MRI MSK 1 Flashcards by Lauren Knight

Why is MRI good for MSK?

Great detail
Very sensitive to disease and trauma
joints don’t move

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What are the common sequences for MSK MR?

T1 : SE, FSE/TSE
T2 : FSE/TSE
PD: FSE/TSE
Fat saturation : (STIR, fatsat, Dixon) (T1, T2 or PD)
Volume scans - isotopic

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What changes may you see in a T1 weighted Joint?

Synovial fluid
Blood products
Effusion
Reactive changes

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What are the technical factors of T1 weighted images?

~ fluid demonstrates as low signal
~ inherently high SNR
~ can use smaller FOV
~ higher matrix resolution
~ ideally true spin echo contrast

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What is T1 good for looking at MSK?

Trabeculae patterns
Good contrast between bone and soft tissue

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What are the technical factors of T2 weighted images?

fluid demonstrated as high signal
demonstrates pathology well
Higher SNR
FSE/TSE used for T2 or PD weighting usually t1 in MSK imaging

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What are the methods of fat saturation? And how do they achieve this?

STIR and chemical fat sat

STIR = (Short T1 inversion recovery) suppressed by time inversion sequence

Chemical FS = fat suppression by radio frequency, pulse centred on fat peak.

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Why is it needed to suppress fat?

To suppress the signal from medullary fat
To demonstrate choncral cartilage defects
To demonstrate oedema/ bone bruising (as high signal).

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Why is MRI useful in the pelvis?

Ruling out occult fractures - NOF, pubic rami, sacrum etc
Tendon injuries, bursitis, or, neoplasms, infection

Often after inconclusive X-ray

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What is the common sequence for an MSK pelvis?

Coronal / axial T1 and STIR

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What is involved with an ankle MRI?

Chimney dedicated coil - foot an ankle

Foot and leg at 90 degreees

Limited rotation for joint

Use immobilisation pads

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What is the sagittal positioning for an ankle MRI?
Why do we use sagittal?

Sagittal perpendicular to joint
Better demonstration of ligaments
Cover laterally to demonstrate ligaments
Use coronal to ensure perpendicular to tibia.

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What is the coronal positioning for an ankle MRI?

Coronal - perpendicular to talus through the malleoli

Cover front to back to include Achilles and anterior tendons

Use sagittal scan to ensure perpendicular to tibia

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What is the positioning or an axial ankle MRI?

Axial - perpendicular to tibia parallel to talus joint

Use sag and cor to plan slices

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What does the axial PD fat sat demonstrate around the tendons or ligaments?

High signal in pathology

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What does oCD stand for?

Osteochondritis dissecans

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What causes OCD?

Original inversion injury
- Compressor force
- Bone is less elastic than cartilage
- Bone fracture without Chondral fracture
- Healing dependent on overlying cartilage (stages 1-4)

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Where and who does oCD mainly affect?

Elbow and knee

Men more than women Moore in adolescence

What are the problems associated with osteochondral defects form an inversion injury?

Can be hard to clinically diagnose

May become necrotic

Can develop into a loose body

What are the goals of imaging for Osteochondral defects?

To detect, localise and classify prior to treatment

What is stage 1 OCD?

Compression fracture

What is stage 2 OCD?

Partially avulsed

What is stage 3 OCD?

Avulsed but un-displaced

Cortical fragments separated by intermediate signal intensity, material from the concave, bony defect beneath it .

What is stage 4 OCD?

Displaced osteochondral fragment - crater develops beneath thee fragment

What is involved with scanning the Achilles tendon?

The ankle coil, extremity coil, head coil or torso coil may be used Positioning : neutral position in plantar flexion, otherwise gaps due to rupture maybe missed.

Where is the insertion of the Achilles tendon?

High into the calf muscle The water shed is 2-4 cm above the insertion

What are the clinical indications for shoulder MRI?

- Pain - Restricted movement - Recurrent dislocations

What is the positioning for shoulder MRI?

Pt supine Shoulder externally rotated - extends tendon to assist in detecting pathology Avoid hand over abdo - keep hand still Immobilised strap arm down Shoulder off centre for optimism fat sat

What is the planning positioning for shoulder MRI?

Axial positioning Cover from AC joint to sub glenoid labrum 4mm slice and 1mm gap Used as a localiser for coronal and sag obliques

What is the planning for coronal obl for shoulder MRI?

Coverage of joint capsule 3mm slice and 1 mm gap Perpendicular to glenoid

What are the sequences for MRI shoulder? And what are their benefits?

T1 SE - Coronal obl = Excellent, anatomical view of the muscles and ligaments of the shoulder = Effusion and pathology demonstrated as low signal . T1 SE - sag obl = used to assess the degree of impingement of the supraspinatous muscle by the AC joint = Demonstrates bone, bruising

What is the planning for Saggital obl MRI shoulder?

3mm slice and 1 mm gap Parallel with glenoid Perpendicular to coronal

What is the clinical presentation of rotator cuff tear?

* painful movement in all directions * restriction on abduction and flexion * acute pain * history of trauma or overuse * problems with ADL

What is impingement syndrome in the shoulder?

- degeneration of tendon - Swelling - impingement against the chromium and coracoacromial ligament - Spur formation - Supraspinous, eventually tears

What is a bank art lesion?

Avulsion of labrum From anterior Glenoid - diagnosed when fluid separates labour from glenoid

What are MR arthrograms? What are they used to detect?

Arthrography gives additional detail if intra-articular structures Useful for clarification of inconclusive findings on a standard MRI Better detection and assessment of : - Small, loose bodies - Cartilage flaps - Glenoid labour tears - Better assessment of the undersurface of the rotator cuff ( a frequent site of partial tears)

What is the positioning for a wrist MRI?

Dedicated coil Better with pt prone (superman position) however supine with wrist by side can also be done (my need wide bore) Uncomfortable position - superman

What is the positioning for a wrist MRI?

Neutral position - aligned long access of radius with central metacarpal axis Incorrect positioning can result in pseudo instability of capitolunate angle on the sagittal.

What are the sequences used for wrist MRI?

~ T1 - anatomy ~ Fatsat (STIR if metallic artefact) - bone oedema /fractures ~ T2* - cartilage / ligaments / TFCC ~ axial useful for tendons and ligaments in cross section

What does TFCC stand for?

Triangular fibrocartilage complex

Where it’s the TFCC?

In the wrist Between the ulna and carpal bones

What are the technical consideration for wrist imaging?

High spatial resolution - high matrices - thin slices - interleaving

What are the common places of scaphoid fractures?

70% - occur at the waist 20% occur at the proximal pole Non-union fractures may result in AVN