Chap 7 HR.PDF - Extraoral Radiographic Projections

7. Extraoral radiographic projections - Purpose: to cover areas not fully covered by intraoral projections → Cranium → Maxilla and Mandible → Cervical Spine (C1 - C7) - Detects: diseases, impacted teeth, trauma, T.M.J, growth & development, treatment progression Anatomical imaging planes Anatom...

7. Extraoral radiographic projections - Purpose: to cover areas not fully covered by intraoral projections → Cranium → Maxilla and Mandible → Cervical Spine (C1 - C7) - Detects: diseases, impacted teeth, trauma, T.M.J, growth & development, treatment progression Anatomical imaging planes Anatomical planes: A. Frontal (coronal) Plane : body into the front and back B. Sagittal Plane : body into left and right halves C. Horizontal (transverse/axial) Plane : body into upper (cranial) and lower Cephalometric Landmarks A. Frankfurt Plane : Porion → Infraorbital point B. Canthomeatal Line : External Auditory Meatus → lateral canthus C. Auricular line : External Auditory Meatus → Porion Conventional Extraoral Radiographic Projections 1. Frontal Skull Projection 2) Posteroanterior Skull Projection The x-ray beam is sent from posterior to anterior. (1) Occipital-Frontal-Film - The film : in front of the patient - Head of the patient: The canthomeatal line is perpendicular to the receptor - X-ray beam : Perpendicular to the receptor; passing from posterior to anterior - Studies : Facial growth, Trauma, Frontal sinuses, TMJ, Orbit, Nasal cavity and Calvaria (skull cap) - Observe / Interpretation : Interpretation step 1 = calvaria 1. Sutures 2. Intracranial calcifications 3. Mastoid air cells 4. Petrous ridge 5. Compare both sides 6. Symmetry Interpretation step 2 = upper and middle face a) Orbits b) Sinuses c) Zygomatic processes d) Nasal cavity e) Middle and inferior turbinates f) Nasal septum g) Hard palate Interpretation step 3 = lower face – mandible a) Condyle b) Coronoid process c) Ramus d) Angle e) Body Interpretation step 4 = cervical spine 1. Dens 2. Superior border of C2 3. Inferior border of CI Interpretation step 5 = alveolar bone and teeth (2) Occipital-Mento-Film (a.k.a Waters Projection) [Know the indications, Why its important for us and Where is it classified – posteroanterior skull projection] - The film is positioned in front of the patient - Head of the patient: Titled upwards, so that the canthomeatal line forms a 37° angle with the receptor - Mouth : normally open (but can also be closed) - X-ray beam: Perpendicular to the receptor: passing from posterior to anterior - Indications : Trauma & Maxillary sinuses - Observe : Cranial cavities (sinus); implemented when the patient may be suspected of having maxillary sinusitis. - It has 2 variations : ✴Grasey ✴Blondeau 2) Anteroposterior Skull Projection (Towne Projection) 1 = x-ray source 2 = canthomeatal line 3 = film The x-ray beam is sent from the anterior to posterior The film is positioned perpendicular to the floor; the occipital bone is supported on the receptor Head of the patient: Tilted downwards, so that the canthomeatal line forms a 25° to 30° angle with the receptor Mouth: Open, with the chin resting on the chest X-ray beam: 25-30° to the canthomeatal line; it comes from above Purpose: study the base of the skull, condyles Indication: Diagnosis of condylar fractures (beam goes through the condyle) and mandibular ramus, coronoid process (& mouth open !!!) 2. Lateral Skull Projection (Lateral Cephalometric Projection) It is usually indicated for orthodontic purposes The patient is seated The film is positioned parallel to the patients midsagittal plane The site of interest of the head is placed towards the receptor i.e. of the left side is being examined, then the left side is placed against the receptor The x-ray beam is perpendicular and centered over the external auditory meatus  The difference between cephalometric and conventional lateral projection is that in cephalometric studies, the patients head is at a greater distance from the film, while in conventional projections the head is next to the film. Observe: Base of the skull, Calvaria, Mastoid air cells, Clivus, Clinois process, Sella turca, Sphenoid sinuses, Roof of orbit, Orbit, Sinuses, Pterygomaxillary fissure, Pterygoid plates, Zygomatic process, Anterior nasal spine, Mandible Cephalometric analysis : - To perceive the growth of the patients head. - Analysis of the dental and skeletal relationships in the head. - Soft tissue. Facial growth. - Used by dentists, orthodontists, oral and maxillofacial surgeons (leading to orthognathic surgery; when the orthodontics cannot move the bone because there is a skeletal problem) - By doctors : Steiner & Ricketts - Frankfurt plane : parallel to the floor - Occlusal position - Sagittal plane: parallel to the film - Central x-ray beam: perpendicular and centred over external auditory meatus. Lateral Skull Projection: Schuller Technique There are variations in lateral skull projection; the Schuller technique rotates the patients head slight and the angulation of the x-ray beam is changed. It is indicated for mandibular fractures. Transparietal radiographic technique for TMJ analysis The side affected is over the film External auditory meatus is supported on the receptor X-ray beam is 7-8cm above the external auditory meatus of the opposing ear 20-25° with canthomeatal line Rotate head 5° 3. Submentovertex (Skull Base) Projection (Hirtz Technique) [Where can we see paranasal? Submentovertex] [Where can we see base of the skull? Submentovertex] Indication: Study of the base of the skull/cranium (i.e. trauma; fx. of the skull base) - Occipital bone / Sphenoid bone / Palatine bone / Condyles Other indications: Paranasal sinuses, TMJ disorders, Zygomatic arch, Base of the skull, Mandible ramus, Hard palate Film: Parallel to the patients transverse plane Patients head: - Base/Top of the skull is supported on the receptor - Patient’s neck is extended as far backwards as possible X-ray beam: Canthomeatal line is parallel to the film The x-ray source is perpendicular to the film and canthomeatal line