Critical Care Registered Nurse (CCRN) Practice Exam

What is used to manipulate and gather hydrogen signals in an MRA?

1. Electrodes

2. Contrast dye

3. Magnetic field

4. X-ray

The correct answer is: Magnetic field

In Magnetic Resonance Angiography (MRA), a magnetic field is essential for manipulating and gathering hydrogen signals. The principle behind MRA revolves around the behavior of hydrogen protons in a strong magnetic field. When a patient is placed within the magnetic field of the MRI scanner, the protons in the body's tissues align with this field. Radiofrequency pulses are then used to disturb this alignment, causing the protons to emit signals as they return to their original state. These emitted signals are what create the detailed images of blood vessels in the body, such as arteries and veins, allowing visual assessment of vascular structures and conditions. Other options, such as electrodes, are not utilized for signal manipulation in MRA, nor is X-ray technology relevant in this context as MRA relies specifically on the magnetic properties of hydrogen rather than ionizing radiation. While contrast dye can be used to enhance the visualization of blood vessels in some imaging modalities, it is not the primary means for manipulating hydrogen signals within an MRA setup. Therefore, the magnetic field is vital for the MRA technique.