MRI in Practice Review Exam Questions With Actual Correct Detailed Answers.

There are essentially two ways of explaining the fundamentals of MRI: - correct answer Classically and via quantum physics . All things are made of ____, including the human body. - correct answer atoms The mass number or atomic weight is the sum of the ______ in the nucleus - correct answer protons and neutrons MR active nuclei are characterized by their tendency to align their axis of rotation to an applied: - correct answer magnetic field MR active nuclei that have a net charge and are spinning, automatically acquire a/an _____ and can align with an external magnetic field. - correct answer magnetic moment The isotope of the hydrogen nucleus called _____ is the MR active nucleus used in clinical MRI. - correct answer protium ______ law of electromagnetic induction states that a magnetic field is created by a charged moving particle that creates an electric field. - correct answer Faraday's In the absence of an applied magnetic field, the magnetic moments of hydrogen nuclei are ______ orientated and produce ______ overall magnetic effect. - correct answer randomly, no Quantum theory uses the ______ of the spins (or hydrogen nuclei) to illustrate alignment. - correct answer energy level Magnetic moments of hydrogen spins are constantly changing their orientation because, due to __________, they are always moving between high and low-energy states. - correct answer Zeeman Interaction According to ______ law, there are about 6 x 1023 molecules per gram of tissue. - correct answer Avogrado's The precessional frequency is often called the ______ frequency. - correct answer Larmor The ______ expresses the relationship between angular momentum and the magnetic moment of each MR-active nucleus. - correct answer gyromagnetic ratio _____ is a phenomenon that occurs when an object is exposed to an oscillating perturbation that has frequency close to its own natural frequency of oscillation. - correct answer resonance Application of an RF pulse that causes resonance is termed: - correct answer excitation The combination of development of phase coherence and _______ results in coherent magnetization that precesses in the transverse plane. - correct answer nutation If just the right amount of energy is absorbed, the NMV lies in the transverse plane at ______ degrees to B0. - correct answer 90 The magnitude of the flip angle depends on the ______ of the RF excitation pulse. 1. amplitude 2. duration 3. phase - correct answer 1 & 2 only The emf is defined as the energy available from a unit of charge traveling once around a: - correct answer loop of wire Voltage signal is produced when ___ magnetization cuts across a coil placed in the area of a moving magnetic field. - correct answer coherent The process by which hydrogen loses energy is called: - correct answer relaxation A very simplified pulse sequence is a combination of RF: 1. pulses 2. signals 3. intervening periods of relaxation 4. all of the above - correct answer 4. all of the above One of the main advantages of MRI compared to other imaging modalities is its excellent ______ discrimination. - correct answer soft tissue Extrinsic contrast parameters include all except: 1. TR 2. Flip Angle 3. Value 4. Flow - correct answer flow The recovery of longitudinal magnetization is caused by a process termed: - correct answer T1 Recovery The typical T1 recovery time of fat in brain tissue at 1T is ____ ms. - correct answer 200 T2 decay is caused by the magnetic fields of neighboring hydrogen nuclei interacting with: - correct answer each other ______ are areas within the magnetic field that do not exactly match the external magnetic field strength. - correct answer inhomogeneties ________ is the time it takes for 63% of the transverse magnetization to dephase in a tissue. - correct answer T2 Decay Time An MR image has contrast if there are areas of high signal (______) and areas of low signal (______). - correct answer hyperintenisty, hypo- intensity Generally, the two extremes of contrast in MRI are: - correct answer fat and water Fat molecules contain atoms of hydrogen arranged with ____ and ____. - correct answer carbon and oxygen The ______ molecular tumbling in fat allows the T1 recovery process to be relatively ______. - correct answer slow, rapid