Downloaded 112 times
Uploaded byMukhtar Khan
Basicsofmri 090416164546-phpapp01
MRI utilizes the magnetic properties of hydrogen protons in the body to generate detailed images of tissues and structures. A strong external magnetic field aligns protons within the body. Radiofrequency pulses then excite the protons, causing them to emit signals detected by receivers in the MRI scanner. Repeated excitation and signal detection allows the scanner to build up a 3D map of proton density and behavior throughout the scanned region. By varying pulse sequences, different tissue contrasts can be obtained to visualize anatomy and identify abnormalities across multiple MRI sequences. While a powerful tool, MRI has limitations such as long scan times and inability to image certain tissues like bone. Careful clinical indication and sequence selection are needed to optimize MRI for diagnostic purposes.
More Related Content
Similar to Basicsofmri 090416164546-phpapp01
Basicsofmri 090416164546-phpapp01
- 1. Kipling’s honest servingmenKipling’s honest serving men I keep six honest serving-menI keep six honest serving-men (They taught me all I knew);(They taught me all I knew); Their names are What and Why andTheir names are What and Why and WhenWhen And How and Where and Who.And How and Where and Who. Rudyard KiplingRudyard Kipling
- 2. MRI: What, WhyandMRI: What, Why and When?When? Dr Keshav KulkarniDr Keshav Kulkarni Consultant RadiologistConsultant Radiologist
- 3. ““Without history humanisWithout history human is demoted to lower animals”demoted to lower animals” ► Dr Isidor Rabi (Nobel in 1944), discovered NMRDr Isidor Rabi (Nobel in 1944), discovered NMR (Nuclear Magnetic Resonance) in the late(Nuclear Magnetic Resonance) in the late 1930s, but considered it to be an artefact of his1930s, but considered it to be an artefact of his apparatus!apparatus! ► Bloch and Purcell were awarded the Nobel PrizeBloch and Purcell were awarded the Nobel Prize for Physics in 1952 for the discovery of NMR,for Physics in 1952 for the discovery of NMR, and is widely used in assessing complexand is widely used in assessing complex chemical compunds.chemical compunds.
- 4. We are soclose to the man behindWe are so close to the man behind MRIMRI ►Prof Peter Mansfield was awarded Nobel inProf Peter Mansfield was awarded Nobel in 2003 for his discoveries in MRI (with Prof2003 for his discoveries in MRI (with Prof Paul C Lauterbur of USA)Paul C Lauterbur of USA) ►Peter Mansfield is from NottinghamPeter Mansfield is from Nottingham University, UKUniversity, UK
- 5. MRI: What isit?MRI: What is it? Magnetic Resonance ImagingMagnetic Resonance Imaging MagnetMagnet Radio FrequencyRadio Frequency ImagingImaging
- 6. WE ARE MAGNETS!WEARE MAGNETS! Really?Really?
- 7. We all aremade up of elementsWe all are made up of elements ►92 elements occur naturally on earth.92 elements occur naturally on earth. ►Human body is built of only 26 elements.Human body is built of only 26 elements. ►Oxygen, hydrogen, carbon, nitrogenOxygen, hydrogen, carbon, nitrogen elements constitute 96 % of human bodyelements constitute 96 % of human body mass.mass. ►Oxygen is 65 % of body mass; carbon isOxygen is 65 % of body mass; carbon is 18.5 %,18.5 %, hydrogen 9.5 %hydrogen 9.5 %, nitrogen 3.2 %., nitrogen 3.2 %. ►Let us ignore all elements but Hydrogen.Let us ignore all elements but Hydrogen.
- 8. Why hydrogen?Why hydrogen? ►Simplestelement with atomic number of 1Simplest element with atomic number of 1 and atomic weight of 1and atomic weight of 1 ►When in ionic state (H+), it is nothing but aWhen in ionic state (H+), it is nothing but a proton.proton. ►Proton is not only positively charged, butProton is not only positively charged, but also has magnetic spin (wobble)!also has magnetic spin (wobble)! ►MRI utilizes this magnetic spin property ofMRI utilizes this magnetic spin property of protons of hydrogen to elicit images!!protons of hydrogen to elicit images!! ►We are magnets!We are magnets!
- 9. But why wecan’t act likeBut why we can’t act like magnets?magnets? ► The protons (i.e.The protons (i.e. Hydrogen ions) in bodyHydrogen ions) in body are spinning in a hapare spinning in a hap hazard fashion, andhazard fashion, and cancel all thecancel all the magnetism. That is ourmagnetism. That is our natural state!natural state! ► We need to disciplineWe need to discipline them first, how?them first, how?
- 10. We need abig magnet fromWe need a big magnet from outside!outside! ►Magnetic field strength: 0.3 – 7 T (2500Magnetic field strength: 0.3 – 7 T (2500 times more than earth’s magnetic field).times more than earth’s magnetic field). Average field strength – 1.5 TAverage field strength – 1.5 T ►Open magnet – less field strength, lessOpen magnet – less field strength, less claustrophobicclaustrophobic ►Closed magnet – more field strength,Closed magnet – more field strength, claustrophobicclaustrophobic
- 11. Proton alignmentProton alignment ►Compass aligns withCompass aligns with the earththe earth ► In a similar fashion,In a similar fashion, ► Our body protonsOur body protons (hydrogen) align with(hydrogen) align with this external magneticthis external magnetic field.field. ► Now, we areNow, we are disciplined (spinningdisciplined (spinning in line with eachin line with each other!), what next?other!), what next?
- 12. Now, its timeto listen to radio inNow, its time to listen to radio in RESONANCE.RESONANCE. ►Pushing a swing in time with natural intervalPushing a swing in time with natural interval of the swing will make the swing higher andof the swing will make the swing higher and higher.higher. ►Similarly, radio frequency pulses inSimilarly, radio frequency pulses in resonance push the aligned protons (H+) toresonance push the aligned protons (H+) to a higher energy level.a higher energy level.
- 13. What is RadioFrequency pulse?What is Radio Frequency pulse? ►Same as Radio waves – high wavelength,Same as Radio waves – high wavelength, low energy electromagnetic waveslow energy electromagnetic waves ►Radiofrequency coilsRadiofrequency coils Act as transmitter and receiverAct as transmitter and receiver Different types of coilsDifferent types of coils
- 14. Turn off theradioTurn off the radio ►The higher energy gained by the protons isThe higher energy gained by the protons is retransmitted (NMR signal)retransmitted (NMR signal) ►The original magnetization begins toThe original magnetization begins to recover (T1)recover (T1) ►The excessive spin begins to dephase (T2)The excessive spin begins to dephase (T2)
- 15. Now, we re-transmitthe energyNow, we re-transmit the energy for image processingfor image processing ►The emitted energy is too small (despiteThe emitted energy is too small (despite 2500 times the magnetic field with2500 times the magnetic field with resonance RF pulse) to convert them intoresonance RF pulse) to convert them into images.images. ►Hence, repeated “ON-OFF” of RF pulsesHence, repeated “ON-OFF” of RF pulses are required.are required. ►The emitted energy is stored (K-space),The emitted energy is stored (K-space), analysed and converted into images.analysed and converted into images. ►What kind of images?What kind of images?
- 16. What kind ofimages?What kind of images? ► T1WIT1WI ► T2WIT2WI ► PDWIPDWI ► DWIDWI ► ADCADC ► GEGE ► Perfusion imagesPerfusion images ► fMRIfMRI ► BOLD imagesBOLD images ► MRAMRA ► MRVMRV ► Post-Gd imagesPost-Gd images ► Volumetric imagesVolumetric images ► MR arthrogramsMR arthrograms ► FLAIRFLAIR ► STIRSTIR ► Etc etc etcEtc etc etc
- 17. Copyright ©Radiological Societyof North America, 2005 Pooley, R. A. Radiographics 2005;25:1087-1099 T1-weighted contrast
- 18. Copyright ©Radiological Societyof North America, 2005 Pooley, R. A. Radiographics 2005;25:1087-1099 T2-weighted contrast
- 19. Tissue AppearanceTissue Appearance WTWTFATFAT H2OH2O MUSCMUSC LIGLIG BONEBONE T1T1 BB DD II DD DD ProtonProton DensityDensity II II II DD DD T2T2 II BB II DD DD
- 21. A bit ofsequence exerciseA bit of sequence exercise
- 22. Which sequence isit? T2Which sequence is it? T2
- 23. Which sequence isit? T1Which sequence is it? T1
- 24. Which sequence isit? FLAIRWhich sequence is it? FLAIR
- 25. Which sequence isit? DWIWhich sequence is it? DWI
- 26. Which sequence isit? ADCWhich sequence is it? ADC
- 27. Which sequence isit? GEWhich sequence is it? GE
- 28. Which sequence isit? PostGdWhich sequence is it? PostGd
- 29. Which sequence isit? MRVWhich sequence is it? MRV
- 30. Which sequence isit?, 3D MRVWhich sequence is it?, 3D MRV
- 31. Which sequence isit? MRAWhich sequence is it? MRA
- 32. Which sequence isit? T2Which sequence is it? T2
- 33. Which sequence isit? T1Which sequence is it? T1
- 34. Which sequence isit? STIRWhich sequence is it? STIR
- 35. Which sequence isit? MRWhich sequence is it? MR arthrogramarthrogram
- 36. I hope Iwas able to confuse you!I hope I was able to confuse you!
- 37. How MR isdone?How MR is done?
- 38. In a Tunnel,of course!In a Tunnel, of course!
- 39. Before entering tunnel,there isBefore entering tunnel, there is a checklist!a checklist! ► No mobiles, no credit cards, please!No mobiles, no credit cards, please! ► Known potential safety concerns due to largeKnown potential safety concerns due to large static magnetic field:static magnetic field: Internal cardiac pacemakersInternal cardiac pacemakers Steel cerebral aneurysm clips (ferromagnetic)Steel cerebral aneurysm clips (ferromagnetic) Small steel slivers embedded in eyeSmall steel slivers embedded in eye Life-support equipment with magnetic steelLife-support equipment with magnetic steel Cochlear implantsCochlear implants Stents anywhere in the bodyStents anywhere in the body
- 40. Further checklist!Further checklist! ►Malfunction: ICDs, neurostimulators, bone growthMalfunction: ICDs, neurostimulators, bone growth stimulators (prosthetic heart valves)stimulators (prosthetic heart valves) ► Superficial burns (uninsulated wire leads)Superficial burns (uninsulated wire leads) ► NEED sedation: infants, younger peds, agitatedNEED sedation: infants, younger peds, agitated adults (claustrophobia)adults (claustrophobia) ► Precautions: magnetic plastic cards, watches,Precautions: magnetic plastic cards, watches, hearing aids, ferromagnetic steel objects (LEAVEhearing aids, ferromagnetic steel objects (LEAVE OUTSIDE)OUTSIDE) ► Loud noise (long-term hearing loss)Loud noise (long-term hearing loss) ► Pregnancy!Pregnancy!
- 41. Is entering thetunnel safe?Is entering the tunnel safe? ►No definite long-term harmful effectsNo definite long-term harmful effects ►Pregnancy is a relative contraindication, asPregnancy is a relative contraindication, as we will never be able to tell with 100%we will never be able to tell with 100% certainty that MRI is 100% safe duringcertainty that MRI is 100% safe during pregnancy!pregnancy! ►Babies and children need sedation or GABabies and children need sedation or GA ►Some people fear tunnels (claustrophobia)Some people fear tunnels (claustrophobia)
- 42. What happens inMRI?What happens in MRI? ►Stay still for 15 minutes to 45 minutes!Stay still for 15 minutes to 45 minutes! ►Noise, Noise and Noise!Noise, Noise and Noise! ►Listen to music in darknessListen to music in darkness ►Alien (radiographers) like voices in between,Alien (radiographers) like voices in between, “another 5 minutes to go”,or, “please stay“another 5 minutes to go”,or, “please stay still”.still”. ►Somebody can come and inject.Somebody can come and inject.
- 43. Clinical Aspects ofMRIClinical Aspects of MRI
- 44. When to MRI?Whento MRI? ►When everything else fails, there is MRIWhen everything else fails, there is MRI ►When you want to borrow time from theWhen you want to borrow time from the patient, request MRI and hope that thepatient, request MRI and hope that the waiting time will take care of the patientwaiting time will take care of the patient
- 45. Advantages of MRIAdvantagesof MRI 1.1. No ionizing radiation & no short/long-termNo ionizing radiation & no short/long-term effects demonstratedeffects demonstrated 2.2. Variable thickness, any planeVariable thickness, any plane 3.3. Better contrast resolution & tissueBetter contrast resolution & tissue discriminationdiscrimination 4.4. Various sequences to play with toVarious sequences to play with to characterise the abnormal tissuecharacterise the abnormal tissue 5.5. Many details without I.V contrastMany details without I.V contrast
- 46. Disadvantages of MRIDisadvantagesof MRI ►Time consumingTime consuming ►Not easily available (long waiting list)Not easily available (long waiting list) ►No on-call serviceNo on-call service ►Need to tweak sequences as per the clinicalNeed to tweak sequences as per the clinical questions; hence cannot be generalisedquestions; hence cannot be generalised Pain abdomen - ? causePain abdomen - ? cause
- 47. Nothing is perfectin this worldNothing is perfect in this world ►MRI has limitations:MRI has limitations: BoneBone AirAir Time consumingTime consuming Poor spatial resolutionPoor spatial resolution Expertise!Expertise!
- 48. We presumed MRcontrast isWe presumed MR contrast is safesafe ►No side effectsNo side effects ►No allergy ( as with Iodine)No allergy ( as with Iodine) ►Can be used in renal impairmentCan be used in renal impairment ►Can be used as CT contrast when a patientCan be used as CT contrast when a patient has impaired renal functions!has impaired renal functions!
- 49. Necrotising Systemic FibrosisNecrotisingSystemic Fibrosis ►No cases identified prior to 1997No cases identified prior to 1997 ►Initial research were targeting dialysisInitial research were targeting dialysis and/or renal transplant as triggering causeand/or renal transplant as triggering cause (someone even suggested Anthrax(someone even suggested Anthrax ourbreak!)ourbreak!) ►Two reports in 2006 changed it all!Two reports in 2006 changed it all! ►Disfiguring and potentially disabling or fatalDisfiguring and potentially disabling or fatal disorder involving skin, muscles, lungs,disorder involving skin, muscles, lungs, pleura, pericardium, and bones.pleura, pericardium, and bones.
- 50. We need toget used to artefacts,We need to get used to artefacts, and sometimes are majorand sometimes are major limitationslimitations
- 51. How to getthe best from MRI?How to get the best from MRI? ►Ask a specific questionAsk a specific question ►Get a specific answerGet a specific answer ►Because the sequences can be tailoredBecause the sequences can be tailored accordingly.accordingly.
- 52. MRMR ► FasterFaster ► LessexpensiveLess expensive ► Less sensitive to patientLess sensitive to patient movementsmovements ► Easier in claustrophobicsEasier in claustrophobics ► Acute haemorrhageAcute haemorrhage ► CalcificationCalcification ► Bone detailsBone details ► Foreign bodyForeign body ► No ionising radiationNo ionising radiation ► Greater details, henceGreater details, hence more sensitive and moremore sensitive and more specificspecific ► Any plane scanningAny plane scanning ► Contrast less allergicContrast less allergic ► No beam hardeningNo beam hardening artefactartefact CTCT
- 53. Neuroimaging = MRINeuroimaging= MRI ►No neurology or neurosurgery without MRINo neurology or neurosurgery without MRI ►MR brain has largely replaced CT brain inMR brain has largely replaced CT brain in USA (but for head injury, suspected acuteUSA (but for head injury, suspected acute intracranial haemorrhage)intracranial haemorrhage) ►Superior to CT in most occasionsSuperior to CT in most occasions ►CT is poor man’s MRI in all otherCT is poor man’s MRI in all other indications!indications! ►Show me a person with migraine who hasShow me a person with migraine who has not undergone MRI in USA!not undergone MRI in USA!
- 54. Indications (almost everything)Indications(almost everything) ► AnatomyAnatomy ► Congenital anomaliesCongenital anomalies ► Hereditary andHereditary and metabolic diseasesmetabolic diseases ► InfectionsInfections ► DemyelinationDemyelination ► Vascular eventVascular event ► TumoursTumours ► TraumaTrauma ► DementiaDementia ► HydrocephalusHydrocephalus ► Cranial nervesCranial nerves ► ArteriogramsArteriograms ► VenogramsVenograms ► Skull baseSkull base ► Pituitary glandPituitary gland
- 55. Tools in neuroimagingToolsin neuroimaging ► T2WIT2WI ► T1WIT1WI ► FLAIRFLAIR ► MRAMRA ► MRVMRV ► GEGE ► GadoliniumGadolinium ► DWIDWI ► ADCADC ► Diffusion tensorDiffusion tensor imagingimaging ► fMRIfMRI ► Perfusion mappingPerfusion mapping ► CSF flow mappingCSF flow mapping ► MR spectroscopyMR spectroscopy
- 56. Stroke imagingStroke imaging ►MRsuperior to CT in diagnosing hyperacuteMR superior to CT in diagnosing hyperacute infarctinfarct ►MR is as sensitive as CT in diagnosingMR is as sensitive as CT in diagnosing acute intracranial haemorrhageacute intracranial haemorrhage ►MR is more expensive and less easilyMR is more expensive and less easily available compared to CT in the UKavailable compared to CT in the UK ►CT is currently widely used to exlcudeCT is currently widely used to exlcude haemorhage before thrombolysishaemorhage before thrombolysis
- 57. Acute infarct bestshown on DWIAcute infarct best shown on DWI
- 58. When to skipCT?When to skip CT? ►Babies and children (avoid ionisingBabies and children (avoid ionising radiation)radiation) ►Evaluation of headache (controversial inEvaluation of headache (controversial in NHS setting)NHS setting) ►Suspected demyelination, dysmyelination,Suspected demyelination, dysmyelination, vasculitis, SOLs, hydrocephalus, pituitaryvasculitis, SOLs, hydrocephalus, pituitary lesionslesions ►Non-invasive, non-contrast MRA and MRVNon-invasive, non-contrast MRA and MRV ►Cranial nerve evaluationCranial nerve evaluation
- 59.
- 60.
- 61. Spine imagingSpine imaging ►MRis the investigation of choiceMR is the investigation of choice ►Conventional CT, CT myelogram andConventional CT, CT myelogram and conventional myelogram are no longerconventional myelogram are no longer performed, unless MR is contraindicated.performed, unless MR is contraindicated. ►Indications and contraindications – sameIndications and contraindications – same ►First line of investigation in suspected spinalFirst line of investigation in suspected spinal infection, cord compression, cauda equina,infection, cord compression, cauda equina, sciaticasciatica
- 62. Disc lesion andMRIDisc lesion and MRI ►Virtually everyone after the age of 40 yearsVirtually everyone after the age of 40 years will have at least one degenerative disc/ endwill have at least one degenerative disc/ end plateplate ►Not all patients with sciatica will have aNot all patients with sciatica will have a positive MRIpositive MRI ►Ask MRI to answer a specific question;Ask MRI to answer a specific question; otherwise MRI might completely mislead theotherwise MRI might completely mislead the clinician.clinician.
- 63.
- 64. Head and NeckimagingHead and Neck imaging ► MR is complementary or second line ofMR is complementary or second line of investigation in many of head and neckinvestigation in many of head and neck pathologiespathologies ► Superior to CT in staging head and neckSuperior to CT in staging head and neck malignanciesmalignancies ► Characterise the head and neck lesions betterCharacterise the head and neck lesions better than CTthan CT ► Complementary to CT in petrous temporal andComplementary to CT in petrous temporal and paranasal sinus evaluationparanasal sinus evaluation ► First line of investigation in orbital lesionsFirst line of investigation in orbital lesions
- 65. Second branchial cleftcystSecond branchial cleft cyst
- 66. Tongue base carcinomaTonguebase carcinoma
- 67. Musculoskeletal imagingMusculoskeletal imaging ►Initialevaluation of bones – Plain films; thenInitial evaluation of bones – Plain films; then MRIMRI ►MRI sensitive than CT in diagnosing occultMRI sensitive than CT in diagnosing occult fracturesfractures ►Initial evaluation of soft tissues – USG; thenInitial evaluation of soft tissues – USG; then MRIMRI ►Joint imaging = MRIJoint imaging = MRI
- 68. Tools in MSKimagingTools in MSK imaging ► T1WIT1WI ► T2WIT2WI ► Fat sat T1Fat sat T1 ► STIRSTIR ► Fat sat T2Fat sat T2 ► Gadolinium studiesGadolinium studies ► MR arthrographyMR arthrography
- 69. IndicationsIndications ►Occult fracturesOccult fractures ►MarrowabnormalityMarrow abnormality ►Ligament pathologiesLigament pathologies ►Tendon pathologiesTendon pathologies ►Muscular injuriesMuscular injuries ►InfectionInfection ►Bone and soft tissue tumourBone and soft tissue tumour ►Labral pathologiesLabral pathologies
- 70.
- 71.
- 72. Rotator cuff tearRotatorcuff tear
- 73. Bankart and HillsachslesionsBankart and Hillsachs lesions
- 74. Abdominal MRIAbdominal MRI ►Problemsolving tool in liver, pancreatic,Problem solving tool in liver, pancreatic, renal and adrenal lesionsrenal and adrenal lesions ►Primary modality in local staging of rectalPrimary modality in local staging of rectal ca, endometrial ca, cervical ca, prostate ca,ca, endometrial ca, cervical ca, prostate ca, vaginal cavaginal ca ►Non-invasive modality in evaluatingNon-invasive modality in evaluating pancreaticobiliary tract – MRCPpancreaticobiliary tract – MRCP ►Scrotal and penile imagingScrotal and penile imaging ►Uterus and ovary imagingUterus and ovary imaging
- 75.
- 76.
- 77. Vascular MRIVascular MRI ►Peripheralvascular arteriogram with orPeripheral vascular arteriogram with or without I.V contrastwithout I.V contrast ►AortogramAortogram DissectionDissection ►Pulmonary arteriogramPulmonary arteriogram When CT is contraindicatedWhen CT is contraindicated
- 78. Cardiac MRICardiac MRI ►Comingin a big wayComing in a big way ►Very useful in congenital heart diseases,Very useful in congenital heart diseases, cardiomyopathiescardiomyopathies ►Evidence is emerging in the evaluation ofEvidence is emerging in the evaluation of myocardial infarctionmyocardial infarction
- 79. Breast MRIBreast MRI ►ProblemsolvingProblem solving Breast implantsBreast implants RecurrenceRecurrence Multifocal diseaseMultifocal disease
- 80. Foetal MRIFoetal MRI ►Assessmentof congenital anomaliesAssessment of congenital anomalies ►Placental abnormalitiesPlacental abnormalities ►Twin assessmentTwin assessment
- 81. SummarySummary ►Expensive time-consuming investigationExpensivetime-consuming investigation ►Complex physics, too many sequences,Complex physics, too many sequences, difficult to interpret to untrained eyesdifficult to interpret to untrained eyes ►Relatively safe, but there are definiteRelatively safe, but there are definite contraindicationscontraindications ►Ask specific question to get the right answerAsk specific question to get the right answer
- 82. SummarySummary ►MRI invaluable imagingtool in the diagnosisMRI invaluable imaging tool in the diagnosis of various diseases from head to toeof various diseases from head to toe ►Chief modality in neuroimaging, andChief modality in neuroimaging, and musculoskeletal imagingmusculoskeletal imaging ►Problem solving tool in abdominalProblem solving tool in abdominal pathologiespathologies ►Invaluable tool in local staging of most ofInvaluable tool in local staging of most of the malignanciesthe malignancies
- 83.
- 84.