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