Radiographic Techniques Facial Bones and Sinuses Lecture 3 PDF

Radiographic Techniques Facial bones and sinuses Lec 3 BY AHMED JASEM ABASS MSC of Medical Imaging 1 2 3 4  The occipito-mental (OM) projection shows the floor of the orbits, nasal region, the maxillae, inferior parts of the frontal bone and the zygomatic bone. The OM...

Radiographic Techniques Facial bones and sinuses Lec 3 BY AHMED JASEM ABASS MSC of Medical Imaging 1 2 3 4  The occipito-mental (OM) projection shows the floor of the orbits, nasal region, the maxillae, inferior parts of the frontal bone and the zygomatic bone. The OM projection is designed to project the petrous parts of the temporal bone (which overlies the region and would cause unwanted ‘noise’ on a facial bone image) below the inferior part of the maxilla. 5  Position of patient and image receptor  The projection is best performed with the patient erect, seated facing the Bucky/receptor.  The patient’s nose and chin are placed in contact with the midline of the Bucky/receptor and then the head is adjusted to bring the orbito-meatal baseline to a 45° angle to the Bucky/receptor.  The horizontal central line of the Bucky/receptor should be at the level of the lower orbital margins.  Ensure the median sagittal plane is at right-angles to the Bucky/receptor by checking the outer canthus of the eyes and the EAMs are equidistant. 6  Direction and location of the X-ray beam  The collimated horizontal beam is centred to the Bucky/ receptor before positioning is undertaken.  To check the beam is centered properly, the crosslines on the Bucky/receptor should coincide with the patient’s anterior nasal spine.  Essential image characteristics  The petrous ridges should be demonstrated inferior to the floors of the maxillary sinuses.  There should be no rotation. This can be checked by ensuring the distance from the lateral orbital wall to the outer skull margins is equidistant on both sides. 7 8 9  This projection is used to demonstrate the frontal and ethmoid sinuses.  Position of patient and image receptor  The patient is seated facing the vertical Bucky/skull unit cassette holder so the median sagittal plane is coincident with the midline of the Bucky and is also perpendicular to it.  The head is positioned so that orbito-meatal baseline is raised 15° to the horizontal.  Ensure the nasion is positioned in the centre of the Bucky. 10  Direction and location of the X-ray beam  The central ray is directed perpendicular to the vertical Bucky along the median sagittal plane so the beam exits at the nasion.  A collimation field should be set to include the ethmoidal and frontal sinuses.  The size of the frontal sinuses can vary from one individual to another.  Essential image characteristics (Fig. 8.41b)  All the relevant sinuses should be included within the image.  It is important to ensure the skull is not rotated. This can be assessed by measuring the distance from a point in the midline of the skull to the lateral orbital margins. If this is the same on both sides of the skull then it is not rotated. 11 12  In cases of injury this projection should be specifically requested and taken using a horizontal beam. The patient may be positioned erect or supine.  Position of patient and image receptor  Erect  The patient sits facing the vertical Bucky/receptor. The head is rotated such that the side under examination is in contact with the Bucky/receptor.  The arm on the same side is extended comfortably by the trunk whilst the other arm may be used to grip the Bucky/ receptor for stability.  The Bucky/receptor height is altered such that its centre is 2.5 cm inferior to the outer canthus of the eye. 13  Supine  The patient lies on the trolley with their arms extended by the sides and the median sagittal plane vertical to the trolley top.  CR cassette is supported vertically against the side under examination so that the centre of the receptor is 2.5 cm inferior to the outer canthus of the eye.In either case the median sagittal plane is brought parallel to the Bucky/receptor by ensuring that the interorbital line is at right-angles to the Bucky/receptor.  Direction and location of the X-ray beam  The collimated horizontal beam is centred to a point 2.5 cm inferior to the outer canthus of the eye. 14  Essential image characteristics (Fig. 8.32c)  The image should contain all of the facial bones sinuses, including the frontal sinus.  A true lateral will have been obtained if the lateral portions of the floor of the anterior cranial fossa are superimposed. 15 16 17  Position of patient and image receptor  The patient sits facing an 18 × 24 cm CR cassette supported in the cassette stand of a vertical Bucky.  The head turned so the median sagittal plane is parallel with the image receptor  and the interpupillary line is perpendicular to the image receptor.  The nose should be roughly coincident with the centre of the image receptor.  Direction and location of the X-ray beam  A horizontal central ray is directed through the centre of the nasal bones and collimated to include the nose. 18  Nasal bones with soft tissue nasal structures, the frontonasal suture, and the anterior nasal spine are demonstrated.  Nasal bones are demonstrated without rotation.  Collimation to area of interest.  Exposure: Contrast and density (brightness) are sufficient to visualize nasal bone and soft tissue structures. Sharp bony structures indicate no motion. 19 20 Thank You Best Wishes For All 21