NEX and NSA in MRI

These flashcards cover the key terms and concepts associated with the Number of Excitation Pulses (NEX) and Number of Sample Acquisitions (NSA) in MRI, including definitions of important metrics and their implications for image quality and scanning parameters.

NEX

Number of Excitations, referring to the number of times K-space is acquired for each slice in a series.

NSA

Number of Sample Acquisitions, synonymous with NEX, indicating the sampling rate during MRI scans.

Signal to Noise Ratio (SNR)

A comparison between the diagnostic signal received from the patient and corrupting random noise.

K-space

A data space used in MRI, representing frequency information collected during the scanning process.

Acquisition

The act of capturing image data during the MRI scan, typically performed multiple times to enhance image quality.

TR

Repetition Time; the time between successive pulse sequences applied to the same slice.

FOV

Field of View; the extent of the observable image area during scanning.

Slice Thickness

The thickness of the imaging slice in an MRI scan, impacting image resolution and SNR.

Coil Selection

Choosing the appropriate coil for MRI scanning, which can influence image quality and SNR.

Square Root of 2 Increase

Doubling NEX will increase SNR by a factor of √2 (approximately 1.41 or 41%).

Scan Time Formula

TR x Ny x NEX; a formula to calculate total scan time based on Repetition Time, number of phase encoding steps, and NEX.