Fluid sensitive sequences like FSPD (fat saturated Proton Density) and STIR are given more importance by many readers while interpreting musculoskeletal MRI.
T1 weighted sequences are usually ignored as the images are considered as "anatomy weighted".
In this review,
we discuss the importance of T1 weighted sequences in detecting different pathologies of the musculoskeletal system.
From Known to Unknown- utility of T1 weighted images.
Broad concepts On T1W- What is known :
1. View the "Dark side" with suspicion
If marrow lesions are darker than muscle,
they are likely pathological,
either due to marrow infiltration or infection.
Bright signal of bone marrow often seen on fluid-sensitive sequences like STIR and FSPD,
and appears brighter than muscle are not pathological.
Two examples shown are hematopoietic / red marrow and increased microvascularity due to prior trauma.
2.
"Fat is a Friend "
Fatty lipomatous lesions are well seen on T1 and homogenous bright signal imply a benign lipoma,
while increased linear or nodular signal on T1 can imply a possible sarcomatous change.
3.
"Blood is thicker than water"
Identification of lipo- hemarthrosis on T1W sequences in traumatic joint effusions is an important indicator to the presence of an intra-articular cortical fracture; blood is denser than fluid and tends to be dependent.
4.
Synovial thickening is not seen on T1W?
Effacement of normal fat in the joint recesses is a sign of synovial thickening.
For example effacement of the acetabular fat pad,
5.
T1 is not useful in spine imaging ?
T1 not only helps in evaluating nerve root impingement,
detection of conjoint nerve roots,
pars breaks and also differentiating between ligamentum flavum thickening vs facet osteophytes.
In Cervical spondylotic myelopathy,
presence of T1 dark signal in myelomalacia has worse prognosis.
6.
Fractures are not seen on MR?
Fracture fragments as well as fracture lines are routinely and excellently seen on T1 weighted images.