MSK mri

Musculoskeletal MRI Goals ► What types of MR studies are available for evaluation of the musculoskeletal system? ► Considerations when ordering a study  Remember one of the roles of the radiologist is as consultant to work with you in determining the best study for the patient’s needs (it’s in the job description)… talk to them! ► Most common pathologies for which MSK MRI is performed Exam Types ► MRI without contrast  Most common  Evaluation of ligaments, tendons, occult fracture, cartilage ► MRI with contrast  Evaluation of bone or soft tissue tumor, osteomyelitis, abscess ► MR Arthrogram  Evaluation of labrum, intercarpal ligaments Body Part ► When ordering any study must have a ddx in mind, particularly with MRI (not a screening tool) ► Cannot perform an MRI of a whole extremity (time, pt motion, protocol issues) ► Must identify part to be imaged – be specific  A joint, a bone (prox, mid, distal), a muscle (origin, belly, insertion) ► Must have plain radiograph Most Common Indications ► ► ► ► ► ► ► Occult fx or stress fx Early osteonecrosis – in pt with risk factors & pain, known AVN of one hip Osteomyelitis – plain film is insensitive (30-50% loss of bone density) BUT necessary for MRI interpretation, nucs has poor resolution Osteochondral lesion – evaluate stability Ligament/tendon injury – knee, shoulder, ankle > other jts Bone tumor – MUST HAVE X-RAY 1st, imperative in providing ddx on MRI (dx on x-ray, determine extent on MR) Soft tissue mass/muscle injury Considerations when ordering an MRI ► ► ► ► ► ► ► Joint replacement in joint of interest – don’t it Pacemaker – don’t it Claustrophobia - sedation Unable to hold still/follow instructions – sedation Metal in area of interest (susceptibility artifact) – consult radiologist, may vary technique or recommend another study Metal not in area of interest ie orbits (motion, overheating) If you only remember one thing, remember this:  cannot a PE protocol chest CT without contrast Metal Artifact Small metal foreign body results in large area of signal void Metal or gas = black hole General Principles ► Fluid, edema, inflammation is bright on T2 ► Fat is bright on T1 & T2 (can have fat sat) ► Blood is often bright on T1 ► Tendons & ligaments are black on all sequences ► Cartilage is bright on T2 ► Muscle is intermediate in signal Pelvis & Hip – Normal Anatomy ► Joints – sacroiliac, pubic symphysis, hips ► Tendons – iliopsoas, gluteal, hamstrings, rectus femoris ► Bursa – trochanteric, iliopsoas ► Bones – evaluate for bone marrow replacing process (MM, mets), AVN, occult or stress fx ► Acetabular labrum – need intra-articular gadolinium Femoral Head Osteonecrosis ► Groin pain ► Many predisposing factors: trauma (fem neck fx, dislocation), steroids, SLE, sickle cell dz, pancreatitis, alcohol abuse, Gaucher’s dz ► Increased risk of contralateral AVN, must evaluate other side, most sensitive study is MRI ► MRI:  Early – bone marrow edema  Later – geographic area of abnormal signal in the anterosuperior femoral head; double line sign on T2  Even later – subchondral collapse, femoral head collapse, degenerative joint dz Supraspinatus Tendinopathy ► Underlying degenerated tendon as evidenced by thickening and abnormal signal Labral Tear ► ► ► Young pts