Interobserver and intraobserver reliability of skull base angles measured on magnetic resonance images.

Background: Determination of platybasia and basilar kyphosis are significant parts of routine cranial magnetic resonance (MR) interpretations. These situations may explain a patient's symptoms or may be associated with other anomalies.

Aim: To indicate the interobserver and intraobserver reliability of the skull base angles (SBA) (Koenigsberg standard) and modified SBA (mSBA) measurement techniques.

Methods: In total, 391 patients who had undergone cranial MR imaging were re-assessed regarding the SBA measurements. The SBA and mSBA techniques were used on MR images. Two reviewers independently measured the same angles twice within a 15-day interval, using different monitors. Intraclass correlation coefficient (ICC) was calculated to reveal the intraobserver and interobserver agreements.

Results: There was an excellent agreement between reviewers regarding both angle measurements (ICC was 0.998 for SBA and mSBA). Excellent agreement levels were also observed for intraobserver measurements. ICC was 0.998 for SBA and 0.999 for mSBA for reviewer 1. ICC was 0.997 for SBA and 0.999 for mSBA according to the measurement results of reviewer 2. Higher SBA and mSBA values were observed for females compared to males. There was no correlation between SBA and age for SBA. However, a negative and low-level correlation was observed between mSBA values and age for both reviewers.

Conclusion: SBA and mSBA measurements indicated excellent agreement regarding interobserver and intraobserver differences. The study results showed that SBA angles were reliable measurement techniques to be used on MR images.