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

1. 3D sequence MRI in the assessment of meniscofemoral and ligament lesions of the knee MA.Chaabouni,A.Daghfous, A.BenOthman,L.RezguiMarhoul Radiologydepartement Trauma center, Tunisia MK9

2. Magneticresonanceimaging (MRI) is sensitive and specific in the diagnosis of internal derangements of the knee . • The fast spin-echo (SE) intermediate-weightedsequence widelyused to evaluate ligaments, tendons, and fibrocartilage owing to its favorable contrast and signal-to-noise ratio . • Multiplanarimaging or 3D sequence, whichusuallytakes longer, is often used for knee MR imaging because of the necessary assessment of complexmusculoskeletal structures. • Volumetricimagingalso offers an opportunity to reduce the imaging time by allowing multiplanar reformations. INTRODUCTION

3. Our objective is to determinewhether 3D sequences canimprove the diagnostic performance of a routine MR protocol for detectingmeniscal and ligament lesion of the knee.

4. Retrospectivestudy : 56 patients whohadknee MRI 1,5 Tesla for suspectedmeniscal and/or ligament lesions. • Twoyears: donebetween January2010 and December 2011. • Our protocoluncludesconventional sequences (coronal, sagittal and axial Proton DensityFast-Spin Echo and sagittal T 1) and systematicsequence 3D thin sections. • We propose it as the basis for the analysis of meniscal and ligament lesions. MATERIALS AND METHODS

5. All meniscal and ligament tears was shown equally well with 2D and 3D sequences. • The 3D sequenceallows a more preciseanalysis of these lesions. • Of the 56 cases studied by MR imaging,14 were normal,24 hadmeniscaltears,15 had ACL tears and 3 had PCL tears. • Nine of the menisciwere longitudinal tears, 6 vertical tears , 4 radial tears, 3 complextears and 2 sealcovetears. RESULTS

6. a b Fig.1: A 34 -year-oldfemale patient with PCL tear ( ) of the right knee Sagittal images obtainedwith 2D FSE (a) and 3D sequences (b) at 1,5T

7. b a Fig.2:A 38-year-old male patient with a complex tear of the medialmeniscusposteriorhorn. ( )Sagittal images obtainedwith2D (a) and 3D sequences (b) at 1,5 T.Axial images obtainedwith 2D (c) and 3D FSE sequences (d) at 1,5T. c d

8. b a d c Fig.3:A 45-year-old male patient with a longitudinal tear of the medialmeniscusposterior horn. Sagittal and axial images obtainedwith2D (a,c) and 3D FSE sequences (b,d )at 1,5T. The tearis not visualised on the axial 2D FSE sequence but wellvisualised on 3D

9. a c Fig.4: A 21 -year-oldfemale patient with a seal cove tear of the medialmeniscusposteriorhorn ( )Coronal and sagittal images obtainedwith2D (a,c) and 3D FSE sequences (b,d) at 1,5T. d b

10. a b Fig.5: A 27-year-old male patient with ACL tear of the leftknee.Sagittal images obtainedwith 2D (a) and 3D FSE sequences (b) at 1,5T.

11. The described 3D isotropicfast SE intermediateweighted MR sequenceenablesthin-section data acquisition without intersection gaps and multiplanar image reformation in standard and nonstandardplanes that may be helpful for the detection and analysis of complex structures. • The 3D Fourier transform acquisition is conceptually attractive for musculoskeletalMR imaging because it facilitates image reformation in complex oblique planes after image acquisition. . DISCUSSION

12. 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.

13. In our serie, both the 2D and the 3D sequences provided subjectively high-quality images with comparable anatomicdetail. 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 .

14. 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.

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

16. 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 meniscaltears, it yields accuracy that is not significantly different from the accuracy of 2D fast SE MR imaging . CONCLUSION