Comparison of standard-dose and reduced-dose expiratory MDCT techniques for assessment of tracheomalacia in children.

RATIONALE AND OBJECTIVES

The aim of this study was to assess the effects of radiation dose reduction on the assessment of the tracheal lumen on expiratory multidetector computed tomographic (MDCT) images of pediatric patients referred for evaluation for tracheomalacia (TM).

MATERIALS AND METHODS

The hospital information system was used to retrospectively identify 20 standard-dose and 20 reduced-dose paired inspiratory and expiratory MDCT studies performed for the evaluation of suspected TM in pediatric patients (aged <or= 18 years). The reduced-dose technique used a 50% reduction of the tube current for the expiratory portion of the study compared to the standard-dose technique. Two experienced pediatric radiologists, who were blinded to the tube current of the study, reported their levels of confidence for measuring the tracheal lumen using a four-point scale ranging from zero (no confidence) to three (highest level of confidence). The difference in confidence level between the two groups of studies was analyzed using the Mann-Whitney U test. The percentage of radiation dose reduction using the reduced-dose technique in comparison to the standard-dose technique was estimated using anthropomorphic thorax phantoms. The presence or absence of TM (>or=50% expiratory reduction in tracheal cross-sectional luminal area) on MDCT imaging was compared to bronchoscopic results for the subset of 32 patients who underwent both procedures.

RESULTS

A high level of confidence was reported for measuring the tracheal lumen on MDCT imaging for both standard-dose (median, 3.0) and reduced-dose (median, 3.0) expiratory sequences (P = .80). The total radiation dose of the paired inspiratory-expiratory computed tomographic (CT) exam was decreased by 23% with the reduced-dose technique. TM was diagnosed by CT imaging in seven patients who underwent standard-dose and six patients who underwent reduced-dose paired inspiratory and expiratory MDCT studies. CT results for the presence or absence of TM were concordant with the results of bronchoscopy in all 32 patients who underwent both procedures.

CONCLUSION

The radiation dose of paired inspiratory-expiratory CT imaging can be reduced by 23% while maintaining similar diagnostic confidence for assessment of the tracheal lumen compared to a standard-dose technique in pediatric patients. Thus, a reduced-dose technique is recommended for evaluating TM in children.