Knee MRI pitfalls

27.01.16
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Radiology Research and
Practice Center, Moscow
Pitfalls of knee MRI
Sergey Morozov, MD, PhD, MPH
Irina Trofimenko, MD, PhD
Agenda
•  Knee trauma diagnosis
•  Role of MRI
•  Multi-center trial of MRI effectiveness
•  Major pitfalls of MRI
•  Recommendations and regional
solutions

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3
Clinical symptoms of knee
injury
•  Pain, limitation of movement
•  Hemarthrosis
•  Instability
→ Clinical Dx
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 20, No 7 (September), 2004: pp 696-700
Trained and experienced traumatologist has
100% accuracy in ACL tear diagnosis
Lachman
test
Med. Men. Lat. Men. ACL
Clin. Dx MRI Clin. Dx MRI Clin. Dx MRI
Accuracy 80 80 92 90 100 98
Sens 87 80 75 85 100 96
Spec 68 79 95 97 100 96

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5
MRI – preoperative verification of Dx
•  MRI as predictor for arthroscopic treatment
–  Senc 79%
–  Spec 100%
Vincken et al. Radiology 2002; 223:739.
Strategy with MRI Strategy without MRI
Arthroscopy, % 57 92
Treatment costs 1296 961
Sick leaves, % 44 58
Sick days 11,8 15,8
Knee MRI dilemma
Lateral meniscus tear ACL tear
Sn 69,5 70 (55,2-84,7)
Sp 94,5 94,5
NPV 80,5 59,6
PPV 90,5 96,5
Radiology 2002; 223:739–746

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Sources of pitfalls
Technical
aspects
Normal
variants
Pathology
Purpose
• To analyze variability of
preoperative knee MRI by
means of retrospective multi-
institutional study

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Design of study
A
C
B
D
E
Arthroscopy
(1 surgeon)
MRI centers
Traumatologist
consultation
(3 physicians)
Retrospective analysis
Ortho General
1.5-3.0 T A, E B
0.5-1.0 T C D
Materials and Methods
% of patients with pathology at each MRI center
A B C D E
Med. Meniscus 58,3 35,7 52,5 52,5 46,9
Lat. Meniscus 18,3 35,7 22,5 27,9 18,8
ACL 88,3 81,0 87,5 86,9 84,4
Cartilage 51,7 85,7 55,0 67,2 62,5
•  203 patients
•  15-74 y.o. (35.0 ± 12.7 years)
•  Difference in age among diagnostic
centers - NS
43,30
%
56,70
%
malefemale
p<0.05

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Materials and Methods: study
flow chart
1.  Retrieval of data from MRI and arthroscopy
protocols (203 patients; 35.0 ± 12.7 y.o.)
2.  Standardization and systematization of data
3.  Database management
4.  Data analysis:
–  Diagnostic effectiveness of MRI
(relative to arthroscopy)
–  ROC
5.  MR images revision
Results: menisci
Medial meniscus
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
0 0,2 0,4 0,6 0,8 1
A B C D E
Lateral meniscus
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
0 0,2 0,4 0,6 0,8 1
A B C D E
AUC: 0.57-0.87
Significant difference between MRI centers
for medial meniscus
AUC: 0.56-0.80

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0,87
0,78
0,67
0,87
0,77
0 0,5 1 1,5
Sensitivity
A
B
C
D
E
0,76
0,38
0,79
0,85
0,76
0 0,5 1 1,5
Specificity
Medial meniscus: Significant difference in
specificity of MRI between centers B and D
Results: medial meniscus
A
B
C
D
E
0,67
0,47
0,33
0,60
0,64
0 0,5 1 1,5
Sensitivity
Lateral meniscus: No significant difference
between MRI centers
Results: lateral meniscus
A
B
C
D
E
1,00
0,89
0,94
0,92
0,89
0 0,5 1 1,5
Specificity
A
B
C
D
E

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Results: anterior cruciate
ligament
0
0,2
0,4
0,6
0,8
1
0 0,2 0,4 0,6 0,8 1
A B C D E
0,75
0,86
1,00
0,75
1,00
0 0,2 0,4 0,6 0,8 1 1,2
0,47
0,82
0,77
0,49
0,59
0 0,2 0,4 0,6 0,8 1
AUC: 0.67-0.89
Significant difference
between centers A, B, D
Sensitivity
Specificity
A
B
C
D
E
A
B
C
D
E
Example 1 MRI report: Partial tear of ACL
Arthroscopy: Full-thickness tear of ACL

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Example 2 MRI report: Tear of posterior horn of MM
Arthroscopy:
no tear of menisci
Sources of pitfalls
Technical
aspects
Normal
variants
Pathology

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19
Incomplete MRI protocol
Flow artifacts
A>>P
•  The same shape
as popliteal
vessels
•  Strongly
depends on
phase encoding
directionH>>F

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Flow artifacts
• Solution 1 = change phase-encoding
direction
frequency-encoding
phase-encoding
K-space
K-space
center
• Solution 2 = PROPELLER/
BLADE reconstruction
• K-space center is oversampled →
↑SNR, ↑CNR
•↑ time of reconstruction, ↑SAR
Magic angle artifact
TE 20 ms
•  ↑ SI at 550 relative
B0
•  Affects only
structured collagen
fibers (tendons,
cartilage, menisci,
ligaments)
TE 70 ms
B
0
55
0

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Magic angle artifact
TE 20 ms
•  Only exists with
short TE (<
37ms)
TE 70 ms
Inadequate fat suppression
•  Mimics edema
•  Off-center or at the
edge of the coil
•  Solution = STIR

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Inadequate fat suppression
• Solution 1 = STIR
- tolerance to B0 and B1 inhomogeneity
- ↓ SNR
• Solution 2 = SPAIR
- combination of CHESS+STIR
- uses adiabatic inverting pulse →
↓sensitivity to B1
- longer time than STIR
• Solution 3 = DIXON
- ↓ insensitive to B0 and B1 inhomogeneity
- increases minimal TR
Sources of pitfalls
Technical
aspects
Normal
variants
Pathology

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Fatty synovial folds
•  Mimics loose
bodies at fat
sat
•  ↑SI at T1-WI
Lateral tibial plateau cartilage
•  Mimics
chondrocalcinosis
True
chondrocalcinosis

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Meniscal flounce
Mohancumar et al, AJR:
203
•  Up to 5% of MM
•  Transient physiologic
distortion
•  Seen with knee flexed,
disappears with full
extension
Lateral meniscus anterior
horn
•  Striated
appearance =
normal
•  Isolated tears
LMAH only 16%
of all LM tears

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Menisco-femoral ligament
•  When MFL hyperplasia mimics PCL tear or bucket-
handle meniscal tear
Menisco-femoral ligament / LM
junction
•  Mimics radial
vertical
tears
•  Attention:
Wrisberg rip
(ACL tear)
Pseudo-tear True-tear

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Medial meniscus: menisco-
capsular injury
Menisco-capsular
injury
Menisco-capsular
recess
•  Fluid SI between
PHMM and
capsule
•  Recessus: fluid SI
doesn’t reach both
meniscal surfaces
Anterior transverse ligament
•  Mimics LM
anterior horn
tear

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Popliteus tendon
•  PT / LM
posterior horn
interface mimic
LM tear
Patella bi/tripartite
•  Typical location SL
pole
•  2% of population
•  D e g e n e r a t i v e
remodelling

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Patella dorsal defect
Patella dorsal defect Chondromalacia 4
grade
•  Subchondral
bone
irregularity
with intact
overlying
cartilage
Courtesy of Dr. D. Zimmermann Stefani
(Radiopaedia.org )
Haematopoetic bone marrow
•  Red bone marrow
mimics edema or
infarction
•  ↑ SI than muscle
on T1-WI
•  Signal drop at
opposed phase
images

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Sources of pitfalls
Technica
l aspects
Normal
variants
Pathology
Flap meniscal tear
normalpericapsular flap
tear
Dandy DJ. The arthroscopic anatomy of symptomatic meniscal lesions. J Bone Joint
Surg Br 1990; 72-B:628-633
•  ~ 6% of
meniscal
tears

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Root meniscal tear
•  Often
associated
with meniscal
extrusion
•  28% of MM
tears
Bin SI et al Radial tears of the posterior horn of the medial
meniscus. Arthroscopy. 2004 Apr. 20(4):373-8.
Chronic ACL tear
•  Fibrotic tissue
mimics ↓ SI of
normal ligament
•  Normal ACL =
layered

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Partial ACL tear
Postoperative ACL
•  Graft made from
harmstring
tendon normally
shows layered
structure
•  Mimics
longitudinal tear

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Iliotibial tract syndrom
•  Frequently
overestimated
Posterolateral corner injuries
•  Frequently
overlooked with
ACL tears

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Fat pad impingement
•  Underestimated
reason of
anterior knee
pain
Take home points
•  Remember what is frequently missed:
•  Menisco-capsular junction injuries
•  ACL tears (multiplanar evaluation!)
•  Posterolateral corner injuries
•  Anterior fat pads impingement
+ Over-diagnosis of medial meniscus tears

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Take home points
•  Technical issues:
•  Check phase encoding direction
•  Choose appropriate fat suppression
technique
•  Remember the magic angle
•  Anatomical issues:
•  carefully assess menisco-capsular junction
Major cause of
MRI mistakes –
lack of
cooperation with
orthopedic
surgeons

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Moscow RIS
RIS installed in February 2015
•  63 out-patient departments
•  CT 61
•  MRI 40
•  > 85000 studies
Second opinion
•  100 consultations per week
•  400 audits per week
•  3320 errors
Teaching
•  124 radiologists
•  97 technicians
www.rpcmr.org.ru

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Conclusions
– Standard imaging protocol
– Correct interpretation (templates,
terminology, classifications)
– Second opinion (PACS, RIS)
– Cooperation with clinicians (MDT)
– Teaching by radiologists and
traumatologists (focus: radiologists
and technicians)
THANK YOU FOR
YOUR KIND ATTENTION!
morozov@rpcmr.org.ru
www.rpcmr.org.ru
itrofimenko@emcmos.ru
www.emc-school.ru

Knee MRI pitfalls

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