The period of time required to collect the image data. This time does not include the time necessary to reconstruct the image. The total time for performing a scan must take into consideration the additional image reconstruction time when determining how quickly the image may be viewed.

Variations in the value of TR and TE have an important effect on the control of image contrast characteristics.
Short values of TR (less than e.g. 1000 ms) and TE (less than e.g. 25 ms) are common in images exhibiting T1 contrast.
Long values of TR (greater than e.g. 1500 ms) and TE (greater than e.g.60 ms) are common in images exhibiting T2 contrast.
Middle TR values (e.g. from 1000 to 1500 ms) and middle TE values (e.g. from 25 to 60 ms) are common for density weighted contrast.
The values are depending on the field strength. TR is also a major factor in total scan time.

Various reconstruction filters can be applied to MR images to reduce noise.

The quality of magnetic resonance imaging is particularly dependent on image resolution (matrix, field of view, slice thickness), contrast (TE, TR), signal to noise ratio (bandwidth, signal averaging) and lack of artifacts. These MRI parameters are affected by the field homogeneity, the field strength, the coil, the pulse sequence type and imaging techniques like parallel imaging.

See also Image Contrast Characteristics.

The mathematical process of converting the composite signals obtained during the data acquisition phase into an image.