Purpose or Case Report: Pectus excavatum is the most common chest wall deformity, often causing psychosocial distress and cardiopulmonary issues when severe. The Haller Index (HI) obtained on CT remains the standard for assessing severity, despite its limitations and reproducibility on radiograph. Photon-counting detector CTs can reduce radiation dose while maintaining image quality. We hypothesize that significantly lowering radiation will not compromise presurgical evaluation of pectus excavatum.
Methods & Materials: An ultra-low dose chest CT protocol was designed to match radiation levels of standard chest radiographs. Thirty patients underwent preoperative scans using this protocol. Of these, 20 had surgery and completed follow-up. The control cohort consisted of 35 patients who underwent presurgical standard radiation dose CTs of the chest prior to development of the new protocol and similarly underwent surgery and were cleared on follow-up.

The primary outcomes for comparison between the two groups were clinical outcomes (presence or absence of complications). BMI, and disease severity as represented by the HI were also compared given their effect on surgical outcomes. Clinical outcomes were compared between groups tracking surgical complications at the 1-3 month follow up appointment using a Fisher’s exact test. Age, SSDE, and HI were compared between groups using Wilcoxon rank sum tests, and BMI was compared between groups using a two-sample t-test with equal variances. Both unadjusted and adjusted p-values were calculated.
Results: No significant difference was observed between the control and intervention cohort with respect to patient age (unadjusted p=0.323, adjusted p = 1), disease severity (HI) (unadjusted p=0.266, adjusted p=1), and BMI (unadjusted p=0.440, adjusted p=1). There was a significant difference in effective dose with a median of 2.34 mSv in the standard dose CT versus 0.06 mSv in the ultra-low dose group (unadjusted and adjusted p = <0.0001). There were no observed differences between the two groups for clinical outcomes (unadjusted and adjusted p=1).
Conclusions: Ultra-low radiation dose CT of the chest may be performed for pre-surgical evaluation of chest wall deformities. A photon counting detector CT can obtain clinically useful images using less radiation than that of a standard single view chest radiograph. Further research is warranted to assess ultra-low dose scanning techniques in the evaluation of pediatric osseous structures.