FACIAL BONES

21


FACIAL BONES*




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Radiation Protection


Protection of the patient from unnecessary radiation is a professional responsibility of the radiographer (see Chapter 1 for specific guidelines). In this chapter (with a few exceptions), because of central ray angulations, radiation shielding of the patient is not specified or illustrated because the professional community and the federal government have reported that a lead shield over the patient’s pelvis does not significantly reduce gonadal exposure during radiography of the facial bones. Nonetheless, shielding the abdomen of a pregnant woman is recommended by the authors of this atlas.


Infants and children should be protected from radiation by shielding the thyroid and thymus glands and the gonads. The protective lead shielding used to cover the thyroid and thymus glands can also assist in immobilizing pediatric patients.


The most effective way to protect patients from unnecessary radiation is to restrict the radiation beam by using proper collimation. Taking care to ensure that the patient is properly instructed and immobilized also reduces the chance of having to repeat the procedure and expose the patient to more radiation.



Facial Bones



image LATERAL PROJECTION



R or L position










image PARIETOACANTHIAL PROJECTION


WATERS METHOD1











MODIFIED PARIETOACANTHIAL PROJECTION


MODIFIED WATERS METHOD


Although the parietoacanthial projection (Waters method) is widely used, many institutions modify the projection by radiographing the patient using less extension of the patient’s neck. This modification, although sometimes called a “shallow” Waters, actually increases the angulation of the OML by placing it more perpendicular to the plane of the IR. The patient’s head is positioned as described using the Waters method, but the neck is extended a lesser amount. In the modification, the OML is adjusted to form an approximately 55-degree angle with the plane of the IR (Figs. 21-9 to 21-11). The resulting radiograph shows the facial bones with less axial angulation than with the Waters method (see Fig. 21-8). With the modified Waters method, the petrous ridges are projected immediately below the inferior border of the orbits at a level midway through the maxillary sinuses (Fig. 21-12).






The modified Waters method is a good projection to show blowout fractures. This method places the orbital floor perpendicular to the IR and parallel to the central ray, showing inferior displacement of the orbital floor and the commonly associated opacified maxillary sinus.



imageACANTHIOPARIETAL PROJECTION


REVERSE WATERS METHOD




The reverse Waters method is used to show the facial bones when the patient cannot be placed in the prone position.










image PA AXIAL PROJECTION


CALDWELL METHOD










Structures shown: The PA axial projection, Caldwell method, shows the orbital rims, maxillae, nasal septum, zygomatic bones, and anterior nasal spine. When the central ray is angled 15 degrees caudad to the nasion, the petrous ridges are projected into the lower third of the orbits (Fig. 21-17). When the central ray is angled 30 degrees caudad, the petrous ridges are projected below the inferior margins of the orbits.






Nasal Bones



image LATERAL PROJECTION



R and L positions










Mar 3, 2016 | Posted by in GENERAL RADIOLOGY | Comments Off on FACIAL BONES
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