Chest X-ray Dose Equivalent Low-dose CT with Tin Filtration: Potential Role for the Assessment of Pectus Excavatum.

RATIONALE AND OBJECTIVES:To determine the value of chest CT with tin filtration applying a dose equivalent to chest x-ray for the assessment of the Haller index for evaluation of pectus excavatum. MATERIALS AND METHODS:Two hundred seventy-two patients from a prospective single center study were included and underwent a clinical standard dose chest CT (effective dose 1.8 ± 0.7 mSv) followed by a low-dose CT (0.13 ± 0.01 mSv) in the same session. Two blinded readers independently evaluated all data sets. Image quality for bony chest wall assessment was noted. Radiologists further assessed (a) transverse thoracic diameter, (b) anteroposterior thoracic diameter, and calculated (c) Haller index by dividing transverse diameter by anteroposterior diameter. The agreement of both readers in standard dose and low-dose CT was assessed using Lin's concordance correlation coefficient (pc). RESULTS:Subjective image quality was lower for low dose compared to standard dose CT images by both readers (p < 0.001). In total, 99% (n = 540) of low-dose CT scans were rated as diagnostic for bony chest wall assessment by both readers. There was a high agreement for assessment of transverse diameter, anteroposterior diameter and Haller index comparing both readers in standard dose and low-dose CT with pc values indicating substantial agreement (i.e., 0.95> and ≤0.99) in 12/18 (67%) and almost perfect agreement (i.e., >0.99) in 6/18 (33%). CONCLUSION:Our study suggests that low-dose CT with tin filtration applying a radiation dose equivalent to a plain chest X-ray is excellent for assessing the Haller index.