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DIAGNOSTIC IMAGING FOR THE
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ORAL AND MAXILLOFACIAL SURGERY PATIENT
CHAPTER 5
Sonali A. Rathore, A. Omar Abubaker
1. What are the basic units of radiation?
The units of absorbed radiation:
• Gray(Gy)  • Rads Theunitsofbiologicallyeffectiveradiation:  • Rem  • Sieverts(Sv) Conversionbetweenunits:  • 1Gy=100rad  • 1mSv=0.001Gy
2. What are the radiographic patterns of disease on an X-ray exam of the chest?
Thepatternsofdiseaseonachestradiographarelimited.Thethreemostcommonpatternsare:  1. Alveolar.Pulmonaryalveolardiseaseisthemostcommonpatternandappearsasalocalized,
homogeneous,uffydensity.Itcanrepresentwater,blood,pus,ortumorwithinthealveoli.
2. Interstitial.Theinterstitialpatternmaybereticular(linear),nodular,oracombinationofthetwo
(reticulonodular).Thereticularpatternusuallyisbilateralanddiffuse.
3. Nodular.Thenodularpatternofdiseaseappearsasdiscrete,well-circumscribed,radiopaque
massesinthelungfield.
3. What is the diagnostic value of posteroanterior (PA) chest films?
APAchestfilm(Fig.5-1)istakenbydirectinganX-raybeamfromposteriortoanterioronthechest.
Thisradiographisusefultoevaluatethesofttissueandbonytissuesofthechest,thediaphragm,the heartandmediastinum,thehilaofthelungs,andtheentirePAviewofthelungfields.
4. What are the main uses of a lateral chest film (Fig. 5-2)?
• Localizinglesionstoaspecificareaofthelungsormediastinum  • Diagnosingsmallpleuraleffusions(bluntingoftheposteriorcostophrenicangles)  • Diagnosingvertebralandsternalabnormalities
5. What is the chest X-ray appearance of a pneumothorax (Fig. 5-3)?
Pneumothoraxisusuallyrepresentedbyathin,lineardensitythatparallelsthechestwall.Nolong
markingsshouldbeseenperipheraltothisline.Intensionpneumothorax,ashiftinthemediastinumis seen,especiallywithalargetensionpneumothorax.
6. What radiographic changes are associated with chronic obstructive pulmonary
disease (COPD)?
• Hyperexpandedlungfields  • Alarge,radiolucentzonebehindthesternum  • Flatteningofthediaphragm  • Elongatedheart
7. What radiographic changes are associated with chronic bronchitis?
Chestradiographsofchronicbronchitisshowincreasedbronchiovascularmarkingsatthebaseofthe
lungs.Inpatientswithemphysema,chestradiographsshowoverdistensionofthelungs,atteningof thediaphragm,andemphysematousbullae.
62
CHAPTER 5 DIAGNOSTIC IMAGING FOR THE ORAL AND MAXILLOFACIAL SURGERY PATIENT 63
Apex
Trachea
Clavicle
Aortic
Costophrenic
angle
diaphragm
Costophrenic
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Right hilum
Figure 5-1. Posteroanteriorchestprojection. (From Long BW, Frank ED, Ehrlich RA: Bony thorax, chest, and abdomen. In Long BW, Frank ED, Ehrlich RA, editors: Radiographyessentialsforlimitedpractice, ed 2, St Louis, 2006, Saunders.)
knob
Left hilum
Heart
Lung apices
angles
Figure 5-2. Lateralchestprojection. (From Long BW, Frank ED, Ehrlich RA: Bony thorax, chest, and abdomen. In Long BW, Frank ED, Ehrlich RA, editors: Radiographyessentialsforlimitedpractice, ed 2, St Louis, 2006, Saunders.)
8. How do lung masses show up on chest films?
Lungmassesusuallyfollowthenodularpatternofdisease.Masseswithinthelungfieldscanbe
dividedintocavitaryandnoncavitarylesionsandrepresenteithertumororinfection.Othercausesof massesincludevascularmalformations,butthesearefarlesscommonthantumorandinfection.
9. What is a lordotic chest radiograph used for?
Alordoticchestradiographpermitsbettervisualizationoftheapicesofthelung.Thisviewshouldbe
obtainedwhenaquestionablelesionisseenintheseareasonastandardchestradiograph.
Aortic arch
Heart
Dome of
64 PART I PATIENT EVALUATION
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Figure 5-3. Posteroanteriorchestfilmshowingaleftpneumothorax(arrow). (From Bosker JI, Powers MP, Bosker H: Management of nonpenetrating chest trauma. In Fonseca RJ, Walker RV, Betts NJ, editors: Oralandmaxillofacialtrauma, ed 3, St Louis, 2005, Saunders.)
10. What is the common chest radiographic finding in AIDS patients?
Infectiouspulmonarydisease.Pneumocystis cariniipneumonia,themostcommoninfection,usually
hasthepatternofafine,diffusereticularprocess.
11. Which views are included in an acute abdominal series? When are they used?
• Supineanduprightabdominalfilms(toviewthekidneys,ureter,andbladder)  • Chestradiograph Theseviewsareusedfortheinitialevaluationofacuteabdominalpainortrauma.
12. What is a KUB?
AKUBisaradiographicviewtoevaluatethekidneys,ureters,andbladder.Theseries,whichisalso
knownasasupineabdominalradiograph,isusefulintheinitialwork-upofabdominalpain,distention ofthebowel,andchangeofbowelhabits.Italsoisusedforevaluationofurinarytractproblems. Renalstonesand10%to20%ofgallstonesarevisualizedbyaKUB.EvaluationoftheKUBviews involvesexaminingthebowelgaspatternandlookingforcalcificationsandradiopaqueforeignbodies. Thepsoas;renal,liver,andsplenicshadows;ankstripes;vertebralbodies;andpelvicbonesalsoare examined.
13. What is a barium swallow (esophagram)?
Anesophagram,usuallyperformedwithbarium,awater-solublecontrastagent,isusedtoevaluate
theswallowingmechanismandtolookforesophageallesionsorabnormalperistalsis.Nopreparation isrequiredforthisstudy.
14. What is the upper gastrointestinal series (UGI)?
UGI,whichincludesanesophagram,isusedtostudythestomachandduodenum.Thisdouble-
contraststudyusesbariumandairandisusefulfordetectionofgastritis,ulcers,masses,hiatal hernias,andgastrointestinalreux.Itisalsoanimportantpartofthework-upofheme-positivestools andupperabdominalpain.
15. What is an intravenous pyelogram (IVP)?
Thisimagingtechniqueusesintravenous(IV)contrasttoevaluatethekidneys,ureters,andblad-
der.Thistestisindicatedforpatientswithhematuria,kidneystones,urinarytractinfection,and suspectedmalignancyofthekidneyorbladderandisusedforthework-upofpatientswithank pain.
CHAPTER 5 DIAGNOSTIC IMAGING FOR THE ORAL AND MAXILLOFACIAL SURGERY PATIENT 65
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16. What are the different nuclear scans and their uses?
Innuclearscans,ornuclearmedicinestudies,radionuclidesareinjectedintravenously,andresultsare
basedondetectionofthetissueuptakeoftheseradionuclides,specificallythedegreeofuptake,the timeintervalsbetweenthestudies,andtheinjectionoftheradionuclides.
Abonescanisanuclearscanstudythatusesradioactivetracers,suchastechnetium99,to detectareasofincreasedordecreasedbonemetabolism(turnover).Areasthatabsorblittletracer appearasdarkor“cold”spots,whichmayindicatealackofbloodsupplytotheboneorthepresence ofcertaintypesofcancer.Areasofrapidbonegrowthorrepairabsorbincreasedamountsofthe tracerandshowupasbrightor“hot”spotsinthepictures,whichindicatethepresenceofatumor, afracture,oraninfection.Bonescansareusedinmetastaticwork-ups,especiallyinpatientswith cancerthathasapredilectiontometastasizetobone(e.g.,breast,prostate,kidney,lung,thyroid). Theyarealsousedasscreeningtestsforprimarytumors,osteomyelitis,avascularnecrosis,and stressfractures.
Agalliumscanisusedtolocateabscessesthataremorethan5to10daysold.Whenusedin combinationwithabonescan,thegalliumscanisveryspecificforosteomyelitis.Indium111white bloodcellscanscanbesubstitutedforgalliumscanningtodetectosteomyelitis.
Thecardiacscanhasbecomeincreasinglypopularinrecentyearsandisusedformany purposes,includingdetectionofmyocardialinfarctionandischemia,stresstesting,andevaluationof ejectionfractions,cardiacoutput,andventricularaneurysms.
Aliver-spleenscanisusedtoestimateparenchymaldisease,abscess,tumors,andcystsin theseorgans.Thecurrentpreferenceforcomputedtomography(CT)scanninghassignificantly decreasedtheuseoftheliver-spleenscan.
Theventilation-perfusionlungscanisusedprincipallyfortheevaluationofpulmonaryemboli. AlthoughnotassensitiveorspecificasapulmonaryangiogramorspiralCT,theventilation-perfusion scanislessinvasiveandoftenisobtainedfollowingachestradiographwhenthediagnosisofpulmo­naryembolusissuspected.
17. What (plain film) views are included in a facial series, and what are they used for?
AfacialseriesusuallyincludesCaldwell’sview,Waters’view,lateralskullview,andsubmentovertex
view(viewofthezygomaticarches).Thesestudiesareusedfortheinitialwork-upoffacialtrauma.
18. What plain film views are included on a mandibular series, and what are they used for?
AmandibularseriesincludesaTowne’sview,aPAskullview,bothobliqueviewsofthemandible,and
apanoramicview.Thisseriesisusedmainlyforevaluationofthemandiblefollowingfacialtrauma.
19. What views are included in a nasal bone series?
Anasalboneseriesincludesananteroposterior(AP)skullviewandbothlateralviewsofthenasal
bones.Thisseriesisusedforevaluationoftraumatothenose.
20. What are the normal anatomic radiographic landmarks on a panoramic image?
See Figure5-4.
21. What is a sinus series?
Asinusseriesisusedforevaluatingtheparanasalsinuses,includingthefrontal,ethmoid,maxillary,
andsphenoidsinuses.TheviewstakenusuallyincludeaCaldwell’s,Waters’,lateral,andsubmento­vertex.Thisseriesisusedfortheinitialevaluationofsinusitisorsinusmasses.
22. What views are included in the cervical spine series?
ThecervicalspineseriesusuallyincludesPAandlateralviews,bothobliqueviews,andodontoid
viewsofthecervicalspine.Thisseriesisusefulforevaluatingtraumaticinjury,neckpain,andneuro­logicsymptomsreferabletotheupperextremities.Allsevencervicalvertebraemustbeseenforthe examtobeconsideredacceptable.
23. What views are included in airway films?
AirwayfilmsincludeAPandlateralviewsofthenecktoprovidegoodvisualizationoftheairwaysand
adjacentsofttissues.Theyareusedastheinitialstepinthework-upofmasses,foreignbodies,and infectionsoftheairway.
24. What are the uses and advantages of plain film tomography?
WiththeadventofCT,plainfilmtomographynowhasonlylimitedutilityintheevaluationofproblems
withintheheadandneck.Itsprincipaladvantageisthatitdoesnotshowthemetallicartifactthat
66 PART I PATIENT EVALUATION
29
21. Sigmoid notch
10. Nasal septum
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A
1
2
3
28
30
25
B
1. Pterygomaxillary fissure
2. Posterior border of maxilla
3. Maxillary tuberosity
4. Maxillary sinus
5. Floor of the maxillary sinus
6. Medial border of maxillary sinus/ lateral border of the nasal cavity
7. Floor of the orbit
8. Infraorbital canal
9. Nasal cavity
10
6
8
4
9
11
5
14
12
13
27
26
11. Floor of the nasal cavity
12. Anterior nasal spine
13. Incisive foramen
14. Hard palate/floor of the nasal cavity
15. Zygomatic process of the maxilla
16. Zygomatic arch
17. Articular eminence
18. External auditory meatus
19. Styloid process
20. Mandibular condyle
7
16
15
17
22
21
25
22. Coronoid process
23. Posterior border of ramus
24. Angle of mandible
25. Hyoid bone
26. Inferior border of mandible
27. Mental foramen
28. Mandibular canal
29. Cervical vertebrae
30. Epiglottis
23
24
18
20
19
30
L
Figure 5-4. Panoramicradiographshowingnumberedanatomiclandmarks.(From White SC, Pharoah MJ, OralRadiology: PrinciplesandInterpretation, ed 7, St. Louis, Mosby, 2014.)
oftenobscurestheCTevaluationofpostoperativepatients.Italsohastheadvantageofallowing three-planeevaluationofbonystructures,whichcanonlybeaccomplishedwithCTscansbyrecon­structionofaxialviews.Inevaluatingtemporomandibularjoints(TMJs),sagittaltomographyfrequently providesmoreinformationaboutthebonyarchitectureofthesejointsthanaxialCTscansdo.
25. When are CT scans of the head and neck indicated?
• HeadCT:Headtraumatoruleoutintracranialinjuryorpathologyandtoevaluateforskullfractures  • MaxFaceCT:Headorfacialtraumatoevaluatemidfaceand/ororbitalfractures  • MaxFaceCTwithextensionthroughthemandible:Headorfacialtraumatoevaluatemidfaceand/or
orbitalfractures,withsuspectedmandiblefracturealso  • NeckCT:Toevaluatethemandibleand/orairwayfortraumaand/orinfection  • C-spineCT:Whenacervicalspineseriesisdeemedinadequate
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26. When is contrast indicated/contraindicated for head and neck CT scans?
ContrastagentsareusedinCTexamsandinotherradiologyprocedurestoimprovevisualizationof
structures.Somecontrastsarenatural,suchasairorwater.Iodineorbariumsulfateoralorrectal contrastisusuallygivenwhenexaminingtheabdomenorcells,butnotwhenscanningthebrainor chest.IodineisthemostwidelyusedIVcontrastagentandisgiventhroughanIVneedle.Iodinein contrastmediumhasalargeatomicnumberandthuseffectivelyabsorbsX-rays.
Indications:Toilluminateanatomy,malignantfacialtumors(morevascularized),enlargedlymph
nodescontainingmetastaticcarcinoma.
Contraindications:Allergicreaction,renalfailure,elevatedcreatinine.
27. What prophylactic measures may be taken for patients who have a previous
allergy to IV contrast?
Anaphylacticreactionstocontrastagentsusedduringendoscopicretrogradecholangiopancreatog-
raphy(ERCP)arerare.Nevertheless,ahistoryofsensitivitytoiodinecontrastordrugshouldalways beconsideredinthepreprocedureassessmentandintheinformedconsentprocess.Inpatientswith
priorallergytocontrastmedia,prophylacticmeasuresadoptedbymostendoscopistsinclude:  • Useofnonionic/lowosmolaritycontrastmedia.  • PremedicationwithoralsteroidsstartingthedaybeforeERCP,orIVsteroidswhenallergyisdis-
coveredjustbeforetheprocedure.SomeendoscopistsalsogiveanIVantihistamineincombination withthesteroids.
28. What is sialography?
Sialographyisanimagingstudyusedfortheradiographicdemonstrationofthesalivaryglandductal
system.Itisaccomplishedbycannulatingtheductsofthesubmandibularandparotidglandsand
injectingaradiopaquecontrastmedium.
29. When is sialography indicated?
• Todetectorconfirmsmallradiopaqueorradiolucentsialolithsorforeignbodies  • Toevaluatedamagesecondarytorecurrentinammation  • Toprovideamoredetailedevaluationofsuspectedneoplasms,suchassize,location,andexten-
sion into adjacent tissues
• Toevaluatefistulas,strictures,anddiverticulaoftheductalsystem,especiallyinposttraumatic
cases
• Todetectchronicsialadenitisandchronicstricture(rarelyused)
30. When is sialography contraindicated?
• Inpatientswithknownsensitivitytoiodinecompounds  • Inacutesalivaryinammation
31. What does the obstructive form of salivary gland disease look like on a
sialogram?
Intheacuteformofobstructivesalivaryglanddiseaseandacutesialadenitis,sialographyisrarely
performedandmostlycontraindicated.However,asialogramperformedduringaclinicallyquiescent
periodofthediseaseinapatientwiththeobstructiveformofthediseaseusuallyshowsafocal
narrowing(stricture)ofthemainductandacentraldilatation(sialectasia),withtheseductstapering
dramaticallytonormalperipheralducts.Iftheaciniarecompressedanddestroyedbythecellular
infiltrate,theperipheralductsandaciniarenotvisualized,evenonatechnicallygoodsialogram.
32. What is the appearance of Sjögren’s syndrome on a sialogram?
Sjögren’ssyndromeinitiallyinvolvesonlytheperipheralintraglandularductsandacini.Accordingly,
theearlystagesofthediseasearemanifestedonasialogramasanormalcentralductsystemand
numerous,uniform,peripheralpunctatecollectionsofcontrastmaterialthroughoutthegland.These
changesaretheearliestsialographicfeaturesandarediagnosticofthedisease.Asthediseasepro-
gresses,thesialogramissaidtoresemblealeaessfruit-ladentreeoramulberrytree.Theadvanced
formofthediseaseisseenonasialogramasdilatationofthecentralductsand,eventually,alarge
peripheralcollectionofthecontrastmaterialandtheassociatedchangesofsialadenitissuperimposed
onthepunctateandglobularfindingsofSjögren’ssyndrome.
33. What is the best imaging technique to diagnose TMJ disc displacement (Fig. 5-5)?
Currently,magneticresonanceimaging(MRI)istheimagingofchoicetoshowdiscdisplacementwith
andwithoutreduction.DynamicMRItechniquesarealsousedtoenhancethediagnosticqualityofthe
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A
Figure 5-5. Magneticresonanceimagingofopen(A)andclosed(B)viewsofrighttemporomandibularjointwithearly anteriordiscdisplacementwithreduction. (From Quinn PD: Diagnostic imaging of the temporomandibular joint. In Quinn PD, editor: Coloratlasoftemporomandibularjointsurgery, St Louis, 1998, Mosby.)
image.Althoughanarthrogramwasusedinthepasttomakesuchadiagnosis,itiscurrentlyrarely
usedforsuchpurpose.
34. How are disc perforations of the TMJ diagnosed?
AlthoughMRIisusuallythefirstchoiceforsofttissueimagingoftheTMJinmostclinicalsituations,the
bestimagingmodalityavailabletodiagnosediscperforationsisarthrography.Becauseoftherecent
decreaseinuseofarthrography,diagnosisofdiscperforationcurrentlyisbasedonclinicalexam.
35. What are the advantages and disadvantages of MRI for the diagnosis of TMJ
pathology?
Advantages
• ProvidesanimageofbothhardandsofttissuestructuresoftheTMJinmultipleplanes  • Doesnotuseradiation  • Isnottechnicallydemanding
Disadvantages
• Isexpensiveforpatients  • Isnotwelltoleratedbypatientssufferingfromclaustrophobia
36. What are the indications and contraindications for MRI?
Magneticresonanceimagesarebasedonprotondensityandprotonrelaxationdynamicsdueto
magneticfields.Thesevaryaccordingtothetissueunderexaminationandreectitsphysicaland
chemicalproperties.ThereisnoradiationexposureduringMRI.
Inthedetection,localization,andtreatmentplanningofheadandnecktumors,MRIoffersanadvan­tageoverCTbecauseofitsmultiplanarcapabilities,thetissuecharacterizationpotential,andtheabsence ofboneandteethartifacts.MRIaffordsreadydistinctionofvesselsfromlymphnodes.MRIalsodepicts thecontentsoftheorbit.MRIisabsolutelycontraindicatedinpatientswithcerebralaneurysmclipsand cardiacpacemakers.However,itshouldbenotedthattitaniuminboneplatesanddentalimplantsdonot affecttheMRIexam.RememberthatMRImachinesarelargemagnetsthatneverturnoff!
37. How do you differentiate between T1 and T2 weighted images?
Asaruleofthumb,ifyouseeuiddarkerthansolids,thenitisaT1orprotondensityimage.Ifthe
uidsuchasCSFiswhite,thenyouaredealingwithaT2weightedimage. InaT1weightedimage: DARK=water,cerebrospinaluid(CSF),edema,calcium
LIGHT=lipid,gadolinium
InaT2weightedimage: DARK=calcium,bone
LIGHT=water,CSF,edema
B
38. What is cone beam computed tomography?
Conebeamcomputedtomography(CBCT)isamedicalimageacquisitiontechniquebasedonacone-
shapedX-raybeamcenteredonatwo-dimensional(2D)detector.Thetechnologygetsitsnamefrom useofadivergentpyramidalorcone-shapedsourceofionizingradiation.Imagingisaccomplished
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“Cone” beam geometry
Secondary reconstructions
Basis projections
Figure 5-6. Differenceinacquisitiongeometryin“cone”beamCTand“fan”beamofMDCT. (From Scarfe W, Farman A: What is cone-beam CT and how does it work? DentalClinNAm 52:707–730, 2008.)
byusingarotatinggantrytowhichanX-raysourceanddetectorarefixed.TheX-raysourceand detectorrotatearoundarotationfulcrumfixedwithinthecenteroftheregionofinterest.Theimages arereconstructedinathree-dimensional(3D)datasetusingamodificationoftheoriginalconebeam algorithmdevelopedbyFeldkampetal.
39. What is the basic difference between cone beam CT and traditional medical CT?
InaconebeamCT,theX-raysourceanddetectorrotatearoundarotatingfulcrum,whichisfixed
withinthecenteroftheregionofinterest.Duringrotation,multiple(from150tomorethan600) sequentialplanarprojectionimagesofthefieldofview(FOV)areacquiredinacomplete,orsome­timespartial,arc.Onlyonerotationalsequenceofthegantryisnecessarytoacquireenoughdatafor imagereconstruction.ThisprocedurevariesfromatraditionalmedicalCT,whichusesafan-shaped X-raybeaminahelicalprogressiontoacquireindividualimageslicesoftheFOVandthenstacksthe slicestoobtaina3Drepresentation.Eachslicerequiresaseparatescanandseparate2Dreconstruc­tion(Fig.5-6).
40. What imaging modality is used for dental implant treatment planning?
ThepositionstatementoftheAmericanAcademyofOralandMaxillofacialRadiology(AAOMR)was
releasedinJune2012withregardtodentalimplants.Thepaperstatesthatpanoramicradiography supplementedwithintraoralradiographsshouldbeusedfortheinitialevaluationofthedentalimplant patient.However,anypotentialimplantsiteevaluationshouldincludecross-sectionalimagingorthogonal tothesiteofinterest.Conventionaltomographyprovidescross-sectionalinformationbutistechnique sensitiveandimagesaremoredifficulttointerpretthanCBCT.TheAAOMRrecommendsCBCTimaging asthecurrentmethodofchoiceforcross-sectionalimaginginthatitprovidesthegreatestdiagnostic yieldatanacceptableradiationdoserisk.CBCThelpsindentalimplantplanningbyprovidinginformation onthemorphologiccharacteristicsandorientationoftheresidualalveolarridge(RAR).Italsohelpsin identificationoflocalanatomicorpathologicconditionsrestrictingimplantplacement.
41. What are the applications of cone beam CT in dentistry?
ConebeamCThasfoundvariousclinicalapplicationsindentistry.Themostcommonclinicalapplica-
tionsareimpactedteethandimplantology.Ithasalsofoundapplicationsinspecializeddentistry
“Fan” beam geometry
(for single slice)
Primary
reconstruction
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(orthodontics,endodontics,periodontics,andforensicdentistry).Ithasbeenfoundtobevery promisinginendodontics,especiallytolookforapicallesions,rootfractures,canalidentification,and characterizationofinternalandexternalrootresorption.Inperiodontics,itisusedtovisualizebone topographyandlesionarchitecture.Currentresearchhasfounditnomoresuperiorthan2Dimaging incariesdetection,especiallyinthepresenceofbeam-hardeningartifacts.
42. What are the dose considerations with cone beam CT?
Anyradiographicprocedureshouldconsiderthetrade-offbetweendiagnosticbenefitstodose
detrimentforthepatient.DentalCBCTisrecommendedasadose-sparingtechniqueforthe commonoralandmaxillofacialradiographicimagingtaskscomparedtothealternativestandard medicalCTscans.EffectivedosesfromastandarddentalprotocolscanMDCTareintherange of1.5to12.3timesgreaterthancomparablemediumFOVdentalCBCTscans.Theeffective dosescanvaryforvariousCBCTdevices,rangingfrom29to477mSv,dependingonthetype andmodelofCBCTequipmentandFOVselected.Ifwecomparethesedoseswithmultiplesof asinglepanoramicdoseorbackgroundequivalentradiationdose,CBCTprovidesanequiva­lentpatientradiationdoseof5to74timesthatofasinglefilm-basedpanoramicX-ray,or3to 48daysofbackgroundradiation.
43. What are the different cone beam CT artifacts?
Artifactsaredistortionsorerrorsthatreducethediagnosticqualityoftheresultantimage.
• Beam-hardeningartifacts:Thesecanoccurascuppingartifacts,seenasdistortionsofmetal-
• Patient-relatedartifacts:Thesecanoccurduetopatientmotion,whichcancauseunsharpnessin
• Scanner-relatedartifacts:Thesecanoccurduetopoorcalibrationandappearascircularorring
• Conebeamartifacts:Thesearegroupedtogetheraspartialvolumeaveraging,undersampling,and
• Imagenoiseandpoorsofttissuecontrast
44. What are the advantages and limitations of cone beam CT compared to multi-
Advantages:ThebiggestadvantagesofconebeamCTcomparedtoMDCTarelowradiationdoseand
45. How is diagnostic and interventional angiography used by the oral and maxillo-
Diagnosticandinterventionalangiographyassiststheoralandmaxillofacialsurgeoninthediagnosis
46. What is the role of radionuclide scintigraphy in oral and maxillofacial surgery?
Oralandmaxillofacialsurgeonsuseradionuclidescintigraphytoevaluateboneandjointdiseases
Thedifferenttypesofartifactsare:
licstructures,orstreakingartifacts,wherestreaksanddarkbandsappearbetweentwodense objects.
theresultantimage.
shapesintheimage.
conebeameffect.
detector CT (MDCT)?
reducedcost.Itoffersareal-sizedatasetwithmultiplanarcross-sectionaland3Dreconstructions basedonasinglescan.Ithaspotentialforgenerating2Dimagessuchaspanoramicradiographs, lateralcephalograms,andTMJs.Ithasuser-friendlypostprocessingandviewingsoftware.Itoffers energysavingcomparedtomedicalCT.
Disadvantages:ThemostimportantdisadvantageofCBCTimagingisthelowcontrastresolution andlimitedcapabilityofvisualizingtheinternalsofttissues.Someofitsotherlimitationsareasmall detectorsize,whichlimitsthefieldofview,andtheresultingscannedvolume.Itcannotbeusedfor estimationofHounsfieldunitsascomparedtoMDCT.
facial surgeon?
anddelineationofuncontrollablehemorrhageandvasculartumorsinthemaxillofacialregion.When coupledwithCTandMRIexams,thesurgicalapproachanddefinitivetreatmentcanbeplanned.The useofinterventionalangiographyforembolizationofvasculartumorsbeforeorinsteadofsurgical resectionhasbecomeapopularmodalityinthemanagementofthesetumors.
becauseitprovidesmoresensitiveboneimagingthanconventionalradiologictechniques.Specifically, scintigraphyorbonescanningcanassistintheevaluationofarthriticchangestotheTMJ,condylar hyperplasia,idiopathiccondylarresorption(activeandinactive),metabolicdisorders,viabilityofbone grafts,trauma,dentaldisorders,osteomyelitis,andmalignancies.However,itshouldbenotedthat scintigraphyhasalowspecificityforabnormalfindings,and20%to50%ofpatientsreferredfor routinebonescanmayhaveabnormalactivityinthemandibleorface.
CHAPTER 5 DIAGNOSTIC IMAGING FOR THE ORAL AND MAXILLOFACIAL SURGERY PATIENT 71
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47. What diagnostic imaging modalities are useful for the diagnosis of cysts and benign odontogenic tumors of the jaw?
Mostpathologiesintheoralandmaxillofacialregioncanbedemonstratedthroughconventional
radiographs.Thepanoramicradiographisstilltheprimaryscreeningfilmfortheoralandmaxillofacial surgeon.Traditionally,multiplanarviewswereobtainedprimarilywithmultidetectorCT(MDCT)and magneticresonanceimaging(MRI).WiththeintroductionofCBCT,allthreedimensionsarerecorded bymultiplanar(axial,coronal,andsagittalplanes)imagingofCBCT.Suchmultiplanarviewsprovide importantinformationonthepresenceandextentofboneresorption,sclerosisofneighboringbone, corticalexpansionandinternalorexternalcalcifications,andproximitytoothervitalanatomy.With newerCBCTunits,slicethicknessesareassmallas0.1mm;thesethinslicesallowbettervisualiza­tionofthebonymarginsofthelesion.MDCTisextremelyhelpfulforillustratingcystsandtumorsof themandibleandmaxilla,especiallyifthelesionextendsbeyondthebonycortexwithencroachment ontheadjacentsofttissuestructures.MRIisusefulindifferentiatingcystsfromsolidtumorsand differentiatinguidwithinthecysticlumenfromothercysticcomponentssuchaskeratinandblood degradationproducts.However,comparedtoMDCTandMRI,CBCTunitsarepreferredintheOMFS officeduetosmallerphysicaldimension,lowercost,andeasieroperation.
48. What diagnostic imaging modalities are used for evaluation of malignant diseases of the jaws?
• CT  • CBCT  • MRI  • Radionuclidescanningtechniques  • Panoramicradiography Radiologicevaluationofjawlesionsrequiresanimagethataccuratelydifferentiatesboneand
softtissue.CTpermitstheaccurateassessmentoftumorsize,location,andextentofspreadand detectssubtlebonyinvolvementandcalcifications.Ifamalignancyissuspectedtoinvolveosseous components,cross-sectionalimagingwitheitherMDCTorCBCTcanreliablypredictboneinvasion bythemalignantlesion.However,CBCTimagesarenotusefulinanalyzingsofttissuetumors.Inthis case,MRIorsofttissuewindowMDCTisabetterdiagnostictool.MRIprovideshigh-resolution,thin tomographicimageswithsuperiorsofttissuecontrast.Inaddition,MRIallowsvisualizationofblood vesselswithoutIVcontrastagentsandsomeinformationregardingtissuecomposition.
Inmostcasesofasuspiciousmalignantlesion,acompletediagnosticwork-upofthepatientwill
includemultipleexaminationsusingCBCT,MDCT,MRI,ornuclearmedicine.
49. What are the uses of the different imaging techniques for mandibular fractures?
Initialassessmentofcomplexjawfracturescanbeachievedwithperiapicalorpanoramicradio-
graphs.Inaddition,AP,lateralskull,Waters’,andTowne’sviewsalsocanbehelpful.However,fordiag­nosingrootfractures,multiplejawfractureswithbonedisplacement,andinterarticularfracturesofthe condylarhead,CBCTmaybeavaluableimagingtool.However,theroleofCBCTinfracturediagnosis islimitedtofracturesofteeth,sports-relatedinjuries,orminorassault.MDCTwithorwithoutMRIisa betterimagingchoiceinautomobileorindustrialaccidentsthatinvolvejawsalongwithotherpartsof thebody.
50. Which imaging modalities are used to diagnose midfacial fractures?
TheinitialradiographicsurveyofpatientswithmidfacetraumashouldincludeWaters’,Towne’s,AP,lateral
skull,andsubmentovertexviews.However,becausethefacialbonedivergesinaposterior-to-anterior direction,APviewsdistortboneanatomyandproducemagnifiedandoverlappingstructuralimages. Hence,CTorCBCTisthedefinitivemeansofimagingmidfacialtrauma.CBCThasbeenfoundtobevery usefultostudyfracturesofthezygomatico-maxillarycomplex,inparticularwithregardtosurgicalnaviga­tion,localizationofbonyfragments,andevaluationofscrewanchorage.ThecoronalandsagittalCBCT imagesarealsoveryusefulinpatientswithfracturesofthecribriformplate,nose,orbitaloor,andorbital roof.However,whenclinicalexaminationrevealspotentialintracranial,skullbase,orcranialnervedam­age,MDCTorMRIexaminationisrecommended.Otherinstancessuchasepiduralorsubduralhematoma, cerebralconcussion,andintraorbitalorglobelesionsalsonecessitateanMDCTorMRIexamination.
51. What imaging techniques are used for evaluation of maxillary sinus pathology?
Traditionally,aroutinesinusexaminationconsistedofWaters’sinusviewalongwithCaldwell,lateral
skull,andsubmento-vertexviews.However,theseplainfilmviewsareconsideredinadequatein detectingmaxillarysinusopacificationand“verypoor”indetectingmassesintheethmoid,frontal,
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