In mathematics, a matrix (plural matrices) is a rectangular table of numbers. Matrices are useful to record data that depend on two categories, and to keep track of the coefficients of systems of linear equations and linear transformations.

This sequence type is a TSE counterpart to double echo sequences. To keep the echo train as short as possible, only echoes for PD and T2 weighted images, where the phase encoding gradient has a small amplitude, are measured separately. The echoes that determine resolution are used in both raw data matrices. This reduces the number of echoes required. Also the SAR drops and more slices can be acquired in the same repetition time.

From Hitachi Medical Systems America Inc.;
Hitachi expanded its portfolio with the Echelon™ 1.5T. The MRI scanner combines a compact magnet and a scalable 8-channel RF system with high-performance gradients and slew rate to select short echo times, small field of views, high matrices and thin slices. Standard features of the Echelon MRI system include higher-order active shim, RAPID (parallel imaging for use on brain MRI, body, cardiovascular imaging, and orthopedic coils), multiple coil ports, and an advanced reconstruction engine.

A measurement technique for double contrast sequences, whereat echoes that determines the image resolution are used in both raw data matrices.

A matrix is an array of numbers in rows and columns. The horizontal lines in matrices are called rows and the vertical lines are called columns. A matrix with m rows and n columns is called an m-by-n matrix (or m * n matrix) and m and n are called its dimensions.
The matrix used in MRI determines the scan resolution. See Acquisition Matrix.