Indications for imaging
Trauma, inferior orbital margin, sinusitis (See RCR guide)
polyps, masses and tumours.
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Anatomy Demonstrated
Inferior orbital margin, zygoma, maxilla, inferior orbital
margin, inferior portion of frontal bone, maxillary, ethmoid and
frontal sinuses, nasal spine and septum.
Anatomy
Meschan, I. 1955 An Atlas of Normal Radiographic Anatomy
Saunders, London
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Basic Patient Position
Dentures and oral jewellery should be removed.
The patient sits erect facing the bucky, midsagittal plane in
the midline of the film, coronal plane parallel to the film
interpupillary line parallel to the floor. The chin is raised to
bring the orbital meatal line at 45 degrees to the film.
In some centers the patient is imaged mouth open to demonstrate
the sphenoid sinuses.
Facial Bones OM 30 Patient Position
Based on Movin & Karlsson 1975 Skeletal
projections for Diagnostic Radiology Lippincott
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Radiation protection
Direct lead rubber thyroid protection advisable.
A beam delineating cone / diaphragm will limit the area
irradiated reducing the scatter to the thyroid region.
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Central Ray
The horizontal central ray is angled 30 degrees caudally centered
in the midline so that the emergent ray exits the patient
in the midline at the level of the inferior orbital margin.
Note the projection requires an angle of 75 degrees between the
OM line and the central ray if the patient is unable to raise
the chin sufficiently then the central ray may need to be angled
caudally to maintain the 45 degree angle.
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Exposure Factors
| Kv |
mAS |
FFD (cm) |
Grid |
Focus |
AEC |
Cassette |
| 85 |
60 |
100 |
Yes |
Fine |
Yes |
18 x 24 cm |
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Evaluation of the Image
ID and anatomical markers must be present and correct in the
appropriate area of the film.
Optimal exposure should penetrate all the bone structures and
contrast should be low enough to visualise fully the bone and
soft tissue structures.
Limits of the examination, superiorly the frontal sinuses, laterally
the orbital rims and inferiorly the lower borders of the
maxillary sinuses.
The lower orbital margins should be in the center of the film.
The symmetric facial structures should be projected symmetrically
about the midline, the lower border of the maxillary sinuses
should be projected well above the petrous bones.
Facial Bones OM 30 Radiograph
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| Related Projections
Skull PA 20
Skull Reverse Townes
Skull SMV
Skull Lateral
Facial Bones OM
Facial Bones Lateral
Nose Lateral
Mandible PA
Mandible oblique
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Additional modalities
CT
MRI
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