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1. BASICS OF MRI AND ITS APPLICATION IN ENT NAME – DR . BANSARI AKBARI 1 st YEAR ENT RESIDENT UNDER GUIDANCE OF DR VIRAL SIR , DR VATSAL SIR

2. BASICS OF MRI- This modality uses Magnetic field to study tissues.
MRI depends upon the gyromagnetic properties of protons.
Raymond Damadian -Father of MRI MRI is based on the nuclear magnetic resonance (NMR)and is dependent on protons present in the body.

3. Sequences in mri - Various sequences are used in MRI which include:
• T1 weighted
• T2 weighted
• DWI(Diffusion weighted imaging) SWI(Susceptibility weighted imaging) Gadolinium enhanced mri FLAIR(Fluid attenuated inversion recovery )
STIR(Short tau inversion recovery )
Magnetic resonance angiography

4. Principle of MRI: When the patient is sent into the tunnel, small protons ( acts as tiny magnets) in the body align themselves as per the magnetic field of the MRI machine.As the tissues are subjected to high magnetic field, their protons realign with the magnetic field,lose energy, and produce a signal which can be measured and reconstructed into an image
Machines have a magnetic strength of 0.5, 1.5 or 3 Tesla.
MRI is a multiplanar imaging, images are acquired in various planes like axial, coronal, sagital . Whereas in CT scan, imaging is in axial plane and them it is structured into multiple planes.

5. CONTRAINDICATIONS OF MRI- Absolute contradiction-Patients with cardiac pacemaker , Advances in this field are made, and MRls for patients with pacemakers are being done under supervision.
Cochlear implants.
Aneurysmal clips
Claustrophobia- relative contraindication, patient is sedated in such cases.
Recent metallic implants and prosthesis , eg -immediately after the surgery.
Tattoos on the body are a relative contraindication.
Dental implants .

6. MRI PREFERRED IN – Soft tissue pathology, as MRI has excellent resolution for soft tissues like -
Muscles, Nerves (neurogenic tumours )
Cartilage (suspected meniscal tear) Ligament -Patient with a knee injury (ACL tear) Bone pathologies involving marrow
Head trauma conditions-like diffuse axonal injury.

7. T1WMRI ,T2WMRI AND FLAIR-

8. To Differentiate Between TI-Weighted, T2-Weighted and FLAIR MRI. FLAIR stands for Fluid Attenuation Inversion Recovery.
Firstly look for fluid (water),If it appears white: T2-wMRI.
If it appears black then look for white matter ,If the white matter appears white, then it is a T1wMRI,If water and the white matter appear black: FLAIR MRI

9. TO DIFFERENTIATE T1W MRI PRECONTRAST OR POSTCONTRAST -

10. DIFFUSION WEIGHTED IMAGING - In DWI , it is devoid of skull outline and the scalp. Diffusion means movement , which is based on the Brownian motion of the protons .
Importance: Few pathologies show restricted diffusion, which narrows the differential diagnosis. ACUTE INFARCTS- it can be picked up within 30 mins,the most sensitive investigation for acute infarct is DWI. BRAIN ABSCESS - In the center of the abscess, thick pus in present, which restricts the motion of protons . Thus there is restricted diffusion in the centre with peripheral (wall) enhancement. ARACHNOID CYSTS VS EPIDERMOID CYSTS . BRAIN TUMOURS – hypercellular tumours like lymphoma,medulloblastoma ( hypercellularity doesn’t allows the cells to move .

11. APPARENT DIFFUSION COEFFICIENT (ADI)- Pathology DWI-Bright
Pathology ADC Dark

12. SWI - SUSCEPTIBILITY WEIGHTED IMAGING SWI is more sensitive and is based on the susceptibility of the magnetic field to the substance like:Iron-Hemosiderin in the hemorrhage ,Calcium-Calcification SWI is the investigation of choice for diffuse axonal injury. Black dots are known as of blooming . Identification of SWI sequence -
MRI sequence with black dotted areas.
In SW1, the ventricles do not appear bright.

13. JUVENILE NASOPHARYNGEAL ANGIOFIBROMA -