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MRI Signal Equation.html

@@ -579,8 +579,8 @@ <h2>Relaxation during signal acquisition<a class="headerlink" href="#relaxation-
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 <p>Thus the reconstructed image will corrupted by a convolution (denoted by <span class="math notranslate nohighlight">\(*\)</span>) based on the k-space amplitude weighting</p>
@@ -626,8 +626,8 @@ <h2>Relaxation during signal acquisition<a class="headerlink" href="#relaxation-
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 <p>In the above plots, the height of the main peak in the center represents the expected SNR, including losses due to blurring, while the signal amplitude outside of the main peak represents blurring that will occur.   These show that the blurring and signal loss from <span class="math notranslate nohighlight">\(T_2^*\)</span> gets worse as the relaxation time is shorter, the blurring it is much worse for EPI (in phase encoding direction) versus Cartesian trajectories.</p>
@@ -698,8 +698,8 @@ <h2>Off-resonance and Chemical Shift<a class="headerlink" href="#off-resonance-a
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 <p>For frequency shift, the main peak of the convolution kernels is shifted frfom the origin.  This will result in a shift in the reconstructed image.  The shift is much larger for EPI and is in the phase encoding instead of the frequency encoding direction.  (The residual side lobes are due to sinc interpolation effects, similar to Gibbs ringing.)</p>

Spatial Encoding.html

@@ -588,12 +588,12 @@ <h3>Frequency Encoding<a class="headerlink" href="#frequency-encoding" title="Pe
 We recommend using the qt toolkit instead.
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+<img alt="_images/94f0bb94ef66078a0702a9a60652e1592422b13023ec17d8caf206975519be25.png" src="_images/94f0bb94ef66078a0702a9a60652e1592422b13023ec17d8caf206975519be25.png" />
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@@ -647,14 +647,14 @@ <h2>Phase Encoding<a class="headerlink" href="#phase-encoding" title="Permalink
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+<img alt="_images/d70e301f75685957891808a298dc6593fb63e3e55c93ea5d37ae1cf4ed3bf08c.png" src="_images/d70e301f75685957891808a298dc6593fb63e3e55c93ea5d37ae1cf4ed3bf08c.png" />
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@@ -730,10 +730,10 @@ <h3>K-space trajectories<a class="headerlink" href="#id1" title="Permalink to th
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+<img alt="_images/3df8147b59babb1a31f57dc4d963cbcbf25f36d944827ba26639642004bc6998.png" src="_images/3df8147b59babb1a31f57dc4d963cbcbf25f36d944827ba26639642004bc6998.png" />
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 <p>These movies illustrate the phase accumulation during non-Cartesian trajectories</p>

Spectral-Spatial RF Pulses.html

@@ -691,8 +691,8 @@ <h2>Spectral-Spatial RF Pulse Design<a class="headerlink" href="#spectral-spatia
 <div class="output stream highlight-myst-ansi notranslate"><div class="highlight"><pre><span></span>ans = -11.589
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 <p>The spectral pulse, <span class="math notranslate nohighlight">\(H_f(k_f)\)</span>, creates the overall envelope, and is applied as a weighting for repeated versions of the spatial pulse, <span class="math notranslate nohighlight">\(H_z(k_z)\)</span>.  This creates the excitation k-space profile, <span class="math notranslate nohighlight">\(B_1(k_f, k_z)\)</span> shown above, which results in the spectral-spatial profile shown below:</p>

_sources/Questions.md

@@ -1,28 +1,171 @@
 # MRI Questions
 
+Note that questions may have multiple possible answers.
 
 ## MRI System
 
-
+Clinical MRI systems (i.e. 3T and 1.5T) operate in the same frequency range as ..
+* Xray
+* Visible light
+* FM
+* AM
+
+The main magnetic field, $B_0$, is for ...
+* polarization
+* excitation
+* acquisition
+
+Which coil(s) generates a magnetic field(s) that are perpendicular to the main field $B_0$?
+* RF coils
+* gradient coils in the x direction
+* gradient coils in the y direction
+* gradient coils in the z direction
+
+(T/F) In MRI, the imaging plane is determined by proper assignment on the x, y, and z gradients
+
+Match the following components with the approximate amplitude of their magnetic field
+* Components: $B_0$, RF transmit coil, RF receive coil, magnetic field gradients
+* frequency of magnetic field: 0 Hz, 1 kHz, 100 MHz
+* amplitude of magnetic field: 1 $\mu T$ , 10 $\mu T$, 10 $m T$, 1 $ T$
+
+
+Which of the following steps are conducted in a calibration scan?
+* Center frequency / B0 calibration
+* RF power, transmit gain
+* RF receiver gain
+* Gradient calibration
+
+<!-- 
+Which of the following parameter(s) change with the main magnetic field strength?
+* Resonance frequency
+* Magnetic field gradients
+* Equilibrium magnetization, $M_0$
+* Amount of displacement due to fat/water chemical shift
+* Magnetic field distortions due to magnetic susceptibility differences
+* Intensity of motion artifacts
+-->
 
 ## MR Physics
 
+Which of the following isotopes cannot
+be imaged with MRI?
+* $^1H$
+* $^{12}C$
+* $^{13}C$
+* $^{19}F$
+* $^2H$
+
+Human tissue is ...
+* diamagnetic
+* paramagnetic
+* ferromagnetic
+
+(T/F) When placed in a magnetic field, all the protons ($^1 H$) in the body will line up with the field.
+
+(T/F) When placed in a magnetic field, spins immediately are preferentially aligned with that field.
+
+(T/F) A spin's precession frequency (Larmor frequency) is proportional to the magnetic field it's in.
+
+(T/F) The net magnetization, $\vec{M}$, does not precess at equilibirum.
+
+To create signals in MRI, we need to apply an RF pulse that is ...
+* perpendicular to the main field $B_{0}$, oscillating at frequency $0$ Hz (static)
+* parallel to the main field $B_{0}$, oscillating at frequency $0$ Hz (static)
+* parallel to the main field $B_{0}$, oscillating at a frequency $\gamma B_0$
+* perpendicular to the main field $B_{0}$, oscillating at  a frequency $\gamma B_0$
 
+(T/F) The z-axis is the same in lab and rotating frame.
 
-## Magnetic Fields and RF Coils
+
+
+## RF Coils
+
+(T/F) The RF receive coils detect magnetic flux directly when collecting signals.
+
+What are the benefit(s) of using phased array receive coils?
+* Increase FOV
+* Increase SNR
+* Enables parallel imaging acceleration
+* Enables compressed sensing acceleration
 
 
 ## Contrast
 
+(T/F) Proton density represents the density of all the protons in a given tissue.
+
+The recovery of longitudinal magnetization is proportional to ...
+* $e^{t/T_1}$
+* $1- e^{t/T_1}$
+* $e^{t/T_2}$
+* $1-e^{t/T_2}$
+
+The decay of the transverse magnetization is proportional to ...
+* $e^{t/T_1}$
+* $1- e^{t/T_1}$
+* $e^{t/T_2}$
+* $1-e^{t/T_2}$
+
+(T/F) The amplitude of the net magnetization doesn't change during relaxation.
+
+Which of the following equations is correct?
+* $T_2 \ge T_2^* \ge T_1$
+* $T_2^* \ge T_2 \ge T_1$
+* $T_1 \ge T_2 \ge T_2^*$
+* $T_1 \ge T_2^* \ge T_2$
+
+T2* relaxation depends on ...
+* magnetic field inhomogeneities
+* spin-spin interactions
+* spin-lattice interactions
+* longitudinal relaxation
+
+(T/F) $M_Z$ doesn't contribute to the MR signal.
+
+Calculate the signal in a spin-echo sequence with a 90-degree flip angle $M_0(1-e^{-TR/T1})e^{-TE/T2}$ when TR = ∞
+* $M_0$
+* $0$
+* $M_0(1-e^{-TR/T1})$
+* $M_0 e^{-TE/T2}$
+
+Calculate the signal in a spin-echo sequence with a 90-degree flip angle $M_0(1-e^{-TR/T1})e^{-TE/T2}$ when TE = ∞
+* $M_0$
+* $0$
+* $M_0(1-e^{-TR/T1})$
+* $M_0 e^{-TE/T2}$
+
+A longer TR ...
+* increases T1 weighting
+* reduces T1 weighting
+* increases T2 weighting
+* reduces T2 weighting
+
+A longer TE ...
+* increases T1 weighting
+* reduces T1 weighting
+* increases T2 weighting
+* reduces T2 weighting
+
 1. What flip angle gives the highest SNR for a spoiled gradient echo pulse sequence?
    - 45-degrees
    - 90-degrees
    - 180-degrees
    - $\cos^{-1} ( \exp(-TR/T_1) )$
 
+The signal of an inversion recovery pulse sequence in the steady-state is proportional to ...
+* $M_{0}\cdot(1-2e^{-TI/T1})$
+* $M_{0}\cdot(1-e^{-TR/T1})$
+* $M_{0}\cdot(1-e^{-TI/T1}+e^{-TR/T1})$
+* $M_{0}\cdot(1-2e^{-TI/T1}+e^{-TR/T1})$
+
+(T/F) In a spin-echo sequence, the dephasing of spins in the transverse plane is only eliminated at the spin-echo.
 
+Which of the following image contrasts can be generated by a spin-echo pulse sequence?
+* PDw
+* T1w
+* T2w
+* T2*w
 
-1. What magnetic resonance  property is used to perform fat/water (Dixon) imaging?
+1. What magnetic resonance property is used to perform fat/water (Dixon) imaging?
    - Proton density
    - T1
    - T2
@@ -45,11 +188,19 @@
 
 ## Pulse Sequence
 
+Which of the following are typically components of a pulse sequence diagram?
+* RF Pulses
+* Main field ($B_0$)
+* Magnetic field gradients ($G_X, G_Y, G_Z$)
+* Data acquisition (DAQ)
+
 In a typical pulse sequence, identify the gradients that serve the following functions:
 1. spoil transverse magnetization
 1. refocus Mxy phase across the slice
 1. move to the edge of k-space
 
+![2D FT sequence](images/pulse_sequence-diagram.png)
+
 
 Which of the following statement is true for the slice select refocusing gradient?
 * The slice select refocusing gradient must have the same gradient amplitude with the slice selective excitation pulse.
@@ -63,10 +214,61 @@ Which of the following statement is true for the slice select refocusing gradien
 
 ## RF Pulses
 
+What is the flip angle 
+θ (in radians) of a constant amplitude (hard) RF pulse with an amplitude 
+$B_{1,0}$ and duration $\tau$?
+* $\theta = \gamma B_{10} \tau$
+* $\theta = \gamma B_{0} \tau$
+* $\theta = B_{10} \tau$
+* $\theta = \gamma \tau$
+
+(T/F) When describing the RF excitation, we usually neglect the relaxation terms in the Bloch equations because the RF pulse duration is usually much shorter than the relaxation time constants.
+
+(T/F) A constant amplitude 180° pulse that is the same duration as a constant amplitude 90° pulse requires twice the power.
+
+In slice-selective excitation, thinner slices can be achieved by
+* decreasing the RF pulse bandwidth, $BW_{RF}$
+* decreasing the receive BW
+* decreasing the slice-select gradient strength
+* increasing the slice-select gradient strength
 
 ## Spatial Encoding
 
+(T/F) During frequency encoding, the MRI signal is in the time domain, corresponding to the spatial frequency domain. The Fourier Transform of the signal is in the frequency domain, which corresponds to the image domain.
+
+When is slice selective gradient turned on?
+* during the RF excitaiton pulse
+* between the RF excitation and the readout
+* during the echo (readout)
+
+When is the frequency encoding gradient turned on?
+* during the RF excitaiton pulse
+* between the RF excitation and the readout
+* during the echo (readout)
+
+When is phase encoding gradient turned on?
+* during the RF excitaiton pulse
+* between the RF excitation and the readout
+* during the echo (readout)
+
+When is DAQ turned on during a 2D FT sequence?
+* When the slice selective gradient is on
+* When the RF is on
+* When the phase encoding gradient is on
+* When the frequency encoding gradient is on
+
+According to the Nyquist theorem, to avoid aliasing:
+* The sampling frequency must be at least half the highest frequency in the signal
+* The sampling frequency must be at least twice the lowest frequency in the signal
+* The sampling frequency must be at least twice the highest frequency in the signal
+* The sampling frequency must be at least half the lowest frequency in the signal
+
+(T/F) Aliasing occurs because of oversampling.
+
+(T/F) During 2D multislice imaging, acquisition for one slice must be completed before the acquisition for the next slice can start.
+
 Which k-space line is acquired by the following magnetic field gradients?
+![k-space line sampling](images/kspace_line_question.png)
 
 In 3DFT imaging, the gradient added to the slice encoding axis (compared to a 2DFT) is a ...
 * frequency encoding gradient