When utilizing a STIR sequence, which tissue signal is primarily targeted for suppression?

In a STIR (Short Tau Inversion Recovery) sequence, the primary focus is on suppressing the signal from fat. This imaging technique is particularly useful in scenarios where differentiating between various types of tissues is necessary, especially when distinguishing pathological tissue from surrounding fat.

The STIR sequence achieves fat suppression by applying an inversion pulse that selectively targets fat's resonance frequency. This effectively nullifies the fat signal, allowing for enhanced visualization of other tissues, such as water or edema, which may have clinical significance. For example, in the assessment of soft tissue injuries or tumors, the suppression of fat helps to reveal underlying fluid or abnormal tissue changes without the confounding high signal from fat that can obscure important diagnostic details.

While edema is typically associated with increased water content and can be seen well on T2-weighted images without fat suppression, the STIR sequence specifically helps in better delineating the borders of edema by reducing background noise from fat. Muscle and fluid are not the primary targets for suppression in this context, as muscle typically has a lower signal intensity compared to fat, and fluid can be effectively visualized without the need for suppression. Therefore, focusing on fat with the STIR technique is essential for achieving clearer and more relevant diagnostic images.