ARMRIT Test 3 Questions With Correct Answers

Different tissues that have signals that appear similar on an MR image are described as: - Answer isointense In a large main magnetic field such as those employed in MRI, the motion of a hydrogen proton has been described as wobbling like a spinning top. this motion is called: - Answer precession magnetic resonance imaging is derived from the process known as: - Answer nuclear magnetic resonance Once the nmv has moved away from equilibrium, the following will occur - Answer the transverse component will increase In MR, substances respond to a specific radio frequency which is known as: - Answer Resonance frequency the introduction of gadolinium based contrast enhancement agents by intra-venous injection can involve passing through an abnormal blood brain barrier. the tissue compartments involved are the: - Answer intravascular to interstitial t2 is the measurement of time for the transverse component of the NMV to decrease what percentage of its maximum value after the application of a 90 degree radio-frequency pulse - Answer 37% in the USA, the MRI system's magnetic field and vector that represents it is symbolized: - Answer B0 The resonance frequency of any substance in a magnetic field can be calculated by employing the: - Answer Larmor equation in a pulse sequence, transmitting an initial 90 degree radio-frequency pulse will cause the NMV to: - Answer shift in both size and direction Which type of electromagnetic coils are designed to stimulate and detect an MR signal - Answer radio-frequency tissues that are less efficient at spin-spin interactions because they contain more free water, such as CSF, should have - Answer High T2 values and produce hyperintense signals magnetism can be defined as the ability of certain substances to attract: - Answer Iron, cobalt, nickel the purpose of magnetic resonance angiography is to image the: - Answer blood flow the strength of very large magnetic fields like those employed in MRI systems, the SI unit most commonly used is: - Answer Tesla the larmor frequency of hydrogen protons in a 1.5 tesla magnetic field is: - Answer 63.9 MHz/Tesla In MR imaging, for chemical substance to be affected by the main magnetic field and the radio-wave it must contain an: - Answer Odd number of total protons and neutrons A 1.5T magnetic field is equal to: - Answer 15,000 gauss the components of the gyromagnetic ratio are: - Answer magnetic moment to angular momentum fast transition phenomenon and entry phenomenon are theories that explain which of the following characterisitics: - Answer Velocity effects the effects of main magnetic field inhomogeneities on the FID signal are corrected for in the spin echo sequence by applying a second radio frequency pulse. the flip angle of this radio frequency pulse is: - Answer 180 degrees of the following statements, which describes part of the basic MR imaging process: - Answer radio frequency signals interact with hydrogen protons which type of electromagnetic coils correct inhomogeneities in the main magnetic field: - Answer shim coils immediately after an initial 90 degree radio frequency pulse is turned off, the hydrogen protons will begin to: - Answer Dephase tissues that are very efficient at spin-lattice interactions near the larmor frequency, such as fatty tissues should have: - Answer Low T1 values and produce hyperintense signals T1 is the measurement of time for the longitudinal component of the NMV to recover what percentage of its original value after the application of a 90 degree radio frequency pulse? - Answer 63% the tissue characteristic which depends more on the state (solid, liquid, gas) of a tissue than any other factor is: - Answer T2 effects the basic process of MR signal generation contains 2 basic steps, they are: - Answer stimulation and relaxation the T1 process is also known as: - Answer spin lattice the T2 process is also known as: - Answer spin spin once in the main magnetic field, a majority of hydrogen protons will align themselves - Answer Parallel to B0 the tissue characteristic that depend heavily on the relative content of fat molecules and free water is: - Answer T1 effects which type of receiver radio frequency coil is placed close to a patient's body for the purpose of imaging superficial anatomic structures - Answer surface coils an equation derived to predict the MR signal intensity of a particular tissue as the result of a spin echo pulse sequence is the: - Answer larmor equation which statement is true of the relaxation process? - Answer without the effects of T2*, T2 decay continues because of the spinning motion of the hydrogen proton it has the same properties as a bar magnent. the hydrogen protons spinning motion gives it a : - Answer magnetic moment On a proton density image, 2 types of tissue that contain very low concentrations of hydrogen and appear very hypointense are: - Answer cerebral tissue and CSF in comparison to CT an advantage of MRI is: - Answer superior soft tissue contrast resolution in a loop of conductor in which an electric current is introduced and maintained a magnetic field will be produced in the center perpendicular to the flow of the electric current. this is called: - Answer Faraday's Law which type of MRI magnet has attainable field strengths of 0.35T to 3T for clinical use in the USA and higher strengths elsewhere and in research? - Answer superconductive the process of relaxation begins when: - Answer B1 is turned off A sinewave is a symbol used to measure electromagnetic energy. A sinewave's 2 components of measurement are: - Answer wavelength and frequency magnetic fields have direction which are usually designated as north and south therefore magnetic fields are described as: - Answer dipoles at any one time, human body tissue, in general, is made up of 50-90% of what substance - Answer H (Hydrogen) which of the following is the larmor equation? - Answer Wo = y x B0 the mechanism of T2 contrast enhancement agents is to : - Answer Decrease T2 relaxation time, therefore producing low signal which type of MRi magnet requires cryogen to cool magnetic coils to 4 degrees kelvin? - Answer superconductive a time constant that characterizes the fast rate of transverse magnetization because of the inhomogeneities of the main magnetic field is: - Answer T2* as the NMV precesses within the transverse plane, it induces an electrical curreny in a: - Answer radio frequency coil to symbolize the flow and area of a magnetic field, lines are used which are called: - Answer field or flux all chemical substances have an assigned constant known as the: - Answer gyro magnetic ratio mri systmes require rooms that provide specific shielding requirements. these rooms are lined with what typer of material? - Answer copper or galvanized steel which type of MRI magnet requires no electricity to maintain its magnetic field and can weigh from 18,000 to 200,000 lb.? - Answer permanent which type of electromagnetic coils are employed as a transmitter, receiver, or both? - Answer radio frequency coils which type of MRI magnet requires a special cooling system to dissipate heat produced by very large currents? - Answer resistive tissues that are efficient in both T1 an T2 interactions have low (short) relaxation times, and therefore have: - Answer high relaxation rates because of only 10-15% variation in most tissues, the tissue characteristic that does not provide much contrast resolution is: - Answer hydrogen concentration the tissue characteristics that is dependent on the strength of the main magnetic field and temperature is: - Answer T1 effects the component Mz is most associated with: - Answer parallel to B0; T1 relaxation; longitudinal magnetization the component Mxy is most associated with: - Answer transverse to B0; T2 relaxation; transverse magnetization in the USA, MRI systems in clinical use have main magnetic field strengths that range from: - Answer 0.06T to 3T On a very basic level, the 3 basic components required to attain MR signals are: - Answer magnetic field, proton, radio wave the main magnetic field of the MRI system is described as constant and always oriented in one set direction, either horizontal or vertical (dependent on the type of magnet). the transmitted radio frequency, in comparison, is described as: - Answer oscillating and always perpendicular to B0 which of the following parameters controls the amount of contrast seen in an image due to T2 relaxation - Answer TE a magnetic field strength of 0.5T is equivalent to: - Answer 5000 G an example of a dipole is: A) a hydrogen nucleus B) a bar magnet C) the earth D) all of the above - Answer all of the above hydrogen nuclei have a magnetic moment because they poses a property called: - Answer spin protons that align in an anti-parallel direction are in: - Answer a high energy state the formula that described the relationship between the static magnetic field and the precessional frequencyof the hydrogen proton is the: - Answer larmor equation to calculate the precessional frequency, the strength of the static magnetic field is multiplied by the constant known as: - Answer the gyromagnetic ratio the field strength of an MR imaging magnet as measured within the bore is most typically expressed in terms of: - Answer tesla the larmor, precessional or resonance frequency of hydrogen proton in a statc magnetic field of .5T is approximately: - Answer 21.288 MHz following RF excitation, as transverse magnetization (Mxy) decays to zero, the MR signal ___________. - Answer decays to zero