TNS Exam 1
What is precession? - ANSWER-Protons precess about an axis and the frequency
depends on external field strength (B0) and the type of atom
What is excitation? - ANSWER-sending energy into spinning nuclei which puts them in
a higher energy level
What are T1 scans? - ANSWER-They involve single 90 degree pulses. As the signal
decays contrast is enhanced, the overall strength signal weakens.
- lightest: white matter
- gray: gray matter
How to read T value? - ANSWER-- larger T-value = the more different the groups are
- more different groups are = better chances that groups are "significant"
How to read P value? - ANSWER-- smaller P value = more different the groups are
- threshold: .05 or .01 usually
- the probability of being wrong if you conclude that your groups are different
When to use an ANOVA test? - ANSWER-When making multiple comparisons between
groups
- because if we were to do a t-test, it would be more likely to make an incorrect
conclusion since each additional comparison with a t-test multiplies probability of
making a mistake
What is the alpha value? - ANSWER-the probability of making a type 1 error (false
positive) that a researcher is willing to make (usually it is 0.05)
- threshold value used to determine whether a test statistic is statistically significant
What is a sampling distribution? - ANSWER-Mean, Proportion, and T-sampling
distribution
- generally uses the central limit theorem for construction
What is the critical value? - ANSWER-It is the cutoff between retaining or rejecting null
hypothesis
- regions where test statistic is unlikely to lie
What is the obtained value? - ANSWER-
What is Magnetic Resonance Imaging? - ANSWER-It is a cylindrical magnet with an
open bore, and has an electromagnet. It is usually super conducting. It various transmit
and receive antennae through radiofrequency.
, What is the primary motivation of experimentation? - ANSWER-To disprove or fail to
disprove a hypothesis
What does the scientific method consist of? - ANSWER-Formalized steps where by a
theory is formed, tested, and revised
What's the purpose of hypothesis testing? - ANSWER-Used to evaluate the strength of
evidence from the sample and provides a framework for making determinations
When should a t-test be used? - ANSWER-When comparing the averages of two
groups, with relatively small samples
How does the magnetic field of MRI work? - ANSWER-As protons rotate, it creates a
tiny magnetic field. The external field (B0) aligns the protons parallel and antiparallel to
B0. There are more protons that align parallel compared to antiparallel.
What is a signal? - ANSWER-It is a simple echo taken at time T1 of a single pulse.
What is T2 scans? - ANSWER-It involves two pulses: one pulse is to flip the protons to
90 degree precession, the other pulse is to flip dephasing protons into phase and at 180
degrees.
- It tales advantage of tissues whose protons take longer to fall out of phase
- darkest: white matter
- gray: gray matter
What is repetition of MRI? - ANSWER-It is the balance of temporal resolution & signal to
noise ratio.
- How long the tissue can relax to B0 before next pulse
What is TE? - ANSWER-The time after 90 degree pulse that the echo is sampled and
depends on magnet strength and type of scan
- T1: 14msec
-T2: 90msec
What is the repetition time (TR) of T1 and T2 MRI? - ANSWER-T1: 500msec
T2: 4000msec
What is fMRI? - ANSWER-has many variations, generally fast scans, must accompany
anatomical scan and is tuned to signal that will reveal something about brain function
FMRI compared to anatomical scans? - ANSWER-- lower spatial resolution but more
images = high temp.
- higher temporal resolution
- motion has effect on signal
What is precession? - ANSWER-Protons precess about an axis and the frequency
depends on external field strength (B0) and the type of atom
What is excitation? - ANSWER-sending energy into spinning nuclei which puts them in
a higher energy level
What are T1 scans? - ANSWER-They involve single 90 degree pulses. As the signal
decays contrast is enhanced, the overall strength signal weakens.
- lightest: white matter
- gray: gray matter
How to read T value? - ANSWER-- larger T-value = the more different the groups are
- more different groups are = better chances that groups are "significant"
How to read P value? - ANSWER-- smaller P value = more different the groups are
- threshold: .05 or .01 usually
- the probability of being wrong if you conclude that your groups are different
When to use an ANOVA test? - ANSWER-When making multiple comparisons between
groups
- because if we were to do a t-test, it would be more likely to make an incorrect
conclusion since each additional comparison with a t-test multiplies probability of
making a mistake
What is the alpha value? - ANSWER-the probability of making a type 1 error (false
positive) that a researcher is willing to make (usually it is 0.05)
- threshold value used to determine whether a test statistic is statistically significant
What is a sampling distribution? - ANSWER-Mean, Proportion, and T-sampling
distribution
- generally uses the central limit theorem for construction
What is the critical value? - ANSWER-It is the cutoff between retaining or rejecting null
hypothesis
- regions where test statistic is unlikely to lie
What is the obtained value? - ANSWER-
What is Magnetic Resonance Imaging? - ANSWER-It is a cylindrical magnet with an
open bore, and has an electromagnet. It is usually super conducting. It various transmit
and receive antennae through radiofrequency.
, What is the primary motivation of experimentation? - ANSWER-To disprove or fail to
disprove a hypothesis
What does the scientific method consist of? - ANSWER-Formalized steps where by a
theory is formed, tested, and revised
What's the purpose of hypothesis testing? - ANSWER-Used to evaluate the strength of
evidence from the sample and provides a framework for making determinations
When should a t-test be used? - ANSWER-When comparing the averages of two
groups, with relatively small samples
How does the magnetic field of MRI work? - ANSWER-As protons rotate, it creates a
tiny magnetic field. The external field (B0) aligns the protons parallel and antiparallel to
B0. There are more protons that align parallel compared to antiparallel.
What is a signal? - ANSWER-It is a simple echo taken at time T1 of a single pulse.
What is T2 scans? - ANSWER-It involves two pulses: one pulse is to flip the protons to
90 degree precession, the other pulse is to flip dephasing protons into phase and at 180
degrees.
- It tales advantage of tissues whose protons take longer to fall out of phase
- darkest: white matter
- gray: gray matter
What is repetition of MRI? - ANSWER-It is the balance of temporal resolution & signal to
noise ratio.
- How long the tissue can relax to B0 before next pulse
What is TE? - ANSWER-The time after 90 degree pulse that the echo is sampled and
depends on magnet strength and type of scan
- T1: 14msec
-T2: 90msec
What is the repetition time (TR) of T1 and T2 MRI? - ANSWER-T1: 500msec
T2: 4000msec
What is fMRI? - ANSWER-has many variations, generally fast scans, must accompany
anatomical scan and is tuned to signal that will reveal something about brain function
FMRI compared to anatomical scans? - ANSWER-- lower spatial resolution but more
images = high temp.
- higher temporal resolution
- motion has effect on signal
