MRI and Musculoskeletal applications Sept 5, 1990

Cape Coral Hospital Jeffrey C. Allard MD

1. Definition: Proton (Hydrogen) imaging

TR- repetition time short long long

TE- excitation time short short long

                                T1-weighted         proton density             T2-weight

FLUID                         black                     grey                         white

FAT                             white                     white                     less white

CORTEX                          black                 black                         black

MUSCLE                          dark                     dark                         dark

TENDON                           black                 black                         black

BLOOD -subacute             bright                 bright                            white

TUMOR                               dark                brighter                        white

INFECTION -typical             dark             brighter                      white

HYALINE CARTILAGE-         grey             grey                         grey

FIBROCARTILAGE -            black                black                        black

MARROW- hematopoitic         grey                     grey                     grey

FATTY MARROW                bright                     bright                     bright

1. Gradient echo sequences use a flip angle less than 90. May be T1 or T2*-weighted. Tissue interfaces result in low signal (example trabeculated bone), hyaline cartilage is brighter, and flowing blood is white.

2. Tumor and infection can look similar. The former may have more mixed signal with necrotic (fluid) or hemorrhagic central parts. Infection less well circumscribed unless there is abscess.

3. Gadolinium enhancement gives signal increase on T1 images to vascular areas. Necrosis, fluid, and normal tissue does not change significantly.

2. Contraindications: metallic foreign body eyes, recent vascular clips, pacemaker, claustrophobia

3. Indications:

a. CNS- metastatic disease, multiple sclerosis, developmental disorders, posterior fossa or skull base pathology, ischemic or vascular pathology

b. Spine- tumors, stenosis, developmental anomaly, trauma, disk herniation

c. Chest- vascular versus solid mass, congenital and degenerative, cardiac anomaly

d. Abdomen- liver tumors, staging of pelvic neoplasms

4. Musculoskeletal:

a. Knee- marrow, articular cartilage, menisci, cruciate and collateral ligaments, cysts

b. Shoulder- impingement, rotator cuff tears, tendonitis

c. Hips- aseptic necrosis, complex congenital dislocation, mets

d. Wrist- carpal tunnel, aseptic necrosis, triangular ligament

e. Ankle- peroneus, posterior tibial, and Achilles tendons, osteocondrosis

f. Foot- neuroma, ganglion, fibromatosis

g. TMJ- arthritis, disk dislocation

h. Extremities- muscle injury, soft tissue tumor, bone tumor