MRI Physics 3

Question 1

In k-space, what does the center of k-space primarily determine?

Accepted Answer

Image contrast

Answer

The center of k-space contains low spatial frequencies that carry the bulk of image contrast and overall signal intensity.

Question 2

Which MRI sequence is most sensitive to hemorrhage detection because of its sensitivity to blood products?

Accepted Answer

Gradient echo (GRE)

Answer

Gradient echo sequences are sensitive to magnetic susceptibility differences caused by hemosiderin and deoxyhemoglobin, making them ideal for detecting hemorrhage.

Question 3

What is the effect of increasing the echo time (TE) on T2-weighted images?

Accepted Answer

Increases T2 weighting by allowing more transverse relaxation

Answer

A longer TE allows more time for T2 decay, so tissues with short T2 lose more signal, increasing contrast between tissues with different T2 values.

Question 4

During inversion recovery, the null point (TI) for fat suppression (STIR) is set to:

Accepted Answer

TI = T1(fat) × ln(2)

Answer

The null point occurs when the recovering longitudinal magnetization of fat passes through zero, which is at TI ≈ T1(fat) × ln(2) ≈ 0.693 × T1(fat).

Question 5

Which gradient is primarily responsible for frequency encoding in MRI?

Accepted Answer

Readout gradient

Answer

The readout (frequency-encoding) gradient is applied during signal acquisition, causing spins at different positions to precess at different frequencies.

MRI - Magnetic Resonance Imaging Practice Test

MRI - Magnetic Resonance Imaging Practice Test

MRI Physics 3