How much weighting does T1 Weighting deserve? – Tips and tricks for reading T1 sequences in Musculoskeletal MR scans

Educational Exhibit at the European Congress of Radiology, Vienna, 2019

(Note: images here are for representation only. Please write to us in case you would like the actual images)

Learning objectives

To learn the importance of T1 weighted sequences in the interpretation of MSK MR scans.

Coronal T1W MR of knee differentiating synovial thickening and fluid in the joint space.

Background

Fluid sensitive sequences like FSPD and STIR are given more importance by many readers while interpreting musculoskeletal MRI. T1 weighted sequences are usually ignored.

Coronal T1W MRI of Wrist for better identification of tenosynovitis

Findings and procedure details

Broad concepts On T1W:

  1. Loss of Fat around ligaments – sign of injury
  2. Loss of Fat around nerves – sign of impingement /invasion
  3. Effaced fat in the normal recess- sign of synovial thickening- – ankle (lateral ankle recess), acetabulum (acetabular fat pad), knee – posterior margin of the Hoffa fat
  4. Differentiation between edema and subchondral cyst
  5. Patchy subchondral FSPD hyperintensity without T1W hypointensity is due to post-traumatic increased microvascularity.
  6. Fat – fluid level inside bone in osteomyelitis implies intramedullary fat necrosis
  7. lipo- hemarthrosis – sign of intra-articular cortical fracture.
  8. Chronic injuries appear hypointense – De Quervain’s, chronic MCL scarring.
  9. Bright on STIR/FSPD and Dark on T1W- Abnormal.
Sagittal T1W MRI showing loss of fat signal around the nerve root

Conclusion

Joint-specific concepts:

Shoulder:

  1. Sagittal T1 – fatty infiltration, Contour of the muscles
  2. Better delineation of glenoid fossa sclerosis.

Spine:

  1. Sagittal T1W- for nerve root
  2. Pars breaks
  3. Ligamentum flavum vs facet joint arthropathy
  4. Calcification of Disc fragment and PLL – Markedly hypointense
  5. Cord – myelomalacia vs. edema
  6. Marrow infiltrative disorder vs hematopoietic disorder – Marrow T1 signal dark than muscles implies infiltrative disorder

Hip: Sub articular bright signal of femoral head alone is insufficient for differentiation among edema, infection or AVN. Subarticular hypointense line on t1 is seen in insufficiency fracture (parallel) and AVN (reverse)

Elbow: axial T1 intermediate signal – lateral epicondylitis

Coronal T1W MRI of Hip depicting the marrow edema and effacement of acetabular fat pad