Knee MRI pitfalls

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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

1.5-3.0T A,E B

0.5-1.0T 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%

male female

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

00,10,20,30,40,50,60,70,80,91

0 0,2 0,4 0,6 0,8 1

A B C D E

Lateral meniscus

00,10,20,30,40,50,60,70,80,91

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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0,870,78

0,670,87

0,77

0 0,5 1 1,5

Sensitivity

A

B

C

D

E 0,760,38

0,790,85

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

0,470,33

0,600,64

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

0,890,94

0,920,89

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 E0,750,86

1,000,75

1,00

0 0,2 0,4 0,6 0,8 1 1,2

0,470,82

0,770,49

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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Incomplete MRI protocol


Flow artifacts

A>>P

•  The same shape

as popliteal

vessels

•  Strongly

depends on

phase encoding

direction H>>F

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Flow artifacts • Solution 1 = change phase-encoding direction

frequency-encoding

phas

e-en

codi

ng

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

B0

550

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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

normal pericapsular 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!

[email protected]

www.rpcmr.org.ru

[email protected] www.emc-school.ru

Knee MRI pitfalls

Health & Medicine

Transcript of Knee MRI pitfalls