3D sequence MRI in the - PowerPoint Presentation

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3D sequence MRI in the assessment of meniscofemoral and ligament lesions of the knee

MA.Chaabouni,A.Daghfous, A.Ben Othman,L.Rezgui Marhoul

Radiology departementTrauma center, Tunisia

MK9

INTRODUCTIONMagnetic resonance imaging

(MRI) is sensitive and specific in the diagnosis of internal derangements of the knee . The fast spin-echo (SE)

intermediate-weighted

sequence

widely

used to evaluate ligaments, tendons, and

fibrocartilage

owing to its favorable contrast

and signal-to-noise ratio .

Multiplanar

imaging

or 3D

sequence

,

which

usually

takes longer, is often used for knee MR imaging because of the necessary assessment

of

complex

musculoskeletal

structures.

Volumetric

imaging

also offers an opportunity to reduce the

imaging time by allowing

multiplanar

reformations.

Our objective is to determine whether 3D sequences can

improve the diagnostic performance of a routine MR protocol for detecting

meniscal and ligament lesion

of the

knee

.

MATERIALS AND METHODS Retrospective study

: 56 patients who had knee MRI 1,5 Tesla for

suspected meniscal and/or ligament

lesions

.

Two

years

:

done

between

January2010 and

December

2011.

Our

protocol

uncludes

conventional

sequences (coronal, sagittal and axial Proton

Density

Fast

-Spin Echo and sagittal T 1) and

systematic

sequence

3D

thin

sections.

We

propose

it

as the basis for the

analysis

of

meniscal

and

ligament

lesions

.

RESULTS All meniscal and ligament tears was shown equally well with 2D and 3D sequences.

The 3D sequence allows a more

precise analysis of

these

lesions

.

Of the 56 cases

studied

by MR

imaging

,14

were

normal,24

had

meniscal

tears

,15

had

ACL

tears

and 3

had

PCL

tears

.

Nine

of the

menisci

were

longitudinal

tears

, 6 vertical

tears

, 4 radial

tears

, 3

complex

tears

and 2

seal

cove

tears

.

Fig.1: A 34 -year-old female

patient with PCL tear ( ) of the right knee

Sagittal images

obtained

with

2D FSE (a) and 3D sequences (b) at 1,5T

a

b

Fig.2:A 38-year-old

male patient with a complex tear of the medial meniscus

posterior

horn

. ( )

Sagittal images

obtained

with

2D (a) and 3D sequences

(b) at 1,5 T.

Axial images

obtained

with

2D (c) and 3D FSE sequences (d) at 1,5T.

a

b

c

d

a

b

c

d

Fig.3:A 45-

year

-

old

male patient

with a longitudinal tear of the

medial

meniscus

posterior

horn

.

Sagittal and axial images

obtained

with

2D (

a,c

) and 3D FSE sequences

(

b,d

)at 1,5T. The tear

is not

visualised on the axial 2D FSE sequence

but

well

visualised

on 3D

Fig.4: A 21 -year-old female patient

with a seal cove tear of the medial meniscus

posterior horn

( )

Coronal and sagittal images

obtained

with

2D (

a,c

) and 3D FSE sequences

(

b,d

) at 1,5T.

a

b

c

d

Fig.5: A 27-year-old male patient with

ACL tear of the left knee

.Sagittal images

obtained

with

2D (a) and 3D FSE sequences (b) at 1,5T.

a

b

DISCUSSIONThe described 3D isotropic

fast SE intermediate weighted MR

sequence enables

thin-section data acquisition without intersection

gaps and

multiplanar

image reformation in standard and

nonstandard

planes that may be helpful for the

detection and analysis of complex structures.

The 3D Fourier transform acquisition is

conceptually

attractive for

musculoskeletal

MR imaging because it facilitates image reformation in

complex oblique planes

after image acquisition.

.

Duc et al (28) reported 3D isovoxel true fast Imaging with steady-state precession to have sensitivities, specificities, and accuracies of 80%, 95%, and 90%,respectively, for the diagnosis of ACL tears; 100%, 82% and 90%, respectively, for the diagnosis of MM tears; and 83%, 83%, and 83%, respectively for the diagnosis of LM tears.

While image quality consistently scored lower with the 3D compared with the 2D FSE sequences, the diagnostic performance was similar, though radiologists felt more confident diagnosing abnormalities with the 2D sequences.

In our serie, both the 2D and the 3D sequences provided subjectively high-quality images with comparable anatomic detail

. All meniscal and ligament tears was shown equally well with both techniques.

John and all showed that for meniscal tears, the superior sensitivity of the 3D sequence became evident .

The thinner slice thickness and resultant dimunition in volume-averaging may have been responsible for this observation, especially in the case of small tears. However, the Heightened sensitivity to intrameniscal signal afforded by the 3D technique also contributes to its decreased specificity relative to SE imaging.

Because a greater volume of signal could be identified within the meniscus, it often became more difficult to determine whether the abnormality communicated with the meniscal surface, thus differentiating internal degeneration

from actual tear

. Long scan times have limited the clinical utility of 3D spin- echo imaging implementations.

CONCLUSION Although the fact that 3D isotropic fast SE intermediate-weighted MR imaging of the knee is a real plus for the analysis of cruciate ligament and

meniscal tears, it yields accuracy that is not significantly different from the accuracy of 2D fast SE MR imaging .