A new coordinates system for cranial organs using magnetic resonance imaging.

We developed a new coordinates system for magnetic resonance imaging (MRI) that utilizes the labyrinth and eyeballs as references to measure the spatial arrangement of cranial organs, and we verified its usefulness by observing small structures in the labyrinth in 39 ears from 33 patients. Our new coordinates system could be used for stereotactic analysis of cranial organs in MRI.To research semicircular canal anatomy in healthy organisms, we propose a method that employs references visible on MRI for stereotactic measurement of cranial structures, and we evaluated the usefulness of our method.Using the new coordinates system and vector analysis, we calculated angles among the semicircular canals and sagittal head plane from MRI volume data containing temporal bone and orbit.The angle between the anterior semicircular canal plane and sagittal plane was 35.3 +/- 4.1 degrees; posterior semicircular canal plane and sagittal plane, 50.9 +/- 4.7 degrees; and horizontal semicircular canal plane and sagittal plane, 90.4 +/- 7.0 degrees. The angle between the anterior and posterior semicircular canal planes was 95.1 +/- 4.2 degrees; anterior and horizontal semicircular canal planes, 92.3 +/- 7.5 degrees; and posterior and horizontal semicircular canal planes, 93.5 +/- 4.9 degrees.