Download - MRI KNEE ORTHOPEDIC APPROACH
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MRI KNEE MRI KNEE ORTHOPEDIC APPROACH ORTHOPEDIC APPROACH
PROF. Dr. : Ahmed M. El-Saeed
MD Ain Shams University
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MRI kneeMRI kneeUses 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
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. = steady state
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In this steady state radio frequency (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 give up this 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
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The rate at which proton returns to their equilibrium positions is regulated by two constants :
T1= spin-lattic relaxation time T2= spin-spin relaxation timeT1=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
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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)
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Fat and bone marrow give bright signals (abundant in H2)
Cortical bone, ligaments, tendon and air appear black (little H2 )
Cartilage, spinal canal and muscles are in the gray scale (intermediate H2)
Fat suppression technique for intense fat signals
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Parameters used for MRI knee :
FOV=12-16cm Slice thickness =3-4mm
planes =Sagittal for menisci and cruciates
=Coronal for collateral ligaments
=Axial for patellofemoral jointContraindications :
absolute= IC aneurysm clips, internal ear devices, pacemakers, defibrillators and metallic eye.
Relative= Cardiac valves, Middle ear devices and Penile prostheses
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FOV < 12cmFOV < 12cm
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Anatomy of the kneeAnatomy of the knee The coil
surrounds knee while imaging
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meniscimenisci Different cuts of
different sites of the meniscus
A B C
A
B
C
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Meniscal Anatomy
SAGITTAL VIEW
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Meniscal AnatomyMeniscal Anatomy(CORONAL VIEW)(CORONAL VIEW)
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Lateral meniscusLateral meniscus
Sagittal plane
lateral meniscus =bow tie appearance
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LAT. MENISCUSLAT. MENISCUSSaSagittal plane gittal plane equal size meniscusequal size meniscus
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DISCOID L. MENISCUS
1 2 3
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Arrangement of ligamentsArrangement of ligaments
MM LM
PCL
ACL
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Coronal anatomyCoronal anatomy MCL
First meniscus to be seen is MM
Iliotibial band
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Medial collateral ligamentMedial collateral ligament
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Lateral knee structuresLateral knee structures
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BICEPS TENDONBICEPS TENDON
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Posterior Coronal sectionPosterior Coronal section
Most posterior of the coronal plane the PCL
Lateral=biceps , LCL
Note MM still seen (larger) than LM
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Intercondylar notchIntercondylar notch Change of femoral
shape Indistinct posterior
border is seen Sharp roof of notch
is seen
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PCL PCL
(convex shape, just medial to post horn MM )(convex shape, just medial to post horn MM )
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ACLACL (entire lig(entire lig. Is seen in one or two adjacent 4mm slices). Is seen in one or two adjacent 4mm slices)
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Grading of meniscal signal= Grading of meniscal signal= G1G1
G1= signal changes not extended to surface
(cut sec—gray)
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Grading of meniscal signal=Grading of meniscal signal=G2G2
G2= linear signals common with capsular margin
cut--linear discoloration due to inter substance deg.
Cut section
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Grading of meniscal signal= Grading of meniscal signal= G3G3
G3= signals extend to articular surface
cut--M tears through surface
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MenisciMenisciMeniscal tears ch.ch.
1) abnormal signal within a meniscus extending to an articular surface
2) alteration in shape and position of meniscus
G3
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Torn Medial MeniscusTorn Medial Meniscus1) Abnormal signal1) Abnormal signal
MM tear extending to under surface of mm
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Flap tear Flap tear 2) 2) Alteration in shapeAlteration in shape
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Bucket handle tear
small post. Segment displaced M. in notch
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Bucket handle tearBucket handle tear
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Menisco-capsular separationMenisco-capsular separation
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Med M. cystMed M. cyst
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MENISCUS ?
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MENISCUS ?
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GRADING ?GRADING ?
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WHERE IS MM?WHERE IS MM?
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ACL TEARACL TEAR1-ill-defined mass
2-Loss of continuity
3-retraction of torn ends
4-signals within ligament
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ACL TEAR ACL TEAR (Signals within lig)(Signals within lig)
ACL
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Secondary signs ACL tearSecondary signs ACL tear
Bone fragment
Tibial shift forward on femur
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Chronic ACL tearChronic ACL tear
ACL attaches to PCLHorizontal ACL
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ACL FOLLOW-UPACL FOLLOW-UP
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PCL TEARPCL TEAR
Retracted ends
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MCL injuryMCL injury
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MCLMCL
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Osteochondritis dissicansOsteochondritis dissicans
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OCDOCD
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Extensor systemExtensor system
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Synovial HerniaSynovial Hernia
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Sometimes Fractures!!!Sometimes Fractures!!!
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ARTICULAR CARTILAGEARTICULAR CARTILAGE
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LOOSE BODYLOOSE BODY
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Gstrocenimius muscleGstrocenimius muscle
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BURSA ?BURSA ?