The second part corresponds to the transverse magnetization decay after the second excitation. The levels of signal intensity that characterize various tissues on T1- and T2-weighted images are shown in , Figure 5 (, 1,, 3,, 4). The contrast and brightness of the image are predominately determined by T1 properties of tissue. This sequence is very sensitive to pathology and makes the differentiation between CSF and an abnormality much easier. Right now I have one image with TR = 2370ms TI = 1000ms and TE = 5.37 ms for which intensity range is in between 0:1200. Variations in the value of TR have an important effect on the control of image contrast characteristics. For example, a T2 sequence with TR of 5000, TE 110 and SNR of 100%, decreasing the TE to 50 will increase the SNR but reduce the T2 effect and produce images with very poor tissue contrast. TR is the delay between excitations. This article presents a simplified approach to recognizing common MRI sequences, but does not concern itself with the particulars of each sequence. The MR signal is acquired at time TE after excitation. Decreasing the TE beyond a certain limit will reduce the T2 effect. As with conventional MR imaging, T2 values define the decay rate of the transverse magnetization. ESSENTIAL MRI CHARTS. So if change TR to 10000 ms how will it affect the intensity range? See also TR. T1 values are a few hundred milliseconds (ms) for most tissues examined.. Approximate values of T1 and T2 at 1.5T To the left is a table listing T1 and T2 values for hydrogen nuclei in various biological tissues. The sequence weighting highlights differences in the T2 relaxation time of tissues. MR Signal Localization. The long TE value allows a longer echo train to be used without significantly changing the overall scanning time. The most common MRI sequences are T1-weighted and T2-weighted scans. T2 weighted image (T2WI) is one of the basic pulse sequences in MRI. An MRI sequence is a number of radiofrequency pulses and gradients that result in a set of images with a particular appearance. Short values of TR ( 1000 ms) are common in images exhibiting T1 contrast, and long values of TR (> 1500 ms) are common in images exhibiting T2 contrast. sequences used, contrast media and the sequence parameters (TR, TE, TI, FA, SNR etc…).

Decreasing the TE beyond a certain limit will reduce the T2 effect.

By setting the TR to short values, tissue contrast will depend on differences in longitudinal magnetization recovery (T1). TR is also a major factor in total scan time. Conversely, T2-weighted images are produced by using longer TE and TR times.