Skull- Special methods

Submento-vertical Remove any movable, radio- opaque material from the patient's skull. Position of patient and cassette: The patient may be imaged erect or supine. If the patient is unsteady, then a supine technique is advisable.

Supine: The patient’s shoulders are raised and the neck is hyperextended to bring the vertex of the skull in contact with the table. The head is adjusted to bring the external auditory meatuses equidistant from the cassette. The median sagittal plane should be at right-angles to the cassette along its midline. The IOML should be as near as possible parallel to the cassette.

Errect: The patient sits a short distance away from a vertical Bucky. The neck is hyperextended to allow the head to fall back until the vertex of the skull makes contact with the centre of the vertical Bucky. The remainder of the positioning is as described for the supine technique

Central Ray CR is perpendicular to infraorbitomeatal line Center at 2cm anterior to level of EAMs (midway between angles of mandible)

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. The entire skull should be visualised

Signs of excellence The symmetrical structures should be projected symmetrically about the midline. (condyles of the mandible) The mandibular symphysis is superimposed with the frontal bone the mandibular condyles anterior to the petrous pyramids the foramen magnum should be projected almost circular. No motion No tilt or rotation

SMV

PA axial projection (Haas method) An alternative view for patients who can’t flex the neck (AP, towne view) but results in magnification of the occipital bone. This view can’t be used when the occipital bone is the area of interest

Patient in erect or prone position Nose and forehead against the table Flex neck until OML is perpendicular to the film Midsagittal plane is perpendicular to the film (EAMs at the same distance from the table)

Central ray 25 degree cephaled to OML CR: midsagittal plane at the level of EAM

Technical factors 24*30 cm 70-80 kVp SID: 100 cm Respiration: suspend respiration

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 The dorsum sella and posterior clinoid processes should be projected in the almost circular foramen magnum petrous ridge is projected above the mastoid The foramen magnum should be projected centrally within the skull outline

Evaluation of the Image Equal distance from foramen magnum to the lateral margin of the skull on both sides No motion: sharp bony margins

Haas method