1、CT AND MRI IMAGING OF NORMAL BRAINNORMAL ANATOMY OF BRAINBrain is separated from calvarium by three meninges-dura mater,arachnoid membrane and pia mater.Divided into supra tentorial and infra tentorial compartments containing:-Supratentorium:Cerebral hemispheres diencephalonInfratentorium:Brain stem
2、 structures cerebellum Each cerebral hemisphere is further divided in to Frontal,Parietal,Temporal and Occipital lobes by fissures BRAIN ANATOMYSagittal surfaceLat vent GenuFornixPituitary gland Mid brainPonsMedullaCingulate gyrusQuadrigeminalcisternSpleniumColliculi4th ventCerebellumThalamusSagitta
3、l surfacei.Pineal glandii.Sup.colliculiiii.Inf.Colliculiiv.Aqueduct of sylviusv.Midbrainvi.Cerebellumvii.4th ventricleviii.Ponsix.Oculomotor nx.Inter thalamic commissure109Inferior surfaceInterhemispheric fissureTemporal lobe Mammillary bodies Frontal lobeOlfactory tractOptic tractPit.stalkponsMedul
4、la oblongataCerebellumVermisBrain stem structuresMid brain:divided into Cerebral peduncles and colliculi.Sup colliculi attached to med.Geniculate&Inf to lateral Geniculate bodySurrounded by Peri-mesencephalic cistern.Pons:divided in to tectum and tegmentum Connects mid brain to medullaMedulla:contin
5、ues as spinal cordContains ascending and descending Spinal tractsCerebellumDivided into two hemispheres by falx cerebelliConnected in the midline by a worm like structure-VermisDivided into I.Anterior lobeii.Middle lobeIii.Flocculo-nodular lobeVentricles of brainLateral ventricle:-C shaped cavity wi
6、th body in the parietal lobe and extensions in the frontal temporal,occipital lobesConnected to third ventricle by foramen of monro.Third ventricle:-lies b/w two thalami.connected to fourth ventricle by cerebral aqueduct.Fourth ventricle:-lies in the cerebellumCSF Flow:-Lat.vent-foramen of monro-3rd
7、 vent-cerebral aqueduct-4th vent-foramen of magindie and luschka-sub arachnoid space finally absorbed by the arachnoid granulationsVentricles of brainBlood supply of the brainBlood supply of the brain By Internal Carotid and Vertebral A Internal carotid A:Middle cerebral A Ant cerebral A Pmunicating
8、 A Ant.Choroidal A Vertebral As:-two Vertebral as join to form Basilar A Branches:Ant inf cerebellar A Sup cerebellar A Pontine As&labyrinthine As Post cerebral AContd.Divides into cortical and perforating APerforating As supply Basal ganglia,Thalami,internal capsuleThalamus:-Perforating br of PCAIn
9、ternal cap:-Med&lat striate br of MCA,recurrent br of ACA,Ant choroidal AMid brain:-Post.cerebral and Sup cerebellar APons:-Pontine br of Basilar ACerebellum:-Sup.cerebellar A,Ant.inf cerebellar A,Post inf cerebellar AMedulla:-Ant&Post spinal A,PICABlood supply of the brainRed:-MCABlue:-ACAGreen:PCA
10、Circle of willisVenous sinuses of brainStraight sinusTorculaherophiliOccipital sinusTransverse sinusSup.Sagittal sinusInf.SagittalsinusVenous sinuses.Transverse sinusStraightsinussigmoidsinusPitutiary glandICA3rd CN4th CN6th CNSphenoid boneVi Vii br Of 5th CNAxial sectionCingulategyrusCaudateheadPin
11、eal glandCorpus callosumLentiform nucleustrigoneSup.cerebellar cisternInt.capsuleThalamusCoronal sectionCT TechniquePatient is kept in supine position and head is placed in the gantry under the cursors.Axial sections are taken at an angle of 10-13 degree to the canthomeatal line.Slice thickness:-Pos
12、terior fossa:-5mmSupra tentorial structures:-10mmPituitary gland and sellar region:-1-3mm(coronal sections)CONTRAST STUDIES:done by injecting 100 ml of 60%iodinated contrast contd.Normal enhancement:Arterial&venous structures Dural structures:-falx,tentorium Choroid plexus Pituitary glandIndications
13、 of CECT:I.Infections:ring enhancing lesions eg tuberculoma,neurocysticercosis,Meningitis,Encephalitis ii.Tumours:astrocytomas,meningiomas iii.Vascular lesions:aneurysms,AV malformationsContraindications of CECT:I.history of allergy,renal failure ii.acute haemorrage ;Axial sections-TopogramFor CT Ax
14、ial sections are taken at an angle of10-13degree to the Canthomeatal lineFor MRI sections are parallel to the reference lineCT Brain contdNormal HU values in NCCT brainGray matter:-+36-42 HUWhite matter:-+26-34 HUCSF:-+4-11HUBone:-+200 to+1000 HUCalcification:-+100 to+220 HUBlood:-+56-80MRI ImagingM
15、ultiplanar modlity so sections can be taken in axial,coronal and sagittal planesSlice thickness is same as CT imaging.Routinely applied sequences are T1 Weigheted spin echo T2 Weigheted spin echo Proton density imagesAnatomy of brain is better explained on T1W seq while pathologies are better studie
16、d on T2W and Proton density sequences.TISSUE CHARACTERISTICSSeq Parameters CSF Gray M WhiteM FatT1W short TR Hypo iso hyper hyper short TE T2W short TR hyper iso hypo iso/long TE hypoProton long TR iso Iso iso/hypo hyperdensity short TE blood vessels appear signal void in all the sequences calcifica
17、tion and fibrous tissue appear hypointense in all sequences MRI Axial section above foramen magnumMaxillary sinusBasilar A.MedullaCerebellar hemisphereCisterna magnaTonsilsPetrous boneSphenoid sinusNasal cavityZygomatic archCT Axial section above foramen magnumFrontal sinusSphenoid sinusTemporal lob
18、eBasilar A.Mastoid cellsCerebellar hemisphereCisterna magnaMedullaOptic nervePituitarySphenoid boneTemporal boneCerebellar tonsilsMRI Axial Section at 4th VentricleLensOptic nervePituitaryTemporal lobeMiddle cerebellar peduncle4th VentricleMedial rectusLateral rectusPonsPetrous temporal boneCerebell
19、ar hemisphereCT Axial section at 4th ventricleFrontal sinusFrontal boneMid.cerebral ABasilar A.Pons4th ventcerebellumMid cerebellarpedunclePetrous boneTemporal hornAnt.cerebral aSella turcicaVermisMRI Axial Section above 4th ventricleSuperior oblique musclePituitary stalkUpper ponsSuperior cerebella
20、r peduncleOptic chiasmaAmbient cisternCerebellar foliaCECT Axial section above 4th ventricle Frontal lobe Ant cerebral A.4TH ventCerebellum Pons Temporal hornInfundibulum Post.cerebral A.Sphenoid boneFrontal boneFrontal sinusMid.cerebral AMRI Axial section at midbrainFrontal lobeInterpeduncularciste
21、rninferiVermisInferior colliculiConfluence of sinusesAmbient cistern UncusOptic tractMid cerebralACerebral peduncleAnt cerebral AMRI Axial section at 3rd ventricleGenu of corpuscallosum Caudate head Lentiform nuleusThalamusSplenium of corpus callosumFrontal hornsInt.capsuleInsula3rd ventricleOccipit
22、al hornsOptic radiationCT Axial section at 3rd ventricleGenu of corpus callosumCaudate nucleusInt.capsule3rd ventriclePineal glandvermisOccipital lobeChoroid plexusThalamusLentiform nucleusFrontal hornPericallosal AMRI Axial section at mid ventricleCingulate gyrusBody of lateralventricleCorpus callo
23、sumCentral sulcusCorpus callosumInter hemisphericfissureCT Axial section at mid ventriclesCingulate gyrusBody of lateral ventricleCorpus callosumFalx cerebriOccipital hornsParietal lobeCorona radiataFrontal hornsConfluence of Sinuses(torcula)MRI Axial section at centrum semiovaleInter hemispheric fi
24、ssureCentrum semiovaleOccipital lobeParietal lobeFrontal lobeCT Axial section at centrum semiovaleFalx cerebriCentrum semiovaleOccipital lobeParietal lobeFrontal lobeMRI Coronal section at 3rd ventricleFrontal hornsFornix3rd ventricleClivusInterpeduncularcisternInsulaSylvian fissureTemporal lobeParo
25、tid glandOdontoid(dens)MRI Coronal section at suprasellar levelInter hemispheric fissureLat ventricleLat.Pterygoid MsNasopharynxMed.Pterygoid Ms.Sylvian fissureSphenoid sinusPituitary glandOptic chiasmAnt cerebral aMid cerebral AMRI Coronal section at post.ventricleParietal lobeSplenium of corpus ca
26、llosumSup.cerebellar cisternTentoriumChoroid plexusAtria of lateral ventricle 4th ventricleMRI Sagittal sectionLat ventGenu3rd ventSphenoid sinusNasopharynxBody of CCSpleniumQuadrigeminal cisternPons4th ventMedullaCerebellumTonsilCingulate gyrusPrepontine cisternCT Coronal section for Pituitary glan
27、dPatient is kept in prone position in sub mento vertical position,in the head rest of CT tableTopogram is taken in this position and planning is done so that cut sections parallel to the line passing from frontal bone to mentis is takenFor pituitary 1-3mm thick sections are taken in the coronal plan
28、e starting from anterior to posterior.CT Coronal section for Pituitary glandLateral ventAnt.cerebral APituitary glandOptic chiasmSphenoid sinusLat.pterygoid plateNasopharynxLat.Pterygoid msMid.cranial fossaCT Coronal section for Pituitary glandLat pterygoid plateSphenoid sinusMid.cerebral aAnt.cereb
29、ral aFrontal sinusInternal carotid aNasopharynxPituitary glandCT Axial section(bone window)Petrous boneMastoid air cellsCarotid canalForamen ovaleSphenoid sinusBase sphenoidEustachian tubeExt.acoustic canalLambdoid sutureOccipital boneCT Axial sections(bone window)Ear ossiclesMastoid air cellscochle
30、aInt.acoustic meatusAditus to antrumSq.temporal boneFacial n canalEthmoidal sinusCT Axial sections(bone window)Occipital boneJugular foramenBase sphenoidSphenoid sinusExt.acoustic CMastoid air cellsCarotid canalGreater wing of sphenoidCT SCAN-Why do it?Advantages of CT:I.Useful in diagnosis of intra
31、cranial bleed in acute head injury ii.Better demarcation of bony pathology iii Easy availability iv.Cost effective v.Less time consuming vi.Easy interpretationsDisadvantages of CT I.Poor demarcation between gray matter and white matter ii.Less effective in very early and very late haemorrage and inf
32、arct iii.Radiation hazardMRI Why do itAdvantages:Multiplanar modalityBetter gray and white matter differentiation or better spatial resolutionBetter for evaluation of posterior fossa structuresNo radiation hazardDisadvantages:Contraindicated in patients with claustrophobiaContraindicated in patients having aneurysmal clips,metal fillings if these are not MRI compatibleNot useful in evaluation of bony pathologies,calcificationsMovement sensitive
