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Musculoskeletal MRI: Tips and Tricks UCSD MRI Review 2001

Musculoskeletal MRI: Tips and Tricks UCSD MRI Review 2001. Siemens Vision Picker Polaris (2) Picker HPQ Vista. Philips NT Hitachi Aires II (2) GE LX. Steven S. Eilenberg, MD Director of MRI North County Radiology. Topics. Some Technical Considerations Special Help with Low Field MRI

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Musculoskeletal MRI: Tips and Tricks UCSD MRI Review 2001

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  1. Musculoskeletal MRI: Tips and TricksUCSD MRI Review 2001

  2. Siemens Vision Picker Polaris (2) Picker HPQ Vista Philips NT Hitachi Aires II (2) GE LX Steven S. Eilenberg, MDDirector of MRINorth County Radiology

  3. Topics • Some Technical Considerations • Special Help with Low Field MRI • Problems and Solutions • Interpretation and Reporting

  4. Getting the Most from this Talk • Be Open Minded to Change • Remember that You are used to your Images and Reports • There is More than One Right Way • (But There Are Definite Wrong Ways) • Guaranteed Improvement • Look for the Asterisk*

  5. The Guarantee • Follow Any Tip Or Suggestion(*) • See Measurable Improvement • mrirad@yahoo.com • Additional Help • Artifact Detective • Protocols • Complaints

  6. The Essentials • Sponges • Pads • Stock and Non-stock* • Tape & More Tape • Velcro • Sandbags* • Bore Conditions • Temperature, Light, Fan, etc.

  7. Optimize Your MR Unit • Review QA Program - Review QA Log • Review Service Logs • When Was Last Supercon Shim? • Periodically Clean Table/ Bore • Inspect Coils and Cables • Walk Around and Through MR Center

  8. Optimal Patient Preparation* • Wigs, Belts, Shoes, Bras • Image Distortion • Magnetic Inhomogeneity • Low SNR • Comfort • Sound/ Video Systems • Special Pad/ Pillows, etc.

  9. Excellent Set-Up Pays • Comfort First • Approximate Anatomic Positioning • Splints, Positioning Aids • Imaged Area Close to Isocenter as Possible * • Instruct Techs on Landmarks • e.g., Widest Part of Patella at Center Knee Coil

  10. All Of You Should Know… • What the Alphanumerics Mean • Are Your Techniques Current? • Have You Tried New Enhancements such as ZIP, TRF (GE Users) • Do You Use/Like Each Sequence? • Have You Optimized? (Ex: Dropped FOV) • Is Each Sequence Worth the Time?

  11. Protocols: Imported vs. Domestic • Cannot Import Protocols Wholesale from One Vendor to Another • Import Your Scan Philosophy • Learn What Each Unit Does Well and Exploit It • Differences Between Same Units: • Homogeneity Differences • Set-Up Differences • Consider Hiring Radiologist Consultant

  12. Musculoskeletal-General • Joints: Image In Three Or More Planes • Uniform Anatomical Landmarks • Non Joint: Image In At Least Two Planes • Axials Usually the Money Images. Spend Time on These & Obtain Them Early • Cover Entire Abnormality • Consider Fast -STIR Scout to Estimate Coverage • Include a Joint for Point of Reference

  13. Use the Smallest Coil You Can Get Away With* • Can Start Exam with Larger Coil and Switch, prn • Be Sure Pathology is Completely Covered • Smallest Coil Especially Crucial at Low Field

  14. Establishing Protocols • Try to Visualize Anatomy and Pathology • Use Localizer Well • Consider Sequence Progression Carefully • Ankle: Use Axial to Create True Cor & Sag • Identify “Money Plane” • Do Relatively Early • Make These Exquisite!

  15. No Formulas Needed • (CNR & SNR & Resolution) Time / Profit • SNR Is Proportional To: • Slice Thickness • Pixel Size • Square Root Of NEX • Divided By Noise

  16. What Does This Mean? • Big Gain in SNR with • Increase Slice Thickness • Increase Pixel Size • Decrease Phase Steps • Increase in FOV • Much Smaller Gain in SNR with • Increasing NEX

  17. Boosting SNR-Other Options • Better Coil • Multichannel Quadrature (Phased Array) • Better Patient Preparation • Decrease Noise Part of Equation • Better Sequence Selection • Consider Narrow Bandwidth Sequences* • 50% BW Decrease Gives 40% More SNR

  18. Narrow Bandwidth Option • All Manufacturers Have This Option • All Call It Something Else • Ex. Philips: High or Low Fat Water Shift • Cost? • May Lose Several Slices • May Obligate Increased TR • Greater Chemical Shift Artifact • Increased Motion Artifact

  19. Problems I Have Observed, Created or Overcome

  20. Problem # 1 • Too Many Protocols per Body Part • Too Many Radiologists (Cooks) Creating Protocols • “I don’t care what he wanted! When I am on, this is what you will do…”

  21. Solution * • Designate a “Protocol Chief” • Establish Protocol Consensus • Better and More Consistent Quality • Fewer Callbacks • Happier Referrers • Happier Technologist

  22. Problem #2 • Too Many Images & Films • Decreases Productivity / Profitability • Fatigues Patient And Tech • Motion and Negative Experience at Center • Overwhelms Reader • Increases Miss Rate • Less is More

  23. Solution • Fewer Images Per Sequence • Make Each Sequence Count • Do Important Sequences Early • Gives Tech Time to Repeat if Motion

  24. Problem # 3 • Poor Positioning • Examination usually Downhill from there • Anatomy and Pathology Looks Alien • Images Will Not Correspond to Anatomic Atlases

  25. Solution • Spend More Time on Setup • Consider Sandbags* • Landmark • Isocenter, if Possible • Progress Logically from One Sequence to Next • Make Every Plane True Anatomical Orthogonal*

  26. Problem # 4 • Imaging Left and Right Joint Simultaneously • For Comparison • To Save Time, If Both Are To Be Imaged • Obligates • Larger FOV • Suboptimal Patient Positioning • Off Center Imaging

  27. Solution • Image Only One Side at a Time* • Use an Atlas*, Not the Other Side • Now You Can: • Use Smallest FOV • Use Smallest Coil • Optimize Patient Positioning • Use Isocenter, if Possible

  28. Problem # 5 • Double Echo FSE For All Long TR Sequences • Suboptimal SNR, CNR, BW (Image Quality) • Time Penalty • May Be Twice as Long as Single Echo • Less Flexibility of Scan Parameters • Do You Need Both Echoes?

  29. Solution • Hand Craft Each Sequence to Maximize* • CNR, SNR, Scan Parameters • Example: • Replace: Double Echo FSE 3000/20,110 • With: • High Resolution T1, or PD • FSE PD With Fat Saturation And MTC • Big Payoff!

  30. My Favorite MSK Sequence* • Fast Spin Echo • TE Low to Intermediate, 15-60msec, prn • TR in T2 Range of 1700-3000msec, prn • Shim, then Fat Saturation • Picker Users can Change % Of Fat Sat • Some Systems may Benefit from MTC • Window for Cartilage/ Fluid Interface

  31. Fat-Sat MSK Sequence Can Be a Double Edged Sword • Increase CNR with Overall Dec. SNR • Artifacts • Poor, or Regional Fat Sat • Accidental Water Sat Can Hide True Pathology • Artifactual Pathology • Ugliness Factor • Especially if use with Long TE Sequences • Clinician Acceptance can be a Problem

  32. How To Maximize Fat Saturation Success • Patient Preparation • Use Smallest Coil - Fill Coil • Isocenter • Volume Shim • Consider the Anatomy • May need Imaging Aid (e.g. Saline Bag) • Keep Non Fat Sat T2 or STIR in Reserve

  33. Problem # 7 • Poor Meniscal Windows • Meniscal Windows are Not Universally Used • Typical Problem: Too Narrow of a Window • May Spuriously Create “Grade III Signal”

  34. Solution • If Windowed Correctly, May Not Need Meniscal Windows • Instruct Technologist on Meniscal Windows Aand Create Hard Copy Example • If Possible, Soft Read Your MRI’s and Window Them on the Fly*

  35. Problem # 8 • Lack of Adequate Patient History • Reading in a Vacuum • May Not Protocol Correctly • May Not Address Specific Question

  36. Solution • Evaluate Patient Scheduling Procedure • Re-Evaluate Patient Intake Form • Insist on a “Clinical Question to Answer” • Try to get Op Reports, Prior Studies, X-rays

  37. Coaxing Good Images From Low Field Open MR

  38. Low Field Open MRI Truisms Image Quality Not that of High Field May Take Months to Get “Good Images” Don’t Cut Corners with Regard to Time* Beware of Magic Angle Artifact Low Field Technologist Personalities*

  39. Who Is The Right Technologist? • Welcomes the Challenge • Excellent with Patients • Puts Time in for Set-up and Prep • Does Not Complain about Examination Length • Important Tip: Monitor Sequence Times* • Decrease time=Fall in Image Quality

  40. Low Field Tips • Generally, Stay Away from Double Echo Sequences (Do PD and T2 Separately) • Avoid Rectangular FOVs and Less than Full Scans (Avoid Half Fourier Technique)* • With FSE, Increase TR More than Needed, Especially with Longer Echo Trains

  41. Echo Train Versus TR • ETL 6 - 3500 • ETL 8 - 4000 • ETL 10- 4500 • Doing This Increases SNR and Improves Image Quality!

  42. Post Processing • Experiment. Images should be Post Processed (but not look It) • Have Techs Produce Examples. Post Process until it Looks “Post Processed”, Then Back it Down a Notch*. • Best Chance to Have Images Resemble High Field • Increases Referring Physician Confidence

  43. Post Processing Tips • Be Critical. Images Should Not Look Painterly* • Filtering and Edge Enhancement are Two Different Techniques • Avoid Edge Enhancement: • T1’s and STIR’s* • Acquire without Edge Enhancement-Can Add Later

  44. Low Field Tips • Be Critical of Using Sat Pulses • If of No Use, Remove • Each Slab Reduces Overall SNR • Use Smallest Coil Possible* • Coils Are Not to Touch Skin • Isocenter, Isocenter, Isocenter* • Comfort, and Sandbag*

  45. My Favorite Low Field, Fat Suppressed T2ish Sequence • Fast STIR with Shortened TI • TI Time Of 80 msec Blackens Fat • TI Of 60 msec Darkens Fat* • Image More Pleasing to Most Eyes • Still Have Good Cartilage and Marrow Pathology Info • Also Works at High Field • Drop TI By 20-30 msec At 1.5 Or 1.0 T

  46. Survey of Referring Docs (The Film) • What Do You Find Most Annoying? • “Too Many Sequences that I Can’t Relate to or Understand” (ex. STIR, Fat Sat T2) • “No Localizers To Guide Me” • Left and Right Side Markers Not Obvious • Motion Artifacts with Statement that “Perhaps Patient Could Return…” More Work for Dr and Office • Difficulty Getting Hardcopy

  47. Survey of Referring Docs (The Report) • Reports that are Too Long/Detailed • Some Rads Hide Behind Descriptions • Reports that are Noncommittal • Reports that Don’t Address Question

  48. Survey of Referring Docs (The Report) • Reports that Regularly Raise More Questions than are Answered • Reports that Regularly Recommend Additional Imaging Studies • Impressions not Matching the Body or Not Ordered by Importance

  49. MRI –Interpretation • Try to get Op/Arthroscopy Report • Try to get Prior Imaging Studies for Comparison • Look at Prior Imaging Studies, If Available • Enhances General Radiology Skill • Minimizes “Looking Silly” • May Otherwise Miss: • Joint Bodies, Some Fractures, and Dystrophic Ca++

  50. When Reading, Be Systematic • Use Same Search Process for each Examination • Don’t be Blindsided by Big Findings • Look at Every Structure in Every Plane • E.g.,Menisci, Collateral and Cruciate Ligaments on Coronal, Sagittal and Axials

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