cranium ch 11.PDF

Chapter 11 Cranium  Anatomy Review: Skull  Composed of 22 separate bones divided into two groups 8 Cranial bones 14 Facial bones  Cranial bones further subdivided into: Calvaria Floor 2 ...

Chapter 11 Cranium  Anatomy Review: Skull  Composed of 22 separate bones divided into two groups 8 Cranial bones 14 Facial bones  Cranial bones further subdivided into: Calvaria Floor 2  Skull (1 of 2) Anterior aspect of cranium Lateral aspect of cranium 3  Skull (2 of 2) Superior aspect of cranial base 4  Cranial Bones  Calvaria  Floor Frontal Ethmoid Occipital Sphenoid Right parietal Right temporal Left parietal Left temporal 5  Skull Anatomy (1 of 2)  Sutures - fibrous joints that connect the bones of the skull Coronal - between frontal and parietal bones Sagittal - on top of head between two parietal bones Squamosal - between temporal bone and parietal bones Lambdoidal - between occipital and parietal bones 6  Skull Anatomy (2 of 2)  Bregma – junction of coronal and sagittal sutures  Lambda – junction of sagittal and lambdoidal sutures  Pterion – junction of the parietal bone, squamosal suture, and greater wing of the sphenoid  Asterion – junction of the occipital bone, parietal bone, and mastoid portion of the temporal bone 7  Fontanels  Fontanels = areas of incomplete ossification in infant skulls (i.e., “soft spots”)  Adult cranial size usually achieved by age 12 8  Cranial Floor  Internally, divided into three regions: Anterior cranial fossa—houses frontal lobes of cerebrum; extends from anterior frontal bone to lesser wings of sphenoid Middle cranial fossa—houses temporal lobes; extends from lesser wings of sphenoid to apices of petrous ridges Posterior cranial fossa—deep depression posterior to petrous ridges; protects cerebellum, pons, and medulla oblongata 9  Skull Morphology (1 of 3)  Typical skull = mesocephalic Petrous pyramids project anteriorly and medially at 47- degree angle from midsagittal plane (MSP) 10  Skull Morphology (2 of 3)  Brachycephalic skull Petrous pyramids project anteriorly and medially at 54-degree angle from MSP Short from front to back, broad from side to side, and shallow from vertex to base 11  Skull Morphology (3 of 3)  Dolichocephalic skull Petrous pyramids project anteriorly and medially at 40-degree angle from MSP Long from front to back, narrow from side to side, and deep from vertex to base Asymmetry of outer features should be noted while positioning; for example, the nose may not always be in the midline 12  Frontal Bone (1 of 3)  Has vertical portion (frontal squama) and horizontal portions  Frontal squama forms forehead and anterior part of cranial vault  Horizontal portions form orbital plates, part of roof of nasal cavity, and greater part of anterior cranial fossa 13  Frontal Bone (2 of 3)  Landmarks to note: Frontal eminences Supraorbital margins Supraciliary arches Supraorbital foramina Glabella 14  Frontal Bone (3 of 3)  Frontal sinuses contained between the two tables of squama on each side of MSP  Articulates with right and left parietals, sphenoid, ethmoid, nasal bones, and zygoma 15  Ethmoid Bone (1 of 4)  Small cube-shaped bone  Consists of: Horizontal plate Vertical plate Two light, spongy masses called labyrinths Anterior aspect 16  Ethmoid Bone (2 of 4)  Located between the orbits and forms part of anterior cranial fossa, nasal cavity, orbital walls, and bony nasal septum  Horizontal portion is called the cribriform plate Lateral Aspect Superior aspect 17  Ethmoid Bone (3 of 4)  Cribriform plate contains numerous foramina for transmission of olfactory nerves  Crista galli is a conical projection at the anterior midline of cribriform plate  Perpendicular plate is the vertical portion; forms superior portion of bony nasal septum Anterior aspect Superior aspect 18  Ethmoid Bone (4 of 4)  Labyrinths: Contain ethmoid sinuses or air cells Walls form part of medial walls of orbits and lateral walls of nasal cavity Have two thin, scroll- shaped projections called superior and middle nasal conchae Superior aspect  Articulates with frontal, sphenoid, lacrimal, maxilla, and vomer 19  Parietal Bones (1 of 2)  Two bones that are somewhat square  Have a convex external surface and concave internal surface  Parietal eminence is a prominent bulge near the center of the external surface External surface of each bone This is the point where the width of the skull should be measured to set technique 20  Parietal Bones (2 of 2)  Articulate with each other at the sagittal suture in MSP, the frontal, temporal, occipital, and sphenoid bones Lateral aspect of cranium 21  Sphenoid Bone (1 of 10)  Irregular, wedge-shaped bone that vaguely resembles a bat  Located in base of cranium anterior to temporal bones and basilar portion of occipital 22  Sphenoid Bone (2 of 10)  Consists of: Body Two lesser wings Two greater wings Two pterygoid processes 23  Sphenoid Bone (3 of 10)  Body contains two sphenoid sinuses and forms posterior bony wall of nasal cavity  Sella turcica is a deep depression on superior surface of body Houses pituitary gland Located in MSP of cranium ¾ inch (1.9 cm) anterior and superior to external acoustic meatus (EAM) 24  Sphenoid Bone (4 of 10)  Tuberculum sellae: anterior border of sella  Dorsum sellae: posterior border of sella  Posterior clinoid processes: top borders of dorsum 25  Sphenoid Bone (5 of 10)  Clivus: slanted area of bone posterior and inferior to dorsum Continuous with basilar area of occipital Supports pons of the brain  Optic groove extends across anterior portion of tuberculum sellae Groove ends on each side at the optic canal 26  Sphenoid Bone (6 of 10)  Optic canal: opening into the apex of orbit for transmission of optic nerve and ophthalmic artery Actual opening is termed optic foramen 27  Sphenoid Bone (7 of 10)  Lesser wings arise from anterior and superior portion of body and lie horizontally on each side Form posteromedial portion of orbital roofs, posterior portion of anterior cranial fossa, upper margin of superior orbital fissure, and optic canals Medial ends form the anterior clinoid processes 28  Sphenoid Bone (8 of 10)  Greater wings arise from sides of body and curve laterally, posteriorly, anteriorly, and superiorly Form part of middle cranial fossa and posterolateral walls of orbit 29  Sphenoid Bone (9 of 10)  Three paired foramina situated on greater wings: Rotundum Ovale Spinosum  Pterygoid processes arise from lateral portions of inferior surface of body and medial portions of inferior surfaces of greater wings 30  Sphenoid Bone (10 of 10)  Pterygoids articulate with: Palatine bones anteriorly Vomer as part of the nasal cavity  Sphenoid articulates with each of the other seven bones of the cranium and the zygoma 31  Occipital Bone (1 of 3)  Situated at posteroinferior part of cranium  Forms posterior half of cranial base and greater portion of posterior cranial fossa  Has four parts: Squama Two occipital condyles Basilar portion 32  Occipital Bone (2 of 3)  Foramen magnum: large opening through which medulla oblongata passes as it exits cranium  External occipital protuberance: prominent process on squama Also called inion Corresponds to internal occipital protuberance 33  Occipital Bone (3 of 3)  Occipital condyles: project anteriorly from each side of squama Fuse at basilar portion to complete foramen magnum Articulate with the two parietals, the two temporals, the sphenoid, and the atlas (C1) 34  Temporal Bones (1 of 8)  Irregular in shape  Situated on each side of cranial base between greater wings of sphenoid and occipital bone  Form large part of middle cranial fossa and a small part of posterior cranial fossa 35  Temporal Bones (2 of 8)  Consist of: Squamous portion Tympanic portion Styloid process Zygomatic process Petromastoid portion, which contains the organs for hearing and equilibrium 36  Temporal Bones (3 of 8)  Squamous portion: thin, upper portion of temporal bone Forms part of side wall of cranium  Zygomatic process: prominent arched process that projects anteriorly to articulate with zygoma and complete the zygomatic arch 37  Temporal Bones (4 of 8)  Articular tubercle: located on inferior border of zygomatic process Forms anterior boundary of mandibular fossa  Mandibular fossa: receives condyle of mandible to form temporomandibular joint (TMJ) 38  Temporal Bones (5 of 8)  Tympanic portion: located below squama and in front of petromastoid portion Forms anterior wall, inferior wall, and part of posterior walls of the EAM  Styloid process: slender, pointed bone projecting inferiorly, anteriorly, and slightly medially from inferior surface of tympanic portion 39  Temporal Bones (6 of 8)  Petromastoid portion combines petrous and mastoid portions Forms the inferior posterior part of the temporal bone Articulates with parietal bone at its superior border and with occipital bone at its posterior border Usually contains air cells, which vary greatly in size, number, and pneumatization 40  Temporal Bones (7 of 8)  Mastoid process: conical process projecting from mastoid portion  Petrous portion projects medially and anteriorly between greater wing of sphenoid and occipital bone Also called petrous pyramid Conical or pyramidal in shape Thickest and densest portion of cranium Contains the organs of hearing and balance 41  Temporal Bones (8 of 8)  Auditory ossicles: bones of middle ear Malleus Incus Stapes  Temporal bone articulates with the parietal, occipital, sphenoid, zygoma, and mandible 42  Review Question (1 of 4) Which cranial bones are paired? A. Temporal B. Sphenoid C. Occipital D. Ethmoid 43  Review Question (2 of 4) Which cranial bone forms the posterior portion of the skull? A. Temporals B. Frontal C. Occipital D. Parietals 44  Review Question (3 of 4) The sella turcica is part of the: A. Ethmoid bone B. Temporal bone C. Sphenoid bone D. Occipital bone 45  Review Question (4 of 4) Which of the following bones are part of the cranial floor? (1) Ethmoid (2) Frontal (3) Temporal A. 1 and 2 only B. 1 and 3 only C. 2 and 3 only D. 1, 2, and 3 46  Anatomy: Facial Bones  14 in total: R and L nasal R and L lacrimal R and L maxillary R and L zygomatic R and L palatine R and L inferior nasal conchae Vomer Mandible 47 Facial Bones 48  Nasal Bones  Two small, thin bones  Vary in size and shape in individuals  Form superior bony wall of nasal cavity Commonly called “bridge of nose”  Articulations: With each other in midsagittal plane Superior - frontal bone Posterosuperior - perpendicular plate of ethmoid bone On each lateral side - maxillae 49  Lacrimal Bones  The two smallest bones in the skull  Located in anterior part of medial wall of orbits between labyrinth of ethmoid and maxilla  Each bone contains a lacrimal foramen through which the tear duct passes  Articulations Frontal Ethmoid Maxilla Inferior nasal concha 50  Maxillary Bones (1 of 3)  Largest immovable bones of face  Each articulates with all other facial bones, except for mandible Also articulate with frontal and ethmoid cranial bones  Form part of lateral walls and most of floor of nasal cavity  Form part of floor of orbit 51  Maxillary Bones (2 of 3)  Form three-fourths of roof of mouth  Have zygomatic process that articulate with zygoma to form part of cheek  Body contains large, pyramidal cavity called the maxillary sinus  Infraorbital foramen: located under each orbit for passage of infraorbital nerve and artery 52  Maxillary Bones (3 of 3)  Alveolar process: inferior borders of spongy bone that support roots of teeth  Anterior nasal spine: forward, pointed process at their midline junction  Acanthion: midpoint of this junction 53  Zygomatic Bones (1 of 2)  Form prominence of cheeks  Form part of side wall and floor of orbits  Temporal process extends posteriorly to join zygomatic process of temporal bone  Zygomatic arch: formed by union of temporal process of zygoma and zygomatic process of temporal bone 54  Zygomatic Bones (2 of 2)  Articulations: Superior = frontal bone Lateral = zygomatic process of temporal bone Anterior = maxilla Posterior = sphenoid 55  Palatine Bones  Two L-shaped bones composed of vertical and horizontal plates  Horizontal plates articulate with maxillae to complete the posterior fourth of bony palate (roof of mouth)  Vertical portions extend upward between maxillae and pterygoid processes of sphenoid in posterior nasal cavity  Superior tips of vertical plates assist in forming posteromedial orbit. 56  Inferior Nasal Conchae  Extend diagonally and inferiorly from lateral walls of nasal cavity at its lower third  Long, narrow, very thin bones with a lateral curl Gives scroll-like appearance  Upper two nasal conchae are processes of ethmoid bone 57  Vomer  Thin plate of bone situated in MSP of floor of nasal cavity  Forms inferior nasal septum  Superior border articulates with body of sphenoid bone  Superior part of anterior border articulates with perpendicular plate of ethmoid bone  Posterior border is free 58  Mandible (1 of 3)  Largest and densest bone of the face  Body: curved horizontal portion  Rami : two vertical portions on each side of body  Angle of mandible: junction of body and ramus Also called gonion  Mental protuberance: anterior, triangular prominence 59  Mandible (2 of 3)  Symphysis: most anterior and central part where left and right halves of mandible fuse  Alveolar portion: superior border of body; consists of spongy bone that supports roots of teeth  Mental foramina: small openings on each side below the second premolar; transmit nerves and blood vessels 60  Mandible (3 of 3)  Coronoid process: anterior process on top of ramus  Condylar process: posterior process on top of ramus; articulates with mandibular fossa of temporal bone to form temporomandibular joint (TMJ)  Mandibular notch: concave area at top of ramus between coronoid and condylar processes 61  Hyoid Bone  Small U-shaped bone situated at the base of the tongue  Accessory bone of axial skeleton—not a facial or cranial bone  Only bone in the body that does not articulate with another bone 62  Orbits  Each is composed of seven bones: Frontal Sphenoid Ethmoid Maxilla Zygoma Lacrimal Palatine 63  Review Question (1 of 2) Which facial bones form part of the hard palate? A. Palatine B. Mandible C. Zygoma D. Lacrimal 64  Review Question (2 of 2) All of the following are part of the bony orbit, except: A. Palatine B. Zygoma C. Lacrimal D. Vomer 65  Paranasal Sinuses  The air-filled cavities located in the frontal, ethmoid, and sphenoid bones of the cranium, as well as the maxillae of the face  So named because of their formation from the nasal mucosa and their continued communication with the nasal fossae 66  Functions  Serve as resonating chamber for the voice  Decrease weight of skull  Aid in warming and moisturizing inhaled air  Act as shock absorbers in trauma  Possibly control the immune system 67  Development  Begins in fetal life  Maxillary sinuses are usually the only ones developed enough to be demonstrated radiographically at birth  By 6 to 7 years of age, frontal and sphenoid are distinguishable from ethmoids  Do not fully develop until 17 to 18 years of age 68  Maxillary Sinuses  Largest and most symmetric  Paired (one in each facial bone)  Vary in size and shape, but are approximately pyramidal in shape 69  Frontal Sinuses  Second largest  Paired  Located between vertical plates of frontal bone  Vary greatly in size and shape  Occasionally absent  Rarely symmetric 70  Ethmoid Sinuses  Located within lateral masses  Composed of air cells divided into three main groups: Anterior Middle Posterior 71  Sphenoid Sinuses  Normally paired  Occupy body of sphenoid bone  Often only one sinus develops, but never more than two  Vary in size and shape  Usually asymmetric  Located below sella turcica and extend between dorsum and posterior ethmoids 72  Review Question (1 of 2) Which paranasal sinuses are divided into three groups? A. Sphenoid B. Maxillae C. Frontal D. Ethmoid 73  Review Question (2 of 2) The only facial bones that contain paranasal sinuses are the: A. Sphenoid B. Maxillae C. Frontal D. Ethmoid 74  Orbits (1 of 3)  Cone-shaped, bony- walled cavities  Formed by seven bones: Cranial bones Frontal Ethmoid Sphenoic Facial bones Lacrimal Palatine Maxillary Zygomatic 75  Orbits (2 of 3)  Parts of orbit: Roof Medial wall Lateral wall Floor  Base: easily palpable, quadrilateral-shaped anterior circumference  Apex: corresponds to the optic foramen  Long axis of each orbit is directed: Obliquely, posteriorly, and medially at 37 degrees to the MSP and superiorly at a 30 degree angle from the OML 76  Orbits (3 of 3)  Serve primarily as bony sockets for the eyeballs  Major and frequently radiographed openings: Optic foramina Superior and inferior orbital sulci  Superior orbital fissure: cleft between greater and lesser wings of sphenoid  Inferior orbital fissure: narrow cleft extending from the lower anterolateral aspect of the sphenoid body anteriorly and laterally between the floor and lateral wall of the orbit 77  Procedural Considerations  Skull topography  Skull morphology  General body position  Cleanliness  Radiation protection 78  Skull Topography (1 of 2)  Glabella  Gonion  Inner canthus  Mental point  Outer canthus  EAM  Nasion  Auricular point  Infraorbital margin  Top of ear attachment  Acanthion (TEA) 79 Skull Topography (2 of 2) 80  Radiographic Landmarks (1 of 2)  Orbitomeatal line (OML) From outer canthus to EAM  Infraorbitomeatal line (IOML) From infraorbital margin to EAM  Glabellomeatal line (GML) From glabella to EAM 81  Radiographic Landmarks (2 of 2)  Interpupillary line (IPL) Perpendicular line between pupils of eyes  Acanthiomeatal line (AML) From acanthion to EAM  Mentomeatal line (MML) From mental point (center of chin) to EAM 82  Skull Morphology  Radiographic positioning guidelines are based on mesocephalic skull size and shape  Adjustments to centering and central ray (CR) and/or part angulation may be required when working with patients with atypical skull shapes 83  General Body Position (1 of 2)  Patient may be examined in upright or recumbent positions  General body position is especially important in hyposthenic, asthenic, and hypersthenic body types 84  General Body Position (2 of 2)  Hyposthenic/asthenic patients usually need support at chest to elevate cervical spine (C-spine) Helps prevent downward tilt of MSP  Hypersthenic patients require radiolucent support at head Helps prevent upward tilt of MSP Asthenic or Hyposthenic Hypersthenic 85  Cleanliness  Hair and skin of face are naturally oily; illness often increases oiliness  Cranial procedures require direct contact of patient’s face with vertical grid device  Clean device after each patient  Wash your hands!!! 86  Radiation Protection  Close collimation  The federal government has reported that placing a lead shield over a patient’s pelvis does not significantly reduce gonadal exposure during imaging of the head  Gonad shielding should be used according to state regulations or to reduce patient anxiety  Optimum technique factors 87  Patient Preparation  Remove all radiopaque artifacts Eyeglasses Dentures and partial plates Hearing aids Jewelry Wigs/hairpieces Hairpins, barrettes, and ponytail holders Prosthetic eyes 88  Review Question (1 of 2) The radiographic baseline used for positioning of the cranium that connects the outer corner of the eye to the EAM is the: A. Orbitomeatal line B. Infraorbitomeatal line C. Outer canthomeatal line D. Canthomeatal line 89  Review Question (2 of 2) The radiographic baseline used for positioning of the cranium that connects the acanthion to the EAM is the: A. Orbitomeatal line B. Infraorbitomeatal line C. Acanthiomeatal line D. Canthomeatal line 90  Essential Projections: Skull  Lateral Right and left lateral positions Dorsal decubitus position  Posteroanterior (PA)  PA axial (Caldwell method)  Anteroposterior (AP)  AP axial  AP axial (Towne method)  Submentovertical (SMV) For cranial base 91  Lateral Projection (1 of 4)  Patient position Anterior oblique position, seated upright or recumbent  Part position MSP of head parallel to image receptor (IR) IPL perpendicular to IR IOML parallel to long axis of IR 92  Lateral Projection (2 of 4)  Central Ray Perpendicular to center of IR Enters 2 inches (5 cm) superior to EAM  Collimation / IR 10 × 12 inches (24 × 30 cm) crosswise Adjust radiation field to extend 1 inch (2.5 cm) beyond the skin line of the skull. Check for light at vertex, anterior, posterior, and base of the skull borders. 93  Lateral Projection (3 of 4)  Structures Shown Superimposed halves of cranium Well demonstrated: Sella turcica Anterior clinoid processes Dorsum sellae Posterior clinoid processes 94  Lateral Projection (4 of 4)  Evaluation Criteria Evidence of proper collimation and side marker Entire cranium without rotation or tilt: Superimposed orbital roofs and greater wings of sphenoid Superimposed mastoid regions and EAM Superimposed TMJs Sella turcica in profile No overlap of cervical spine by mandible Bony detail and surrounding soft tissue 95  PA/PA Axial (Caldwell Method) (1 of 6)  Patient position Seated erect or prone MSP centered to midline Forehead and nose resting on table or upright Bucky  Part position OML perpendicular to IR plane MSP perpendicular to IR IR centered to nasion 96  PA/PA Axial (Caldwell Method) (2 of 6)  CR for PA projection Perpendicular Exits nasion  CR for PA axial (Caldwell) Angled 15 degrees caudad Exits nasion  Collimation IR 10 x 12 inches (24 × 30 cm) lengthwise Adjust radiation field to extend 1 inch (2.5 cm) beyond the skin line of the skull Check for light at vertex and on both sides 97  PA/PA Axial (Caldwell Method) (3 of 6)  Structures shown (PA) Orbits filled by petrous pyramids Posterior ethmoid air cells Crista galli Frontal bone Frontal sinuses Dorsum sellae seen as curved line extending between the orbits just above the ethmoid air cells 98  PA/PA Axial (Caldwell Method) (4 of 6)  Structures shown (PA Axial) Petrous ridges projected into lower third of orbits Anterior ethmoidal air cells Many of the same structures in the PA 99  PA/PA Axial (Caldwell Method) (5 of 6)  Evaluation criteria Evidence of proper collimation and side marker Entire cranium without rotation or tilt: Equal distances from lateral borders of skull to lateral borders of orbits Symmetric petrous ridges MSP of cranium aligned with long axis of collimated field PA axial demonstrates petrous pyramids in lower third of orbit PA Axial (Caldwell) 100  PA/PA Axial (Caldwell Method) (6 of 6)  Evaluation criteria PA shows orbits filled by petrous ridges Entire cranial perimeter showing three distinct tables of squamous bone Bony detail of frontal bone and soft tissue PA Projection 101 AP/AP Axial Projection (Reverse Caldwell) (1 of 4) Note: Provides similar but magnified image when patient cannot be positioned for PA or PA axial projection. 102  AP/AP Axial Projection (Reverse Caldwell) (2 of 4)  Patient and part position Supine MSP centered to midline MSP and OML perpendicular to IR  Central Ray Perpendicular or 15 degrees cephalad Enters nasion  Collimation IR 10 × 12 inches (24 × 30 cm) Adjust radiation field to extend ½ to 1 inch (1.3 to 2.5 cm) beyond the skin line of the skull 103  AP/AP Axial Projection (Reverse Caldwell) (3 of 4)  Structures shown Same as the PA projection Orbits are magnified Distance from lateral margin of orbit to lateral margin of the temporal bone measures less on the AP than on the PA projection. 104  AP/AP Axial Projection (Reverse Caldwell) (4 of 4)  Evaluation criteria Evidence of proper collimation and side marker Entire cranium without rotation or tilt: Equal distances from lateral borders of skull to lateral borders of orbits on both sides Symmetric petrous ridges MSP of cranium aligned with long axis of collimated field Petrous pyramids in lower third of orbit with cephalic CR angle of 15 degrees and filling orbits with a 0 degree CR angle Bony detail of frontal bone and soft tissue 105  AP Axial (Towne Method) (1 of 4)  Patient position Supine or seated erect  Part position Head with MSP perpendicular to the midline of the IR Flex the patient’s neck enough to place either OML or IOML perpendicular to IR IR center at or near foramen magnum 106  AP Axial (Towne Method) (2 of 4)  Central Ray Enters approximately 2.5 inches (6.3 cm) above the glabella passing through the level of the EAM OML—30 degrees caudal IOML—37 degrees caudal  Collimation/IR IR 10 × 12 inches (24 × 30 cm) Adjust the radiation field to extend 1 inch (2.5 cm) beyond the skin line of the skull. Check for light at the vertex and on both sides 107  AP Axial (Towne Method) (3 of 4)  Structures shown Symmetric petrous pyramids Posterior portion of the foramen magnum, dorsum sellae, and posterior clinoid processes within the foramen magnum Occipital bone Posterior portion of the parietal bones 108  AP Axial (Towne Method) (4 of 4)  Evaluation criteria Evidence of proper collimation and side marker Entire cranium without rotation or tilt: Equal distances from lateral borders of skull to lateral margins of foramen magnum Symmetric petrous pyramids MSR of cranium aligned with long axis of collimated field Dorsum sellae and posterior clinoid processes visible within foramen magnum Bony detail of occipital bone and soft tissue 109  SMV Projection (Schüller Method) (1 of 4)  Patient position Seated upright (preferred) or supine Torso elevated if supine  Part position MSP centered to midline Extend neck placing IOML parallel with IR MSP perpendicular to IR 110  SMV Projection (Schüller Method) (2 of 4)  Central Ray Through sella turcica perpendicular to IOML Enters MSP of throat between angles of mandible Passes through a point ¾ inch (1.9 cm) anterior to level of EAM Center IR to CR  Collimation IR 10 × 12 inches (24 × 30 cm) Adjust the radiation field to extend 1 inch (2.5 cm) beyond the shadow of the tip of the nose and 1 inch beyond the lateral borders 111  SMV Projection (Schüller Method) (3 of 4)  Structures shown Symmetric petrosae Mastoid processes Foramina ovale and spinosum Carotid canals Sphenoidal and ethmoidal sinuses Mandible Bony nasal septum Dens Occipital bone Maxillary sinuses superimposed over mandible 112  SMV Projection (Schüller Method) (4 of 4)  Evaluation criteria Evidence of proper collimation and side marker Entire cranium without tilt or rotation: Equal distances from the lateral borders of the skull to the mandibular condyles Symmetric petrosae IOML parallel to IR: Mental protuberance superimposed over anterior frontal bone Mandibular condyles anterior to petrosae Bony detail of cranial base and soft tissue 113  Review Question (1 of 6) What is the CR angle and direction for the PA axial (Caldwell) of the cranium? A. 15 degrees cephalad B. 15 degrees caudad C. 30 degrees cephalad D. 30 degrees caudad 114  Review Question (2 of 6) Which baseline is positioned perpendicular to the IR on the lateral projection of the cranium? A. OML B. IOML C. Interpupillary D. Acanthiomeatal 115  Review Question (3 of 6) If IOML is positioned perpendicular to the IR for the AP axial (Towne) projection of the cranium, what is the CR orientation? A. 15 degrees caudad B. 15 degrees cephalad C. 30 degrees caudad D. 37 degrees caudad 116 Review Question (4 of 6) What projection and method are demonstrated? A. AP axial (Towne) B. PA axial (Caldwell) C. PA D. AP 117 Review Question (5 of 6) What projection is demonstrated? A. AP axial (Towne) B. PA axial (Caldwell) C. SMV D. PA 118 Review Question (6 of 6) What projection is demonstrated? A. AP axial (Towne) B. PA axial (Caldwell) C. SMV D. PA 119  Essential Projections: Facial Bones  Lateral  Parietoacanthial (Waters method)  Modified parietoacanthial (modified Waters method)  Posteroanterior (PA) axial (Caldwell method) 120  Lateral Facial Bones (1 of 3)  Patient position Upright or recumbent anterior oblique position  Part position MSP of head parallel with image receptor (IR) Interpupillary line (IPL) perpendicular to IR Infraorbitomeatal line (IOML) perpendicular to front edge of the IR 121  Lateral Facial Bones (2 of 3)  Central ray (CR) Perpendicular to center of IR Enters the lateral surface of zygomatic bone halfway between outer canthus and external acoustic meatus (EAM)  Collimation/IR Exposure field 6 × 10 inches (15 × 24 cm) Radiation field to extend 1 inch (2.5 cm) beyond the shadow of the tip of the nose, superiorly to 1 inch (2.5 cm) above the supraorbital margins, inferiorly to the gonion, and posteriorly to the EAM 122  Lateral Facial Bones (3 of 3)  Structures shown Lateral image of the facial bones Right and left sides superimposed  Evaluation criteria Evidence of proper collimation and side marker All facial bones in entirety with zygomatic bone centered No rotation or tilt: Almost perfectly superimposed mandibular rami Superimposed orbital roofs Sella turcica in profile Soft tissue and bony trabecular detail 123  Parietoacanthial (Waters) Facial Bones (1 of 3)  Patient position Prone or seated upright Center MSP to midline of upright Bucky  Part position Rest head on tip of extended chin Place orbitomeatal line (OML) to form 37-degree angle with plane of IR Mentomeatal line (MML) perpendicular to IR MSP perpendicular to IR Center IR to level of acanthion 124  Parietoacanthial (Waters) Facial Bones (2 of 3)  Central Ray (CR) Perpendicular to exit acanthion  Collimation/IR IR 10 x 12 inches (24 x 30 cm) Exposure field 8 × 10 inches (18 × 24 cm) Radiation field to 1 inch (2.5 cm) beyond the shadows of the lateral sides of the face, superiorly to include the supraorbital margins and inferiorly to the level of the chin 125  Parietoacanthial (Waters) Facial Bones (3 of 3)  Structures shown Orbits, maxillae, and zygomatic arches  Evaluation criteria Evidence of proper collimation and side marker Entire orbits and facial bones No rotation or tilt: Distances between the lateral borders of the skull and the orbits MSP of head aligned with long axis of collimated field Petrous ridges projected just below maxillary sinuses Soft tissue and bony trabecular detail 126  Modified Parietoacanthial (Modified Waters) (1 of 3)  Head positioned as described using Water’s method  Performed with less extension of the patient’s neck  Increases the angulation of the OML  Places OML more perpendicular to the IR plane  Good to demonstrate blowout fractures 127  Modified Parietoacanthial (Modified Waters) (2 of 3)  Patient position Prone or seated upright Center MSP to midline of upright Bucky  Part Position Head positioned as described by Waters method Neck is extended to a lesser degree OML adjusted to form a 55 degree angle with the IR  Central Ray (CR) Perpendicular to exit acanthion 128  Modified Parietoacanthial (Modified Waters) (3 of 3)  Structures shows / Evaluation Criteria Facial bones with less axial angulation than Waters method Petrous ridges projected just below the inferior border of the orbits at a level midway through the maxillary sinuses Orbital floor seen perpendicular to the IR and parallel to the CR Demonstrates inferior displacement of the orbital floor Opacified maxillary sinus 129  PA Axial (Caldwell) (1 of 4)  Patient position Seated erect or prone MSP centered to midline Forehead and nose resting on table or upright Bucky  Part position Adjust flexion of neck to place OML perpendicular to IR plane Align MSP perpendicular to IR IR centered to nasion 130  PA Axial (Caldwell) (2 of 4)  Central Ray (CR) Angled 15 degrees caudad Exits nasion For orbital rims, angle 30 degrees caudad (“exaggerated” Caldwell)  Collimation / IR Exposure field 8 × 10 inches (18 × 24 cm) Radiation field to extend about 1 inch (2.5 cm) beyond the lateral sides of the face, superiorly to include the supraorbital margins, and inferiorly to the chin 131  PA Axial (Caldwell) (3 of 4)  Structures shown Orbital rims Maxillae Nasal septum Zygomatic bones Anterior nasal spine Petrous ridges in lower third of orbits (15 degree caudal angle) Petrous ridges below the inferior margins of the orbits (30 degree caudal angle) 132  PA Axial (Caldwell) (4 of 4)  Evaluation criteria Evidence of proper collimation and side marker Entire orbits and facial bones No rotation or tilt: Equal distances from lateral borders of skull to lateral borders of orbits MSP of head aligned with long axis of collimated field Symmetric petrous ridges lying in lower third of orbit (depending on CR angle Bony detail and surrounding soft tissue 133 Essential Projections: Nasal Bones  Lateral 134  Lateral Nasal Bones (1 of 3)  Patient position Upright or recumbent anterior oblique position MSP of head horizontal  Part position Adjust head to place MSP parallel with tabletop IPL perpendicular to tabletop Adjust flexion of neck to place IOML parallel with transverse axis of IR 135  Lateral Nasal Bones (2 of 3)  Central Ray (CR) Perpendicular to bridge of nose Enters at a point 1 inch (2.5 cm) distal to nasion  Collimation / IR 10 x 12 inches (24 x 30 cm) crosswise for two exposures on one IR Exposure field 3 × 3 inches (8 × 8 cm) Radiation field to extend from the glabella to 1 inch (2.5 cm) inferior to the acanthion and 1 inch (2.5 cm) beyond the tip of the nose 136  Lateral Nasal Bones (3 of 3)  Structures shown Nasal bone and soft tissues of the nose Both sides for comparison  Evaluation criteria Evidence of proper collimation and side marker Nasal bones, anterior nasal spine, and frontonasal suture No rotation of nasal bones Soft tissue and bony trabecular detail 137  Essential Projections: Mandible  PA – rami  PA axial – rami  PA – body  PA axial – body  Axiolateral and axiolateral oblique  Submentovertical (SMV) 138  PA Mandibular Rami (1 of 4)  Patient position Prone or seated upright facing vertical Bucky  Part position Rest patient’s forehead and nose on IR OML perpendicular to IR plane MSP perpendicular to IR plane 139  PA Mandibular Rami (2 of 4)  Central ray (CR) Perpendicular to exit acanthion Center IR and CR  Collimation / IR Exposure field 8 × 10 inches (18 × 24 cm) Radiation field to extend 1 inch (2.5 cm) beyond the lateral sides, above the TMJs and below the chin 140  PA Mandibular Rami (3 of 4)  Structures shown Mandibular body and rami Central part of body not well shown due to superimposed spine Shows medial or lateral displacement of fragments in fractures of the rami 141  PA Mandibular Rami (4 of 4)  Evaluation criteria Evidence of proper collimation and side marker Entire mandible No rotation or tilt: Symmetric mandibular body and rami MSP of head aligned with long axis of collimated field Soft tissue and bony trabecular detail 142  PA Axial Mandibular Rami (1 of 4)  Patient position Prone or seated upright facing vertical Bucky  Part position Rest patient’s forehead and nose on vertical Bucky OML perpendicular to IR plane MSP perpendicular to IR plane 143  PA Axial Mandibular Rami (2 of 4)  Central ray (CR) Directed 20 to 25 degrees cephalad Exits acanthion Center IR and CR  Collimation / IR Exposure field 8 × 10 inches (18 × 24 cm) Radiation field to extend 1 inch (2.5 cm) beyond the lateral sides, above the TMJs and below the chin 144  PA Axial Mandibular Rami (3 of 4)  Structures shown Mandibular body and rami Central part of body not well shown due to superimposed spine Demonstrates medial or lateral displacement of fragments in fractures of the rami 145  PA Axial Mandibular Rami (4 of 4)  Evaluation criteria Evidence of proper collimation and side marker Entire mandible No rotation or tilt: Symmetric mandibular body and rami MSP of head aligned with long axis of collimated field Condylar processes Soft tissue and bony trabecular detail 146  PA Mandibular Body (1 of 3)  Part position Prone or seated upright facing vertical Bucky  Part position Rest patient’s nose and chin on IR Anterior surface of the mandibular symphysis parallel to IR plane AML nearly perpendicular to the IR plane MSP perpendicular to IR plane 147  PA Mandibular Body (2 of 3)  Central ray (CR) Perpendicular to level of lips Center IR to CR  Collimation / IR Exposure field should be no larger than 8 x 10 inches (18 x 24 cm) Adjust radiation field to extend 1 inch (2.5 cm) beyond the lateral sides, above the TMJs and below chin 148  PA Mandibular Body (3 of 3)  Structures shown Mandibular body  Evaluation criteria Evidence of proper collimation and side marker Entire mandible No rotation or tilt: Symmetric mandibular body MSP of head aligned with long axis of collimated field Soft tissue and bony trabecular detail 149  PA Axial Mandibular Body (1 of 3)  Patient position Prone or seated upright facing vertical Bucky  Part position Rest patient’s nose and chin on vertical Bucky Anterior surface of the mandibular symphysis parallel to IR plane AML nearly perpendicular to the IR plane MSP centered and perpendicular to IR plane 150  PA Axial Mandibular Body (2 of 3)  Central ray (CR) Directed midway between the TMJs at a 30 degree cephalic angle Center IR to CR  Collimation / IR Exposure field no larger than 8 x 10 inches (18 x 24 cm) Adjust the radiation field to extend 1 inch (2.5 cm) beyond the lateral sides, above the TMJs and below chin 151  PA Axial Mandibular Body (3 of 3)  Structure shown Mandibular body and TMJs  Evaluation criteria Evidence of proper collimation and side marker Entire mandible TMJs just inferior to the mastoid process No rotation or tilt: Symmetric rami MSP of head aligned with long axis of collimated field Soft tissue and bony trabecular detail 152  Axiolateral and Axiolateral Oblique Mandible (1 of 5) Goal to place desired portion of the mandible parallel with the IR  Patient position Seated upright in anterior oblique position Semiprone or semisupine Mandibular ramus 153  Axiolateral and Axiolateral Oblique Mandible (2 of 5)  Part position Head lateral with IPL perpendicular to IR Mouth closed with teeth together Extend neck to place mandibular body parallel with transverse axis of IR Mandibular body Adjust rotation of head to place area of interest parallel to IR Ramus = head in true lateral Body = rotate head 30 degrees toward IR Symphysis = rotate head 45 degrees toward IR Mandibular symphysis 154 Axiolateral and Axiolateral Oblique Mandible (3 of 5)  Central ray (CR) Angled 25 degrees cephalad to pass directly through the mandibular region of interest Center IR to CR  Collimation / IR Exposure field no more than 8 × 10 inches (18 × 24 cm) Radiation field to extend 1 inch (2.5 cm) beyond the anterior and inferior skin shadows and above the TMJ 155  Axiolateral and Axiolateral Oblique Mandible (4 of 5)  Structures shown Region of the mandible that was parallel with the IR  Evaluation criteria Evidence of proper collimation and side marker Soft tissue and bony trabecular detail Ramus and body No overlap of the ramus by opposite side of mandible No elongation or foreshortening of ramus or body No superimposition of the ramus by Axiolateral oblique the cervical spine 156 Axiolateral and Axiolateral Oblique Mandible (5 of 5)  Evaluation criteria Symphysis No overlap of the mentum region by the opposite side of the mandible No foreshortening of the mentum region Axiolateral oblique 157 Submentovertical (SMV) Mandible (1 of 3)  Patient position Upright or supine Center MSP to midline of grid device  Part position Neck fully extended Rest head on its vertex MSP vertical IOML as parallel as possible with IR plane When neck cannot be extended enough, angle the grid device and place it parallel to IOML 158 Submentovertical (SMV) Mandible (2 of 3)  Central ray (CR) Perpendicular to IOML Centered midway between mandibular angles  Collimation / IR Exposure field no later than 8 x 10 inches (18 x 24 cm) Adjust radiation field to extend 1 inch (2.5 cm) beyond the lateral sides and above the tip of the nose 159  Submentovertical (SMV) Mandible (3 of 3)  Structures shown Coronoid and condyloid process of the rami  Evaluation criteria Evidence of proper collimation and side marker No rotation or tilt: Equidistant lateral border of skull and mandible MSP of head aligned to long axis of collimated field Condyles of mandible anterior to pars petrosal Symphysis extending almost to anterior border of the face (mandible not foreshortened) Soft tissue and bony trabecular detail 160  Essential Projections: TMJs  AP axial  Axiolateral (modified Shuller)  Axiolateral oblique (modified Law) 161  AP Axial TMJs (1 of 3)  Patient position Supine or seated upright Posterior skull in contact with upright bucky  Part position MSP of head perpendicular to IR plane Flex neck to place OML perpendicular to IR plane 162  AP Axial TMJs (2 of 3)  Central ray (CR) Angled 35 degrees caudad Centered midway between TMJs, entering a point 3 inches (7.6 cm) above nasion One exposure made with mouth closed Another made with mouth open, if not contraindicated  Collimation / IR Exposure field no larger than 8 × 10 inches (18 × 24 cm) Radiation field to extend 1 inch (2.5 cm) beyond the lateral sides, superiorly to the glabella, and inferiorly to the lips 163  AP Axial TMJs (3 of 3)  Structures shown Mandibular condyles and fossae of the temporal bones  Evaluation criteria Evidence of proper collimation and side marker No rotation of head Minimal superimposition of petrosa on the condyle (closed- mouth) Condyle and temporomandibular articulation below pars petrosa (open-mouth) Soft tissue and bony trabecular detail 164  Axiolateral TMJs (1 of 4)  Patient position Semiprone or seated before a vertical grid device  Part position Center a point 0.5 inches (1.3 cm) anterior to the EAM to IR Head in lateral position MSP parallel with IR plane IPL perpendicular to IR plane Affected side closest to IR 165  Axiolateral TMJs (2 of 4)  Central ray (CR) Angle 25 or 30 degrees caudad Enters about 0.5 inches (1.3 cm) anterior and 2 inches (5 cm) superior to the upside EAM One exposure made with mouth closed Another made with mouth open, if not contraindicated  Collimation / IR Exposure field no larger than 8 x 10 inches (18 x 24 cm) Adjust radiation field to extend 1 inch (2.5 cm) beyond the anterior skin line, posterior and inferior to the TMJs 166  Axiolateral TMJs (3 of 4)  Structures shown TMJ with mouth open and closed Both sides for comparison  Evaluation criteria Evidence of proper collimation and side marker TMJ anterior to the EAM Condyle in mandibular fossa (closed-mouth) Condyle inferior to the articular tubercle (open-mouth) Closed-mouth Soft tissue and bony trabecular detail 167  Axiolateral TMJs (4 of 4) Closed-mouth Open-mouth 168  Axiolateral Oblique TMJs (modified Law) (1 of 4)  Patient position Semiprone or seated upright One exposure made with mouth closed and, if possible, another with mouth open Both sides for comparison  Part position Center a point ½ inch (1.3 cm) anterior to EAM to IR Rest cheek against grid device Rotate MSP of head 15 degrees toward IR IPL perpendicular to IR plane AML parallel with transverse axis of IR 169  Axiolateral Oblique TMJs (modified Law) (2 of 4)  Central ray (CR) Angled 15 degrees caudad Exits through TMJ closer to IR Enters approximately 1½ inch (3.8 cm) superior to upside EAM  Collimation / IR Exposure field 5 x 5 inches (12.5 x 12.5 cm) Radiation field to extend from the outer canthus to the posterior edge of the auricle and from the midparietal region to the inferior edge of the auricle 170  Axiolateral Oblique TMJs (modified Law) (3 of 4)  Structures shown Condyles and necks of the mandible Relationship between mandibular fossa and condyle Open-mouth – mandibular fossa and inferior and anterior excursion of the condyle Closed-mouth – fractures of the neck and condyle of the ramus 171  Axiolateral Oblique TMJs (modified Law) (4 of 4)  Evaluation criteria Evidence of proper collimation and side marker TMJ articulation Condyle lying in mandibular fossa in closed-mouth position Condyle lying inferior to articular tubercle in open- mouth position, if normal Bony trabecular detail and surrounding soft tissues 172  Review Question (1 of 5) What is the CR orientation for the PA axial projection of the mandibular body? A. Perpendicular to the IR B. 15 degrees caudad C. Perpendicular to AML D. 30 degrees cephalad 173  Review Question (2 of 5) To demonstrate the mandibular body in an Axiolateral oblique projection, how is the head positioned ? A. True lateral B. Rotated 15 degrees toward IR C. Rotated 30 degrees toward IR D. Rotated 45 degrees toward IR 174 Review Question (3 of 5) Where does the CR enter the patient for this projection? A. EAM B. Sella turcica C. Outer canthus D. Zygoma 175 Review Question (4 of 5) What projection (method) is demonstrated in this image? A. Parietoacanthial (modified Waters) B. Parietoacanthial (Waters) C. AP axial (Towne) D. PA axial (Caldwell) 176 Review Question (5 of 5) What is the baseline and its position used to obtain this image? A. MML—perpendicular B. AML—37 degrees from plane of IR C. OML—55 degrees from plane of IR D. OML—37 degrees from plane of IR 177  Essential Projections  Lateral  Posteroanterior (PA) axial (Caldwell method)  Parietoacanthial (Waters method)  Parietoacanthial (Waters method) open-mouth modification  Submentovertical (SMV) 178  Technical Considerations  Upright position necessary to demonstrate fluid levels  Central ray (CR) should remain horizontal  Appropriate exposure factors necessary  Well collimated radiation field will ensure optimum digital image quality at the lowest possible patient dose  When head position is changed or patient’s neck flexed or extended, several minutes should be allowed before exposure is made 179  Lateral Projection (1 of 4)  Patient position Seated erect in anterior oblique position If upright not possible, can use dorsal decubitus position  Part position Head in true lateral Midsagittal plane (MSP) of head parallel with IR plane Interpupillary line (IPL) perpendicular to IR plane Infraorbitomeatal line (IOML) horizontal to ensure proper extension of the head IOML perpendicular to front edge of vertical grid device 180  Lateral Projection (2 of 4)  Central ray (CR) Horizontal and perpendicular to IR Enters 1 inch (2.5 cm) posterior to outer canthus Center IR to CR  Collimation / IR Exposure field no larger than 8 × 10 inches (18 × 24 cm) Radiation field to extend 1 inch (2.5 cm) beyond the tip of the nose, superiorly to 3 inches above the nasion, inferiorly to the occlusal plane, and posteriorly to the auricle 181  Lateral Projection (3 of 4)  SID For preoperative measurements, use a 72 inch (183 cm) SID to minimize magnification and distortion  Structures shown All four sinuses AP and superoinferior dimensions of the paranasal sinuses and relationship to surrounding structures Thickness of the outer table of the frontal bone 182  Lateral Projection (4 of 4)  Evaluation criteria Evidence of proper collimation and side marker All four sinus groups Sphenoidal sinus best demonstrated No rotation or tilt: Sella turcica in profile Superimposed orbital roofs Superimposed mandibular rami Soft tissue, bony trabecular detail Air-fluid levels (if present) 183  PA Axial Projection (Caldwell Method) (1 of 5)  Patient position Seated upright facing vertical grid device MSP centered to midline  Part position (Angled grid technique) Tilt vertical Bucky down 15 degrees Rest patient’s forehead and nose on device Center nasion to IR MSP and orbitomeatal line (OML) perpendicular to IR plane 184  PA Axial Projection (Caldwell Method) (2 of 5)  Part position (Vertical grid technique) Extend neck to rest the tip of nose of the grid device Position patient’s OML at 15- degree angle to horizontal CR Radiolucent support may be needed at forehead Center nasion to IR MSP of head perpendicular to IR plane This method is not preferred because of increased object-to- image receptor distance (OID), which results in decreased resolution 185  PA Axial Projection (Caldwell Method) (3 of 5)  Central ray (CR) Horizontal Exits nasion 15-degree relationship between the CR and the OML Center IR and CR  Collimation / IR Exposure field no larger than 8 × 10 inches (18 × 24 cm) Radiation field to extend 1 inch (2.5 cm) beyond the lateral skin shadows, superiorly to include just the shadow of the top of the head, and inferiorly to the occlusal plane 186  PA Axial Projection (Caldwell Method) (4 of 5)  Structures shown Frontal sinuses superior to frontonasal suture Anterior ethmoid air cells on each side of nasal fossae and below frontal sinuses Sphenoid sinuses seen through nasal fossa below or between ethmoidal air cells Petrous pyramids in lower third of orbits Primarily demonstrates the frontal sinuses and anterior ethmoidal air cells 187  PA Axial Projection (Caldwell Method) (5 of 5)  Evaluation criteria Evidence of proper collimation and side marker Frontal sinuses lying above the frontonasal suture Anterior ethmoidal air cells lying above petrous ridges No rotation or tilt: Equidistant lateral borders of the skull and later borders of the orbits Symmetric petrous ridges MSP of head aligned with long axis of collimated field Petrous ridge lying in the lower third of orbit Soft tissue, bony trabecular detail Air-fluid levels (if present) 188  Parietoacanthial Projection (Waters Method) (1 of 4)  Patient position Seated erect facing vertical grid device MSP centered to midline  Part position Rest chin on vertical grid device Hyperextend neck to place OML at 37-degree angle from IR plane MSP and mentomeatal line (MML) perpendicular to IR plane Center IR to acanthion 189  Parietoacanthial Projection (Waters Method) (2 of 4)  Central ray (CR) Horizontal Exits acanthion  Collimation / IR Exposure field no larger than 8 × 10 inches (18 × 24 cm) Radiation field to extend 1 inch (2.5 cm) beyond the lateral skin shadows, superiorly to include just the shadow of the top of the head, and inferiorly to the occlusal plane 190  Parietoacanthial Projection (Waters Method) (3 of 4)  Structures shown Maxillary sinuses Petrous pyramids lying inferior to maxillary floor Frontal and ethmoid sinuses are distorted Insufficient extension of neck: petrosa are projected over the inferior portions of the maxillary sinuses Overextension of neck: maxillary sinuses are foreshortened, and antral floors not shown 191  Parietoacanthial Projection (Waters Method) (4 of 4)  Evaluation criteria Evidence of proper collimation and side marker Maxillary sinuses OML in proper position: Petrous pyramids lying immediately inferior to the floor of the maxillary sinuses Symmetric orbits and maxillary sinuses MSP of head aligned with long axis of collimated field Soft tissue, bony trabecular detail Air-fluid levels (if present) 192  Parietoacanthial Projection (Open- Mouth Waters Method) (1 of 4)  Patient position Seated erect facing vertical grid device MSP centered to midline  Part position Rest patient’s chin on vertical grid device Hyperextend neck to place OML at 37-degree angle from IR plane MSP perpendicular to IR plane Open mouth wide while holding position 193 Parietoacanthial Projection (Open- Mouth Waters Method) (2 of 4)  Central ray (CR) Horizontal Exits acanthion  Collimation / IR Exposure field no larger than 8 × 10 inch (18 × 24 cm) Radiation field to extend 1 inch (2.5 cm) beyond the lateral skin shadows, superiorly to include just the shadow of the top of the head, and inferiorly to the occlusal plane 194  Parietoacanthial Projection (Open- Mouth Waters Method) (3 of 4)  Structures shown Sphenoidal sinuses projected through open mouth Maxillary sinuses 195  Parietoacanthial Projection (Open- Mouth Waters Method) (4 of 4)  Evaluation criteria Evidence of proper collimation and side marker Sphenoidal sinuses projected through the open mouth Maxillary sinuses OML in proper position: Petrous pyramids lying just inferior to the floor of the maxillary sinuses No rotation or tilt: Equidistant lateral borders of skull to lateral border of the orbit Symmetric orbits and maxillary sinuses MSP of head aligned with long axis of collimated field Soft tissue, bony trabecular detail Air-fluid levels (if present) 196  SMV Projection (1 of 4)  Patient position Upright  Part position Hyperextend neck and rest vertex of head on vertical grid device Adjust head to place MSP perpendicular to IR plane Neck extended to place IOML parallel to IR plane 197  SMV Projection (2 of 4)  Central ray (CR) Horizontal and perpendicular to IOML Enters MSP ¾ inch (1.9 cm) anterior to level of external acoustic meatus (EAM)  Collimation / IR Exposure field no larger than 8 × 10 inches (18 × 24 cm) Radiation field to extend 1 inch (2.5 cm) beyond the tip of the nose and on the lateral sides 198  SMV Projection (3 of 4)  Structures shown Sphenoid sinus Ethmoid air cells 199  SMV Projection (4 of 4)  Evaluation criteria Evidence of proper collimation and side marker Sphenoid and ethmoid sinuses No tilt: Equidistant lateral border of skull to mandibular condyles IOML parallel to IR: Superimposition of anterior frontal bone by mental protuberance Insufficient neck extension will cause mandible to superimpose ethmoid sinuses Mandibular condyles anterior to petrous pyramids Soft tissue, bony trabecular detail Air-fluid levels (if present) 200  Review Question (1 of 6) Which sinuses are best demonstrated on the parietoacanthial projection (Waters method)? A. Maxillary B. Sphenoid C. Ethmoids D. All sinuses are equally demonstrated 201  Review Question (2 of 6) Which sinuses are best demonstrated on the PA axial projection (Caldwell method)? A. Maxillary B. Sphenoid C. Frontal D. All sinuses are equally demonstrated 202  Review Question (3 of 6) Which projection demonstrates all four sinuses? A. PA axial (Caldwell) B. Patietoacanthial (Waters) C. SMV D. Lateral 203 Review Question (4 of 6) Which sinuses are indicated by the arrow? A. Frontal B. Maxillary C. Anterior ethmoids D. Sphenoid 204 Review Question (5 of 6) Which sinuses are demonstrated in this projection? 1) Maxillary 2) Frontal 3) Anterior ethmoids A. 1 and 2 only B. 1 and 3 only C. 2 and 3 only D. 1, 2, and 3 205 Review Question (6 of 6) This projection is a modification to demonstrate the: A. Frontal sinuses B. Maxillary sinuses C. Anterior ethmoids D. Sphenoid sinuses 206  Essential Projections  Lateral  PA axial  Parietoacanthial (modified Waters) 207  Preliminary Examination  Performed to determine whether a radiographically demonstrated foreign body is present.  May be used for metallic foreign body screening before MRI procedures  Evaluate trauma to bony orbits 208  Lateral Projection (1 of 2)  Patient position Upright or recumbent anterior oblique  Part position Outer canthus of affected eye adjacent and centered to IR Adjust patient’s head to place MSP parallel with IR plane IPL perpendicular to IR plane Adjust neck flexion to place IOML perpendicular to front IR edge 209  Lateral Projection (2 of 2)  Central ray (CR) Perpendicular through outer canthus  Evaluation criteria Entire orbit(s) No rotation: Superimposed orbital roofs Close beam restriction centered to orbital region Bony orbit and soft tissues of the eye for localization of foreign bodies 210  PA Axial (1 of 2)  Patient position Upright or recumbent  Part position Rest patient’s forehead and nose on the IR IR centered to ¾ inches (1.9 cm) distal to nasion Adjust head to place MSP and OML perpendicular to the IR plane Nongrid (very high resolution) technique recommended to reduce magnification and eliminate possible artifacts 211  PA Axial (2 of 2)  Central ray (CR) Through center of orbits Caudal angulation of 30 degrees  Evaluation criteria Entire orbit Petrous pyramids lying below orbital shadows No rotation of cranium: Symmetric orbits Close beam restriction to orbital region Bony details of orbit and soft tissue for localization of foreign bodies 212 Parietoacanthial (Modified Waters) (1 of 2)  Patient position Upright or recumbent  Part position IR centered at the level of the center of orbits Rest chin on IR holder Adjust head to place MSP perpendicular to IR plane Adjust flexion of neck to form 50-degree angle between OML and IR plane 213  Parietoacanthial (Modified Waters) (2 of 2)  Central ray (CR) Perpendicular through mid- orbits  Evaluation criteria Entire orbit(s) Petrous pyramids lying well below orbital shadows No rotation: Symmetric orbits Close beam restriction to orbital region Bony orbit and soft tissue of the eye for localization of foreign bodies 214