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MRI KNEE ORTHOPEDIC APPROACH

MRI KNEE ORTHOPEDIC APPROACH. PROF. Dr . : Ahmed M. El- Saeed MD Ain Shams University. MRI knee. Uses non ionizing radiation created by placing patients in strong magnetic field (30.000 times stronger than earth`s m.f.) Has no demonstrated adverse biological effects

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MRI KNEE ORTHOPEDIC APPROACH

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  1. MRI KNEE ORTHOPEDIC APPROACH PROF. Dr. : Ahmed M. El-Saeed MD Ain Shams University

  2. MRI knee • Uses non ionizing radiation • created by placing patients in strong magneticfield(30.000 times stronger than earth`s m.f.) • Has no demonstrated adverse biological effects • Depends on Hydrogen atom (single proton) • When hydrogen proton is placed in magnetic field it align its own m.f. to the direction of external m.f. = steadystate

  3. In this steady state radiofrequency(RF) pulse is applied ----- excites the magnetized proton in the field ----- proton change its alignment with MF • When RF pulse is turned off ---- tendency of the proton to giveupthis energy to restore its alignment in MF before RFP • As proton do so emits RF signals of its own-- through a receiver coil or antenna these signals used to generate images

  4. The rate at which proton returns to their equilibrium positions is regulated by two constants : T1= spin-lattic relaxation time T2= spin-spin relaxation time • T1=results from interaction of the hydrogen nucleus with its molecular environment • T2 =reflects local MF strength surrounding each individual proton • T1&T2 are property of tissue and will vary for different tissues

  5. T1 images have the advantage of being obtainable in relatively short periods while providing good anatomic details • T2 images are excellent for lesion detection because almost all pathologic processes prolong T2 • By varying timing of application of RF pulses (TR=repetition time) and timing of acquisition of the returning signals (TE=echo time) an imaging sequence can accentuate T1 (short TR & TE) or T2 (long TR&TE)

  6. Fat and bone marrow give bright signals (abundant in H2) • Cortical bone, ligaments, tendon and air appearblack(littleH2) • Cartilage, spinal canal and muscles are in the grayscale(intermediate H2) • Fat suppression technique for intense fat signals

  7. Parametersused for MRI knee : FOV=12-16cm Slicethickness =3-4mm planes=Sagittalfor menisci and cruciates =Coronal for collateral ligaments =Axial for patellofemoral joint • Contraindications: absolute= IC aneurysm clips, internal ear devices, pacemakers, defibrillators and metallic eye. Relative= Cardiac valves, Middle ear devices and Penile prostheses

  8. FOV < 12cm

  9. Anatomy of the knee • The coil surrounds knee while imaging

  10. menisci • Different cuts of different sites of the meniscus B C A A B C

  11. Meniscal Anatomy SAGITTAL VIEW

  12. Meniscal Anatomy(CORONAL VIEW)

  13. Lateral meniscus • Sagittal plane • lateralmeniscus =bow tie appearance

  14. LAT. MENISCUSSagittal plane equal size meniscus

  15. DISCOID L. MENISCUS 1 2 3

  16. Arrangement of ligaments PCL MM LM ACL

  17. Coronal anatomy • MCL • First meniscus to be seen is MM • Iliotibial band

  18. Medial collateral ligament

  19. Lateral knee structures

  20. BICEPS TENDON

  21. Posterior Coronal section • Most posterior of the coronal plane the PCL • Lateral=biceps , LCL • Note MM still seen (larger) than LM

  22. Intercondylar notch • Change of femoral shape • Indistinct posterior border is seen • Sharp roof of notch is seen

  23. PCL (convex shape, just medial to post horn MM )

  24. ACL(entire lig. Is seen in one or two adjacent 4mm slices)

  25. Grading of meniscal signal= G1 • G1= signal changes not extended to surface • (cut sec—gray)

  26. Grading of meniscal signal=G2 • G2= linear signals common with capsular margin • cut--linear discoloration due to inter substance deg. Cut section

  27. Grading of meniscal signal= G3 • G3= signals extend to articular surface • cut--M tears through surface

  28. Menisci Meniscaltears ch.ch. • abnormalsignal within a meniscus extending to an articular surface 2) alteration in shape and position of meniscus G3

  29. Torn Medial Meniscus1) Abnormal signal • MM tear extending to under surface of mm

  30. Flap tear 2) Alteration in shape

  31. Bucket handle tear small post. Segment displaced M. in notch

  32. Bucket handle tear

  33. Menisco-capsular separation

  34. Med M. cyst

  35. MENISCUS ?

  36. MENISCUS ?

  37. GRADING ?

  38. WHERE IS MM?

  39. ACL TEAR 1-ill-defined mass 2-Loss of continuity 3-retraction of torn ends 4-signals within ligament

  40. ACL TEAR (Signals within lig) ACL

  41. Secondary signs ACL tear • Bone fragment • Tibial shift forward on femur

  42. Chronic ACL tear ACL attaches to PCL Horizontal ACL

  43. ACL FOLLOW-UP

  44. PCL TEAR Retracted ends

  45. MCL injury

  46. MCL

  47. Osteochondritis dissicans

  48. OCD

  49. Extensor system

  50. Synovial Hernia

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