Role of New MRI Modalities (MR Spectroscopy, Perfusion and Diffusion Tensor Imaging) in multiple Sclerosis

Abstract

MSisachallengingdiseaseinallaspectsrangingfrometiologytodiagnosisand treatment. Itisalsoadisease thathasgreater heterogeneity in termsofclinicalforms,imagingappearance, andtreatmentresponse. Withtheever-advancingtechnology,MRimagingwillcertainly further improveourunderstandingoftheMSdiseaseandcontinuetoplay an extremelyimportantrolegoingforward(Ge,2006). Despitetechnologicaladvancesinimaging,multiple sclerosis(MS) remainsaclinical diagnosisthatissupported, butnotreplaced, by laboratory orimagingfindings.However,imagingisessentialinthe currentdiagnosticcriteriaofMS,forpredictionofthelikelihoodofMS for patientswithclinically isolatedsyndromes,correlationwithlesion pathologyandassessmentoftreatmentoutcome(Ramlietal.,2010). Complementary totheclinicalevaluation,conventionalmagnetic resonanceimaging(cMRI) playsaprominentrolefor diagnosisand assessment of patientswithmultiplesclerosis.Itprovidesreliable detectionandquantitativeestimationoffocalwhitematterlesionsin vivo.ModerncriteriainvolveMRIparametersforthediagnosisofMS andfor predictingconversiontoclinically definiteMSinpatientswho presentwithafirstclinicalepisode suggestive ofdisease onset.A diagnosisofmultiple sclerosisisbased onshowingdiseasedissemination inspaceandtimeandexcludingother neurological disordersthatcan clinicallyandradiologicallymimicmultiplesclerosis(Andreadou,2012).cMRIthemostimportantparaclinicaltoolinsupporting a diagnosis ofMSandestablishinga prognosisattheclinicalonset of the disease (Filippietal.,2011b). However, neurological impairment of patientswithMS is poorly associatedwiththe lesionloadobservedonconventionalMRI scans.The discrepancy betweenclinicalandconventionalMRIfindings inMS is explained,atleastpartially,by thelow sensitivity ofconventionalMRIin the detectionof grey-matterinvolvementanddiffusedamageinwhite matter(Andreadou,2012). And,forclinicians,itstillremainsunclearhowandwhencMRI shouldbeused, notonly attheonsetofthedisease,butalsoduringthe subsequentdiseasephases(Filippietal.,2011b). TheseinherentlimitationsofcMRIhavepromptedthedevelopment andapplication of quantitative MR‘non-conventional’techniques (Filippietal.,2011b).(eg, MR spectroscopy,DTI,perfusion-weighted imaging)offeropportunitiesforimprovedspecificity andsensitivity in diagnosingandmonitoringMS(Lövbladetal.,2010). Theseadvancesare expectedtohelpin understandingthe underlying diseaseprocessesandtheaccumulationofirreversibledisability and therefore are promisingtools instudies of disease evolutionandclinical trials(Andreadou,2012). ConventionalMRIdescribesthe physicalcharacteristicsofaregionof tissuerelativetosurroundingregionsby measuringalterationsintissue watercontentanddynamicsbyprotonexcitation.ProtonMR spectroscopy(1H-MRS)isanoninvasivemethodthatdepictsthe chemicalpropertiesofaregionofbraintissuebyinvestigatingotherproton-containingcellularmetabolites.Itprovides information on tissue metabolism andfunctionofaselectedbrainareavolumerelativeto surroundingregions.Thereforeitcouldbeusedtostudybiochemical changes occurringin lesionsand normalappearingwhitematterover the course ofMS(Andreadou,2012).1H-MRSisa valuable tool thatcould contributeinobjectively followingtheevolutionofMS,tothe understandingofitspathogenesis,evaluatingdiseaseseverity, establishingprognosis,andassessingtheefficacy of therapeutic interventions(Sajjaetal.,2009). MRSisemergingasavaluabletooltodemonstratewidespreadchanges