1Normal Radiographic Anatomy of the Skull(and you thought the SPINE was complicated)Sarah Tibbs, BVetMedz Skull radiography is performed relatively infrequently, so it is unfamiliarz Anatomy is very complex z Knowledge of anatomy is essentialz There are species skull differencesSkull RadiographySkull Radiographyz Skull type variation exists Brachycephalic – ex. Boston TerrierMesaticephalic – ex. German ShepherdDoliocephalic – ex. Colliez Variation between individuals within breedsBoston TerrierGerman ShepherdSkull Radiographyz Proper patient positioning is VITALz In order to produce standard views in a standard way to avoid image distortion that can complicate interpretation z So that oblique views will allow you to see normal structures that are usually obscuredz Types of view(s) selected will depend on the clinical questions to be answeredz General anesthesia is mandatory in all but the simplest clinical questions (where did that fishhook go?)Skull Radiographyz Multiple views are almost always necessaryz Exposure factors are highz Skull radiographs are fairly expensive because of anesthesia, multiple views, and technician time z Because of the complexity of anatomy and similar appearance of various pathology findings are often very non-specificSkull Imagingz STRONG CONSIDERATION should be given to using CT(computed tomography) or MRI(magnetic resonance imaging) as the PRIMARY means of imaging the skullz CT and MRI provides MUCH more thorough and clear information, but are somewhat more expensive, and certainly less availableFluid in R bullaNasal Tumor2Radiographs vs. CTBrain TumorLateral ViewPositioning:z When relaxed the nose points down and mandible falls toward the tablez Therefore positioning devices should be used to elevate the nose parallel with the table and maintain the two halves of the mandible parallel to each otherz The beam should be centered over the external ear canalLateral ViewCan indentify:1. Calvarium2. Cribiform plate3. Osseous tentorium4. External occipitalprotuberance 5. Occipital condyles6. Altanto-occipital joint7. Tympanic bullae8. Petrous portion oftemporal bone9. Zygomatic arch123456789Lateral View124397568Lateral View12345678910zCan Identifyz Maxilla1. Hard palate 2. Soft palate 3. Nasopharynx4. Oropharynxz Can evaluate the mandible (although its two halves are superimposed)5. Body (horizontal portion)6. Vertical rami7. Coronoid processes8. Condyloid processes (TMJ)9. Angular processes10. Mental foramenLateral View101234567893Lateral Viewz Can evaluate nasal cavity and frontal sinuses (although superimposed)z Nasal turbinatesz Ethmoid turbinatesz Frontal sinusNote: some brachycephalic dogs do not have a fontal sinus!zBones of the HYOID apparatus zStylohyoidzEpihyoidzCeratohyoidzBasihyoid (unpaired)zThyrohyoidLateral ViewDorsoventral ViewPositioning:z The head has natural parallel positioning devices for this view – the mandibles.z Therefore place the animal in sternalrecumbency and let it’s mandibles do the positioning for youz Beam should be centered over level of interestDorsoventral ViewShould be able to identify:1. Calvarium2. Mandible3. Tempero-mandibularjoint4. Zygomatic Arch5. Cribiform plate6. Occipital condyles123456Dorsoventral View1234456Dorsoventral Viewz Should be able to identify:z External ear canals z Tympanic bullae and Petrous temporal bones which are superimposed4Dorsoventral Viewz Should be able to identify:Osseous nasal septum(also called the Vomer)Nasal turbinatesEthmoid turbinatesFrontal sinuses (maybe)Open-mouth VD ViewPositioning:z The animal must be anesthetized for this viewz The endotracheal tube must be positioned onto the mandible so as not to superimpose on the maxilla/nasal cavityz The tube must be angled at 25-30ºOpen Mouth VDz Can identify:z Structures usually seen on the DV view that are rostral to the cribiform plate z nasal cavity, nasal and ethmoidturbinatesz Vomer/osseous nasal septumz maxillaz As well as the palatine fissures ***Open-mouth VD Viewz Advantage is absence of superimposition of the mandible and tonguez Disadvantage is mild distortion (because the beam is not perpendicular to film)Same dogDV ViewIntraoral Views z DV intraoral to evaluate maxilla and nasal structuresz VD intraoral to evaluate mandiblez Provides higher detail, but more limited view (due to constraints of mouth anatomy)z Place corner of cassette (or non-screen film) into mouthz “dental radiographs” are a subset of intraoral viewsIntraoral Views•DV Intraoralto see the maxilla•VD Intraoralto see the mandible5Fractured Right MandibleAbnormally thickened bone on R maxilla•DV Intraoralto see the maxilla•VD Intraoralto see the mandibleIntraoral Viewsz Lift and angle either the mandible or maxilla off the table with positioning devicesz With the mouth open one side of the maxilla, mandible or dental arcades can be visualizedz Or either the right or left tympanic bulla can be highlightedz Oblique views may also be used to evaluate the frontal sinuses or frontal bones Lateral Oblique Viewsz Also can be used to improve visualization of the TMJ z Oblique the rostral portion of the head 25-30º to better visualize the TMJLateral Oblique Views Lateral Oblique Viewsz Positioning and labeling are confusing z Try to be consistent in bothz Always use both the left and right markerz Markers no longer indicate the animals recumbency but now it tries to indicate the sides of the head z One side will be projected dorsally to the otherz Convert 3D patient into 2D imageLateral Oblique Viewsz To evaluate Maxilla or Tympanic bulla similar technique and labelingz To evaluate the right side, place animal in right recumbency and use a wedge under the mandible to lift and angle itz This will project the rightmaxilla (or tympanic bulla) ventral in the final image Lateral Oblique ViewsRight side is Ventral6z To evaluate Mandiblez For the right side, place animal in right recumbency and use a wedge under the maxilla to lift and angle itz This will project the right mandible dorsalin the final imageLateral Oblique Views Lateral Oblique ViewsRight side is DorsalFrontal Viewz Positioningz Dorsally recumbentz Point nose straight up toward tubez Mouth closedz Center beam over frontal sinuses and collimate other structures outz Can evaluatez Frontal Sinusesz Frontal Bonesz Other structures are to distorted and superimposed to be usefulFrontal ViewBasilar Viewz Positioningz Same as for a frontal view but open the mouthz May have