Normal Radiographic Anatomy of the Skull

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					                                                                  Skull Radiography
       Normal Radiographic
       Anatomy of the Skull                              Skull radiography is performed relatively
                                                         infrequently, so it is unfamiliar
      (and you thought the SPINE was
                complicated)                             Anatomy is very complex
                                                         Knowledge of anatomy is essential
                                                         There are species skull differences




                Sarah Tibbs, BVetMed




           Skull Radiography                                      Skull Radiography
  Skull type variation exists                             Proper patient positioning is VITAL
Brachycephalic – ex.                                        In order to produce standard views in a
                                                            standard way to avoid image distortion that
  Boston Terrier                                            can complicate interpretation
Mesaticephalic – ex.                   Boston Terrier       So that oblique views will allow you to see
  German Shepherd                                           normal structures that are usually obscured
Doliocephalic – ex. Collie                                Types of view(s) selected will depend on
  Variation between                                       the clinical questions to be answered
  individuals within breeds                               General anesthesia is mandatory in all but
                                                          the simplest clinical questions (where did
                                   German Shepherd
                                                          that fishhook go?)




                                                                                                   Nasal Tumor


           Skull Radiography                                        Skull Imaging
  Multiple views are almost always                      STRONG CONSIDERATION
  necessary                                             should be given to using CT
  Exposure factors are high                             (computed tomography) or MRI
                                                        (magnetic resonance imaging) as
  Skull radiographs are fairly expensive                the PRIMARY means of imaging
  because of anesthesia, multiple views,                the skull
  and technician time
                                                        CT and MRI provides MUCH more
  Because of the complexity of anatomy and              thorough and clear information, but
  similar appearance of various pathology               are somewhat more expensive,
  findings are often very non-specific                  and certainly less available
                                                                                                       Fluid in
                                                                                                       R bulla




                                                                                                                  1
                Radiographs vs. CT                                                       Lateral View
                                                         Brain Tumor   Positioning:
                                                                         When relaxed the nose
                                                                         points down and mandible
                                                                         falls toward the table
                                                                         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
                                                                         other
                                                                         The beam should be
                                                                         centered over the external
                                                                         ear canal




                       Lateral View                                                      Lateral View
Can indentify:
                                                          4
1. Calvarium                               9   1
                                                     3                                                                                          4
2. Cribiform plate                    2                                                                                     1
                                               8                                                                    9           3
3. Osseous tentorium                                7    56                                                     2
4. External occipital                                                                                                               8       5
   protuberance                                                                                                                                 6
                                                                                                                                        7
5. Occipital condyles
6. Altanto-occipital
   joint
7. Tympanic bullae
8. Petrous portion of
   temporal bone
9. Zygomatic arch




                       Lateral View                                                      Lateral View
   Can Identify
        Maxilla
   1.   Hard palate
   2.   Soft palate
   3.   Nasopharynx                                                                                                     7
   4.   Oropharynx                1            7                                                       1                                8
                                                                                                                            3
    Can evaluate the                               32
                                                    86
                                           4                                                                            4               2
    mandible                                         9                                                                                      9
                                                                                                                                6
(although its two halves
are superimposed)                              5
   5. Body (horizontal portion)                                                                                         5
   6. Vertical rami                   10                                                                   10
   7. Coronoid processes
   8. Condyloid processes (TMJ)
   9. Angular processes
   10. Mental foramen




                                                                                                                                                    2
                    Lateral View                                                  Lateral View
  Can evaluate nasal
  cavity and frontal
  sinuses (although
  superimposed)
        Nasal turbinates
        Ethmoid turbinates
        Frontal sinus
                                                                                              Bones of the HYOID apparatus
                                                                                                 Stylohyoid
                                                                                                 Epihyoid
                                                                                                 Ceratohyoid
        Note: some brachycephalic dogs do not have a
                                                                                                 Basihyoid (unpaired)
        fontal sinus!                                                                            Thyrohyoid




             Dorsoventral View                                                Dorsoventral View
Positioning:                                                         Should be able to
  The head has natural                                                  identify:
  parallel positioning
  devices for this view – the                                        1. Calvarium
  mandibles.                                                         2. Mandible
  Therefore place the
                                                                     3. Tempero-mandibular            2
  animal in sternal
  recumbency and let it’s                                               joint                                 5
  mandibles do the                                                   4. Zygomatic Arch                    1
  positioning for you                                                                                         4
                                                                                                              3
  Beam should be centered                                            5. Cribiform plate
                                                                                                              6
  over level of interest                                             6. Occipital condyles




             Dorsoventral View                                                Dorsoventral View
                                                                      Should be able to
                                                 2                    identify:
                                                                        External ear canals
                                                                        Tympanic bullae and
                                                 5
                                                                        Petrous temporal
                                                                 4
                                       4                                bones which are
                                                     1                  superimposed
                                                             3



                                                         6




                                                                                                                             3
            Dorsoventral View                                  Open-mouth VD View
 Should be able to identify:                          Positioning:
Osseous nasal septum                                    The animal must be
(also called the Vomer)                                 anesthetized for this view
                                                        The endotracheal tube
                                                        must be positioned onto
Nasal turbinates                                        the mandible so as not to
                                                        superimpose on the
Ethmoid turbinates                                      maxilla/nasal cavity
                                                        The tube must be angled
                                                        at 25-30º
Frontal sinuses (maybe)




              Open Mouth VD                                    Open-mouth VD View
Can identify:                                             Advantage is absence of superimposition of
   Structures usually           *   *                     the mandible and tongue
   seen on the DV view
   that are rostral to the                                Disadvantage is mild distortion (because the
   cribiform plate                                        beam is not perpendicular to film)
       nasal cavity, nasal                                                                      Same dog
       and ethmoid                                                                              DV View
       turbinates
       Vomer/osseous
       nasal septum
       maxilla
   As well as the palatine
   fissures *




                Intraoral Views                                       Intraoral Views
                                                     •DV Intraoral           •VD Intraoral
DV intraoral to evaluate maxilla and nasal                to see the maxilla      to see the mandible
structures
VD intraoral to evaluate mandible
Provides higher detail, but more limited view
(due to constraints of mouth anatomy)
Place corner of cassette (or non-screen film) into
mouth
“dental radiographs” are a subset of intraoral
views




                                                                                                           4
                    Intraoral Views                                         Lateral Oblique Views
•DV Intraoral           •VD Intraoral
     to see the maxilla                                               Lift and angle either the mandible or maxilla off
                             to see the mandible                      the table with positioning devices
                                                                      With the mouth open one side of the maxilla,
                                                                      mandible or dental arcades can be visualized
                                                                      Or either the right or left tympanic bulla can be
                                                                      highlighted
                                                                      Oblique views may also be used to evaluate the
                                                                      frontal sinuses or frontal bones



  Abnormally thickened bone on R maxilla   Fractured Right Mandible




            Lateral Oblique Views                                           Lateral Oblique Views
 Also can be used to improve visualization                            Positioning and labeling are confusing
 of the TMJ
                                                                      Try to be consistent in both
 Oblique the rostral portion of the head 25-
 30º to better                                                        Always use both the left and right marker
 visualize the TMJ                                                    Markers no longer indicate the animals
                                                                      recumbency but now it tries to indicate the
                                                                      sides of the head
                                                                      One side will be projected dorsally to the
                                                                      other
                                                                      Convert 3D patient into 2D image




            Lateral Oblique Views                                           Lateral Oblique Views
   To evaluate Maxilla or
   Tympanic bulla similar
   technique and labeling
   To evaluate the right side,
   place animal in right
   recumbency and use a
   wedge under the
   mandible to lift and angle
   it
   This will project the right
   maxilla (or tympanic
   bulla) ventral in the final
   image
                                                                                                     Right side is Ventral




                                                                                                                             5
       Lateral Oblique Views                                     Lateral Oblique Views
                                                                           Right side is Dorsal
 To evaluate Mandible
 For the right side,
 place animal in right
 recumbency and use
 a wedge under the
 maxilla to lift and
 angle it
 This will project the
 right mandible dorsal
 in the final image




               Frontal View                                          Frontal View
Positioning                   Can evaluate
  Dorsally                       Frontal Sinuses
  recumbent                      Frontal Bones
  Point nose straight         Other structures are to
  up toward tube              distorted and superimposed
                              to be useful
  Mouth closed
  Center beam over
  frontal sinuses and
  collimate other
  structures out




                Basilar View                                         Basilar View
 Positioning                 Use to evaluate:
   Same as for a frontal          TMJ                                                             Dens
   view but open the              Tympanic bullae
   mouth                          Dens (safe?)
   May have to adjust                                      TMJ
   angle of animals head
   depending on bread
   Again, other structures
   not really helpful,
   collimate as much as
   practical
                                                                      Normal       Diseased
                                                                       Tympanic Bullae




                                                                                                         6
      Another View for Tympanic Bullae                                                        Dental Considerations
                                                                                       Teeth can be evaluated
       It may be difficult to                                                          on skull films, although
       achieve a basilar view                                                          dental films may be
       on some                                                                         preferred if available
       brachycephalic                                                                  Dental films take
       breeds and cats                                                                 advantage of non screen
                                                                                                                      Dental radiograph
       This Rostro-10º                                                                 system to improve detail
       ventral to caudodorsal                                                          Be aware of the animals
       oblique view can be                                                             age and the way teeth
       used                                                                            change with age
       Mouth closed, tilt
       head 10º dorsally

                                                                                                                                 Lateral skull radiograph




                Basic Dental Anatomy                                                                 Tooth Disease tooth root abscess
                                                                                                              Peri-apical

                                                                                            Normal
                                        Enamel



                                    Pulp canal

                                    Lamina dura                                                                        Severe periodontal disease

Dental Radiograph


               Periodontal ligament

                                                                 DV skull radiograph
  Don’t forget that you can use skull radiography to evaluate teeth, especially
  Using oblique projections with the mouth open




                            Effect of Age                                                             Effect of Age

       Teeth change with age
       Early on deciduous teeth can be seen with
       permanent teeth underlying them
       The apical foramen closes a few months                                                         3 month old                         5 month old
       after tooth eruption
       The pulp cavity shrinks with age
       The lamina dura gets less distinct with age
       The alveolar bone becomes more sclerotic
       with age
                                                                                                         4 year old                         12 year old




                                                                                                                                                            7
            Feline differences            Feline Differences
  Cats vary much less            Laterally-protruding
between breeds and have
some distinct differences        zygomatic arches
from dog                         noted on the
The shape of the skull is        dorsoventral view
different on the lateral view
having more convex shaped         Large post-orbital
frontal and nasal bones
 Reduced nasal chambers
                                 processes
and prominent ethmoid
turbinates
  Two compartments of the
tympanic bullae
  Prominent osseous
tentorium




                                            Fractured Skull


    Clinical Correlation




          Fractured Mandible          Cranial Osteosarcoma




                                                               8
Ear Disease


                            Questions?




       Mass in middle eat




                                         9

				
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