Magnetic Resonance Imaging (MRI) Practice Test

What type of pulse sequence does an IR sequence consist of?

1. A 90-degree pulse followed by a 180-degree combination

2. A 180-degree pulse followed by a 90/180 combination

3. A series of spin echoes

4. A continuous gradient echo

The correct answer is: A 180-degree pulse followed by a 90/180 combination

An inversion recovery (IR) sequence is characterized by the use of a 180-degree inversion pulse followed by a 90-degree excitation pulse. The purpose of the 180-degree pulse is to invert the longitudinal magnetization of the tissue, effectively preparing the spins for the subsequent imaging. After the inversion pulse, the 90-degree pulse is applied to generate the desired signal for imaging, allowing for a more effective suppression of certain tissue signals, such as fat or fluid, depending on the timing of the pulses and the choice of inversion time (TI). This pulse sequence is particularly useful in various clinical applications, such as identifying lesions or abnormalities where specific contrast between different tissue types is needed. The unique combination of the inversion and excitation pulses in an IR sequence enhances contrast and can highlight pathological changes within tissues that other sequences may not adequately visualize.