MRI question & answers 2023 updated

MRI question & answers 2023 updatedMRI: magnetic resonance imaging - correct answer Ideal for visualizing soft tissues of the body Uses the detection of radio frequency signals produced by displaced radio waves in a magnetic field. Nucleus has magnetic properties and acts as a dipole moment - correct answer Hydrogen is the most abundant element in the human body. Hydrogen protons align with the magnetic field when the human body is placed in an MR magnet. MRI mechanism - correct answer When a patient's body is placed in a magnetic field, the hydrogen protons line up in the direction of that magnetic field. --> Radio waves are passed through the magnetized area, which makes the atoms rotate (or spin) in a uniform fashion. When radio waves are discontinued, atoms rebound toward the orientation of the magnetic field. --> This synchronized rebound produces a local magnetic field that is detected by energy detectors surrounding the patient. *An image can be constructed because the protons in different tissues return to their equilibrium state at different rates, which is a difference that can be detected. T1-weighted MRI - correct answer T1 relaxation = time it takes for proton to process back into alignment with magnetic field. -differentiating fat from water, with water darker and fat brighter. T2-weighted MRI - correct answer T2 relaxation = time it takes for the protons to lose their phase; shorter than T1. -Like T1, fat is differentiated from water, but in this case fat shows darker, and water lighter. FLAIR (fluid attenuated inverted recovery) - correct answer -Used to null signal from fluids. -Used in brain imaging to suppress cerebrospinal fluid (CSF) so as to bring out the periventricular hyperintense lesions, such as multiple sclerosis (MS) plaques. Diffusion Weighed MRI (DWI) - correct answer -Measures microscopic water movements (diffusion) in tissues. -Increased restriction of water diffusion as a result of cytotoxic edema (cellular swelling) --> responsible for hyperintensity-signals seen on DWI scans. *useful in diagnosing acute strokes.