What is the difference between T1 and T2 relaxation?

T1-weighted images are produced by using short TE and TR times. The contrast and brightness of the image are predominately determined by T1 properties of tissue. Conversely, T2-weighted images are produced by using longer TE and TR times.

Is T2 shorter than T1?

T2 is tissue-specific and is always shorter than T1. Transverse relaxation is faster than longitudinal relaxation. T2 values are unrelated to field strength.

How do T1 and T2 values vary as a function of field strength?

Relaxation & Field Strength. How do T1 and T2 values vary as a function of field strength? In brief for most tissues, T1 increases and T2 doesn’t change very much as field strength increases. Molecules tumbling faster or slower are less efficient at spin-lattice relaxation and have longer T1s.

What is the difference between T2 and T2 * in MRI?

T2* can be considered an “observed” or “effective” T2, whereas the first T2 can be considered the “natural” or “true” T2 of the tissue being imaged. T2* is always less than or equal to T2. T2* results principally from inhomogeneities in the main magnetic field.

Why is T2 less than T1?

Typically (as shown in the first figure), T2 values of tissue are considerably lower than T1 values, i. e., the transverse magnetization decays quicker than the longitudinal relaxation needs for recovery. For most tissues in vivo, T1 varies between about 300 ms and 3 s, while T2 varies between about 10 ms and 200 ms.

Why does water have a long T1 and T2 decay time?

Why does water have a long T1 and T2 decay time? Because water has a high inherent energy, a fast molecular tumbling rate and its molecules are spaced far apart. This means energy exchange and spin-spin interactions are inefficient and therefore T1 and T2 relaxation respectively occurs slowly.

Why does fat have short T1 and T2 times?

2. Why does fat have a short T1 and T2 relaxation time? Because fat has a low inherent energy, a slow molecular tumbling rate and its molecules are packed together. This means energy exchange and spin-spin interactions are efficient and therefore T1 and T2 relaxation respectively occurs quickly.

Why does T1 depend on the static magnetic field?

T1 values depend on the strength of the magnetic field. This is because the field strength affects the resonant frequency of the protons. As field strength is increased, the resonant frequency also increases and becomes less matched to the molecular motion frequencies.

How do you remember T1 vs T2 MRI?

Mnemonics. The first two mnemonics use the first letters of the words and word pairs to denote the signal characteristics of blood at each stage as isointense (I), bright (B), or dark (D). The first bold letter in each pair denotes the typical T1 signal finding, while the second denotes the T2 signal change.

What is the relationship between T1 and T2 Mcq?

Discussion Forum

What are T1 and T2 relaxation times?

The approach of the system to thermal equilibrium is known as relaxation and T1 and T2 are relaxation times (relaxation rates R1(2)=1/T1(2) are also used). Both relaxation times are time constants used to characterize what are assumed to be first order rate processes.

Why does water have a long T1?

3. Why does water have a long T1 and T2 decay time? Because water has a high inherent energy, a fast molecular tumbling rate and its molecules are spaced far apart. This means energy exchange and spin-spin interactions are inefficient and therefore T1 and T2 relaxation respectively occurs slowly.