MRI IN PRACTICE FINAL EXAM ACCOMPANEID WITH VERIFIED QUESTIONS & ANSWERS.., Exams of Company Secretarial Practice

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MRI IN PRACTICE FINAL EXAM

ACCOMPANEID WITH VERIFIED QUESTIONS

& ANSWERS..

Resonance - CORRECT ANSWER --A phenomenon that occurs when two objects naturally vibrate at the same frequency. Results of resonance - CORRECT ANSWER --The direction of the NVM shifts as they transition to high energy. Away from Bo The angle to which the NMV moves out of alignment with the Bo is called FLIP ANGLE Effect of RF Pulse - CORRECT ANSWER --1)hydrogen protons absorbs the RF energy 2)increases the # of spin down hydrogen nuclei SPIN UP NUCLEI GAIN ENERGY THROUGH RESONANCE Flip angle - CORRECT ANSWER --the angle to which the longitudinal magnetization is tipped into the transverse plane, following the initial RF excitation pulse Faraday's Law - CORRECT ANSWER --When a conductive receiver coil is placed in the area of a moving magnetic field, a voltage is induced in it. Resonance causes protons to precession in phase in the transverse plane, this generates an electric current. The MR signal is produced when when in-phase magnetization cuts across the coil. Magnitude of MR signal - CORRECT ANSWER --Depends on the amount of magnetization present in the transverse plane

• Small magnetization transverse plane=LOW SIGNAL {Hypo-intense, DARK}
• Large magnetization=HIGH SIGNAL {hyper-intense, BRIGHT} relaxation - CORRECT ANSWER --The process by which hydrogen transition back to low energy state. When the RF pulse is removed the NMV, the NMV is influenced by Bo: 1.The protons move out of phase (dephase) with each other causing the transverse magnetization to slowly disappear. 2.Protons return to lower energy level (relax) to the resting state of net longitudinal magnetization (Mz) Free Induction Decay Signal (FID) - CORRECT ANSWER --The loss of signal/voltage As the transverse magnetization decreases, so does the magnitude induced in the receiver coil. This occurs by the inhomogeneities, causing the protons to lose coherency (deodars) pulse sequence - CORRECT ANSWER --a series of RF pulses, gradient applications and intervening time periods

Dramatically impacts the appearance of a MRI image MRI obtain various contrast images using pulse sequence. All help to visualize different anatomy and pathology pulse timing parameters - CORRECT ANSWER --a. A sequence of transmitting rf pulses during precise times with interviening periods of recovery. Repetition Time (TR) Echo Time (TE) Echo Time (TE) - CORRECT ANSWER --Time in milliseconds from the application of the RF pulse to the peak of the signal induced in the coil. TE determines how much decay of transverse magnetization is allowed to occur Intrinsic Contrast Parameters - CORRECT ANSWER --those parameters that cannot be changed because they are inherent to the body's tissues T1 recovery time T2 Decay Time Proton density Flow Apparent diffusion coefficient (ADC) Extrinsic Contrast Parameters - CORRECT ANSWER --those parameters that can be changed at the operator console Repetition time (TR) Echo time (TE) Flip angle Inversion Time (TI) Turbo factor or echo train Length (ETL) T1 RECOVERY (SPIN LATTICE RELAXATION) - CORRECT ANSWER --Recovery of longitudinal magnetization (Gradually INCREASES). Time it takes the protons to recover 63% of its longitudinal magnetization Involves the nuclei giving up their energy to the surrounding environment Occurs at different rates in different tissues Repetition Time (TR) - CORRECT ANSWER --time between each excitation pulse T2 Decay (Spin spin relaxation) - CORRECT ANSWER --loss of transverse magnetization as a result of spin-spin relaxation Interactions between neighboring nuclei cause dephasing (energy loss) Involves loss of phase coherence T2 Decay Time - CORRECT ANSWER --The time it takes 63% of the transverse magnetization to dephase (37% in-phase) in a tissue. The rate of decay is also an exponential process & occurs in different tissues. T2* Decay - CORRECT ANSWER --Caused by the immediate deplaning of spins in the transverse Mxy plane once the RF pulse is turned off. Detected by receiver coil immediately after the termination of the RF pulse.

Happens 10x faster than T2. Why T2* is faster than T2 - CORRECT ANSWER --1)Dephasing due to magnetic field inhomogeneities *inhomogeneities may be result of intrinsic defect in magnet *magnetic susceptibility effects produced by the tissue/patient or other materials placed within the field 2)T2 decay itself; the inherent tissue in T2 decay takes longer to dephase T2 decay - CORRECT ANSWER --the decay of transverse magnetization (Gradually DECREASES) T1 or T2 - which is longer? - CORRECT ANSWER --T Repetition Time (TR) - CORRECT ANSWER --The time from the application of one RF pulse to the application of the next RF pulse Measured in milliseconds (ms) magnetic moment - CORRECT ANSWER --a measure of an object's tendency to align with a magnetic field Vector - CORRECT ANSWER --A quantity that has size (magnitude) and direction Expressed as an arrow Basic MRI Process - CORRECT ANSWER --Patient put in magnetic RF signal is sent RF signal is switched off Patient emits a signal which is used for reconstruction or image Hydrogen - CORRECT ANSWER --Has 1+ proton. (Odd mass #) Spin around it's own axis. MR active Nuclei More__=more signal=better image quality Precessional frequency - CORRECT ANSWER --Speed at which the magnetic moments of hydrogen wobble around B0. MHz Precessional Phase - CORRECT ANSWER --The position of the magnetic moments on their precessional path at any moment in time. In-Phase - CORRECT ANSWER --mm are in the same place on the precessional path Out of Phase - CORRECT ANSWER --MM are NOT in the same place on the precessional path Radiofrequency Excitation - CORRECT ANSWER --Protons must be perturbed "pushed out" of their resting equilibrium state.

RF pulse - CORRECT ANSWER --short burst of RF energy that excites nuclei into a high-energy stage B1 - CORRECT ANSWER --Magnetic Field exerted by RF pulse Must be transmitted perpendicular to Bo Longitudinal magnetization - CORRECT ANSWER --Not measurable by Bo is larger Must be moved away from Bo in order to generate a signal. H + Bo=Spin up - > Nuclei pointing in different direction cancel out= NMV called

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Motion of Atom - CORRECT ANSWER --1) Nucleus spins on its own axis 2)Electrons orbit the nucleus

3. Electrons spin on their own axis Principle of MRI based on this* angular momentum - CORRECT ANSWER --rotational momentum of a spinning or orbiting object law of electromagnetic induction - CORRECT ANSWER --MR Active Nuclei have an electrical charge and are spinning, therefore, require a magnetic field. Parallel Alignment - CORRECT ANSWER --Spin Up Low Energy (Preferred energy) Anti-parallel alignment - CORRECT ANSWER --Spin down High Energy What Affects Hydrogen Alignment? - CORRECT ANSWER --Strength of the Bo

• High Bo = more Spin Up Thermal Energy / Temperature
• Low temp = Spin Up
• High temp = Spin down Net Magnetic Vector (NMV) - CORRECT ANSWER --Magnetic moment of unpaired nuclei. Aligns along longitudinal axis (Z axis) higher ___ will produce better signal Precession - CORRECT ANSWER --Secondary spin of MM around Bo. Wobble like spinning top. Laramor Equation - CORRECT ANSWER --Wo= Bo x ¥ Stronger Bo = Higher Wo Wo - CORRECT ANSWER --Precessional Frequency (MHz)

¥ - CORRECT ANSWER --Gyromagnetic Ratio (MHz/T) Unique for each nucleus ¥ for Hydrogen - CORRECT ANSWER --42.57 MHz/T Bo - CORRECT ANSWER --Strength of magnetic field (T) THE READ-OUT GRADIENT IS ALSO KNOWN AS THE - CORRECT ANSWER -- FREQUENCY ENCODING GRADIENT INVERSION RECOVER IMAGING ALLOWS FOR THE - CORRECT ANSWER -- NULLING OF A SIGNAL FROM A GIVEN TISSUE WHEN THE X-GRADIENT COIL IS USED FOR SLICE SELECTION, THE IMAGING PLANE PRODUCED WILL BE - CORRECT ANSWER --SAGITTAL WHICH OF THE FOLLOWING PULSE SEQUENCES DOES NOT USE A 180* REFOCUSING RF PULSE? - CORRECT ANSWER --GRADIENT ECHO The receive bandwidth is related to the slope of which gradient? - CORRECT ANSWER --frequency encoding gradient A fixed transmit bandwidth with a shallow slice select gradient will result in - CORRECT ANSWER --An increase in slice thickness In gradient echo, the spins are mainly rephased by ___ to produce an echo - CORRECT ANSWER --frequency encoding gradient Which of the following slice encode gradient has to be turn on to select an oblique slice for a supine patient in a superconducting magnet? - CORRECT ANSWER --XY Gradient coils linearly change the value of Bo along the xy and z directions. A gradient alters Bo in such a way that the center of the bore remains unaffected. - CORRECT ANSWER --TRUE Slice Thickness is determined by - CORRECT ANSWER --transmit bandwidth and gradient slope In a superconducting magnet, if an axial slice of the body is produced, the ___ graident is the slice selection gradient - CORRECT ANSWER --Z A gradient coil, when active, causes which of the following result on the main magnetic field? - CORRECT ANSWER --The field becomes stronger from one end and weaker at the other. A lont T1(about 2000 ms) will provide a pulse sequence called: - CORRECT ANSWER --FLAIR Gradient echo sequence are accomplished using which of the following events? - CORRECT ANSWER --Less than 90* RF pulse, gradient reversal.

A gradient echo sequence cannot delivery true T2 image contrast because of: - CORRECT ANSWER --Shorter TE Which of the following is a disadvantage of a gradient echo pulse sequence? - CORRECT ANSWER --No compensatin for magnetic field inhomogeneity The gradient that is on during the production of the echo is the: - CORRECT ANSWER --Frequency Encoding Spatial information and encoding of the signal is performed by - CORRECT ANSWER --Gradients magnetic field Referencing an axial image of the body, if the x-direction is used for frequency encoding, which gradient is used for phase encoding? - CORRECT ANSWER --Y- gradient The slice select gradient is always applied - CORRECT ANSWER --at the same time as the RF pulse Gradient echo pulse sequence are usually associtated with much shorter scan times than spin echo pulse sequences. - CORRECT ANSWER --TRUE To null signal from a specific tissue, the T1 selected should be ___ of the T relaxation time of that tissue. - CORRECT ANSWER --69% In a pulse sequence, phase encoding is performed - CORRECT ANSWER --prior frequency endcoding Steep frequency encoding gradient will produce a ___ - CORRECT ANSWER -- Small field of view The contrast produced during a SE pulse sequence using a short TR and a short TE produces ___ types of image contrast - CORRECT ANSWER --T1 weighted Coherent gradient echo uses - CORRECT ANSWER --both FID and stimulated echo In a gradient echo sequence, the TR is the time between - CORRECT ANSWER -- Flip angle The term for the range of frequencies in the transmit RF pulse is refered to as - CORRECT ANSWER --transmit bandwith Which of the following pulse sequence can begin with a 60* RF pulse and follow by an echo? - CORRECT ANSWER --Gradient Echo What function does the initial 180* RF pulse have in IR pulse sequence? - CORRECT ANSWER --Flips the net magnetization into the the negative longitudinal plane for greater T1 relaxation.

When a short T1 is selected, this sequence is known as a - CORRECT ANSWER -- STIR FLAIR - CORRECT ANSWER --Suppressed signal from fluid Coherent Gradient Echo - CORRECT ANSWER --Uses a rewinder gradient Incoherent Gradient Echo - CORRECT ANSWER --uses a spoiler STIR - CORRECT ANSWER --Suppressed signal from fat Gradient Echo - CORRECT ANSWER --Provide a T2 image Transverse magnetization which is left over from the previous RF pulses in the steady state condition is called - CORRECT ANSWER --residual transverse magnetization If the TR of a gradient echo pulse sequence is considerably less than the T2 (and T2), the condition that will exist is known as - CORRECT ANSWER --steady state A gradient echo sequence in which any residual transverse magnetization is removed prior to the next excitation pulse is known as - CORRECT ANSWER -- incoherent Residual Transverse magnetization which is "in phase" is called coherent residual transverse magnetization - CORRECT ANSWER --TRUE The process of spoiling residual transverse magnetization can be accomplished in 2 ways, - CORRECT ANSWER --RF spoiling and gradient spoiling In imaging the head (or brain), the long axis of the anatomy usually lies along the anterior superiors axis of the magnet, so in this case, the ___ will perform the frequency encoding - CORRECT ANSWER --Y Gradient What parameters are used to create spin echo T2 weighted images - CORRECT ANSWER --Long TE and Long TR Residual transverse magnetization which is "out of phase" is called incoherent residual transverse magnetization - CORRECT ANSWER --TRUE The Y gradient alters the magnetic field strength along the longitudinal axis of the magnetic - CORRECT ANSWER --FALSE In fast spin echo imaging, the long row of 180 pulses is called an - CORRECT ANSWER --Echo train length Gradient echo T2 weighting - CORRECT ANSWER --flip angle small TR long TE long

Gradient Echo T1 Weighting - CORRECT ANSWER --Flip angle large TR short TE long What is the time interval between the initial 90 RF pulse and a subsequent 90 RF pulse for each slice - CORRECT ANSWER --Repetition time The decay of transverse magnetization is caused by a process termed - CORRECT ANSWER --T2 decay In a Double Echo SE sequence the 1st signal will provide a ____ picture and the 2nd signal will provide a ___ picture. - CORRECT ANSWER --PD ; T On a T2 weighted image, why does CSF appear bright? - CORRECT ANSWER -- CSF has a long T2 relaxation time What is the time interval between the 90* RF pulse and the echo - CORRECT ANSWER --Echo time Which of the following parameter controls the amount of contrast seen on a T weighted image? - CORRECT ANSWER --TR To produce a PD image contrast, the TR should be ___ and TE should be ___ - CORRECT ANSWER --Long ; Short What is the purpose of the 180 degree RF pulse following the 90 degree RF pulse in a spin echo pulse sequence? - CORRECT ANSWER --To reverse the direction and rephase the net magnetization vector What parameters are used to create spin echo T2 weighted images? - CORRECT ANSWER --long TR and long TE In fast spin echo imaging, the long row of 180* pulses is called an - CORRECT ANSWER --Echo train length Which of these extrinsic parameter is manipulated to acquire images with varying amounts of T2 contrast? - CORRECT ANSWER --TE A long T1 (about 2000 ms) will provide a pulse sequence called - CORRECT ANSWER --FLAIR What is the term for the time from the excitation pulse to the refocusing pulse and from the refocusing pulse to the echo? - CORRECT ANSWER --TAU time What function does the initial 180 RF pulse have in an inversion recovery pulse sequence? - CORRECT ANSWER --Flips the net magnetization into the negative longitudinal plane for greater T1 relaxation time. A FLAIR sequence can suppres the signal of - CORRECT ANSWER --water

When a short T1 is selected, the sequence is known as a - CORRECT ANSWER -- STIR Spin echo - CORRECT ANSWER --Produce a true T2 Weighted image Fast Spin Echo - CORRECT ANSWER --Use a series of 180 RF pulses after the initial 90 RF pulse Inversion Recovery - CORRECT ANSWER --Nulling of a signal from certain tissue In IR pulse sequence, the time between the initial 180 RF pulse and the 90 RF is called - CORRECT ANSWER --inversion time A STIR sequence suppress can suppress the signal of - CORRECT ANSWER --fat