SOURCES OF RADIOGRAPHIC DISTORTION IN CONVENTIONAL AND COMPUTED-TOMOGRAPHY OF THE TEMPORAL BONE

Objectives: To identify those bony regions of the glenoid fossa where, due to the inclination, there is an increased risk of radiographic di stortion in conventional and computed tomography (CT). Methods: The in clination of the roof and posterior wall of the glenoid fossa was dete rmined relative to established imaging planes. Measurements were perfo rmed on 50 corrected coronal MR and 50 axial CT images and 200 sagitta l cryosections of 50 temporomandibular joints (TMJs). The location of regions with unfavourable bone wall inclination was identified using t he condyle as a reference. Results: The inclination of parts of the fo ssa roof exceeded the limit for reliable depiction in corrected sagitt al and coronal planes in 40% and 8% of the joints respectively. The in clination of parts of the posterior wall of the fossa exceeded the lim it for reliable depiction in corrected sagittal and in true sagittal p lanes in 100% and 84% of the joints respectively. In 84% of the joints the inclination exceeded the limit for reliable depiction in the axia l plane. For both bone walls the regions with unfavourable inclination were in the medial part of the joint. Conclusions: The angulation of parts of the roof and posterior wall of the glenoid fossa in relation to established imaging planes makes them highly susceptible to distort ion. The oblique coronal projection is well suited for depiction of th e roof of the fossa and preferable to a sagittal projection. An obliqu e axial projection is required for the posterior wall.