The Skull

9 The Skull




SKULL BASELINES


ISOCENTRIC TECHNIQUE


• Basic equipment positions

SKULL


• Occipitofrontal

• Pineal

• Half-axial

• Lateral

FACIAL BONES


• Occipitomental 15°

• Occipitomental 30°

NON-ISOCENTRIC TECHNIQUE



SKULL BASELINES



Orbitomeatal baseline


Line joins the outer canthus of the eye to the midpoint of the external auditory meatus



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Anthropological baseline


Line joins the infraorbital margin to the superior border of the external auditory meatus.


The difference in angles between the orbitomeatal baseline and the anthropological baseline is 10°



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Auricular line


Line passes perpendicular to the anthropological baseline through the centre of the external auditory meatus



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Interpupillary line


Line joins the centre of the two orbits and is perpendicular to the median sagittal plane



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ISOCENTRIC TECHNIQUE





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Reference position



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Facial bones reference position




image Total immobilisation of the patient is essential


image Patient can be examined erect or supine – easier to immobilise when supine


image Overexposure can be tolerated more than underexposure


image Dulac technique is positioning patient so that the area of interest is in the centre of a sphere – isocentre


image Unsure of your position – move the tube 180° to check the other side


image Up to 50% reduction in dose can be achieved


image Radiation protection – use cones and collimators to limit the beam – most important – to avoid the need for repeats


image Some radiographs may appear different – due to decrease in distortion and true representation of the patient


image Skull #s – linear is most common – stellate is star shaped.


image Depressed – detached fragment and may be comminuted


image Where possible the patient should remain in a comfortable position – different projections achieved by moving the tube




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Planes




• Median sagittal plane = Vertical


• Anthropological plane = Vertical


• Auricular plane = Horizontal



Reference position




• Patient supine


• Head resting on non-opaque pad over the head support



Tube column




• Tube and vertical arm is set to 0° so that it is perpendicular to the table top


• Sagittal light beam should coincide with median sagittal plane and the transverse light beam with the anthropological plane


• Horizontal beam must pass through auditory canals and coincide with auricular plane

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Mar 6, 2016 | Posted by in GENERAL RADIOLOGY | Comments Off on The Skull

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