MR Orthopedic Imaging

Identify Anatomy Demonstrate technical considerations Perform Artifact reduction techniques Select sequences for orthopedic imaging Demonstrate coil and patient positioning MR Orthopedic Imaging Clinical Indications A noninvasive imaging technique to evaluate: Soft tissue (muscles, tendons and ligaments) Bone Blood vessels Cartilage injury   Ganglion cyst   Ligament tear   Neuroma   Occult fracture   Osteomyelitis   Pain   Evaluate for labral (shoulder) tear   Slap tear (shoulder) Cartilage injury   Ganglion cyst   Ligament tear   Neuroma   Occult fracture   Osteomyelitis   Tumor Evaluate for meniscal tear (knee) Technical Considerations Fat Saturation – Weak   Fat Saturation – Strong   Inversion Recovery (STIR)   Water Excitation   SPAIR   Dixon Fixed Fat Sat flip angle used   Shorter duration of RF Pulse   Fat and bone marrow appear gray   Recommended for orthopedic imaging Optimized Fat Sat flip angle used   Based on TR and number of slices to ensure smallest signal from fat   Longer duration of RF pulse   Fat and bone marrow appear dark STIR Short tau inversion Recovery   TI Inversion Pulse   Advantages More uniform Off-center imaging Presence of metal   Disadvantages Increased SAR Increase minimum TR Possibility of hiding pathology       TI = 180 ms TI = 150 ms Uses a 90 -180 - 90 Degree RF pulsing scheme   Available only on spin echo and gradient echo sequences   Advantages Uniform fat saturation   Disadvantages Increase in TR SPAIR - Spectrally Adiabatic Inversion Recovery Uses an adiabatic frequency selective inversion pulse used to null the fat signal Alternative to the fat saturation methods Only fat spins are affected, so no STIR like contrast   Benefits Robust due to the optimized pulse design Ideal for body regions with high susceptibility differences Fast acquisition time due to its compatibility with iPAT (integrated Parallel Acquisition Techniques) 3T Insensitive to B1 inhomogeneity SPAIR sequences available at 1.5T and 3T Spin Echo Turbo Spin Echo HASTE SPACE VIBE Diff-epi (REVEAL Applications)   SPAIR Options Strong and Weak (For MSK) Two point Dixon Technique VIBE & TSE Sequence   Four contrasts in one measurement In phase Out of phase Water Fat Multi-channel array coils required   Decrease acquisition time   Higher resolution imaging possible with reasonable acquisition time Coil calibration Calculation of 'artificial' echoes Knowledge of the coil sensitivty profiles Array coil elements Coil 1 Coil 2 GRAPPA Recon GRAPPA Recon FFT FFT Full FoV without aliasing FFT & array comb Under-sampled k-space Complete k-space Conventional  TA 4:24 minute PAT x 3 TA 1:43 minute PAT x 2 TA 2:23 minute PAT x 4 TA 1:22 minute MAGNETOM Syphony, MRIDC 8-channel Extremity MEDIC 3D Res 0.3x0.6x2.5mm3 Sequence Considerations Spin Echo (SE) Preferred by some Radiologists   Positives This technique allows for better visualization of smaller structures or smaller pathology   Negatives Could be a very long scan time depending on matrix Spin Echo sequences typically fill one line of k-space at a time until all lines of k-space are filled with data Turbo Spin Echo (TSE) Collects groups of k-space at one time called ETL (echo train length or turbo factor)   This acquisition method fills k-space much faster than conventional spin echo   Positives Faster scan times   Negatives Could over see small abnormalities due to high ETL’s Spin Echo T1 Coronal Turbo Spin Echo T1 Coronal ETL=5, Acq. Time = 4.00 min ETL=7, Acq. Time = 3.00 min     ETL=11, Acq. Time = 2.00 min ETL=15, Acq. Time = 1.20 min Factors that control Echo Spacing Bandwidth   Turbo Factor   RF Pulse Type   Gradient Mode Echo spacing = 21 Echo spacing = 11 Echo spacing = 21 Echo spacing = 11 Chemical Shift VIBE with Water Excitation 3D DESS 3D T1 SPACE Multi-planar Reconstructions   Artifacts Turbo Spin Echo sequences vs. Spin Echo   Increase receiver bandwidth   Swap phase and frequency encoding direction   Metal Reduction Techniques **Metal Implant Disclaimer: The MRI restrictions (if any) of the metal implant must be considered prior to patient undergoing MRI exam. MR imaging of patients with metallic implants brings specific risks. However, certain implants are approved by the governing regulatory bodies to be MR conditional safe. For such implants, the previously mentioned warning may not be applicable. Please contact the implant manufacturer for the specific conditional information. The conditions for MR safety are the responsibility of the implant manufacturer, not of Siemens   Reduces susceptibility artifacts   High bandwidth RF-pulses used to reduce artifacts caused by off-resonance effects occurring in the vicinity of MR conditional implants** **Metal Implant Disclaimer: The MRI restrictions (if any) of the metal implant must be considered prior to patient undergoing MRI exam. MR imaging of patients with metallic implants brings specific risks. However, certain implants are approved by the governing regulatory bodies to be MR conditional safe. For such implants, the previously mentioned warning may not be applicable. Please contact the implant manufacturer for the specific conditional information. The conditions for MR safety are the responsibility of the implant manufacturer, not of Siemens   VAT – View Angle Tilting technique VAT reduces these in-plane distortions (readout direction) by applying additional frequency encoding gradients VAT – 0% = Off VAT – 100% = Max VAT   Tips to reduce blurring High readout bandwidth Thin slices Reduce VAT % Advanced WARP includes Slice Encoding for Metal Artifact Correction (SEMAC)   SEMAC provides through-plane distortion correction by performing an additional phase encoding step in the slice direction   SEMAC is most effective for severe field distortions, for example near large metal structures such as full joint replacement of the hip or knee   SEMAC can only be applied in combination with: View Angle Tilting (VAT) set to 100% Slice Distance of 0% Metal Implant Disclaimer: The MRI restrictions (if any) of the metal implant must be considered prior to patient undergoing MRI exam. MR imaging of patients with metallic implants brings specific risks. However, certain implants are approved by the governing regulatory bodies to be MR conditional safe. For such implants, the previously mentioned warning may not be applicable. Please contact the implant manufacturer for the specific conditional information. The conditions for MR safety are the responsibility of the implant manufacturer, not of Siemens   Since SEMAC increases Signal-to-Noise, a reduction in scan time can be achieved by decreasing the averages, utilizing parallel imaging, or the use of Partial Fourier.   The required number of SEMAC phase-encoding steps depends on the size, shape and material of the implant and may vary from patient to patient.   Joint arthroplasty: 8-12 SEMAC steps are typically recommended. Metals causing stronger artifacts, such as stainless steel or cobalt chromium alloys, require higher SEMAC steps. Titanium implants usually require lower SEMAC values or no SEMAC at all.   SEMAC cannot be used in combination with 3D TSE, BLADE, TimCT, multiple slice groups, or DIXON. Standard TSE VAT SEMAC TSE with correction for inplane motion   Radial k-space filling   BLADE Contrasts TI Inversion Recovery STIR PD TSE T2 TSE Dark Fluid Contrast   Multi-channel coils   Compatible with iPAT   Utilized in any orientation   Applications Head Spine Orthopedics TA:  3:22 Minutes   FoV:  120   Matrix:  256 x 256   Slice Thickness:  3 mm   Without BLADE With BLADE Shoulder MR Exam           Flex Coil   Shoulder Coil (Small/Large) Bones Clavical Humerus Scapula   Ligaments Glenohumeral (inferior, middle, superior) Coracoacromial, coracoclavicular, coracohumeral Transverse humeral   Glenoid Labrum Anterior segment Posterior segment Muscles Bicep and deltoid Infraspinatus, supraspinatus Subscapularis Teres major and minor   Tendons Bicep and deltoid Infraspinatus, supraspinatus Subscapularis Teres minor Rotator cuff Infraspinatus, supraspinatus, teres minor and subscapularis muscles   Bursae   Neurovascular bundle Brachial plexus Cervical nerves (5,6,7,8) First thoracic nerve Axillary artery and vein Subclavian artery   Supraspinatus muscle & tendon Deltoid Muscle Biceps Tendon Coracobrachialis muscle Superior glenoid labrum Inferior glenoid labrum Supraspinatus tendon Humerus Clavical Glenoid / Scapula Inferior glenoid labrum Axial plane displays the supraspinatus muscle and tendon   Align Oblique Coronals parallel with the supraspinatus Humeral head and shaft in profile   Supraspinatus muscle and tendon seen in entirety Elbow MR Exam Bones Humerus Radius Ulna Muscles Flexors Brachialis Biceps brachialis Brachialradialis Extensors Triceps brachii Anconeus Muscles (cont.) Pronation Pronator teres Supination Biceps Supinator Tendons Bicep Triceps Ligaments Ulnar collateral Radial collateral Nerves Median Radial Ulnar Biceps Radial Head Humerus Olecranon Lateral epicondyle Capitulum Biceps tendon tear Very common injury Include the radial tuberosity to evaluate attachment Biceps tendon has different angles. Use the 3-point cursor found in the position toolbar in the Exam Card to better localize this tendon.   Biceps tendon pathology example To visualize Osteochondral defects (OCD) of the radial head or capitellum: Use a 3D DESS Reconstruct a 360 degree MPR Wrist MR Exam Small and Large Flex Matrix Coils Hand and Wrist 16 channel coil Use the below landmarks for proper positioning Do not use carpal tunnel as a landmark for coronal Carpal Tunnel Syndrome Inflammation of the median nerves and/or compression Due to mass, fluid pressure or tendon pathology   Flexor/Extensor Pathologies Tenosynovitis Inflammation of the tendon sheath Tendonitis Inflammation of the tendons   Scapho-Lunate (S-l) ligament   Luno-Triquestral (L-T) ligament   Triangular Fibrocartilage (TFC)   Articular cartilage thinning and defects   Bone Marrow disorders (AVN) Triangular Fibrocartilage (TFC) tears Luno-Triquestral (L-T) Tear Hammate fracture with bone bruising tfc tear tfc tear l-t tear tfc tear tfc tear l-t tear l-t tear Extensors  Flexors hook of hamate fx1 hook of hamate fx1 Hip MR Exam Body Matrix Coil Large Flex Coil Bones Femur Ilium Ischium Pubis Acetabulum Ligaments Capsular Cotyloid Ilio-femoral Teres Transverse Muscles Ilicus Psoas Rectus Gluteous minimus Obturator externus and internus Pyriformis Labrum Articular Cartilage Greater Tuberosity Acetabulum Femoral Head Teres ligament Avascular necrosis   Occult fracture   Ligament injury   Impingement   Acetabular rim syndrome   Tumor STIR Axial T1 Coronal Knee MR Exam     8-Channel Knee coil Knee Tx/Rx 15 Bones Femur, Tibia, Fibula, Patella   Meniscus Medial and Lateral   Ligaments Anterior and Posterior cruciate (ACL and PCL) Accessory ligaments (Humphrey/Wrisbeg) Lateral and Medial collateral ligaments (LCL and MCL) Articular Cartilage Patello-Femoral Femoral condyles   Extendor Mechanism Patello-Femoral Complex Quadriceps Complex   Femur Ant. Cruciate Ligament Post. Cruciate Ligament Tibia Muscle and Tendon tears   Inflammation   Ligament tears   Meniscal changes   Bone bruising   Avascular necrosis   Fracture Straight knee and angle approximately 10-15 degrees with your slices for ACL   Use the axial and/or Coronal for positioning Axial localizer image - Angle medially toward the other knee Right Knee Left Knee Coronal Image Ankle MR Exam 8 channel foot/ankle coil 16 channel foot and ankle coil 8 channel knee coil Knee Tx/Rx 15 Foot flexed at right angle Coronal slices from navicular bone of the foot to plantar fascia   Angle with the malleoli   Achilles tendon gets covered on the Sagittal Sagittal orientation angle with the outer edge of tarsal bone Tendonitis   Achilles tendon rupture   Sinus tarsi syndrome   Tarsal tunnel syndrome   Tarsal collalition   Avascular necrosis   Osteochondral lesions Carpal Bones Navicular (Scaphoid) Lunate Triquetrum Pisiform Greater Multangular (Trapezium) Lesser Multangular (Trapezoid) Capitate Hamate Ligaments Extendor ligaments Flexor ligaments form the carpal tunnel Bones Tibia Fibula Talus (talar dome) Calcaneous Navicular Cuboid Tendons Plantar flexors Dorsiflexors (extensors) Achilles   Ligaments Medial collateral (deltoid) ligament Lateral collateral ligament complex Syndesmotic ligament complex Sinus tarsi   Tibia  Talus Calcaneus Navicular Foot MR Exam 8 channel foot/ankle coil 16 channel foot and ankle coil Knee Tx/Rx 15 The coronal foot and the axial foot is reverse of the ankle.   Sagittal must use a double angle Use the angle of the metatarsal pathology Use flexor hallicus longus tendon or general angle of metatarsals.   Sagital Axial Coronal Long Bone MR Exam Body 6 Body 18 Peripheral Angio 36 Spine 24 Spine 32 Body 6 Body 18     Identify Anatomy Demonstrate technical considerations Perform Artifact reduction techniques Select sequences for orthopedic imaging Demonstrate coil and patient positioning       4-channel Flex Matrix Carpal Bones Navicular (Scaphoid) Lunate Triquetrum Pisiform Greater Multangular (Trapezium) Lesser Multangular (Trapezoid) Capitate Hamate Ligaments Extendor ligaments Flexor ligaments form the carpal tunnel Hamate Triquetrum Scaphoid Radius Ulna Use the below landmarks for proper positioning Do not use carpal tunnel as a landmark for coronal Tuberosity Trapezium Hook of Ham Bones Phalanges (14) Metatarsal bones (5) Cuneforms (3) Navicular Cuboid Talus Calcaneous Tendons Tibialis posterior Flexor digitorum longus Flexor hallucus longus Cuneiform 1 Metatarsals Cuboid Phalanges • Humerus (upper arm) • Ulna and Radius (forearm) • Femur (upper leg) • Tibia and Fibula (lower leg) Humerus