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 surfacePineal glandSup.colliculiInf.ColliculiAqueduct of sylviusMidbrainCerebellum4th ventriclePonsOculomotor nInter thalamic commissure109Inferior surfaceInterhemispheric fissureTemporal lobe Mammillary bodies Frontal lobeOlfactory tractOptic tractPit.stalkponsMedulla oblongataCerebellumVermisBra
4、in 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:continues as spinal cordContains asce
5、nding and descending Spinal tractsCerebellum Divided into two hemispheres by falx cerebelli Connected in the midline by a worm like structure-Vermis Divided into I.Anterior lobe ii.Middle lobe Iii.Flocculo-nodular lobeVentricles of brainLateral ventricle:-C shaped cavity with body in the parietal lo
6、be 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 vent-cerebral aqueduct-4t
7、h 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 A Ant.Choroidal A Vertebr
8、al 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 PCAInternal cap:-Med&lat striat
9、e 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:PCACircle of willisVenous sin
10、uses of brainStraight sinusTorculaherophiliOccipital sinusTransverse sinusSup.Sagittal sinusInf.SagittalsinusVenous sinuses.Transverse sinusStraightsinussigmoidsinusPitutiary glandICA3rd CN4th CN6th CNSphenoid boneVi Vii br Of 5th CNAxial sectionCingulategyrusCaudateheadPineal glandCorpus callosumLe
11、ntiform 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:-Posterior fossa:-5mmSupra ten
12、torial 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 of CECT:I.Infections:ring
13、 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 Axial sections are taken at
14、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 ImagingMultiplanar modlity so sect
15、ions 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 studied on T2W and Proton densit
16、y 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 calcification and fibrous tissue ap
17、pear 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 lobeBasilar A.Mastoid cellsCe
18、rebellar hemisphereCisterna magnaMedullaOptic nervePituitarySphenoid boneTemporal boneCerebellar tonsilsMRI Axial Section at 4th VentricleLensOptic nervePituitaryTemporal lobeMiddle cerebellar peduncle4th VentricleMedial rectusLateral rectusPonsPetrous temporal boneCerebellar hemisphereCT Axial sect
19、ion 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 cerebellar peduncleOptic chiasmaAmb
20、ient 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 lobeInterpeduncularcisterninferiVermisInferior col
21、liculiConfluence 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 ventricleOccipital hornsOptic radiationCT
22、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 callosumCentral sulcusCorpus ca
23、llosumInter 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 fissureCentrum semiovaleOcci
24、pital lobeParietal lobeFrontal lobeCT Axial section at centrum semiovaleFalx cerebriCentrum semiovaleOccipital lobeParietal lobeFrontal lobeMRI Coronal section at 3rd ventricleFrontal hornsFornix3rd ventricleClivusInterpeduncularcisternInsulaSylvian fissureTemporal lobeParotid glandOdontoid(dens)MRI
25、 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 callosumSup.cerebellar ciste
26、rnTentoriumChoroid plexusAtria of lateral ventricle 4th ventricleMRI Sagittal sectionLat ventGenu3rd ventSphenoid sinusNasopharynxBody of CCSpleniumQuadrigeminal cisternPons4th ventMedullaCerebellumTonsilCingulate gyrusPrepontine cisternCT Coronal section for Pituitary glandPatient is kept in prone
27、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 plane starting from anterior t
28、o 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.cerebral aFrontal sinusInternal
29、 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 cellscochleaInt.acoustic meatusAditus
30、 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 intracranial bleed in acute hea
31、d 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 infarct iii.Radiation hazardM
32、RI 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
