Contents of this talk Introduction. MRI of brain. MRI of spine. Others.My aim is to focus on commonand significant findings.
Tiny motion of protons in amagnetic field isresponsible for MR images.Difficult to believe buttrue !
How does MRI (Magnetic ResonanceImaging) work..? Design of MRI Magnet
Inventors of MRIPeter Paul RaymondMansfield Lautebur DamadianNobel prize for physiology ormedicine 2003
What`s so special about MRI.. Its unique multiecho technique gives tremendous insight to living body in health and disease.
What is T1 sequence.. T1 image of brain T1 refers to time taken for return of net magnetization. A T1 weighted image is produced by this property. Practically , we need to identify T1 weighted image. Remember FLUID IS BLACK on T1.
What is T2 sequence.. T2 image of brain T2 refers to loss of transverse magnetization. A T2 weighted image is produced by using this property. Practically we need to know FLUID IS BRIGHT on T2More than 100 differentsequences are there FLAIR,STIR,CISS,SPACE,GRE,SSSFE ,FSE,TSE………..
Brain MRI is the gold standard in detecting intracranial lesions. It approaches histopathology , can predict functional outcome of treatment, assess brain vessels. It does have few limitations
What we will do.. Anatomy/ Identifying lobes. Few case examples.
Case 1. 39 year old male with headache and left frontal seizures. CT brain shows edema right frontal lobe.
T2 hypointensity with edema in rightfrontal lobe.
Conglomerate ring enhancinglesions. Consistent withtuberculoma.
Is MRI pathognomonic in diagnosis of tuberculoma..? No. Ring enhancing lesion with T2 hypointensity in appropriate clinical situation suggests tuberculoma. Lesion needs follow up. Presence of caseation is responsible for T2 hypointensity.
Case 2 Headache in 28 year old female Papilloedema present CT -? Filling defect in venous sinuses.
Lack of visualization of superior sagittal sinus andleft lateral sinus. Suggestive of thrombus.
Brain images show mild edema in right frontallobe.
MRI with venogram is the modality of choice in assessing venous sinus thrombus and its complications. Normal MR venogram.
Case 3. 21 year old lady with previous history of vision loss. Now complains of numbness of lower limbs.
Diffusion imaging shows areas of recent ischemia / infarct well. It also has other applications.Diffusion imaging shows areas ofdiffusion restriction.
Diagnosis– Mitochondrial cytopathy /Leigh`s disease Bilateral symmetrical areas of abnormal signal in an infant with diffusion restriction in an infant is suggestive of mitochondrial disease. Findings need to be confirmed with serum lactate estimation.
Spine imaging… MRI is widely used to image spine. It has become first line investigation in spine imaging. Key in spine MRI is to pick up the significant and discard insignificant.
Axial section at L4-L5 disc Axial section at vertebral bodylevel , shows L4 root exiting out level , shows pedicles , nerveof neural foramen , L5 root at roots in cauda equinalateral recess
• Lateral recess is the space bordered anteriorly by posterior vertebral body , posteriorly by superior articular facet , laterally by pedicle. In lumbar spine , nerve root is usually trapped by herniated disc here.
Old fractureat D12vertebrallevel.Presence of fatsignal is helpful indifferentiating fatfrom edemasignal.
Case 5 63 year old lady with sudden onset of renal function deterioration. Pulses not felt in lower limbs. Color doppler -- ? Renal artery embolus.
Aortic occlusion , left renal artery alsooccluded.
Patient wasthrombolysed.Follow up MRIafter 1 weekshows goodimprovement
Case 6 Middle aged male with history of right side sensory symptoms. CT showing right thalamic lesion, ?infarct/ SOL
Normal Glioma spectrum.MR SpectroscopyThis graph is called spectroscopy , a sort of chemicalassessment of brain lesions.showing normalmetabolites
spectroscopy As different lesions have different chemical composition , spectroscopy gives different graphs to different lesions. Though not 100% accuracy , is a good tool in assessing brain lesions. This case was a high grade glioma.
Which MRI is betteropen or 1.5 Tesla ..? Open 0.2 T 1.5 Tesla
I have a patient with metallic implant , can I ask forMRI..? A titanium implant can be done immediately after surgery. Rest of metallic implant , better wait for 6 weeks and then proceed for MRI. J MRI 2002
Is MRI safe in pregnancy…? No harmful effects demonstrated so far to mother and fetus. However concerns remain , FDA has not declared MRI is completely safe in pregnancy. Present consensus is that MRI to be done under Definite indications for mother and fetus.
Why musculoskeletal system notdiscussed.. Sorry , as other systems were thought more relevant to today`s audience..
Are MRI contrast gadolinium basedcompounds harmful in renal failure.. Use is safe in mild- moderate renal failure. It should be used with caution in patients with severe renal failure. Large amounts of MR contrast when used in severe CRF (GFR less than 30 ml/minute) is suspected to cause a disease called NSF (nephrogenic systemic fibrosis). Hence caution is indicated in these circumstances.
Summary …. MRI has made tremendous clinical impact. Findings need interpretation with caution and after proper discussion.