Purpose
Observation from the long axis of the petrous bone.
Observation of the auditory canal, temporomandibular joint, and mastoid sinuses.
*Currently, detailed diagnosis is possible with CT.
This imaging allows for the observation of dilation of the internal auditory canal caused by acoustic neuroma.
Prior confirmation
Remove any obstructing objects (hairpins, glasses, earrings, necklaces, dentures, etc.).
Positioning
Prone position (seated position is also acceptable).
-> For the supine position imaging, it is called the Arcelin method.
Tilt the mid-sagittal plane towards the side being examined and set it at a 45° angle to the cassette.
Align the German horizontal line perpendicular to the cassette.
Place a marker (R/L).
Align the midpoint between the examination side’s external auditory meatus and outer canthus with the center of the cassette.
CR, distance, field size
CR : Direct the X-ray beam towards a point located three fingerbreadths from the external auditory meatus of the non-examined side, towards the external occipital protuberance, at an angulation of 12 degrees caudally.
(Some sources may suggest aligning the OML line perpendicular to the cassette and performing a perpendicular X-ray beam entry.)
Distance : 100cm.
Field size : Approximately 15x15cm, including the area from the mastoid process to the medial aspect of the pyramid.
Exposure condition
70kV / 25mAs
Grid ( + )
Suspend respiration.
Image, check-point
Normal (Radiopaedia)
In the central part of the irradiation field, the entire pyramidal bone ridge and the mastoid process are depicted.
The posterior margin of the mandibular ramus aligns with the posterior margin of the cervical vertebrae, and the condyle of the mandible overlaps with the cervical vertebrae.
The pyramidal bone is depicted widely throughout its entirety. Below the pyramidal bone ridge, the bony labyrinth consisting of the internal auditory canal, cochlea, and three semicircular canals is depicted.
There is clear contrast and tolerance from the mastoid process to the interior of the pyramidal bone. (Housyasen gazou gijutu gaku / Ishiyaku Publishers)
Markers are placed on both sides.
Videos
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