Eric Lévêque, Benoit Hainaux, HOW I DO IT ? KNEE IMAGING Eric Lévêque, Benoit Hainaux, Nathalie Chemla M.D Paris V Clinic, France
COIL Dedicated 8 channels phased array Or flex coil type Closer to B0 center for a better FAT SAT Use flex coil type with positioning system Put the coil in the middle of B0, the opposite leg against the tunnel
PATIENT POSITION Lying on his back Slightly flexed by an angle of 15° External rotation of the lower limb by an angle of 10/15° Mustn’t contract thigh and move foot to clear the ACL (Anterior cruciate ligament) from the intercondylar notch (Blumensaat line) to verticalize ACL, maintained with sand bag Mustn’t move the entire body (domino effect)
SLICES POSITION Sagittal : Internal rotation by 5° compared with the transcondylar line. Overflow of 2 or 3 slices in external to cover the head of fibula and femoral biceps Coronal : Parallel to the bi-condylar plane. Cover menisci forward and head of fibula and biceps femoris muscle backward Strict axial from the top of the patella to the anterior tibial tuberosity fb
CRITERIA OF SUCCESS fb pm ACL cleared from the blumensaat line on sagittal plane and verticalized on coronal plane Insertion of biceps femoris and popliteus muscle on posterior coronal slices Cover menisci in coronal plane From top of patella to att fb pm
KNEE IMAGING MRI accurate non invasive technique Used to asses internal derangement of knee 2 principals methods Current conventional two dimensonial (2D) MR imaging More recenntly, three dimensional (3D) Isotropic MR (CUBE).
WHAT IS CUBE? 3D Séquence FastSpin écho Isotropic Multi-contrast ( T1, PD, T2, FLAIR ) With or without Fat Sat
WHY DO WE USE CUBE? GOAL: easy to use on knee MRI THREE IMPORTANT CONDITIONS: Total time < 3 DP FS sequences Same contrast as 2D (méniscus, ligaments, bone marrow and cartilages ) Quality of reformat as good even better than 2D
MRI OF KNEE Time consuming Thick sections Small gaps between sections 2D MR ISOTROPIC 3D MR Time consuming Thick sections Small gaps between sections Partial volume artifacts 3 planes,sagittal, axial and coronal Thin section data acquisition Without intersection gap Imagis reformatted in arbitrary planes Helpfull in analysis of complex structures DP FAT SAT ET FAST SPIN ECHO
2D versus 3D MRI DP FAT SAT Non isotropics pixels. 2D protocol 3D protocol Time 2D three planes= 3mn07 +2mn+2mn + 20s of pré scanning for each séquence (60s) DP FAT SAT Non isotropics pixels. Multiplanar reformat not possible. Gap between slice is bad for good visualization of cartilage defects. Time 3D cube=6’30 +/- 30s + 20s of pré scanning (less time to permorf study of all knee) Isotropic pixel Fast Spin Echo Multi contrast T1, T2, DP, T2 FLAIR With or without FAt SAT
CORONAL, SAGITTAL AND AXIAL REFORMATS OBTAINED AFTER 3D CUBE ACQUISITION
CUBE APPLIED TO PATHOLOGY CARTILAGINOUS DEFECT MENISCAL TEARS ACL EXPLORATION OTHERS….
T2 MAPPING
CUBE AND PATHOLOGY ARTHRO CT CARTILAGINOUS DEFECT
CARTILAGINOUS DEFECT 2D 3D REFORMAT 0,5 mm
MENISCAL TEAR AND CARTILAGINOUS LESION
BUCKET HANDLE MENISCAL LESION Cobra sign 3D REFORMAT
2D/3D
ACL : 2 distincts ligaments AM Ligament FOR A LONG TIME WE HAVE THINK THAT acl is unic ligament Yellow star red star Now we know that it is in fact done of two groups of fibers PL Ligament
« d play with track ball 3D CUBE ACQUISITION
3D MRI MULTIPLANAR REFORMAT Than you can give to the surgeon good slice in the plane of ligament
PARTIAL TEAR OF ACL
MR ARTHROGRAPHY SAGITTAL FST1 SAGITTAL FAT SAT FST1
3D CUBE MRI First developped to improve cartilage analysis because good contrast betwween joint fluid (hyper T2) and cartilage (intermediar signal) and gap between slice in 2D acquisition not good for good visualization of cartilage defects. Than proved superiority in analysis of ligaments and meniscus Princial hardware: motion artifact
CONCLUSION Favorable tissue contrast of isotropic 3D fast SE in the assessment of ligaments, menisci, and cartilage yields high sensitivity and specificity that seems tu us better with those yielded by conventional 2D fast SE MR imaging