Cranium Flashcards
1
Q
The skull is divided into two main sets of bones:
A
8 cranial bones and 14 facial bones
2
Q
The 8 bones of the cranium are divided into:
A
the calvarium (skullcap) and the floor. Each consist of four bones.
3
Q
The skullcap consists of which four bones?
A
Frontal, right parietal, left parietal and occipital
4
Q
The floor of the cranium consists of which four bones?
A
Right temporal, left temporal, sphenoid, and ethmoid.
5
Q
This bone contributes to the formation of the forehead and the superior part of each orbit:
A
Frontal bone.
6
Q
The squamous portion of any the frontal bone is the ______ portion.
A
vertical.
7
Q
The orbital portion of the skull is the ______ portion.
A
horizontal.
8
Q
This is the smooth, raised prominence between the eyebrows just above the bridge of the nose:
A
Glabella.
9
Q
This is the slight depression above each eyebrow:
A
The supraorbital groove (SOG).
10
Q
Why is the supraorbital groove an important landmark?
A
It corresponds to the floor of the anterior fossa of the cranial vault, which is also at the level of the orbital plate or at the highest level of the facial bone mass.
11
Q
The superior rim of each orbit is the :
A
supraorbital margin (SOM).
12
Q
This is a small hole or opening within the SOM slightly medial to its midpoint:
A
Supraorbital notch (foramen.).
13
Q
On each side of the squamous portion of the fontal bone above the SOG is a larger, rounded prominence termed the:
A
Frontal turberosity (eminence).
14
Q
These form the superior part of each orbit:
A
Orbital plates.
15
Q
Each orbital late is separated from the other by the:
A
ethmoidal notch.
16
Q
The frontal bone articulates with which four cranial bones?
A
Right and left parietals, sphenoid, and ethmoid.
17
Q
The lateral walls of the cranium and part of the roof are formed by two:
A
parietal bones.
18
Q
The widest portion of the entire skull is located between the:
A
parietal tubercles (eminences) of the two parietal bones.
19
Q
Each parietal bone articulates with these five cranial bones:
A
frontal, occipital, temporal, sphenoid, and opposite parietal.
20
Q
The inferoposterior portion of the skullcap is formed by:
A
the single occipital bone.
21
Q
The external surface of the occipital bone presents a rounded part called the:
A
squamous portion.
22
Q
The squamous portion of the occipital bone forms most of the back of the head and is the part of the occipital bone that is superior to the:
A
external occipital protuberance, or inion.
23
Q
The large opening at the base of the occipital bone through which the spinal cord passes is called the:
A
foramen magnum.
24
Q
These oval processes with convex surfaces on each side of the foramen magnum are called the:
A
occipital condyles
25
The occipital bone articulates with these six bones:
Two parietals, two temporals, sphenoid and atlas.
26
The right and left temporal bones house what?
the delicate organs of hearing and balance.
27
Extending anteriorly from the squamous portion of the temporal bone is an arch of bone termed:
the zygomatic process.
28
____ and _____ have largely replaced conventional radiography for imaging of mastoids and petrous pyramids.
CT and MRI
29
The mastoids and petrous pyramids are locations for organs of:
hearing and equilibrium.
30
The three divisions of the ear are:
External
Middle
Internal
31
The parts of the external ear include:
The auricle, tragus, EAM, Mastoid process, mastoid tip, and styloid process.
32
The function of the tympanic membrane is to:
transmit sound vibrations.
33
The tympanic membrane is part of the:
*middle* ear
34
The three parts of the middle ear are:
Tympanic membrane, tympanic cavity, auditory ossicles
35
The partition between the external and middle ear is the:
tympanic membrane.
36
The space between the tympanic membrane and the bony labyrinth is called:
the tympanic cavity.
37
The tympanic cavity communicates with the nasopharynx by ________.
the eustachian tube.
38
The tympanic cavity is further divided into two parts:
tympanic cavity proper, which is opposite the eardrum, and epitympanic recess, which is the area above the level of the EAM and eardrum.
39
The bony projection to which the tympanic membrane is attached:
Drum crest. (separates EAM from epitympanic recess)
40
The passageway between the middle ear and the nasopharynx is:
the eustachian tube.
41
The eustachian tube equalizes pressure within:
the middle ear to the outside air.
42
The eustachian tube is a direct connection between:
the middle ear and nasopharynx, which allows disease organisms direct passage from throat to middle ear.
43
What is smaller in diameter than the EAM and difficult to demonstrate on conventional radiographs?
The internal acoustic meatus (IAM)
44
Another direct communication with the middle ear besides the eustachian tube is:
the mastoids.
45
The aditus is:
the opening between the epitympanic recess and the mastoid portion of the temporal bone.
46
The aditus, or the opening between the epitympanic recess and mastoid, allows infection in the middle ear, which may have originated in the throat, to pass to the:
mastoids. Infection is then separated from brain tissue by only thin bone.
47
Auditory ossicles transmit sound vibrations from:
tympanic membrane to sensory apparatus of hearing in the internal ear.
48
The auditory ossicles are named:
Malleus (hammer), Incus (anvil), Stapes (stirrup).
49
Describe how the auditory aussicles articulate between the tympanic membrane to the sensory apparatus of hearing in the internal ear:
The handle of the malleus is attached to the tympanic membrane and the head of the malleus articulates with the incus. The head of the stapes articulates with the incus and its base fits into the oval window of the inner ear.
50
The inner ear contains:
sensory apparatus of hearing and equilibrium within the densest portion of the petrous pyramids.
51
The inner ear is divided into two parts:
The osseous (bony) labyrinth and the membranous labyrinth.
52
The osseous labyrinth is a bony chamber that houses:
the membranous labyrinth.
53
The membranous labyrinth is a series of:
intercommunicating duts and sacs.
54
The osseous labyrinth is divided into three distinctly shaped parts:
the cochlea, the vestibule, and the semicircular canals.
55
The cochlea communicates with:
the middle ear through the round window.
56
The vestibule is the central portion of the osseous labyrinth that communicates with:
the middle ear by way of the oval window.
57
The semi-circular canals are located:
posterior to the other inner ear structures and are named according to their position (anterior, posterior and lateral.)
58
The cochlear and vestibular nerve pass through the IAM from:
respective parts of the membranous labyrinth to the brain.
59
The semi-circular canals relate to _______, and the cochlea relates to ________.
the sense of direction or equilibrium, the sense of hearing.
60
The oval window receives vibrations from:
the external ear through the stapes of the middle ear.
61
The oval window transmits vibrations to
vestibule of inner ear.
62
The round window is located at:
the base of the cochlear.
63
The round window allows movement of:
fluid within the closed duct system of the membranous labyrinth.
64
The oval window moves slightly _____ with a vibration.
inward
65
The round window moves _____ with a vibration.
outward
66
Vibrations and slight fluid movements within the cochlea produces:
impulses that are transmitted to the auditory nerve within the IAM, creating a sense of hearing.
67
SMV projection:
from inferior aspect of the mandible, in superior direction.
68
Long axis of orbit projects superiorly ___ degrees and projects medially ____ degrees.
30 and 37.
69
The base of the orbit is made of three bones:
The orbital plate of the frontal bone, and the zygoma and maxilla bones.
70
The orbits are composed of ___ cranial bones and ____ facial bones.
3 and 4
71
Which cranial bones help make up the orbits:
Ethmoid, frontal and sphenoid.
72
Which facial bones help make up the orbits?
Lacrimal, maxillary, palatine, and zygomatic.
73
Openings in the orbit include:
Optic foramen and superior orbital fissure separated by the sphenoid strut, and the inferior orbital fissure.
74
```
Which of the following facial bones is unpaired?
Maxillary
Palatine
Lacrimal
Vomer
```
Vomer
75
```
The anterior nasal spine is an aspect of the _____ bone.
Maxillary
Zygomatic
Mandibular
Inferior nasal conchae
```
Maxillary
76
```
The palatine process is an aspect of the _____ bone.
Lacrimal
Maxillary
Palatine
Zygomatic
```
Maxillary
77
```
Lacrimal is derived from a word meaning:
Water
Oil
Tear
Duct
```
Tear
78
```
Which facial bone forms an aspect of the bony nasal septum?
Nasal
Maxillary
Ethmoid
Vomer
```
Vomer
79
```
What is the name of the process of the mandible in which the lower teeth are embedded?
Frontal process
Alveolar process
Body
Mental symphysis
```
Alveolar process
80
The older term "antrum of Highmore" describes the:
maxillary sinuses
81
Which paranasal sinus is the last one to develop?
Ethmoid
82
The posterior aspect of the bony orbit is termed the:
Apex
83
```
Which of the following bones makes up most of the lateral wall of the orbit?
Maxillary
Lacrimal
Zygomatic
Vomer
```
Zygomatic
84
What passes through the optic foramen?
The optic nerve
85
Plain radiographs will show presence or absence of skull fractures but won't indicate _______.
underlying brain injury. A CT/MRI is performed to assess brain tissue.
86
Linear fractures of the skull appear as:
jagged or irregular lucent lines that lie at right angles to the axis of the bone.
87
Depressed fractures of the skull looks like:
a fragment of bone is separated and depressed into the cranial cavity. Also called ping pong fractures.
88
What view may be used to determine the degree of depression of a depressed fracture if CT is not available?
Tangential.
89
Basal skull fractures are
fractures through the dense inner structures of the temporal bone.
90
Why are basal fractures difficult to visualize on plain radiographs?
Because of the complexity of the anatomy in the temporal bone.
91
A finding suggestive of a basal skull fracture is:
an air fluid level in the sphenoid sinus on a horizontal beam lateral.
92
Complications of basal skull fracture:
Leakage of CSF
Meningitis
Damage to facial nerve
Damage to auditory apparatus.
93
Gunshot wounds can be visualized by plain images that typically are performed to:
localize bullets in gunshot victims in an antemortem or postmortem examination.
94
Neoplasms are:
new and abnormal growths.
95
Metastases are:
primary malignant neoplasms that dread to distant sites via blood and the lymphatic system. They can be characterized as osteolytic, osteoblastic or a combination of both.
96
Osteolytic lesions are:
destructive lesions with irregular margins.
97
Osteoblastic lesions are:
proliferative bony lesions of increased density.
98
Combination osteolyic and osteoblastic lesions appear:
“moth eaten” due to mix of destructive and blastic lesions
99
Describe multiple myeloma?
Consist of one or more bone tumors that originate in bone marrow.
Skull is a common affected site.
100
What does a pituitary adenoma look like on a radiograph?
enlargement of sella turcica and erosion of dorsum sellae
101
How does Paget’s disease (osteitis deformans) present on a radiograph?
Areas of lucency demonstrate destructive stage.
| “Cotton-wool” appearance with irregular areas of increased density shows reparative stage.
102
Describe Mastoiditis:
Bacterial infection that can destroy inner part of mastoid process. Air cells are replaced with fluid-filled abscess.
Can lead to hearing loss.
103
What modality best shows the fluid filled abscesses of mastoiditis?
CT
104
Describe an Acoustic Neuroma:
Benign tumor (neoplasm) of auditory nerve.
Originates in IAC.
Symptoms: hearing loss, dizziness and loss of balance.
Seen best on CT or MRI.
Seen on plain images as expansion and asymmetry of affected IAC in advanced cases.
105
Describe a Cholesteatoma:
Benign cyst-like mass or tumor
Most common in middle ear or mastoid region secondary to trauma to this region
Destroys bone
Can lead to hearing loss
106
What is a Polyp:
Growth that arises from a mucous membrane and projects into cavity (sinus)
May cause chronic sinusitis
107
What is Otosclerosis?
Abnormal sponge-like bone grows in middle ear.
oto-=ear.
Sclerosis=hard.
Maybe heredity component.
108
Mesocephalic Skull:
Average head.
Width 75% to 80% of length.
Petrous pyramids project anteriorly and medially at an angle of 47 degrees from the midsagittal plane of the skull.
109
Brachycephalic skull:
```
Short from front to back
Broad from side to side
Shallow from vertex to base
Petrous pyramids form a wider angle with MSP
Average angle of 54°
Width is 80% or greater than the length
```
110
Dolichocephalic skull:
```
Long from front to back
Narrow from side to side
Deep from vertex to base
Long axes of petrous pyramids less frontal in position
Form an average angle of 40° with MSP
Width is less than 75% of the length.
```
111
CR angles and head rotations used for skull positioning are based on _______-shaped (_________) skull
average, Mesocephalic
112
Benefits of upright position for skull X-ray:
Allows patient to be quickly and easily positioned.
| Permits use of horizontal beam to demonstrate air/fluid levels within cranial or sinus cavities.
113
Respiration suspended during exposure except in cases of
severe trauma.
114
Because cranial and facial radiography requires patient’s face to be in direct contact with radiographer’s hands and table/upright Bucky surface,
be sure to wash hands and the Bucky before and after every exam.
115
Exposure Factors for Cranium and Facial Bones:
- Medium kV (65 to 85 analog); (75 to 90 kV digital systems)
- Small focal spot less than 200 mA
- Short exposure time
- Minimum SID 40” (102 cm)
116
How to ensure proper Radiation Protection during cranium radiography:
- close collimation
- Minimize repeats
- Immobilization
- Center properly
- Shielding of radiosensitive organs recommended
117
Five Common Positioning Errors:
```
Rotation
Tilt
Excessive flexion
Excessive extension
Incorrect CR angle
```
118
To prevent superior or inferior pull on head resulting in angulation or tilt:
Place patient’s body so long axis of cervical vertebrae coincides with level of foramen magnum
119
Things to consider when xray'ing the cranium of a child:
Communication, Immobilization, Exposure factors
120
Pediatric communication for cranium xray:
- Clear explanation to gain trust of patient and guardian
| - Distraction techniques
121
Immobilization considerations for pediatric skull xray:
- Immobilization devices support patient and reduce need for patient to be held
- Reduces radiation exposure
- Provide lead for persons holding patients; if female ensure no possibility of pregnancy
122
Exposure factors to consider during pediatric skull X-ray:
Vary with patient sizes and pathologies
| High mA and short exposure times reduce motion
123
Things to consider during geriatric skull X-ray:
Communication and comfort, and exposure factors
124
Things to consider to ensure pt communication and comfort during geriatric skull X-ray:
- Sensory loss because of aging may result in need for additional assistance, time and patience for skull/facial bone/sinus radiography
- Radiolucent mattress
- Extra blankets
- Reassurance and attention
- Increased kyphosis
- Upright
- Horizontal beam lateral if necessary
125
Exposure factors to keep in mind during geriatric skull X-ray:
- Osteoporosis in geriatric patients may require 15% decrease if manual factors are used
- Tremors or unsteadiness: may require use of short exposure time (with high mA)
126
What is the most commonly performed neuroimaging procedure?
CT
127
CT and MRI provides sectional images of brain and bones of skull in ___, _____ or ____ planes
axial, sagittal or coronal
128
CT can differentiate between:
blood clots, white and gray matter, CSF, cerebral edema and neoplasms
129
Qualities unique to MRI skull exams:
- Increased sensitivity in detecting differences between normal and abnormal tissues in brain and soft tissues
- No ionizing radiation.
- Limited usefullness for evaluating bone; superior in evaluating soft tissue
- Useful for TMJ syndrome for diagnosing damage to articular disk of TM fossa
130
Ultrasound of brain of neonate (through fontanels) in ICU to for rapid evaluation and screening of premature infants for
intracranial hemorrhage
131
Why is US preferred over CT or MRI?
Highly portable
Less expensive
No sedation required
No ionizing radiation
132
What is Craniosynostosis?
premature cranial suture closure
133
Routine Skull Series:
AP axial (Towne method)
Lateral
PA axial 15º (Caldwell method) or PA axial (25º to 30º
PA 0º
134
Radionuclide bone scan is a sensitive diagnostic procedure for detection of ___________ that may not be demonstrated on radiographic images
osteomyelitis and occult fractures
135
Special skull series:
```
Submentovertex (SMV)
PA axial (Haas method)
```
136
Routine Optic Foramina and Orbits:
Parieto-orbital oblique (Rhese method)
| Parietoacanthial (Waters method)
137
Special Optic Foramina and Orbits:
Modified parietoacanthial (modified Waters method)
138
Routine TMJ's
AP axial (modified Towne method
139
Special TMJ's
Axiolateral 15º oblique (modified Law method)
| Axiolateral (Schuller method)
140
Towne's method is to view what bone?
Occipital
141
Clinical indications for Towne's method:
Skull fractures (medial and lateral displacement)
Neoplastic processes
Paget’s disease
142
Technical factors for Towne's method:
Minimum SID—40 in. (102 cm)
IR Size– 24x30 cm (10x12 in), lengthwise
Analog—70 to 80 kV range
Digital systems—80 to 85 kV range
143
Patient position for Towne's method:
All metal, plastic and other removable objects removed from patient’s head
Radiograph may be taken supine or erect
144
For Towne's method, chin is depressed until ___ is perpendicular to IR
OML
145
For Towne's, If patient cannot flex neck place ____ perpendicular
CR angle is increased to:
IOML, 7°
146
For Towne's, MSP aligned to __ and __________.
Ensure no _________.
Ensure ______ is in x-ray field
CR, midline of IR, rotation or tilt, vertex.
147
For Towne's, CR is angled:
30° to OML
| or 37° to IOML
148
For Towne's, CR enters:
MSP 2 ½ inches above glabella to pass through foramen magnum
| Center IR to projected CR
149
Anatomy demonstrated by Towne's method:
Occipital bone, petrous pyramids and foramen magnum demonstrated
Dorsum sellae and posterior clinoids visualized in the shadow of the foramen magnum
150
How do you know you have achieved the correct positioning for a Towne's method?
Symmetric petrous ridges:
Indicating no rotation.
Dorsum sellae and posterior clinoids projected in foramen magnum:
indicating correct CR angle and proper neck flexion/extension.
151
For Towne's method Underangulation of CR or insufficient flexion of neck projects dorsum sellae :
superior to the foramen magnum
152
For Towne's method Overangulation of CR or excessive flexion superimposes the ________ over the dorsum sellae within the foramen magnum and produces ________ of the dorsum sellae
anterior arch of C1 , foreshortening
153
For Towne's method, Shifting of anterior or posterior clinoid processes laterally within the foramen magnum indicates
tilt
154
For Towne's method, Density (brightness) and contrast sufficient to visualize _________ within foramen magnum
occipital bone and sellar structures
155
Clinical indications for left lateral:
Skull fractures, neoplastic processes and Paget’s disease.
| Both R and L laterals are generally performed for a skull series.
156
Trauma routine for left lateral:
Horizontal beam lateral for trauma may demonstrate air-fluid levels in sphenoid sinus—a sign of a basal skull fracture if intracranial bleeding occurs
157
Technical factors for left lateral:
```
Minimum SID—40 in. (102 cm)
IR size—24x30 cm (10x12 in. crosswise)
Grid
Analog—70-80 kV range
Digital systems—80 to 85 kV range
```
158
Patient position for left lateral:
All metal, plastic or other removable objects removed from patient’s head
Patient radiographed in erect or recumbent semiprone position
159
Part position for left lateral:
Head placed in true lateral position with side of interest closest to IR.
Patient’s body in semiprone position with MSP parallel to IR ensuring no rotation or tilt
160
For left lateral, Align ___ perpendicular to IR, ensuring no tilt of head.
Adjust neck flexion to align ____ perpendicular to front edge of IR.
___ parallel to front edge of IR.
IPL, IOML, GAL
161
For left lateral, Large-chested patients may require radiolucent support under head to prevent
tilt
162
For left lateral, Thin patient may require support under
upper thorax
163
For left lateral, central ray is perpendicular to IR
Enters __________,
Or halfway between ___________ for other types of skull morphologies.
IR centered to __.
2” superior to EAM, glabella and inion, CR
164
Anatomy demonstrated by left lateral:
Entire cranium visualized
Superimposed parietal bones
Sella turcica including:
Anterior and posterior clinoid processes
Dorsum sellae
Sella turcica and clivus demonstrated in profile
165
For left lateral, rotation evident by:
anterior and posterior separation of symmetric vertical bilateral structures:
EAMs
Mandibular rami
Greater wings of sphenoid
166
For left lateral, tilt is evident by:
```
superior and inferior separation of symmetric horizontal structures:
Orbital roofs (plates)
Greater wings of sphenoid
```
167
Clinical indications for PA Caldwell (PA Axial projection)
Skull fractures (medial and lateral displacement)
Neoplastic processes
Paget’s disease
168
Technical factors for PA Caldwell
```
Minimum SID—40 in. (102 cm)
IR size--24x30 cm (10x12”) lengthwise
Grid
Analog—70-80 kV range
Digital systems—80-85 kV range
```
169
Patient position for PA Caldwell:
All metallic or plastic objects removed from patient’s head and neck
May perform erect or prone recumbent
170
Part position for PA Caldwell:
Nose and forehead resting against IR
Neck flexion adjusted so OML is perpendicular to IR
MSP aligned to be perpendicular to midline of grid/table/IR to prevent rotation or tilt
Center IR to CR
171
Central ray for PA Caldwell:
CR angled 15° caudad and centered to exit at nasion (Caldwell method)
OR
CR angled 25° to 30° caudad exits at nasion
172
PA Caldwell: 25º to 30º caudad angle: allows for visualization of:
the superior orbital fissures (black arrows) and foramen rotundum (white arrows), and entire inferior orbital rims
173
15º caudad angle (Caldwell): projects petrous pyramids into
lower third of the orbits
174
For PA Caldwell: Alternate AP axial projection:
15° cephalad angle with OML perpendicular to IR.
Performed when patient is unable to be positioned for PA projection.
Orbits magnified.
175
```
Anatomy Demonstrated:
Caldwell method (15° caudad angle)
```
```
Greater and lesser sphenoid wings
Frontal bone
Superior orbital fissures
Frontal and anterior ethmoid sinuses
Supraorbital margins
Crista galli
```
176
Anatomy demonstrated: PA with 25° to 30° angle:
Structures mentioned for Caldwell method and
Foramen rotundum (white arrows)
Entire superior orbital fissures (black arrows)
Inferior orbital rims
177
How to show evidence of no rotation on PA Caldwell:
Equal distance from midlateral orbital margins to lateral cortex of cranium on each side.
Superior orbital fissures symmetric within orbits with correct extension of neck (OML alignment).
NO tilt with MSP perpendicular to IR.
178
How to show evidence of no rotation on PA Caldwell
| with 15° caudal angle:
Petrous pyramids projected in lower third of orbits.
| Superior orbital margin visualized without superimposition.
179
How to show evidence of no rotation on PA Caldwell with 25° to 30° angle:
Petrous pyramids are projected at or just below inferior orbital rim to allow visualization of entire orbital margin.
180
Correct exposure for PA Caldwell shows:
Density (brightness) and contrast sufficient to visualize frontal bone and sellar structures without overexposure to perimeter regions of skull
181
Clinical Indications for PA Caldwell with no angle:
Skull fractures (medial and lateral displacement)
Neoplastic processes
Paget’s disease
*when frontal bone is of primary interest.*
182
Technical factors for PA Caldwell with no angle:
```
Minimum SID—40” (102 cm)
IR Size--24x30 cm (10x12”) lengthwise
Grid
Analog—70 to 80 kV range
Digital systems—80 to 85 kV range
```
183
Part position for PA Caldwell with no angle:
Nose and forehead rested against IR
Adjust neck flexion until OML is perpendicular to IR
MSP perpendicular to IR (EAM same distance from table/IR)
Center IR to CR
184
Central Ray for PA Caldwell with no angle:
CR is perpendicular to IR (parallel to OML)
CR exits at glabella
(Merrill’s – nasion)
Minimum 40” (100 cm) SID
185
Anatomy demonstrated on PA Caldwell with no angle:
```
Frontal bone
Crista galli
Internal auditory canals
Frontal and anterior ethmoid sinuses
Petrous ridges
Greater and lesser sphenoid wings
Dorsum sellae
```
186
How to show evidence of no rotation on PA Caldwell with no rotation:
Equal distance bilaterally from oblique orbital line to lateral cortex of skull.
Petrous ridges fill orbits and level of supraorbital margin
Posterior and anterior clinioids visualized superior to ethmoid sinuses
187
Trauma AP with no angle:
CR parallel to OML
| CR to glabella
188
Before positioning the patient for an SMV projection, what needs to be ruled out?
Cervical spine fracture or subluxation on trauma patient
189
Clinical indications for SMV projection:
Advanced bony pathology of inner temporal bone structures (skull base)
Possible basal skull fractures
190
Technical factors for SMV projection:
```
Minimum SID—40” (102 cm)
IR size--24x30 cm (10x12”) lengthwise
Grid
Analog—75 to 85 kV range
Digital systems—80 to 90 kV range
```
191
Pt position for SMV projection:
Erect position may be easier for patient—upright table or upright imaging device
Wheelchair can be used; offers support for back and provides greater stability for maintaining position
192
Part position for SMV projection:
Hyperextend neck until IOML is parallel to IR
If patient is unable to extend neck angle CR so it is perpendicular to IOML
Rest patient’s head on vertex
MSP perpendicular to IR
193
Central ray for SMV projection:
Perpendicular to IOML
Center 1 ½ inches inferior to mandibular symphysis (or midway between gonions)
Center IR to CR
194
Anatomy demonstrated for SMV projection:
```
Foramen ovale and spinosum
Mandible
Sphenoid and posterior ethmoid sinuses
Mastoid processes
Petrous ridges
Hard palate
Foramen magnum
Occipital bone
```
195
For SMV projection, Correct extension of neck and relationship between IOML and CR as indicated by:
Manibular condyles projected anterior to petrous pyramids
| Frontal bone and mandibular symphysis superimposed
196
To ensure no rotation for SMV projection:
MSP parallel to edge of IR
197
To ensure no tilt for SMV projection:
Equal distance between mandibular ramus and lateral cranial cortex.
198
Correct exposure for SMV projection evidenced by:
Density (brightness) and contrast sufficient to visualize clearly outline of ethmoid and sphenoid sinuses and cranial foramen
199
What is the Haas method an alternative for, and when is it done?
Haas devised this projection for obtaining an image of the sellar structures projected within the foramen magnum on hypersthenic, obese, or other patients who cannot be adjusted correctly for the AP axial (Towne) projection
200
What are to two largest differences between the Towne method and Haas method?
Occipital bone magnified with this method
| Lower dose to facial structures and thyroid
201
Clinical indications for Haas method:
Skull fractures (medial and lateral displacement)
Neoplastic processes
Paget’s disease
202
Technical factors for Haas method:
```
Minimum SID—40” (102 cm)
IR size—24x30 cm (10x12”), lengthwise
Grid
Analog—70 to 80 kV range
Digital systems—80 to 85 kV range
```
203
Part position for Haas method:
Patient’s nose and forehead rests against imaging device surface
Flex neck until OML is perpendicular to IR
MSP aligned to CR and imaging device surface
MSP perpendicular to IR
Ensure no rotation or tilt
204
Central ray for Haas method:
Angle CR 25° cephalad to OML
Center CR to MSP to pass through level of EAMs and exit 1 ½ inches superior to nasion.
Center IR to projected CR
205
Anatomy demonstrated by Haas method:
Occipital bone
Petrous pyramids
Foramen magnum
Dorsum sellae and posterior clinoids visualized in the shadow of the foramen magnum
206
No rotation on Haas method evidenced by:
Symmetric petrous ridges
207
Correct CR angle and proper neck flexion /extension for Haas method evidenced by:
Dorsum sellae and posterior clinoids visualized in foramen magnum
208
No tilt on Haas method evidenced by:
Correct placement of posterior (book says anterior) clinoids within middle of foramen magnum
209
Correct exposure for Haas method evidenced by:
Density (brightness) and contrast sufficient to visualize occipital b one and sellar structures within foramen magnum. Sharp bony margins indicate no motion
210
```
The width of the dolichocephalic skull is less than ____of the length.
65%
75%
80%
90%
```
75%
211
The angle between the midsagittal plane and the long axis of the petrous portion of the temporal bone in the brachycephalic skull is
45°
40°
38°
47° or greater
47 degrees or greater.
212
The midline point at the junction of the upper lip and the nasal septum is called
Acanthion
Nasion
Glabella
Mentum
Acanthion
213
The tragus is located on the
Lateral border of the orbit
Point above the superciliary arch
External ear
Bridge of the nose
External ear.
214
There is a ___ difference between the orbitomeatal and infraorbitomeatal lines.
2° to 3°
5°
7° to 8°
10° to 12°
7-8 degree
215
Metastatic osteoblastic lesions of the cranium are proliferative bony lesions of increased density.
True
False
True
216
How much CR angle is required for the AP axial projection of the skull if the IOML is perpendicular to the IR?
25°
30°
37°
40°
37 degrees
217
Which positioning error is present if the orbital plates are not superimposed on a lateral skull radiograph?
Incorrect CR angle
Excessive flexion
Rotation
Tilt
Tilt
218
Which variation of the PA (axial) projection of the skull has been performed if the petrous ridges are at the level of the supraorbital margin?
PA 15°
PA 25°
PA 30°
PA 0°
PA no angle.
219
Which positioning error is present if the mandibular condyles are seen within the petrous portion of the temporal bone on an SMV projection?
Excessive extension
Insufficent extension
Rotation
Incorrect CR angle
Insufficient extension
220
What type of CR angle is required for a PA axial (Haas method) projection of the skull?
25° cephalad
30°caudad
37° caudad
15° caudad
25 degrees cephalad
