Acoustic rhinometry: validation by three-dimensionally reconstructed computer tomographic scans

The aim of the present study was a validation of acoustic rhinometry (AR) b y computed tomography (CT). Six healthy subjects were examined by CT and AR . The CT data were processed in a computer program (AutoCAD), and a virtual three-dimensional model of each nasal cavity was constructed. This model p ermitted an individual prediction of the center line of the sound wave prop agation through the air volume of the nasal cavity with the cross-sectional areas oriented perpendicularly to this line. The area-distance curves deri ved from AR and CT were compared. Linear regression analysis revealed a rea sonable agreement of AR and CT in the anterior nose below a mean of 6 cm di stance from the nostrils [r = 0.839, P < 0.01, m = 1.123, b = -0.113 (AR = m x CT + b)]. The measuring accuracy using CT as gold standard revealed a m ean error at the nasal valve of <0.01 cm(2) (4.52%) and at the nasal isthmu s of 0.02 cm(2) (1.87%). Beyond 6 cm, the correlation decreased (r = 0.419) , and overestimation of the true area occurred (>100%). In conclusion, the measurements were reasonably accurate for diagnostic use up to the turbinat e head region. Certain factors induce an overestimation of the true areas b eyond this region. However, these factors are constant and reproducible in a single subject, and intraindividual comparative measurements are possible beyond the turbinate head region.