What Is a T2 Signal in an MRI?

T2 signals in magnetic resonance imaging are signals that occur when protons begin to relax and wobble after their subjection to a magnetic field causes them to align. Normally, such protons have a random alignment, according to the Merck Manual Professional Edition.

The MRI antenna captures both T1 and T2 signals during the relaxation of the protons. Software algorithms analyze these signals and then render detailed anatomical images, indicates the Merck Manual. The differences in the T1 and T2 characteristics of different materials help the device to create a clear picture, while using noninvasive techniques.

Fat generally produces bright T1-weighted images but darker T2-weighted images. Water causes a bright T2-weighted image, but a relatively dark T1-weighted image. Such differences mean that fluid-filled tumors, inflammation and trauma appear brighter in T2-weighted images, reports the Merck Manual. The contrast from these two image types makes MRI scans a better option than computerized tomography scans when doctors need to diagnose issues with the soft tissues, such as musculoskeletal tumors, spinal abnormalities or inflammation.

Doctors use MRI for testing of the female reproductive system, vascular imaging and certain fractures according to the Merck Manual. However, the testing is more expensive than a CT scan and takes longer. It is not appropriate for all patients due to magnet issues, claustrophobia and reactions to the contrast media.