MRI is more accurate than other imaging modalities for ruling out prostate cancer. While PSA testing and biopsy are currently the standard for diagnosing prostate cancer, MRI has higher specificity and can better detect the location and extent of tumors, especially in men with elevated PSA and previous negative biopsies. The addition of MRSI to MRI further improves accuracy by distinguishing cancer from surrounding tissues based on metabolic profiles. Careful patient selection is important to maximize the clinical utility of MRI and MRSI for prostate cancer diagnosis and staging.

1. MRI MORE ACCURATE TO RULE OUT PROSTATE CANCER.
Astuti Mishra
BPKIHS dharan
Bsc.MIT 2012
The current diagnosisandmanagementof prostate cancerislargelybasedonthe use of serumprostate-
specificantigen(PSA) andpathologicriskfactorssuchas Gleasonscore and clinical stage.The use of
serumPSA inclinical practice hasresultedinsignificantstage migrationand,assuch,imagingmodalities
historicallyutilizedtostage prostate cancerare no longerable toreliablyidentifythe small amountsof
prostate cancer mostoftenfoundatpresentation.Molecularimagingtechniqueshave focusedon
improvingsensitivityandspecificityforcancerdetectionthroughknowledge of specificattributesof
disease biology.The evolutionof imagingtechniqueshascreatedanew role forimaginginthe
managementof prostate cancer.
Prostate cancer diagnosisandmanagementhasclearlybeenrevolutionizedbythe clinical inceptionof
prostate-specificantigen(PSA).Itsuse inclinical practice hasallowedearlierdetection,superior
selectionof candidatesforcurative therapy,andaccurate monitoringof patientsforrelapse.Although
PSA levelshistoricallycorrelatewiththe presence of prostate cancer,thistestprovideslittleinformation
regardinglocationandextentof cancer.Testlimitationsincludepoorspecificityincancerdetection,
poor sensitivityindetectionof extraprostaticdisease atlow PSA levels,andpoorcorrelationwith
disease volumeowingtothe large contributionbythe benigncomponentof the gland.
Technological advancesinimaginghave createdanew role forvarioustestsinthe managementof
prostate cancers.Advancesinimagingexploitthe biologyof the disease,andindoingso,allow more
accurate detectionof the location,extent,andaggressivenessof the malignancy.Inthisarticle,we
reviewthe currentstatusof imaginginprostate cancerdiagnosis,staging,andthe monitoringof
recurrence.
The current diagnosisof prostate cancerisbasedon riskstratificationbythe combinationof serumPSA
and digital rectal exam(DRE).The vastmajorityof menpresentlydiagnosed withprostate cancerhave
normal DRE, and as such,the likelihoodof prostate cancercan generallybe baseduponPSA level.
Recentevidence suggeststhatevenatlow levelsof PSA,ariskfor prostate cancerexists.
The use of imaginghashistoricallyprovidedinadequate resolutionforidentificationof small volumesof
cancer withinthe prostate.Effortstoutilize ultrasoundforthe detectionof cancerhave demonstrated
poor specificityandpoornegative predictive value.Assuch,withinthe currentstandardof care,
transrectal ultrasound(TRUS) isusedlargelytoguide biopsiesratherthantoidentifythe locationand
extentof cancer.

2. Newerimagingmodalitiessuchasendorectal coil magneticresonance imaging(MRI) andmagnetic
resonance spectroscopicimaging(MRSI) offerthe potential todetectcancersinthe prostate.Itremains
to be seen,however,whethersuchmodalitiesimprove cancerdetectionrateswhencomparedto
systematicbiopsyinunselectedpopulations.The use of MRI/MRSIat presentmaybe of value tothose
menwithmarkedlyelevatedPSA levelsandone ormore negative biopsies.
In recentyears,a trendtowardsincreasedcore numbersatbiopsy,lowerthresholdsof PSA forbiopsy,
and youngerage at screeninghasresultedinadecliningrole forhypoechoiclesion-directedbiopsiesin
prostate cancer diagnosis.Althoughunlikely,inmostcases,toidentifycancersnotdetectedby
systematicsampling,TRUSremainscritical forguidingtransrectal biopsyasthe locationof biopsy
samplinghasbecome of critical importance inprovidingadequatenegative predictive value(NPV) atthe
time of biopsy.
MRI hasbeenextensivelystudiedforitsabilitytodetectprostate cancers.The use of endorectal coil
MRI allowsbettervisualizationof prostate zonal anatomyandlocationandextentof tumorwithinthe
gland.Patientsare imagedwithbothawhole bodyscannerwithpelvicphasedarraycoil andan
endorectal coil,whichconsistsof amagneticcoil placeddirectlyintothe rectum.T1and T2 weighted
imagesare obtained,butcancervisualizationisgenerallyperformedonT2 weightedimageswhere the
cancer appearsdark.
The use of MRI alone todetectprostate cancerhas beenevaluatedinalimitedfashion.Inunselected
patients,MRIcarriesa relativelypoorsensitivity,due toa likelihoodof isointense lesionsonT2 weighted
images,anda poor specificity. Notunlike ultrasound,the additionof endorectal MRIto routing
systematicbiopsywouldappearunlikelytogreatlyenhance cancerdetection.Inpatientswithprevious
negative biopsiesanda markedlyelevatedserumPSA,endorectal MRImayallow anincreasedabilityto
stratifythe riskof prostate cancer.In a studyof many such patients,patientswere groupedaccordingto
low,intermediate,orhigh riskof cancer on the basisof MRI .At repeatbiopsy,cancerwasfoundinvery
few of themrespectively.Inaprospective evaluationof 38 menundergoingendorectal MRIpriorto
repeatbiopsy,asensitivityof 83%and a PPV of 50% were reported. Although thisexceededthe

3. sensitivityof bothDREand TRUS, it didnot exceedthe PPV of either.Inretrospective evaluationof
pathology,the correlationof endorectal MRIto histologictumorlocationwaspoor.
MRSI is an MRI technique thatattemptstoidentify cancerthroughthe assessmentof tissue metabolites.
As the hydrogenprotonsindifferentmoleculeshave slightlydifferentfrequencies,MRSIprovidesa
spatial mapof signal intensityversusfrequencyasa spectral displayof peaks.(Individualpeaksare
representative of metaboliteswithinthe tissue.The spatial mappingof the tissue isprovidedbyanalysis
of individual areasof the image termedvoxels,representingsmallvolumesof prostate tissue.The
characteristicmetaboliteprofile forprostate cancerisone of highcholine andlow citrate.Citrate and
creatine are oftencombineddue tothe overlappingof theirpeaks.Areasof the prostate richincholine
but poorin citrate/creatineare likelyrepresentative of cancer .
Endorectal magneticresonance spectroscopicimaging(MRSI) demonstratingthe presence of extensive
prostate cancer.(A) An illustrationof the spectral displayof metabolites withinasingle voxel.The
additionof MRSI to MRI improvesthe accuracy of cancer detectionthroughanincrease inspecificity.In
a studyof 53 patientswithknownprostate cancer,MRIand MRSI were comparedto step section
histology.MRIalone hada sensitivityof 77% to 81% and a specificityof 46% to 61%. MRSI improved
specificityto70%to 80% but reducedsensitivityto68% to 73%.

4. On the whole,the additionof MRSIprobablyaddsgreatlytothe evaluationof mensuspectedof
prostate cancer despite negativebiopsies.A clearpotential problemof thisapplicationis the inabilityto
accuratelyassessthe transitionzone forthe presence of tumor. Ashasbeenshownbymany
investigators,cancersidentifiedonrepeatbiopsyare frequentlyfoundinthe lateral peripheralzone or
transitionzone. The use of MRSI priorto repeatbiopsycanallow targetedsamplingof suspiciousareas.
As itis notlikelyorintendedtoreplace systematicbiopsy,itsuse inpatientspresentingforfirsttime
biopsyislimited.Inthose meninwhomsystematicbiopsydemonstratesnocancer,but whose PSA
remainsmarkedlyelevated,MRSI,if available,isavaluable diagnostictoo
Early seriesof CTevaluationof lymphnodesdemonstratedsensitivityof 14% to 30% inthe detectionof
metastases. Incontemporaryseriesincorporatingpatientswithsmallervolume disease,the likelihoodof
detectingsuchlymphnodesisevensmaller.The specificityof lymphnode detectionisaffectedbythe
inabilitytodistinguishinflammatorylymphnodesfrommetastaticlesionswhenthe node isenlarged.
Improvedaccuracyis notedwhenthe size cut-off forabnormalityisreducedandthe CT iscombined
withfine needle aspiration.Whenutilizingsucha strategy,authorshave reportedsensitivityof 50%to
77.6% and a specificityof upto96% to 100%.
MRI fordetection of lymphnode metastasessuffersfromsimilarlimitationstoCT.While,insome
reports,3-dimensionally(3-D) reconstructedT1-weightedimagesmaydefinelargerfoci of metastatic
disease withinlymphnodes,the inabilitytodiscerncancerwithinsmaller lymphnodesremains.Ina
studyof 134 patientswitheitherbladderorprostate cancer,3D T1-weightedimageswere usedto
predictlymphnode metastasesandcorrelatedtopathologicorcytologicfindings.MRIachieveda
sensitivityof 75%,specificityof 98%,accuracy of 90%, andPPV of 94%.
Stagingendorectal MRIat time of prostate cancerdiagnosis.(A) Evidence of leftextraprostaticextension
withinvasiontothe regionof the leftneurovascularbundle.The tumorappearsdarkerthanthe
remainderof the prostate onT2-weightedimage.

5. The keyto improvingthe clinical utilityof stagingwithendorectal MRImaybe properpatientselection.
In a group of 335 high-riskpatientsdefinedbydiseasevolume andPSA > 10 ng/ml,MRI alone carrieda
95% specificityandasensitivityof 69% inthe detectionof ECE. The additionof MRSI hasimprovedthe
stagingabilityof MRI byallowingbetterdelineationof the extentof cancerand distinctionbetweenthe
cancer and surroundingstructures.Indoingso,there maybe a reductionininterobservervariability,
therebyincreasingthe true utilityof the testingeneral practice.
Althoughthe imagingof prostate cancerhasmade tremendousadvancesinrecentyears,difficulty
remainsinidentifyingsmall volumesof prostate cancerbothin the glandand metastaticsites.The use
of molecularimagingtechniquessuchasMRSI,ProstaScint,CombidexinfusionMRI,andPET offera
great opportunitytobetteridentifythe progressionof prostate cancerandprogressour understanding
of itsbiology.Careful selectionof patientsforthe appropriate imagingtestsisessentialandreliesupon
knowledge of the abilityandlimitationsof eachstudy.Inthe diagnosis,staging,andmonitoringof
prostate cancer,the clinical usefulnessof atestisheavilydependentuponthe prevalence of the desired
outcome.Careful assessmentof risk,alongwithtrainingof radiologystaff,willallow increasing
applicationof the emergingimagingmodalities care.
REFERENCES:
 CoakleyFV,QayyumA,KurhanewiczJ.Magneticresonance imagingandspectroscopicimaging
of prostate cancer.J Urol. 2003;170:S69–S75. discussionS75–S76
 Perrotti M, Han KR, EpsteinRE,et al.Prospective evaluationof endorectal magneticresonance
imagingtodetecttumorfoci inmenwithpriornegative prostaticbiopsy:apilotstudy.JUrol.
1999;162:1314–1317.