Black bone MRI morphometry for mandibular cortical bone measurement in head and neck cancer patients: prospective method comparison with CT

Objectives Determine the utility of low-flip angle “black bone” magnetic resonance imaging (MRI) for cortical mandibular bone assessment compared to computed tomography (CT). Methods Quantification of cortical mandibular bone width was performed per Hamada et al. at 15 cross-sectional interdentium locations on pretreatment black bone MRI and CT for 15 oropharyngeal cancer patients, with interobserver analyses on a subset of three patients by 11 observers. CT and MRI measurements were compared using Bland-Altman analysis, Lin’s concordance, and Deming regression; interobserver variability was assessed with absolute variance and intraclass correlation coefficient (ICC). Results Bland Altman and Deming regression analyses showed CT and black bone MRI measurements were comparable within ±0.85mm limits of agreement, and systematically smaller for MRI. ICC (0.60[0.52;0.67]) showed moderate equivalence between modalities. The average absolute variance between the observers was similar on CT (1.13±0.06mm) and MRI (1.15±0.06mm). ICC analysis showed that measurement consistency was significantly higher (p<0.001) for black bone MRI (0.43[0.32;0.56]) than CT (0.22[0.13;0.35]); nonetheless, ICC was poor for both modalities. Conclusion Black bone MRI is a viable alternative to CT for assessing mandibular cortical bone and early detection of anatomical changes like osteoradionecrosis. Both modalities showed similar interobserver variability, which may be reduced through (semi)automated measurement.