Mri knee

IT IS ABOUT PATIENT PREPARATION,POSITIONINMG,PROTOCOL OF MRI KNEE

1. MRI Procedure of Knee Joint

2. Content Introduction Indi ca tions Patient preparation Procedure MRI Technique MRI Parameters MRI Knee Arthography Extremities MRI, Summary, Refrences

3. I n t r oduction Knee is the largest and one of the most complex joints of the body Bones that contribute to form knee joint are femur, tibia and fibula. Joint between distal femur and proximal tibia Distal end of femur has two large ellipsoid surfaces (medial and lateral condyles) and a deep fossa (intercondylar fossa) between them Proximal end of tibia consist flattened condyle and a crest called intercondylar eminence in the centre

4. PatelTar Tibia S Soleus muscle FIG WIRE 0.88 Sagittal, TI-weighted MRI of knee with anterior cruciate ligament.

5. Indi c a tions Internal derangement of the joint (meniscal tears, cruciate ligament tears & reconstruction) Chondromalacia patella and patella tracking Bony mass, instability, injury, pain Post operative changes

6. E quipme n t's Knee phased array coil/extremity knee coil/pair of small circular coils combined as a phased/multi-coil array/large flexible coil. Surface coils are also used when the knee joint is too large or the patient is unable to extend the knee to fit in a rigid coil. Small (47mm) microscopy coils may also be used at high field for optimum resolution. Immobilization pads. Ear plugs.

7. Patient preparation Explain the procedure to the patient Ask the patient to remove anything containing metal (hearing aids, hairpins, body jewelry, watch, etc.) Ask the patient about metallic implants , pacemaker ,denture etc. If possible ask pt., for previous radiographs Ask the patient to undress and offer hospital gown If there is any suspicion or lack of information on the implant , do not take any risk with the patient safety and do not scan the patient . Finally, have the patient go to the restroom before the exam. As the last line of patient safety, it is also a good practice to scan patient with a handheld metal detector before taking the patient to MR room. Offer the patient ear protectors or ear plugs

8. Patient positioning Supine, feet first, leg extended Affected knee into the coil and immobilized with pads Center the joint in the coil such that the center of the coil corresponds to the lower border of patella 10–15° external rotation to bring lateral femoral condyle parallel to sagittal plane and demonstrate anterior cruciate ligament

9. Please make sure that you give the patient alarm bell to patient and ask them to test it before sending in. After landmarking the center of coil using laser lights or touch sensors, you can send the patient in and start the exam. It is always recommended to let the patient know how long the scan is going to take and also keep communicating frequently to make them as comfortable as possible in the MR bore

10. MRI Knee Coils

11. MRI Technique 10–15° flexion of the knee in order to visualize the anterior cruciate ligament (ACL) better a small cushion under the ankle helps to keep the leg straight space between the knee and coil is filled with cotton to keep the knee motionless Incase of any small palpable mass, vitamin E capsule may be used as marker. The anterior cruciate ligament is delineated best at 15–20° of external rotation, the posterior cruciate ligament at 0° or 5° internal rotation

12. MRI Technique Topogarm Position/Landmark : Inferior part of the patella. Mode of Scanning : 2D. Scout : Three plane localization or Coronal in GRE or T1 Axial Slice Thickness : 1-2 mm for cartilage sequence and 3-4 mm for the rest of sequences. Slice Interval : Nil for cartilage sequence and 0-0.5 mm for the rest of the sequences. In children, comparative images of the two knees may be performed with the knees in the head coil. Secure the knees with cushions, and for the sequences either adjust TR according to the number of slices or run the sequences separately for each side

13. If Contrast Examinati o n Contrast Administration : IV Volume of Contrast : 0.2 mmol/kg body weight, gadolinium based CM, rapid injection followed by 10-20 ml saline flush. Post contrast Sequences : Axial T1, Coronal T1, Sagittal T1.

14. Routine knee Imaging Protocol

15. Knee imaging parameters for a multichannel coil at 1.5 T.

16. Bir Hospital Protocol & Parameters Sequences/Parameters TR(ms) TE(ms) FOV (mm) Matrix size PDW SAG, SPAIR 2400 25 161 256*256 PDW TRA/AXIAL, 2750 SPAIR 25 143 256*256 PDW COR, SPAIR 2400 25 168 160*170 T1 SAG, TSE 462 18 161 160*170 T2 COR, TSE 2500 90 168 256*256

17. Summary parameters for MSK Imaging

18. MSK imaging PD weighted protocols Hybrid PD Sequence Tissues like disk, labrum, cartilage, and fluid are isointense in a standard PD weighted images and hypointense in T2 weighted images (when TE is longer than 50 ms). Longer TE provides better signal differences in pathologic changes such as edema (in traumatic cases), tears, cartilage damage, or other tumoral developments but doesn’t help to differentiate the superficial cartilage and bone. The hybrid sequence has intermediate contrast weighting and provides better differentiation for bone-normal and abnormal cartilage tissues and fluid.

19. P D WI To provide this weighting, slightly longer TE (around 35–40 ms) and ETL (8–9) for PD sequences to create somewhat a hybrid PD contrast with additional T2 weighting. As a result, fluid, abnormal cartilage, and pathological structures appear hyperintense while normal cartilage remains isointense. This type of sequence provides better contrast between soft tissue (e.g., cartilage, disk, and labrum) and fluid.

20. Axial planning Thin slices for patellar tracking problems and to identify chondral damage of the patella and ant. femoral condyles. Slices are from the superior surface of the patella to the tibial tuberosity

21. Plan n ing

22. Coronal Planning Medium slices/gap are suggested from the femoral condyles posteriorly to the patella anteriorly Scan lines are oriented parallel to the posterior surface of the femoral condyles

23. Sagittal planning Thin slice from the lateral to the medial collateral ligament in coronal plane Aligned parallel with the anterior cruciate ligament in axial plane. The superior edge of patella to below tibial tuberosity are included For collateral ligaments, the scan plans run perpendicular to the line joining the posterior femoral condyles

24. S t ead y - s t a t e or driven equilibrium Improved contrast between cartilage and other tissues compared to standard sequences. SSFP (fat suppression or even water-selective excitation where possible) TE/TR/flip = 8/16ms/25 °. 3D-DEFT with fat suppression, TE/TR = 20/300ms, 3 mm thickness.

25. PD Fat Sat Coronal Oblique for ACL Plan the coronal slices on the sagittal plane, angle the position block parallel to the ACL. Check the positioning blocks in other two planes An appropriate angle must be given in coronal plane parallel to medial and lateral condyle of the femur. Slices must be sufficient to cover the ACL The phase directions for these coronal obliques scan should be right to left to avoid pulsation artifacts from the popliteal artery. Applying saturation bands above and below the coronal block will further reduce arterial pulsation artefacts.

26. PD Fat Sat Sagittal Oblique for ACL Plan the sagittal oblique on the axial plane, angle the position block parallel to the ACL An appropriate angles must be given in the coronal plane parallel to the ACL

27. 3D coherent GRE PD/T2* Thin slices with a medium to large number of slice locations and an isotropic dataset are required to view anatomy in any plane. This is especially useful if evaluation of anatomy and pathology is difficult. Sagittal acquisitions large enough to include the entire knee, from above the patella to below the tibial tuberosity, are necessary.

28. Protocols tips The sagittal plane is good for cruciate ligaments and menisci. The coronal plane is better for detached meniscal fragments, meniscocapsular separation, and collateral ligaments. The patellofemoral joint is best assessed in the axial plane. T1–W images are useful for meniscal and ligamentous imaging. T2–W images are useful for anterior cruciate ligament tears if T1 images are indeterminate or if fluid is present. PD-weighted images are useful for meniscal tears Fat suppression used to eliminate the bright fat signal to increase conspicuity of bone marrow, meniscus, and cartilage. Contrast enhancement is helpful in bone tumors to define location, and to determine the nature of the tumor and its suitability for biopsy.

29. MRI Knee Arthography It’s an MRI examination followed by the intraarticular injection of CM to demonstrate the joint cavity Indications : - Investigation for loose body, torn meniscus, injury of anterior cruciate ligament, or when non-contrast imaging was inconclusive. Patient Positioning : Supine with feet first, foot rotated externally by 150. Topogarm Position/Landmark : Inferior part of patella. Scout : 3 plane localizer if available or T1 axial. Slice Thickness : 3-4 mm. Slice Interval : Nil. Scan Range : Include the region of the meniscus and the synovial cavity.

30. MRI Knee Art h r og r ap h y Contrast Administration : Intraarticular. Volume of Contrast : 30 to 40 ml of 1% solution of Gd- DTPA diluted with saline. Pulse Sequence : Postcontrast T1 with fat suppression in the Axial, Sagittal and Coronal plane. Comments During positioning, put a small cushion under the ankle which helps to keep the leg straight. Fill the space between the knee and the coil with cotton to keep the knee motionless. After injection of the Gd solution in to the knee joint cavity, mild knee exercise is performed 20-30 min to ensure the uniform distribution of the intraarticular contrast and also forces it in to the tears.

31. MRI Knee Arth r og r ap h y protocols T1-weighted, fat-saturated or GRE, fat-saturated (SAG) T1-weighted, fat-saturated (COR) T1-weighted, fat-saturated (AXIAL) STIR or T2-weighted, fat-saturated (COR)

32. Advanced appli ca tions 1. P h y siolo g i c al Loading Investigation of articular cartilage changes (volume, thickness, and signal intensity) following axial compression is of particular interest. Scans are performed prior to and immediately following the application of a physiologically relevant load. This can be accomplished by means of strenuous exercise undertaken outside the magnet or involve the use of MR- compatible devices for in situ compression, permitting a more controlled investigation.

33. Some open systems, including small bore magnets designed for orthopedic imaging permit dynamic imaging of joints. In the knee this is particularly useful for visualizing patellar tracking but may also be used to image other structures during movement. Dynamic Imaging

34. Delayed Contrast and T 1 Mapping Contrast may be administered and a few hours later the gadolinium penetration into the cartilage can be used to assess glycosaminoglycan content. Several different inversion recovery sequences may be acquired to enable pixel-by-pixel T 1 maps to be calculated demonstrating faster wash-out in diseased cartilage.

35. High Field MRI The extra signal-to-noise advantage of high-field MRI is particularly beneficial to orthopedic work for improving the available image detail. Modern scanners can now produce excellent knee images, with in-plane resolutions down to a 200mm, able to show microtears in ligaments. Trabecular bone, with individual diameters between 50–200 mm is also readily observed at higher field. High-resolution imaging may soon have a role in assisting cellular implantation as treatment for early degeneration of cartilage.

36. ISMRM 2017, Siemens, Magn e t om Teraa, 7 T Fat -saturated sagittal knee image of Enchondroma, acquired with T2 TSE (Turbo spin echo) sequence.

37. Magnetic resonance imaging of the knee at 3 and 7 Tesla: a comparison using dedicated 28 multi-channel coils and optimised 2D and 3D protocols with 8 channel coils

38. Extremities MRI

39. ECR 2018, Samsung, Extremities MRI

40. Samsung is had presented a prototype of Extremity MRI, which is expected to be a game changer in the industry. It is designed to improve not only cost and space efficiency but also patient convenience, as it reduces the need for the whole body to be in the MRI device to scan extremity areas such as arms and legs.

41. Summary Magnetic resonance imaging represents a standard tool in knee evaluation with a high specificity and sensitivity in diagnosing meniscal tears. However, in order to avoid errors of interpretations and pitfalls, there are several factors that should be taken into consideration. The technical platform and the sequence parameters, the awareness of the normal meniscal anatomy, and the knowledge of the patterns of the tears may influence the accuracy of diagnosis. An accurate and a complete description of meniscal tears is important and influences treatment planning.