Magnetic Resonance Imaging (MRI) Practice Test

Which sequences utilize T2 gradient echoes and depend on velocity-induced phase shifts for vascular signal?

1. TOF MRA

2. PC MRA

3. EPI

4. IR

The correct answer is: PC MRA

The choice relating to T2 gradient echoes and their dependence on velocity-induced phase shifts for vascular signals is indeed accurate. Phase-contrast magnetic resonance angiography (PC MRA) specifically employs velocity-induced phase shifts to quantify blood flow. It does this by utilizing the principles of phase contrast imaging, where the velocity of moving protons in the blood generates varying phase shifts depending on the direction and velocity of flow relative to the magnetic field gradient applied. In PC MRA sequences, gradient echo imaging is used to capture the specific phase delays associated with flowing blood, which helps differentiate between static and dynamic tissues. This method is highly effective for visualizing blood vessels and can provide quantitative measurements of flow, which are crucial for diagnosing vascular issues. In contrast, time-of-flight magnetic resonance angiography (TOF MRA) primarily relies on the longitudinal magnetization of flowing blood rather than phase shifts. Echo-planar imaging (EPI) is mainly used for rapid imaging techniques but does not focus specifically on vascular signals from phase shifts. Inversion recovery (IR) sequences are more concerned with recovering longitudinal magnetization and are not designed for vascular flow analysis in the same way as PC MRA. Therefore, the focus of PC MRA on T2 gradient echoes and its