Knowledge Flashcards

What does the term 'repetition time' (TR) refer to in MRI pulse sequences?

Answer: The time between successive RF excitation pulses applied to the same slice

TR is the interval between the beginning of one RF excitation pulse and the beginning of the next for the same slice, controlling T1 contrast.

Which MRI artifact is caused by periodic patient motion such as cardiac or respiratory movement?

Answer: Ghosting (motion) artifact

Ghosting artifacts appear as repeated copies of moving structures along the phase-encoding direction due to periodic physiologic motion.

The flip angle in an MRI sequence refers to which of the following?

Answer: The degree to which the net magnetization vector is rotated from B0 by the RF pulse

The flip angle is how far the net magnetization vector is tipped away from the longitudinal axis by the RF pulse.

Which type of MRI coil surrounds the entire body and is used to transmit RF energy uniformly?

Answer: Body (volume) coil

The body (volume) coil is built into the bore and provides uniform RF transmission across the entire patient.

In MRI, what is k-space?

Answer: The raw data space containing spatial frequency information used to reconstruct images

K-space is the mathematical domain that stores the raw MRI signal as spatial frequencies; a Fourier transform converts it into an image.

What is the primary purpose of fat saturation techniques in MRI?

Answer: To suppress the fat signal so adjacent structures are more conspicuous

Fat saturation applies a frequency-selective RF pulse to null the fat signal, improving visibility of adjacent enhancing or edematous tissue.

Which safety zone in an MRI facility is defined as the area that requires screening and controlled access due to the fringe magnetic field?

Answer: Zone III

Zone III is the area where the fringe field poses risk and requires restricted access; only screened individuals may enter.