Three-dimensional Surface Imaging for Clinical Decision Making in Pectus Excavatum

Abstract

To evaluate pectus excavatum, 3-dimensional surface imaging is a promising radiation-free alternative to computed tomography and plain radiographs. Given that 3-dimensional images concern the external surface, the conventional Haller index, and correction index are not applicable as these are based on internal diameters. Therefore, external equivalents have been introduced for 3-dimensional images. However, cut-off values to help determine surgical candidacy using external indices are lacking. A prospective cohort study was conducted. Consecutive patients referred for suspected pectus excavatum received a computed tomography (≥18 years) or plain radiographs (<18 years). The external Haller index and external correction index were calculated from additionally acquired 3-dimensional images. Cut-off values for the 3-dimensional image derived indices were obtained by receiver-operating characteristic curve analyses, using a conventional Haller index ≥3.25, and computed tomography derived correction index ≥28.0% as indicative for surgery. Sixty-one and 63 patients were included in the computed tomography and radiograph group, respectively. To determine potential surgical candidacy, receiver-operating characteristic analyses found an optimum cut-off of ≥1.83 for the external Haller index in both the computed tomography and radiograph group with a positive predictive value between 0.90 and 0.97 and a negative predictive value between 0.72 and 0.81. The optimal cut-off for the external correction index was ≥15.2% with a positive predictive value of 0.86 and negative predictive value of 0.93. The 3-dimensional image derived external Haller index and external correction index are accurate radiation-free alternatives to facilitate surgical decision-making among patients suspected of pectus excavatum with values of ≥1.83 and ≥15.2% indicative for surgery.

Keywords: Computed tomography; External Haller index; Haller index; Pectus excavatum; Three-dimensional surface imaging.