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208 Cards in this Set
- Front
- Back
RF shielding in the MR scan is accomplished by:
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Copper
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The average humidity in the scan room needs to be:
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50-70%
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The temperature in the scan room should be around:
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65-75 degrees f
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Superconductive magnets use____________wiring for most of the coils inside the scanner.
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titanium (Niobium Titanium)
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In order to form images, Magnetic resonance imaging employs:
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radio waves and magnetic fields
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A vector possesses both:
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magnitude and direction
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On a T2 weighted img, which bandwidth would give the best SNR? 64, 16, 8, 120 ?
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8
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The Larmor frequency of hydrogen nuclei in a 1.5T mag field is:
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63.2 mHz
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The Larmor frequency of hydrogen nuclei in a 1.0 T magnetic field is:
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42.6 mHz
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Represent the Larmor equation
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Wo= yBo
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The Larmor equation is represented by which of the following: Bo=yF | F=yBo | M=Bo | *=Bo F |
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F=yBo
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Wo in Wo=Boy refers to:
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Frequency
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y in "Wo=Boy" refers to:
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Gyromagnetic ratio
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Bo in "Wo=Boy" refers to:
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The strength of the magnet at the center of the bore (B#0)
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The ratio of the magnetic moment to the angular momentum of a hydrogen nucleus is:
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gyromagnetic ratio
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States that voltage applied to a closed loop of wire will produce a magnetic field
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Faraday's Law of Induction
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This signal occurs after the vector has been moved to the transverse plane, is free of the RF pulse, & produces no spatial information
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FID or "dud"
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The effect of narrowing the bandwidth on signal to noise
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increases
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Spin lattice relaxation; regrowth of longitudinal magnetization back to equilibrium is know as what relaxation?
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Longitudinal relaxation (T1)
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The T1 longitudinal relaxation, is the time required for the tissue's longitudinal magnetization to recover_____% of it's equilibrium magnetization?
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63%
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Where is Isocenter?
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at the intersection of the x,y, and z planes
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Contrast goes to the________ of k-space and resolution is places____________ of k-space.
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center / outer edges
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Transverse relaxation is also known as:
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T2 relaxation(T2 decay)
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The function of the shim coils in an MR system is to:
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maintain magnetic field homogeneity
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Another name for the "read-out" encoding gradient in an MR scan is:
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frequency encoding
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The range of RF frequencies in the RF pulse is called the:
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bandwidth
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The rise time of the gradients is:
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time interval to the gradient reaches full magnetic field amp
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Is aliasing caused by oversampling or undersampling in which too much data is collected
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Undersampling (too small FOV)
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These artifacts occur in gradient echo sequences as an area of signal void and geometric distortion, at the air-tissue interface and as the result of refocusing spin by gradient reversal instead of using a 180
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Susceptibility artifacts
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Also known as truncation artifact and it is the result of undersampling.
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Gibbs artifact.
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The gradient amplitude affects the:(same as Gradient)
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minimum FOV that can be used & minimum slice thickness usedremember Frank Smokes MarijuannaFOV; SliceThickness; Matrix
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T/F The following are ALL support systems for the MRI system:chilled water; Halon system; oxygen alarms
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True
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Dewars are nonferromagnetic cylinders for the:
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cryogens of liquid helium
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A resistive magnet system is powered by:
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electricity
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The most important advantage of MR over CT and X-ray is:
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improved soft tissue detail
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For an MR signal to be received net magnetization must be in phase and:
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in the transverse plane
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If you increase the matrix you _________ the signal to noise.
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decrease
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If you decrease the matrix, you _________ the signal to noise.
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Increase
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If you change the FOV from 120mm to 240mm will SNR increase or decrease?
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Increase
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If you change the FOV from 120mm to 240mm, you increase the signal to noise by a factor of:
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4
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Unit used to describe precessional frequency
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Megahertz (mHz)
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Increasing the Field of View (FOV), will result in all of the following except: increase in signal to noise; increase in resolution; increase in partial volume averaging
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except increase in resolution; both PVA and SNR increase
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Faraday's Law of Induction states that if a loop of wire connected to a current will produce:
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magnetism
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How is the homogeneity of the magnetic field measured?
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ppm (parts per million)
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The direction of the magnetic field of a superconductive magnet is:
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horizontal
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The direction of the magnetic field in a permanent magnet is:
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vertical
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The transmit bandwidth affects all of the following except: Slice thickness/ FOV/ Matrix/ Contrast
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Contrast
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Phase contrast imaging involves:
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VENC is selected, bipolar gradients, used to image complex flow
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The initial RF pulse that is transmitted into the body must match:
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The Larmor frequency of the hydrogen protons
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An artifact which results from narrowing the receive bandwidth is _______ and the artifact is in the _______ direction.
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Chemical shift / frequency
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The decay of transverse magnetization is known as
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spin spin relaxation, T2
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If a coil is damaged or improperly tuned, there will be a decrease in
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Signal to noise
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Bo homogeneity is adjusted by:
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adjusting the current in the shim coils
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A magnetic field strength of 1 Tesla equals
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10,000 Gauss
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_______ relaxation is referred to as the time that it takes 63% of the protons to realign back to equilibrium
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T1
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After the 90 RF pulse, hydrogen protons dephase; in order to obtain a spin echo signal a
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180 RF is used
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Where would you place RF saturation bands in order to saturate out the veins of the leg?
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Inferior
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________ relaxation is defined as the time that it takes 63% of the transverse magnetization to decay.
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T2
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The flip angle which gives the maximum signal
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Ernst angle
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Spin density is another term for
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Hydrogen density or Proton density
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The receive bandwidth is associated with the slope of the ________ gradient
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Frequency encoding gradient
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T2* is the result of T2 dephasing and
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Inhomogeneity within the patient and the field
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The gradient which is used to acquire a coronal image is the _____ gradient
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Y gradient
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Precessional frequency is calculated by multiplying the strength of the static magnetic field and a constant, referred to as
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The gyromagnetic ratio Wo=yBo
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The RF energy used in MRI is classified as
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Electromagnetic radiation
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Which gradient is used to aquire an oblique coronal of the shoulder?
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a combination of 2 gradients
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Spectroscopy, is the oldest form of MRI; which of the following are true?
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frequency distribution of a signal / non-invasive molecular composition of tissue / NAA, Cr, and Cho are measured in order to determine if an area is cancerous
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During thermal equilibrium, protons precess
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Out-of phase
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Frequency is defined as
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The rate of phase change per unit time
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Materials such as iron which have a strong attraction to the magnetic field are called
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Ferromagnetic
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As the slice thickness is increased, the spatial resolution is
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Decreased
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Winning a Nobel Peace prize for his efforts in MRI, some consider___________the father MRI
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Damadian / Lauterbur
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The job of the gradients is to
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Spatially encode data
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Slice thickness is controlled by
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The slope of the gradient
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In order to acquire an axial slice, which gradient is applied?
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Z gradient
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To produce a sagittal slice, which physical gradient is applied?
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X gradient
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Where would a technologist scan when looking for a Chiari malformation
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craniocervical junction
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The gyromagnetic ratio for hydrogen on a 1.5 Tesla magnet is
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63.86 Megahertz/Tesla
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The amount of RF needed to produce a flip of 90 degrees is determined by
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The amplitude of the RF pulse; the duration of the RF pulse; the strength of the magnetic field
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The gradient which is applied during the sampling of the echo, also called the readout gradient
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Frequency gradient
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Tissues with a short T1 relaxation time appear _______ on T1 weighted images.
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hyperintense/ bright
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Chemical shift artifact occurs because
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Fat and water precess at different frequencies
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Chemical shift artifacts are more pronounced as
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The receive bandwidth is decreased; the field strength increase
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FID refers to
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free induction decaty
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The measure of the extent to which a substance becomes magnetized is known as its
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magnetic susceptibility
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High and low intensity bands are seen as the result of undersampling, these artifacts are called Truncation or
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Gibbs
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Susceptibility effects are reduced by
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Decreasing the TE
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T2 relaxation occurs faster than T1 relaxation
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True
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Mean to decrease repiratory motion include: Respiratory gating / Increasing the number of signal averaged / Having the patient hold their breath/ All of the above
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All of the mentioned help decrease rep motion
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Which of the following sequences would most decrease the effects of magnetic susceptibility?
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FSE or TSE spin echo
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Black and white banding artifact on the edge of the FOV; often seen on a gradient echo coronal localizer of the abdomen
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Moir'e artifact; zebra artifact
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In order to display subtle hemorrhage in the brain, which sequence would be best?
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Gradient echo
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Raw data is often referred to as
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K-space
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A light bulb going "bad" in a MR scan room could cause
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Zipper/ RF artifacts
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In order to diminish the appearance of Gibb's artifact, a technologist should
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increase the matrix
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Using TR of 3000ms, as the Echo Time (TE) increases, T2 weighting will
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Increase
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Artifacts result from failure to sample data for a sufficient amt of time. Bands of high and low signal intensity running parallel to the tissue interface -occasionally seen in the cervical cord are called
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Gibbs artifacts
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During the imaging process, magnetic field gradients may cause time-varying induced
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Eddy currents
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T1 contrast is predominantly controlled by
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TR
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In order to double the SNR, the NSA must increase by a factor of
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Four
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Chemical shift artifacts are more pronounced at
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high field strengths, and reduced bandwidths
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The FDA limit on time-varying magnetic fields is:
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a limit to where the patient experiences tingling or pain
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What occurs when the interspace thickness between slices is 0 or less than 25%?
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cross excitation/ cross talk
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The strength of the magnetic field is measured in
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Gauss/centimeter or mT/meter
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At isocenter, the field strength is measured in
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Tesla
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The most important element in maintaining a safe MRI environment is
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Education
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Name some properties of the MRI signal that we can measure
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Phase, Frequency, amplitude
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In the presence of a magnetic field, the hydrogen protons wobble, this is called
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Precession
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As you increase the repitition time, what effects occur
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The time increases, the SNR increases, the number o slices available increase
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As you increase the repitition time, what effects occur
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The time increases, the SNR increases, the number of slices available increase
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During pre-scan, the center frequency of the RF should be tuned to match the
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Larmor frequency of hydrogen protons
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106. According to the ____________ theorum, a signal must be sampled at least twice per cycle in order to represcent it accurately
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Nyquist theorem
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If you decrease the voxel volume, you also decrease___________
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Partial volume averaging & Susceptibility artifacts
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The term that represents the difference in brightness beween 2 regions on an image is
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image contrast
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Which coil is more sensitive to alaising artifacts? Small coil with a smalll FOV or Large coil with small FOV
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Large coil with a small FOV
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Another term that refers to a patient's body or a coil toughing the side of the magnet's bore, causing decreased SNR is
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decoupling or detuning
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A _________ is a non-ferrous storage tank for liquid helium, used in a superconducting magnet system.
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Dewar
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In an MR system, a coil of wire wound in the form of a long cylinder is
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solenoid coil
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With conventional spin echo imaging, each line of k-space is filled with each
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Repetition time (TR)
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If the number of signal averages (NSA/NEX) is increased by a factor of 2, the scan time will
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double
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If the number of signal averages (NSA/NEX) is increased by a factor of 2, the Signal to noise will
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increase by the √2
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Chemical misrepresentation: a.) Occurs because fat & water are out of phase in the same voxel..b) Occurs when an echo time is selected that accents the difference in fat and water.
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c) Is seen as a black ring around tissue. d) All of the above
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Specific absorption rate refers to
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amount of energy deposited by RF in a certain amount of tissue
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The U.S. governing body which is responsible for governing MRI is
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FDA
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The limits for SAR in the FDA guidelines for whole body imaging are
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4 W/Kg
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The "dB/dt effect" such as muscular twitches in the hand, face, and back most likely occur with
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Echo planar imaging/DWI
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What tissue is suppressed during FLAIR imaging
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Water/fluid
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The main concern associated with radio frequency is
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Tissue heating
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The amount of RF that can be deposited in a certain amount of tissue is the
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SAR
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A Capnometer is used to measure
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carbon dioxide levels
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The FDA limits the increase in a patient's core body temperature to
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1 degree Celsius
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The force with which an object is attracted to a magnetic field will be dependent upon
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The mass of the object; The field strength of the magnet;The ferromagnetic properties of the object
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Since these two areas of the body do not dissipate heat well, they are very sensitive to RF
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Lens of eyes and testes
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Who should be screened
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Any & everyone entering the scan room
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Lengthening the TR will have all of the following except:increasing scan time/ increasing SNR/ Increasing T1 / Decreasing T1
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Increasing T1
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MR patient screening procedures could include
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checking for aneurysm clips, asking if patient has worked w sheet meta, asking pt if he has had heart surgery
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The best plane in order to display the rotator cuff is
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coronal oblique
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What material should wheelchairs, stretchesrs, and stepstools be made of in order to safely enter the MRI scan room?
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non-ferrous material
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Are called time varying magnetic fields (TVMF)
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gradients
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T/FA peripheral gating device on the finger or toe may be used to monitor critically ill patients
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False
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Cardiac pacemakers, cochlear implants, and artificial hip replacement are all absolute contraindications for MRI scanning
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False; all except hip replacement are
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MRI IV contrast agents are considered__________agents
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paramagnetic
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Conscious sedation may be a concern as it may
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depress respiration
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If MRI is indicated during the first trimester, the scan is usually avoided if possible
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true
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A normal O2 saturation for a patient undergoing MR scanning is
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85 - 100%
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A quench is defined as the
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rapid collapse of magnetic field and release of heat and sudden boil- off of cryogens
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Maximum field strength that is FDA approved for infant and adult patient scanning is
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8.0 T
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As blood moves across the magnetic field, there may be an elevation of the patient's T-wave. This phenomenon is called
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Hemodynamic effect or Magnetic Hydrodynamic effect
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Individuals with pacemakers must remain outside the _____ line
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5 gauss
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This is the name of a malignant kidney tumor commonly found in children
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Wilms tumor
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There are _____ contraindications to gadolinium
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No known
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The cranial nerve known as the facial nerve is the
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7th facial nerve
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Which cranial nerves are considered the IAC
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7th and 8th are considered the IAC
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For a patient with Bells Palsy which cranial nerve would be involved
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7th
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The best view to show the Achilles tendon
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sagittal
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which of the following is hypointense post contrast?mucosa/ pituatary/ pineal/ basal ganglia
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basal ganglia
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Avascular necrosis is predominantly in the
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Head of the femur
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The duramater lining beween the two hemispheres of the brain is called the
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falx cerebri
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The division between the temporal lobe and the frontal lobe is the
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Sylvian fissure
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The inner lining of the uterus is called the
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endometrium
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The inner lining of the uterus is called the
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endometrium
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Name the three components of the brainstem
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Midbrain, pons, medulla
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Name the components of the diencephalon
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Thalmus, epithalmus, subthalmus, hypothalamus
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Which positions are used to display the Internal auditory canal (IAC)
|
Axial and Coronal
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Which positions are used to display the Internal auditory canal (IAC)
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Axial and Coronal
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Which positions are used to display the pituitary gland?
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Sagittal and coronal
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Which vessel is located directly in front of the pons
|
Basilar artery
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Which vessel is the first to branch off to the aorta
|
Right Coronary artery
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The first vessel to branch off the aortic arch is
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The brachiocephalic artery
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Which projection best displays the cruciate ligaments of the knee
|
Sagittal
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Which projection best displays the collateral ligaments of the knee
|
Coronal
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The inferior sagittal sinus drains into
|
Jugular vein
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Where is CSF produced
|
Choroid plexus
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The carotids bifurcate at what level?
|
C3/C4
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Using an Inversion recovery sequence on a 1.5T magnet, what tissue is suppressed if the Inversion Time (TI/Tau) is 150?
|
Fat
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If a sequence has a chain of 180 flip angles, it is referred to as a
|
Fast spin echo/TSE
|
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Gradient moment nulling
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Reduces intra-voxel dephasing, is often called First Order motion comp, and is most effective on slow laminar flow
|
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A sequence which starts with a 180 pulse, then a 90 pulse, then a refocusing 180 pulse is referred to as a
|
Inversion recovery sequence
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The main magnetic field is known as
|
Bo
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In the following scenario, how many lines of K-space are filled with each repetition time? TR 3000| TE 80 | ETL 12 | slice thick 6mm | matrix 256x512 | NSA 1 | FOV 24cm
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12
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A word which is synonymous with fainting
|
Syncope
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Difficulty walking
|
Ataxia
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The colliculi are located in what area
|
Posterior on the midbrain
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The colliculi are located in what area
|
Posterior on the midbrain
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What is the effective TR in this cardiac gated scenario, in which the patient has the following factors? Heart rate 60 bpm; Trigger window 10%; Trigger delay 50 ms
|
1000ms
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For a 1.5 Tesla scanner the difference in precessional frequency between fat and water is
|
220 Hz
|
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When doing a 2dToF to show up the carotid arteries the pre-saturation band should be
|
superior
|
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When imaging the inferior vena cava for flow the saturation band should be placed
|
superior
|
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which artery is known for producing artifacts in the knee area
|
popliteal artery
|
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Which plane best displays the genu, splenium, and the body of the corpus collosum?
|
sagittal
|
|
The Islets of Langerhans are located in what area
|
Pancreas
|
|
Non-living objects that may transmit pathogens (ie linens, telephones, and keyboards:)
|
fomite
|
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In the event that a patient has a life-threatening MVA and is unable to give consent for surgery. This process is called
|
Implied consent
|
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The adnexa is found in what area
|
around the ovaries
|
|
The best plane to display the median nerve
|
axial
|
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The dural sinus which lies in closest proximity to the occipital and temporal lobes
|
transverse sinus
|
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The dural sinus which lies closest to the pituitary gland
|
cavernous sinus
|
|
The omentum is located
|
abdominal area
|
|
When a patient becomes injured as the result of a negligent act that is extremely obvious, it is
|
Res ipsa loquitor
|
|
An animal that spreads disease from person to person
|
vehicle
|
|
The term respondeat superior indicates
|
holds an employer liable for the acts of its employees
|
|
The unlawful touching of the patient without consent is called
|
battery
|
|
The first confirmation of an exam request when a patient enters your department involves
|
verify patient identification
|
|
Verbally spreading confidential patient information is considered a violation of
|
HIPPA
|
|
A type of infection that occurs as the result of a patient being in the hospital is called
|
nosocomial / hospital acquired
|
|
Log rolling is a method of moving patients with a suspected
|
vertebral column injury
|
|
What type of isolation precautions should be used for HIV positive patients
|
Standard/ universal
|
|
The abbreviation that means biopsy is
|
Bx
|