1. BASIC FUNDAMENTALS OF MRI

2. Basic Fundamentals of MRI
Acquisition of MRI images - PHYSICS
Basic Sequences & Advanced applications
Characterisation of Lesions.

3. MRI Physics

4. MRI Physics
Magnetic
Resonance
Imaging

5. MRI Physics MAGNETIC Tissues are made of Protons (H+)
Positive electrical charge spinning
around its own axis.
Moving Electrical charge produces
its own magnetic field.
Protons are analogous to small
BAR MAGNETS.

6. MRI Physics MAGNETIC Presence of a strong magnetic field
This leads to alignment of protons in the tissue acc to the magnetic field- LEVEL 1

7. MRI Physics RESONANCE Apart from spinning motion
these protons are also
vibrating at a frequency.
A specific radiofrequency wave passed in a specific manner & specific plane.
Radiofrequency waves are NOT Radiation.

8. MRI Physics
RESONANCE

9. MRI Physics RESONANCE
Raises further raise the energy level of protons – Level 2
Level of excitation is different for different tissues hence signal is different – CONTRAST

10. IMAGING
Radiofrequncy switched off & excited protons come back to Level1
Energy / Signal is released..
Signal picked up by the Coil & processed by a computer.

11. MRI Physics IN NUTSHELL
Patient is placed in a strong magnetic field.
Radiowave is sent in for a short time & switched off.
Patient emits signal.
Recived & used for reconstruction of image.

12. TESLA FACTOR !! Tesla is the unit of magnetic field strength.
TYPES OF MAGNETS :
Resistive Magnets – Low & Ultralow field strenghts.
Permanent Magnets – Low & Med field strength (upto 0.3 T).
Superconducting Magnets T

13. IMAGE PROCESSING & SEQUENCES
TESLA FACTOR !!
FIELD SRENGTH
GRADIENTS
TYPE OF MAGNETIC FIELD
VERTICAL/ HORIZONTAL
IMAGE
QUALITY
S/N Ratio Contrast
TYPE OF COILS
CAMERA
TYPE OF COMPUTER
IMAGE PROCESSING & SEQUENCES

14. TESLA FACTOR !!
As Magnetic field strength increases SNR increases – true for analyitical NMR But NOT for whole-body MRI.
In higher field strengths body produces an inherent noise.
Most important factor in Medical imaging is tissue contrast – best in medium & low field strngths.

16. TESLA FACTOR !!

17. SEQUENCES BASIC SEQUENCES : T1W. T2W. FAT SUPP T2W/ STIR.
FLUID SUPP T2W/ FLAIR.
ADVANCED APPLICATIONS :
MR ANGIOGRAPHY.
MR CHOLANGIOPANCREATOGRAPHY &
MR UROGRAPHY.
DIFFUSION.
JOINT MOTION STUDY – KINEMATIC MRI.

18. BASIC SEQUENCES
T1 Weighted – ANATOMY.
FAT- WHITE
FLUID- BLACK

19. BASIC SEQUENCES T2 Weighted – PATHOLOGY. FLUID- WHITE FAT- NOT SO

20. BASIC SEQUENCES T2 Weighted FAT SUPP/ STIR.
- PATHOLOGY FOR MOST EXTRACRANIAL REGIONS.
FLUID- WHITE
FAT- BLACK

21. BASIC SEQUENCES
T2 W
T2 W FAT SUPP

22. BASIC SEQUENCES T2 Weighted WATER SUPP/ FLAIR. - BRAIN PATHOLOGY
CSF/ CLEAR FLUID - BLACK
PATHOLOGY/ PATHOLOGICAL FLUID- WHITE

23. BASIC SEQUENCES
T2 W
FLAIR- WATER SUPP

24. ADVANCED APPLICATION DIFFUSION
Very sensitive to motion - picks up microscopic motion of protons in edema.
Can differentiate between Cytotoxic Edema (infarct) & Vasogenic Edema (tumor/infection etc).
Special sequence, picks up infarct within hours (2-3 hrs).
To diffrentiate between Old & Fresh infarct.

25. ADVANCED APPLICATION DIFFUSION
FLAIR
DIFFUSION

26. ADVANCED APPLICATION DIFFUSION
FLAIR
DIFFUSION

27. H/O dense Left Hemiplegia – 3 hrs back.
FLAIR
DIFFUSION

28. ADVANCED APPLICATION MRCP
Heavily T2W sequence – Only Fluid appears bright.
2 types – (1) Single shot breath hold (3 secs)
(2) 3D MRCP.
No contrast / injection.
Non-invasive modality for deliniation of biliary anotomy.
All non-theraputic indications of ERCP.

29. ADVANCED APPLICATION MRCP
T2 W FSE
3D MRCP

30. ADVANCED APPLICATION MRCP
T2 W Axial
Single Shot MRCP - 3 sec

31. ADVANCED APPLICATION MRAngio
Flow sensitive sequences – picks up flow.
No contrast / injection.
Arterial study – Head & Neck vessels(2D/3D TOF)
Venous study – Intracranial venous sinuses
(2D TOF & Phase Contrast)

32. ADVANCED APPLICATION MRAngio
INDICATIONS :
Stroke – infarct (Single vessel / Multiple vessel).
TIA.
Secondary Hemorrhage – AVM, Aneurysm.
VBI.
Trigeminal Neuralgia & Hemifacial spasm – aberrent loops.
Venography - Venous sinus thrombosis .
Contrast Enhanced MRA :
Renal Vessels – RAS.
Limb vessels – Femoral, Popliteal , Subclavian & Brachial.

33. ADVANCED APPLICATION MRAngio
MRA – NECK VESSELS
MRA – CIRCLE OF WILLIS

34. ADVANCED APPLICATION MRAngio
CONTRAST MRA – RENAL VESSELS.

35. ADVANCED APPLICATION MRAngio
AVM
PCA ANEURYSM

36. ADVANCED APPLICATION KINEMATIC STUDY
EXTENSION
NEUTRAL
FLEXION

37. Hypintense on T1 & Hyperintense in T2
Pathology
inflammation, infection, infarct, tumor etc. have high water content
Hypintense on T1 & Hyperintense in T2
SOLID
FLUID
T1W - +++
T2W - +++
FLAIR - SUPP
T1W - +
T2W - +
HIGH PROTEIN FLUID
FAT – T1W +++
T2W ++
CALCIFICATION – T1W+++
T2W+++
FLOW – T1W +++
T2W +++
T1W - ++
T2W - ++
BLOOD- METH Hb
T1W - ++
T2W - ++

38. LESION CHARACTERISATION
BRAIN EDEMA
VASOGENIC
CYTOTOXIC
Due to tumor, infection, venous infarct
Involves only white matter.
NOT along specific arterial distribution
Not bright on diffusion.
CONTRAST MRI INDICATED
Due to arterial infarct.
Extends thru grey-white matter junction (involves grey matter).
Along specific arterial distribution.
Bright on diffusion.

39. LESION CHARACTERISATION BRAIN EDEMA
CYTOTOXIC EDEMA
VASOGENIC EDEMA

40. T1W AXIAL
FLAIR COR
T2W AXIAL
T2W SAG

41. T1W +++
T2W +++
FLAIR NOT SUPP
POST CONT
ENHANCEMENT

42. LESION CHARACTERISATION
T1 W AXIAL ++
T2 W AXIAL
+++
FLAIR AXIAL
+++
H/O headache following vehicular accident.

43. LESION CHARACTERISATION
T1W
T2W
T1W T2W POST CONT T1 T
POST CONT T1

44. LESION CHARACTERISATION
T2W AXIAL.
T1W AXIAL
T2W SAG
T1W SAG

45. LESION CHARACTERISATION
T2W AXIAL.
T1W AXIAL.
T2W SAG
T1W SAG

46. LESION CHARACTERISATION
T1W T2W POST CONT T1

47. LESION CHARACTERISATION
T2W AXIAL.
T1W AXIAL.
T2W CORONAL
T1W CORONAL
T2 FAT SUPP

48. LESION CHARACTERISATION
T2W AXIAL.
T1W AXIAL.
T2W SAG
FAT SUPP COR

49. LESION CHARACTERISATION
T2W AXIAL
T1W AXIAL
T2 SAG
T1 SAG

51. MRI Basics SEQUENCES SEQUENCE FAT FLUID T1W WHITE BLACK T2W
NOT SO WHITE
T2 FAT SUPP
STIR
T2 FLU SUPP
FLAIR
CSF/CLEAR FLUID - BLACK
PATH FLUID- WHITE

52. I've got so much to learn!

53. Thanks !!