4.3±0.5 and 5.0±0.1, respectively (p<0.01). For additional findings on the images, nodules were identified in 13% of ultra-low dose scans and 29% of conventional scans (p<0.01). Follow-up demonstrated no evidence of pulmonary nodule enlargement or associated malignancy.
Conclusions: Ultra-low dose CT has allowed the evaluation of children with PEx at radiation doses approaching that of chest radiography. The radiation dose reduction leads to decreased image quality, likely reflected in the reduced number of lung nodules detected on ultra-low dose scans. However, follow-up of these nodules did not demonstrate clinical significance. These results suggest that ultra-low dose CT is a viable strategy for As Low as Reasonably Achievable (ALARA) imaging of pediatric patients with PEx.