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What is a sinus?
Cavity within a bone
Canal or passageway leading to an absess
dilated channel for venous blood
any cavity having relatively narrow opening
57 different kinds sinuses in human body!
Heart Ankle Brain Coccyx Spleen Kidney Uterus Anus Skull- around the nasal cavity
known as….
Paranasal Sinuses
Each sinus is name after the bone it resides in!
Lateral Aspects of Sinuses
Development
Start as small sacs around nasal meatus & recesses
Grow – invading bone- forming air sinuses and cells
Maxillary seen at birth
By age 6 or 7 frontals & sphenoids
distinguish themselves Ethmoids around puberty
All full developed age 17- 18
All sinuses communicate nasal cavity and each other
Functions of Paranasal Sinuses?
Not definitely known!- but speculated:
decrease weight of skull
resonating chamber for voice
help warm and moisten air
act as airbags in trauma
possibly control immune system
Paranasal sinuses are joined to nasal cavity via small orifices called Ostia (harbour city of ancient Rome)
Ostia easily blocked by allergic
inflammation or swelling of nasal lining
drainage of mucous is disrupted
Sinusitis may result!
What is Sinusitis?
Inflammation of sinuses- caused by bacterial infection of membrane lining- can fill with pus!
Usually from common cold (after first attack, recurrence more likely)
Can spread from upper tooth infection
Jumping in infected water without holding nose
Symptoms of Sinusitis Loss of smell Fever Fullness or tension Pain 37 million Americans suffer every
year Decongestion opens up ostia to
restore drainage
Sinusitis Video
sinusitis.wmv
(Click on icon)
Conditions aggravating Sinusitis
Scuba diving Chlorinated swimming
pools Drinking alcohol Airplane rides (vacuum)
What is Ex-u-date? (Something that exudes!)
Heavy, semi-gelationous material that likes to cling to walls of sinuses (Mucous)
Allow several minutes for material to layer out if going from erect projection to cross-table projection
Clean Image Receptor before and after!!
There are 4 sets of Paranasal Sinuses
FrontalMaxillaryEthmoidSphenoid
Frontal Sinuses
2nd LargestUsually paired-sometimes one, three or none!Great variation in size and shape-almost never symmetrical (califlower)
Frontal Sinuses
Maxillary SinusesLargest (think Maximum!)Two, symmetrical but vary in size and shape from person to personCan be seen at birthApices at bottom of sinus!
Ethmoid SinusesPairedDivided into 3 groups-anterior- 2-8 cellsmiddle- 2-8 cellsposterior 2-6 cells6-22 possible
each side
Sphenoid Sinuses
Paired (sometimes one)Great variation in size and shapeAsymetricDirectly below Sella turcica
Sinuses should always be performed upright with horizontal beam
Horizontal Beam Beam angles up 45 degrees
Beam projected straight downward
If patient cannot sit or stand upright, what is an alternative method for getting equally useful views?
CrossTable Lateral or Dorsal Decubitus
To see an anterior posterior projection--
A Lateral Decubitus!--As long as beam is horizontal, a fluid level can be
demonstrated!
All sinuses views are performed-
With a 40 “ SIDCollimated to area of sinusesErect (or crosstable)
8X10 cassette
4 Basics Projections of Sinus Series
PA Axial (Caldwell) Parietoacanthial (Waters) Lateral SMV (basilar)
PA axial (Caldwell method)
Incorrect! Beam should not be angled- must be horizontal!
X
For proper PA axial of sinuses, either tilt IR 15
degrees forward
Or keep IR vertical, but extend pt.’s head back 15
degrees
PA axial (Caldwell)
beam exits at nasioninterpupillary line horizontal midsagital plane perpendicular to IR8X10 cassetteCollimated to sinuses
Best projection for Frontal sinuses!
How to Judge if you have a good Caldwell projection?
No rotation (equal distance between lateral border of skull and lateral border of orbit)
Petrous ridges in lower 1/3 or orbitClose beam colimation
waters xray.jpg
Parietoacanthial Projection
Waters Method
Parietoacanthial projection (Waters)
Horizontal beam exits
at acanthion
chin touches IR, nose
extends back 1/2” from
IR
Angle of orbito-meatal
line is 37 degrees
(mento-meatal line is
perpendicular to IR)Best projection for Maxillary sinuses!
Proper Waters Position
OML is 37 degrees to IR (cassette)
Not OML 37 deg. to CR!
Improper Parietoacanthial Position
Nose is touching-thus OML is not 37 degrees to IRThis is actually a “Modified” Waters for imaging orbits, nasal bones
An Under-extended Waters projection
Petrous ridges do not sit directly below apices of Maxillary sinuses!
Head needs to be extended back further
Does patient have sinusitis?
Open-mouthed Waters for Sphenoid Sinus
(Board Question)
Lateral Projection
Shows all 4 sets of sinuses at once!
Shows all 4 sinus groups, - mainly for sphenoidSimilar to lateral skull, but collimate to anterior half of skullCR ½” – 1” posterior to outer canthus furthest from filmCR parallel to floor
Lateral Sinus projection
Evaluation Criteria - Lateral Sinus
No rotation of sella turcicaSuperimposed orbital roofsClose beam restriction
SMV (basal) projection
Demonstrates Ethmoid & Sphenoid sinuses best!
SMV - Sinuses
Similar to skull, but collimated to anterior 2/3 of skullCR horizontal, perpendicular to IOMLCR enters 3/4 anterior to level of EAM
If patient can’t extend head back enough--
Alternate SMV Position?
Often times, better to omit SMV, depending on patient’s condition & ageBeam not horizontal!
Evaluation Criteria - SMV Sinuses
Equal distance from lateral border of skull to mandibular condyles on both sides
Mental protuberance superimposes Frontal bone
Condyles anterior to petrous pyramids
Is this an acceptable Waters projection?
No!
Apices of Max. sinus must be immediately above petrous pyramids
The head is underextended!
How about this Waters?
No! Head overextended! Frontal and maxillary
sinuses are foreshortened
Apices too high above petrous ridges
Technical Factors very important with sinuses!
More critical & misleading than any other part of body
Under penetration-miss pathology or simulate false conditions
Over penetration- burn out pathology Need to see both bony structure and soft
tissue
Overpenetrated Waters
Where is the frontal sinus?A bit overextended as wellRemove dentures!
Underpenetrated
Is there fluid in apices or not?
Should you shield?
Federal government has reported placing a lead shield over a pt.’s pelvis does NOT significantly reduce gonadal exposure during skull imaging
Do it anyway!
Best way to reduce Pt. expose to Radiation?
Proper collimation!
Also, infants and children should receive shielding of thymus (lymph gland in chest-later disapears) and thyroid glands, as well as Gonads
Double shield pregnant women