In a FLAIR IR pulse sequence, which of the following is suppressed?

In a FLAIR (Fluid Attenuated Inversion Recovery) IR (Inversion Recovery) pulse sequence, the primary goal is to suppress the signal from fluid, particularly cerebrospinal fluid (CSF), to enhance the visualization of other brain structures such as lesions or subtle abnormalities. The FLAIR technique achieves this by applying an inversion pulse that selectively nulls the signal from fluid, allowing for improved contrast in the images of surrounding tissues.

This suppression is particularly useful in neuroimaging, where the presence of CSF can obscure pathological findings such as multiple sclerosis lesions or other types of brain lesions. By effectively attenuating the fluid signal, FLAIR images can reveal these important details that might otherwise be masked by the bright fluid signal.

The other options do not align with the purpose of the FLAIR sequence. Muscle and fat are not the primary targets for suppression in this technique, as their signals are often desired in brain imaging to assess structural integrity. Air, while it does influence imaging through susceptibility artifacts, is not a direct target for suppression in the same manner as fluid. In summary, the correct answer highlights the specific function of FLAIR in medical imaging, particularly its ability to suppress fluid signals to enhance diagnostic effectiveness.