Sinuses Flashcards
The paranasal sinuses are 4 groups of air containing cavities:
within the cranium: Ethmoid bone, sphenoid bone, and frontal bone. Within the facial bones: maxillary bone.
Each sinus communicates with:
the nasal cavity
Each sinus is lined with:
a mucous membrane.
Functions for paranasal sinuses are believed to be:
resonating chamber for voice. decrease weight of skull. warm and moisten inhaled air. shock absorbers in trauma (like air bags) possibly control immune system.
The paranasal sinuses begin to develop in the fetus, but only the ______ sinuses are demonstrated radiographically at birth.
maxillary
______ & ________ sinuses are visible radiographically at 6 or 7 years old.
Frontal and sphenoid.
______ sinuses are fully developed by late teenage years
Ethmoid
Maxillary sinuses are located:
in the body of each maxillary bone.
Older terms for maxillary sinuses include:
Antrum or Antrum of Highmore
The maxillary sinuses are shaped:
like pyramids in the front and cube-shaped from the side.
Infections starting within the first and second upper molar teeth can spread where? How?
Projecting in to the floor of each maxillary sinus are several conic elevations related to roots of the first and second upper molar feet. Infections in these teeth can therefore spread upward into the maxillary sinuses.
All paranasal sinuses communicate with:
each other and with the nasal cavity which is divided in to two fossae.
The site of communication in the maxillary sinuses is:
the opening to the middle nasal meatus passageway.
Because mucus or fluid trapped in sinuses tend to layer out and form an air-fluid level,
all radiographic positioning for sinuses should be performed in the upright position.
Frontal sinuses are located:
between the inner and outer tables of skull posterior to glabella
The frontal sinuses are rarely aerated before the age of:
6.
The frontal sinuses vary in:
size and are occasionally absent.
Generally the frontal sinuses are two cavities separated by:
a septum, but may be one cavity.
The fontal sinuses are generally larger in:
men.
Ethmoid sinuses are contained:
within lateral masses (labyrinths) of ethmoid.
The ethmoid sinuses are divided into three groups:
Anterior, middle, posterior. All intercommunicate.
Sphenoid sinuses lie in:
body of sphenoid directly below the sella turcica.
The sphenoid sinuses extend between:
posterior ethmoids and dorsum sella.
True or false? The sphenoid sinuses are paired.
True, but can be single. When paired, they are separated by a septum.
The sphenoid sinuses are very close to:
the base of the skull. Air-fluid levels could indicate basal skull fracture after trauma indicating blood or CSF is leaking through fracture into sphenoid sinus (sphenoid effusion)
The osteomeatal complex is:
the pathways of communication between the frontal, maxillary and ethmoid sinuses which provide drainage between them.
An obstructed osteomeatal complex leads to:
infection or sinusitis.
Osteomeatal complex can be imaged with:
CT
The two key passageway of the osteomeatal complex are:
infundibulum and middle nasal meatus.
The maxillary sinuses drain through:
the infundibulum passageway to the middle nasal meatus into the inferior nasal meatus.
The frontal and ethomoid sinuses use drain into the:
ethmoid bulla and then drain through middl nasal meatus into inferior nasal meatus.
On a lateral view, the frontal sinuses are visualized:
between the inner and outer table of skull.
On a lateral view, the sphenoid sinuses appear:
continuous with the ethmoid sinuses.
On a lateral view, roots of the upper teeth appear to extend up through the floor of:
the maxillary sinuses.
A PA (Caldwell) position best demonstrates which sinuses?
Frontal and anterior ethmoid sinuses.
A PA axial (open mouth waters) position is performed so:
sphenoid sinus projects into open mouth.
A submentovertex (SMV) projection shows the sphenoid sinus located:
anterior to the foramen magnum.
On a SMV projection, the ethmoid sinuses are located:
to each side of nasal septum.
On SMV projection, the mandible and teeth superimpose most of:
maxillary sinuses.
The 14 facial bones are:
Two nasal bones, two lacrimal bones, two zygomas, two nasal conchae, two maxilla, one mandible, two palatine bones, vomer.
The lateral masses of the ethmoid bone form:
the medial wall of the obit.
On a lateral projection, the ethmoids fill:
the orbits
The facial bones form several cavities, three of which are:
oral cavity, nasal cavity, and orbits.
Long axis of orbit projects superiorly ___ degrees and projects medially ___ degrees.
30 and 37.
The base of the orbit is made up of these three bones:
The orbital plates of the frontal bone, the zygoma and the maxilla.
What 3 cranial bones and 4 facial bones make up the bones of the orbits?
Ethmoid, frontal and sphenoid are the three cranial bones. The lacrimal, maxillary, palatine and zygomatic bones are the facial bones.
The openings in the orbits are:
The optic foramen, the superior orbital fissure and the inferior orbital fissure.
The parietoorbital oblique projection of the orbits shows the following anatomy:
Orbital plate of the frontal bone Sphenoid bone Optic foramen and canal Superior orbital fissure Infraorbital margin Sphenoid strut Lateral orbital margin Supraorbital margin
Which of the following facial bones is unpaired? Maxillary Palatine Lacrimal Vomer
Vomer
The anterior nasal spine is an aspect of the ______ bone.
Maxillary
The palatine process is an aspect of the ____ bone.
Maxillary
Lacrimal is derived from a word meaning:
Tear
Which facial bone forms an aspect of the bony nasal septum?
Vomer
What is the name of the process of the mandible in which the lower teeth are embedded?
Alveolar process
The older term “antrum of Highmore” describes the:
Maxillary sinuses
Which paranasal sinus is the last one to develop?
ethmoid
The posterior aspect of the bony orbit is termed the:
Apex
Which of the following bones makes up most of the lateral wall of the orbit? Maxillary Lacrimal Zygomatic Vomer
zygomatic
What passes through the optic foramen?
The second cranial nerve (the optic nerve)
Radiographic exams of the sinuses are performed to demonstrate:
mucosal thickening
air-fluid levels
erosion of bony margins.
Blowout fracture:
- Fracture of floor of orbit.
- Caused by object striking eyes straight on.
- Floor ruptures and the inferior rectus muscle is forced through fracture and into maxillary sinus causing entrapment and diplopia.
Tripod fracture:
Caused by blow to cheek.
The zygoma fractures at the orbital process, maxillary process and temporal process, causing a free-floating zygomatic bone
LeForte fractures:
Severe bilateral horizontal fractures of maxillae which may result in unstable detached fragment.
Countrecoup:
Injury/fracture to one side of a structure caused by an impact on the opposite side.
Foreign body of the eye:
Metal or other types of fragments in the eye.
Plain images detect presence of metallic foreign objects but are limited in ability to demonstrate damage.
Neoplasm
new and abnormal growth that may occur in skeletal structures of face.
Osteomyelitis:
Localized infection of bone/bone marrow caused by bacteria from penetrating trauma, postoperative or fracture complication. Spread by flood from distant site.
Sinusitis:
Infection of sinus mucosa. Can be acute or chronic. Symptoms include headache, pain, swelling over affected sinus and possible low grade fever.
Secondary osteomyelitis:
Infection of bone and marry secondary to sinusitis. Results in erosion of bony margins of sinus.
TMJ Syndrome:
Describes a set of symptoms which may include pain and clicking that indicate dysfunction of the TMJ. Causes include malocclusion, stress, muscle spasm or inflammation.
Clinical indications of facial and paranasal sinuses:
Blowout fracture, Tripod fracture, LeForte fracture, Contrecoup, Foreign body of the eye neoplasm, osteomyelitis, sinusitis, secondary osteomyelitis, TMJ syndrome.
Erect position for facial bones and paranasal sinuses allows for _______ and permits use of horizontal beam to demonstrate:
patient to be quickly and easily positioned.
air/fluid levels within sinus cavities
Respiration suspended during exposure except in cases of
severe trauma
Cranial and facial radiography requires patient’s face to be in direct contact with radiographer’s hands and table/upright Bucky surface, therefore,
wash hands and sanitize table/Bucky before and after every exam.
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)
Exposure Factors for Paranasal Sinuses:
Medium kV (65 to 85 analog); (75 to 90 kV digital systems) commonly used to provide sufficient contrast
Optimal density (mAs) to visualize pathology in sinuses
Small focal spot for maximum detail
Minimum SID 40” (102 cm)
To ensure Radiation Protection:
close collimation
Minimize repeats (Immobilization)
Center properly
Shielding of radiosensitive organs recommended
Five Common Positioning Errors
Rotation Tilt Excessive flexion Excessive extension Incorrect CR angle
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
Dense internal bony structures of the skull (petrous pyramids) superimpose the facial bones on _____ projections.
AP/PA
Because the petrous pyramids superimpose the facial bones on AP/PA projections:
very specific CR angles and head positions are required.
In a PA skull projection, the petrous ridges are projected into:
orbits and very little facial bone detail can be demonstrated with radiographs.
Parietoacanthial projections is also known as:
Waters method.
In the Waters method, the petrous pyramids are removed from the facial bone area of interest by:
raising the chin to project the petrous pyramids below the maxillary sinuses.
In the Waters method, the facial bones are projected where?
Superior to petrous pyramids (except for the mandible).
Upright positioning preferred for facial bone and sinus radiography to demonstrate possible
air-fluid levels.
Things to remember during pediatric exams:
Communication, Immobilization, Exposure factors
How and why we communicate more during pediatric exam?
Clear explanation to gain trust of patient and guardian.
Distraction techniques.
What to remember for immobilization techniques during pediatric exam?
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.
Exposure factors to remember during pediatric exams:
Vary with patient sizes and pathologies.
High mA and short exposure times reduce motion.
Things to remember during geriatric exams:
Communication, comfort and exposure factors.
Things to remember when communicating with geriatric patients:
Sensory loss because of aging may result in need for additional assistance, time and patience for skull/facial bone/sinus radiography.
Things to remember to ensure comfort of geriatric patients:
Radiolucent mattress Extra blankets Reassurance and attention Be aware of Increased kyphosis Perform exam Upright if possible Horizontal beam lateral if necessary
Exposure factors to remember during a geriatric exam:
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).
Things to consider during digital imaging of facial bones:
Correct central ray angle and centering to body part and image receptor.
Close collimation.
Following ALARA principles.
Post-porcessing evaluation of exposure indices.
Alternative modalities for facial bones and paranasal sinuses:
- CT* (most commonly performed neuroimaging procedure.)
- MRI* (views three different planes, superior in evaluating soft tissue)
- Ultrasound* (exam of brain of neonate (through the fontanels) in ICU for rapid evaluation and screening of premature infants for intracranial hemorrhage.)
- Nuclear Med* (provides screening for detection of skeletal metastases.)
Routine projections for orbits:
Lateral
Parietoacanthial (Waters method)
PA axial (Caldwell method)
Special projections for orbits:
Modified Parietoacanthial (modified Waters method)
Routine projections for nasal bones:
Lateral
Parietoacanthial (Waters method)
Special projections for nasal bones:
Superioinferior (axial)
Routine projections for Optic foramina and orbits:
Parieto-orbital oblique (Rhese method)
Parietoacanthial (Waters method)
Special projections for optic foramina and orbits:
Modified parietoacanthial (modified Waters method)
Routine projections for zygomatic arches:
Submentovertex (SMV)
Oblique inferosuperior (tangential)
AP axial (Modified Towne’s)
Paritoacantial (Waters method)
Routine projections for mandible:
Axiolateral Oblique
PA 0º and PA axial 20º to 25º
AP axial (Towne method)
Special projections for mandible:
Submentovertex (SMV)
Ortopantotomography
Routine projections for TMJ’s:
AP axial (modified Towne’s method)
Special projections for TMJ’s:
Axiolateral 15º oblique (modified Law method)
Axiolateral (Schuller method)
Routine projections for paranasal sinuses:
Lateral
PA (Caldwell method)
Parietoacanthial (Waters method)
Special projections for paranasal sinuses:
Submentovertex (SMV) Parietoacanthial transoral (open mouth Waters method)
Clinical indications for lateral position for facial bones:
Fractures and neoplastic/inflammatory processes of facial bones, orbits and mandible. Single lateral (affected side down) usually performed.
Technical factors for lateral position for facial bones:
40" SID 18x24cm or 8x10 inch IR lengthwise Grid Analog 65-75 Digital 70-80
Patient position for lateral position of facial bones:
All metal and plastic removed
Pt is erect or semi-prone.
Part position for lateral position of facial bones:
- Lateral aspect of head against IR- side of interest closest to IR.
- Head adjusted in true lateral position and oblique body as needed (inion and glabella equidistant from imaging device.)
- MSP parallel to IR
- IPL perpendicular to IR. IOML perpendicular to front edge of IR.
Central ray for lateral position of facial bones:
Perpendicular to IR.
CR enters zygoma midway between outer canthus and EAM.
Center IR to CR.
Structures shown on lateral view of facial bones:
Superimposed facial bones. greater wings of sphenoid orbital roofs. sella turcica. zygoma. mandible.
How to determine if pt was accurately positioned by looking at image:
No rotation of vertical structures such as mandibular rami.
No tilt of horizontal structures such as orbital roofs, which should be superimposed.
Correct exposure of lateral image of facial bones should show:
Contrast and density sufficient to visualize maxillary region.
Clinical indications for Parietoacanthial Projection (Waters method): Facial bones
Fractures including Tripod and LeForge, Neoplastic/inflammatory processes
Foreign bodies in the eye
Technical factors for Parietoacanthial projection (Waters method) for Facial bones:
40" SID 24x30cm or 10x12" IR lenthwise grid analog 70-80 kvp digital 75-85
Part position for Parietoacanthial projection (Waters method) for facial bones:
Extend neck and rest chin against IR.
Head is adjusted until MML is perpendicular to IR; OML forms 37º angle with imaging device surface.
MSP is perpenducular
To check for rotation on a TT Parietoacanthial projection (Waters method) for facial bones:
palpate mastoid processes on each side and lateral orbital margins with thumb and fingertips to ensure these lines are equidistant from TT.
Parietoacanthial projection: Waters method: Facial bones: How is the central ray related to the IR and where does it exit the pt?
The central ray is perpendicular to the IR and exits the pt at the acanthion.
Anatomy demonstrated on Parietoacanthial projection (Waters method) for facial bones:
Inferior orbital margins (IOM's) Maxillae Nasal septum Zygomas Zygomatic arches Anterior nasal spine.
Position criteria for Parietoacanthial projection (Waters method) Facial bones:
- Petrous ridges just inferior to maxillary sinuses indicates correct neck extension.
- Equal distance from mid lateral orbital margin to lateral cortex of cranium on each sides indicates NO patient rotation.
Exposure criteria for Parietoacanthial projection (Waters method) for Facial bones:
Contrast and density sufficient to visualize maxillary region. No motion (sharp bony margins)
Clinical indications: PA Axial Projection: Facial bones: Caldwell method:
Fractures and neoplastic/inflammatory processes of facial bones.
Technical factors: PA Axial Projection: Facial Bones: Caldwell method:
40" SID IR size 24x30 cm or 10x12". Grid Analog 70-80 Digital 75-85
Pt position: PA Axial Projection: Facial Bones: Caldwell method:
All metallic or plastic objects removed from head and neck.
Erect or prone (erect is preferred if patient condition allows)
Part Position: PA Axial Projection: Facial Bones: Caldwell method:
Forehead and nose rests against IR
OML is perpendicular to IR
MSP is perpendicular to IR
Ensure no rotation or tilt of head.
Central Ray: PA Axial Projection: Facial Bones: Caldwell method:
Angle CR 15º caudad to exit at nasion.
If area of interest is the orbital floors, angle CR 30º caudal to project the petrous ridges below the inferior orbital margins.
Structures shown on PA Axial Projection: Facial Bones: Caldwell method:
Orbital rim Maxillae Nasal septum Zygomatic bones Anterior nasal spine.
Position criteria: PA Axial Projection: Facial bones: Caldwell method:
- Correct pt position/CR angulation shows petrous ridges in lower 1/3 of orbits.
- If using 30º caudal angle, petrous ridges projected below inferior margin on orbits.
- No rotation: Equal distance from mid lateral orbital margin to outer skull on each side.
- Symmetric fissures.
Correct exposure: PA Axial projection: Facial bones: Caldwell method:
Contrast and brightness are sufficient to visualize maxillary region and orbital floor.
How Modified Parietoacanthial Projection (Modified Waters) compares to Waters method:
Modified Waters method uses less extension of pt’s neck.
Sometimes called “shallow” Waters.
Demonstrates petrous ridges in about lower half of maxillary sinuses.
Clinical indications for MOdified Parietoacanthial Projection
Orbital fractures, especially blowout fracture as it places the orbital floor perpendicular to IR and parallel to CR and will demonstrate inferior displacement of orbital floor.
Foreign bodies in the eye may also be demonstrated.
Technical factors for Modified Parietoacanthial Projection:
SID 40" IR size of 8x10, lengthwise Grid Analog 70-80 kV Digital 75-85 kV
Part position for Modified Parietoacanthial Projection:
Extend neck, restin chin and nose against IR. LML is perpendicular OML forms 55º angle with IR MSP perpendicular No rotation or tilt of head.
Central Ray for Modified Parietoacanthial Projection:
Perpendicular exits at acanthion.
Center IR to CR.
Anatomy demonstrated for Modified Parietoacanthial Projection:
Orbital floors are perpendicular to IR.
Les distorted view of entire orbital rims than with Waters method.
Evaluation Criteria: Position for Modified Parietoacanthial Projection:
Correct position/CR angle indicated by: Petrous ridges projected into lower half of maxillary sinuses below IOMs.
No rotation: Equal distance from mid lateral orbital margin to the lateral cortex of the cranium.
Clinical indications for nasal bones:
Nasal bone fractures
Both side examined for comparison
Side closest to IR is best demonstrated.
Technical factors for nasal bones:
SID 40" IR size 8x10 crosswise Analog 50-60 kVp Digital 60-70 kVp AEC not recommended.
Part position for lateral nasal bones:
Lateral aspect of head rests against IR, side of interest closest to IR.
Nasal bones positioned to center of IR.
HEad adjusted to true lateral position obliquing body as needed for patient’s comfort.
MSP parallel with IR surface.
IPL perpendicular to IR surface.
IOML perpendicular to front edge of IR.
Central ray for lateral nasal bones:
Perpendicular to IR and enters half an inch inferior to nasion.
Recommended collimation for lateral nasal bones:
All sides to within 2” of nasal bone.
Anatomy demonstrated for lateral nasal bones:
Nasal bones with soft tissue nasal structures, front nasal suture and anterior nasal spine.
Position for lateral nasal bones:
Nasal bones demonstrated without rotation.
Part position for Parietoacanthial projection of nasal bones:
Extent neck and rest chin against IR.
Head is adjusted until MML is perpendicular to IR; OML forms 37º angle with imaging device surface. MSP is perpendicular. No rotation or tilt.
Central ray for Parietoacanthial projection of nasal bones:
Perpendicular to IR, exits at acanthion.
Center IR to CR.
Clinical indications for Superoinferior tangential (axial) projection of nasal bones:
Fracture of nasal bones with medial-lateral displacement.
Pt position for Superoinferior tangential (axial) projection of nasal bones:
Seated erect in a chair at end of table or in prone position on table.
Part position for Superoinferior tangential (axial) projection of nasal bones:
Chin is extended and resting on IR.
Angle support placed under IR to place IR perpendicular to GAL.
MSP perpendicular to CR and IR midline.
Central ray for Superoinferior tangential (axial) projection of nasal bones:
Centered to nasion and angled as needed to be parallel with GAL.
Anatomy demonstrated for Superoinferior tangential (axial) projection of nasal bones:
Tangential projection of mid nasal and vital nasal bones and nasal soft tissue, with little superimposition of glabella or alveolar ridge.
Position for superoinferior Tangential (axial) projection of nasal bones:
No rotation indicated by equal distance from anterior nasal spine to outer soft tissue borders on each side.
Incorrect neck position indicated by visualization of alveolar ridge (excessive extension) or visualization of too much glabella (excessive flexion)
Clinical indications for SMV of zygomatic arches:
Fractures of zygomatic arch
Neoplastic/inflammatory processes.
Technical factors for SMV of zygomatic arches:
40” SID
Grid
Analog 60-70 kV
Digital 70-80 kV
Patient position for SMV of zygomatic arches:
All metallic or plastic objects from head and next removed.
May be radiographed erect or supine.
Upright position usually easier for patient.
Part position for SMV of zygomatic arches:
Neck hyperextended until IOML is parallel to IR.
Head rests on vertex.
MSP perpendicular.
Avoid tilt and/or rotation.
Anatomy demonstrated for SMV of zygomatic arches:
zygomatic arches laterally from each mandibular ramus.
Position for SMV of zygomatic arches:
IOML/CR relationship correct if mandibular symphysis is superimposed on frontal bone.
No rotation if zygomatic arches visualized symmetrically.
Clinical indications for Oblique inferosuperior (Tangential) projection of zygomatic arches:
Fractures of the zygomatic arch.
Projection especially useful for depressed zygomatic arches caused by trauma or skull morphology.
Both sides generally taken for comparison.
Technical factors for Oblique inferosuperior (tangential) projection of zygomatic arches.
SID 40”
Grid
Analog 60-70
Digital 70-80
Part position for oblique inferosupeirior (tangential) projection of zygomatic arches:
All metallic or plastic objects removed from head/neck
Erect or supine.
Erect, which is easier for the pt, may be done with upright table or upright imaging device.
Pt Position for Oblique inferosuperior (Tangential) projection of zygomatic arches:
Neck hyperextended until IOML is parallel to IR.
Head rests on vertex.
Head is rotated 15º toward the side being examined.
Chin is tilted 15º toward the side being examined.
Central ray for Oblique inferosuperior (Tangential) projection of zygomatic arches:
CR perpendicular to IR and IOML.
Enters zygomatic arch of interest (skims madibular ramus, passes through arch and skims parietal eminence on down side.)
Adjust IR to be parallel to IOML and perpendicular to CR.
If pt cannot extend neck enough, angle CR perpendicular to IOML. IR should be angled to maintain CR/IR perpendicular relationship.
Anatomy demonstrated for Oblique inferosuperior (tangential) projection of zygomatic arches:
Single zygomatic arch free of superimposition.
Position for oblique inferosuperior (tangential) projection of zygomatic arches:
Correct position indicated by demonstration of zygomatic arch without superimposition of parietal bone or mandible.
Clinical indications for AP Axial projection of zygomatic arches (Modified Towne method)
Fractures of zygomatic arches
Neoplastic/inflammatory processes of zygomatic arches.
Technical factors for AP Axial projection of zygomatic arches (Modified Towne method)
SID 40" IR size 8x10 crosswise grid Analog 60-70 Digital 70-80 AEC not recommended.
Part position for AP Axial projection of zygomatic arches (Modified Towne method)
Skull rests against IR
Tuck chin until OML (or IOML if patient cannot depress chin) is perpendicular to IR.
MSP is perpendicular to IR.
Central ray for AP axial projection fo zygomatic arches (Modified Towne method)
30º caudad to OML; or 37º caudad to IOML.
CR enters 1 inch above glabella and passes through mid arches at level of gonion.
IR centered to projected CR.
Anatomy demonstrated for AP axial projection of zygomatic arches (Modified Towne method)
Bilateral zygomatic arches.
Position for AP axial projection of zygomatic arches (Modified Towne method)
No rotation indicated by bilateral symmetric appearance of zygomatic arches.
Parietoorbital projection (Rhese Method) for optic foramina is sometimes referred to as:
a “three-point landing” position.
Pt rests zygoma, chin and nose on IR.
Clinical indications for parietoorbital oblique projection (Rhese Method) of optic foramina:
Bony abnormalities of the optic foramen.
Demonstrates lateral margins of orbits and foreign bodies within the eye.
Both sides are radiographed for comparison.
Technical factors for parietoorbital oblique projection (Rhese method):
40" SID 8x10 IR Grid Analog 70-80 kVp Digital 75-85 kVp AEC not recommended.
Part position for Parietoorbital oblique projection (Rhese method):
- Start with head prone and MSP perpendicular to IR (as reference point)
- Adjust patient to AML is perpendicular to IR.
- Adjust pt’s head so the chin, cheek, and nose will touch IR.
- Head is rotated 37º toward affected side. Angle formed between MSP and plane of IR will measure 53º
Central ray for parietoorbital oblique projection (Rhese method):
Perpendicular to IR at mid portion of downside orbit.
Anatomy demonstrated for parietoorbital oblique projection (Rhese method):
Bilarteral non distorted view of the optic foramen.
Lateral orbital margins demonstrated.
Evaluation criteria: Position for parietoorbital oblique projection (Rhese method):
Accurate positioning projects the optic foramen into the lower outer quadrant of the orbit. Any lateral deviation of this indicated incorrect rotation of head. Any longitudinal deviation indicates incorrect placement of AML.
Structures shown on parietoorbital oblique projection (Rhese method):
Optic canal “on end” and a nondistored view of optic foramen.
Radiographic criteria: Position for Parietoorbital oblique projection (Rhese method):
Optic foramen and canal lie in the inferior and lateral quadrant of the orbit. Any lateral deviation of this indicates incorrect rotation of head. Any longitudinal deviation indicates incorrect placement of AML.
Clinical indications for Axiolateral oblique projection of the mandible:
Fractures and neoplastic/inflammatory processes.
Both sides radiographed for comparison.
The goal of the axiolateral oblique projection is to place the desired portion of the mandible (ramus, body, or mentum) parallel with the IR.)
Technical factors for Axiolateral oblique projection of the mandible:
40" SID 8x10" IR Grid (or non-grid) Analog 70-80 kVp Digital 75-80 kVp AEC not used.
Part position for Axiolateral oblique projection of the mandible:
Head placed in true lateral position, with side of interest against IR.
If possible have patient close mouth and bring teeth together.
Neck is extended slightly to prevent gonion from superimposing c-spine.
The head is rotated toward IR to place area of interest parallel with IR-degree of obliquity depends on which section of the mandible is of interest.
How many degrees is the head rotated towards the IR to the ramus during a Axiolateral oblique projection of the mandible?
0º (true lateral)
How many degrees is the head rotated towards the IR to image the body of the mandible during an Axiolateral oblique projection of the mandible?
30º.
How many degrees is the head rotated towards the IR to image the mentum of the mandible during an Axiolateral oblique projection of the mandible?
45º
How many degrees is the head rotated towards the IR to image a general survey of the mandible during an Axiolateral oblique projection of the mandible?
10º - 15º.
What are the three methods of CR angulation suggested for the axiolateral oblique projection of the mandible?
- Angle CR 25º cephalic from IPL (for the horizontal beam trauma position, angle CR and additional 5º to 10º posteriorly.)
- Employ a combo of tilt on the head and CR angle not to exceed 25º.
- Employ 25º of head tilt toward IR, and use perpendicular CR.
Direct CR to exit mandibular region of interest.
Evaluation criteria: structures shownL axiolateral oblique projection of mandible:
Rami, condylar and coronoid processes, body and mentum of mandible nearest the IR.
Evaluation criteria: Position: axiolateral obique projection of mandible:
- For the ramus and body, the ramus of interest is demonstrated with no superimposition from the oppostie mandible. (indicating correct CR angulation)
- No superimposition of the cervical spine by the ramus should occur (indicating sufficient extension of neck.)
- The ramus and body should be demonstrated without foreshortening (indicating correct rotation on head)
- The area of interest in demonstrated with minimal superimposition and minimal foreshortening.
Pathology demonstrated in PA or PA Axial projection of the mandible:
Fractures and neoplastic/inflammatory processes.
Optional PA axial best demonstrates proximal rami and elongated view of condyles.
Technical factors for PA or PA axial projection of the mandible:
40" SID 8x10 IR size. Grid Analog 70-80 kVp Digital 75-80 kVp AEC not used.
Part position for PA or PA axial projection of the mandible:
Forehead and nose rested against IR.
Tuck chin until OML is perpendicular to IR.
MSP perpendicular to IR.
For a true PA projection of the body, if this is the area of interest, raise chin to bring AML perpendicular to IR.
Central ray for PA or PA axial projection of the mandible:
PA: CR perpendicular to IR centered to exit at junction of lips. (For trauma pt’s, best performed supine.)
Optional PA axial: Angle 20º to 25º cephalad centered to exit at acanthion.
Anatomy demonstrated on PA or PA axial projection of mandible:
Mandibular rami and lateral portion of body are visible.
On the optional PA axial: TMJ region and condyle heads visible through mastoid processes; slightly elongated condyloid processes are well visualized (slightly elongated.)
