What is the difference between stir and T2 fat sat?

STIR sequences have the advantage of increasing the relative signal intensity of fluid as a result of the additive T1 and T2 contrast effect. This allows STIR images to have greater contrast between fluid and other tissues than fat-suppressed T2-weighted fast spin-echo images.

What does fat Sat MRI mean?

Fat-Sat pulses are short-duration RF-pulses tuned to the resonance frequency of fat. They are applied immediately before the start of an MR imaging sequence. These chemically selective pulses cause the signal from fat to be nulled (saturated) while the water signal is relatively unaffected.

What does stir mean on MRI?

STIR (Short Tau Inversion Recovery) images are highly water-sensitive and the timing of the pulse sequence used acts to suppress signal coming from fatty tissues – so ONLY WATER is bright. A combination of standard T1 images and STIR images can be compared to determine the amount of fat or water within a body part.

How to identify T2 fat saturated MRI images?

MRI image appearance The easiest way to identify T2 weighted fat saturated images is to look for adipose tissues in the body (e.g. subcutaneous fat and fat in bone marrow). Areas contain adipose tissues appear dark on T2 weighted fat saturated images.

How are stir and SPIR used in MRI?

STIR sequences result in a nonselective suppression of fat as well as other tissues with short T1 values. STIR will tend to hide gadolinium enhancement (since gadolinium-containing tissues may have T1 values shortened into the fat range.) SPIR, however, through its selective suppression of fat is widely used for postcontrast MR imaging.

Why are fats bright in a stir MRI?

Fluids normally appear bright and fat appear very dark in a STIR image. Pathological processes normally increase the water content in tissues. Due to the added water component this results in a signal increase on STIR images.

What is the tinull value of stir in MRI?

STIR stands for Short-TI Inversion Recovery and is typically used to null the signal from fat. At 1.5T fat has a T1 value of approximately 260 ms, so its TInull value is approximately 0.69 x 250 = 180 ms.