MRI Image Processing Fundamentals

The time between successive RF pulses applied to the same slice.

The time between the delivery of the RF pulse and the reception of the echo signal.

An MRI image where signal intensity is primarily determined by the rate at which tissues regain their magnetization after a pulse (T1).

Tissue A has a shorter T1 relaxation time than tissue B. Signal intensity is stronger for tissue A.

A short TR (time between pulses) allows tissue A to regain more magnetization compared to tissue B, resulting in a stronger signal for tissue A.

The time between the 90 degree pulse and the 180 degree pulse in a spin echo sequence.

The time between the initial 90 degree pulse and the echo signal in a spin echo sequence.

A sequence that uses one 90 degree pulse and at least one 180 degree pulse to generate an echo signal.

The process where protons in a magnetic field lose their alignment and return to their original state after a 90 degree pulse.

The time constant that describes the rate at which the protons lose their alignment after a 90 degree pulse due to the magnetic field inhomogeneities.

The time constant that describes the rate at which the protons lose their alignment after a 90 degree pulse due to interactions between the protons.

The signal intensity of an image is determined by the strength of the transverse magnetization.

The ability of an imaging technique to differentiate between different tissues based on their characteristics.

A process that is used to select a specific slice of tissue within the body for imaging.

A magnetic field gradient that is used to select a specific slice of tissue by assigning different frequencies to protons based on their position along the gradient.

The thickness of the slice that is being imaged can be controlled by altering the range of frequencies used in the slice selection gradient.

The thickness of the slice can also be adjusted by changing the steepness of the magnetic field gradient; a steeper gradient means more variation in precession frequencies, leading to thinner slices.

A magnetic field gradient applied in the y-axis after slice selection to differentiate protons along that axis based on their precession frequencies. This allows for distinguishing signals originating from different columns in the final image.

A magnetic field gradient applied in the x-axis after the RF pulse. It causes protons along the x-axis to precess at different frequencies, resulting in phase shifts in the signals. This allows for distinguishing the signals from different rows in the final image.

The process of using the signals from different frequencies and phases to reconstruct an image. Each signal corresponds to a specific spatial location within the slice.

The ability to distinguish between different types of tissues depends on their unique properties. Properties such as T1 and T2 relaxation times influence the signal intensity of a tissue and can be manipulated to highlight specific structures in the image.