MRI T1 and T2 Weighted Images Quiz

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Questions and Answers

What is the appearance of fatty structures in T1 recovery-weighted images?

They appear brighter (correct)

They appear dark

They appear grey

They appear black

What is the effect of increasing TR time in T1 recovery-weighted imaging?

It decreases T1 relaxation time

It influences fluid visibility

More structures are brighter (correct)

Structures become darker

In T2-weighted imaging, how is fluid visualized?

As bright (correct)

As grey

Not visible at all

As dark

What is the preferred TE time to observe fluid in T2-weighted images?

Right before fluid starts to dephase Signup and view all the answers

To achieve a 'long drink' in T2-weighted imaging, what is the strategy regarding TR and TE times?

Long TR and long TE Signup and view all the answers

Which structure in T1-weighted imaging is typically seen as darker?

Fluid Signup and view all the answers

What primarily controls T2-weighted imaging contrast?

TE time Signup and view all the answers

How does increasing TE time affect visibility of only fluid in T2-weighted images?

Increases fluid visibility Signup and view all the answers

What is the reason for slow T1 recovery in water compared to fat?

Water has a higher energy than fat. Signup and view all the answers

How does matrix size affect scan time and spatial resolution?

Increasing matrix size increases scan time and improves spatial resolution. Signup and view all the answers

Which structure is expected to produce the highest signal in a T1 weighted image?

Tightly bound hydrogen nuclei Signup and view all the answers

What is the primary purpose of the gradient coils in MRI?

To manipulate the magnetic field. Signup and view all the answers

For a T1 weighted image, which of the following describes the TR?

It is the time between RF pulses. Signup and view all the answers

When assessing structures in the brain, which image is best suited for differentiating between white and grey matter?

Proton density image Signup and view all the answers

Why is the axial plane commonly used for brain scans?

It shows the brain best for analyzing lesions. Signup and view all the answers

Which imaging technique utilizes a flip angle of 90 degrees in spin echo sequences?

T1 weighted imaging Signup and view all the answers

What effect does the additional magnetic field have on the main magnetic field?

It can add or subtract from the main magnetic field linearly and predictably. Signup and view all the answers

What is a key reason for using T2* (gradient echo) sequences?

They are useful for identifying magnetic susceptibility artifacts. Signup and view all the answers

Why should gradient echo not be used for patients with metal implants?

It will show significant artifacts affecting image quality. Signup and view all the answers

What happens to the slices when a gradient is applied?

Only the slice at the specific frequency is excited. Signup and view all the answers

What is the implication of using smaller flip angles in imaging?

They speed up the exam by creating shorter TR times. Signup and view all the answers

What distinguishes gradient echo sequences from spin echo sequences in terms of scan time?

Gradient echo sequences process in the 100s of milliseconds. Signup and view all the answers

What is one main drawback of gradient echo sequences?

They are susceptible to inhomogeneities due to metal artifacts. Signup and view all the answers

What is the relationship between TR, phase encoding, and the number of excitations in scanning?

Scan time is calculated as TR multiplied by the number of excitations and phase encoding. Signup and view all the answers

Study Notes

T1 Recovery/Weighted Images

Fatty structures appear brighter in images
White matter (containing myelin, which is fatty) appears paler than gray matter
Fluid appears dark
TR (repetition time) of 400-650ms allows for structure recovery, excluding fluid
300ms for pure fat; 400ms for fatty structures
CSF, gray, and white matter require a longer TR for contrast differentiation.
Images can be taken with an echo time (TE) of 15ms before fat decays.
Short TE and short TR are used for T1 weighted images
Fat dephases quickly; resulting in faster T1 recovery. Fat has a greater longitudinal magnetization.

T2 Decay/Weighted Images

Fluid appears bright in images
Golden standard for assessing cancers, edema, and inflammation
Cancers often contain fluid.
Edema and inflammation frequently show associated fluid.
Fluid needs to be in transverse plane and in phase to appear as bright.
Waiting for fluid to recover and decay allows all structures to be in the same axis.
This isn't ideal; TR doesn't control T2 weighting.
TE controls T2 weighted images
Wait for fatty structures to decay to choose the right TE time before fluid dephases.

Additional Notes

Fluid dephases rapidly at 90° TE. Higher TE with a long TR will result in a faster scan time. Longer TE is used to only see the fluid.
TR control is used for assessing structures, and TE is used for assessing fluids.
Best sequence is chosen for a particular pathology and then repeated if possible.
Radiologist should be consulted for patient agitation.
TR controls image weighting.
Longer TR means structures are brighter
TR determines the amount of T1 relaxation.
Time between RF pulses; signal listens for time between pulses. Signal time will never be more than TR.
Myographic effect for spine (CSF surrounds chord): Very bright T2 weighted image to visualize fluid, increase the TE value to almost 800ms.
Water has higher energy than fat and doesn't absorb the RF pulse energy as much.
Water diphases less readily than fat, because the protons do not collide as frequently. Molecular tumbling is faster than the frequency, leading to slower recovery in water.
Matrix of 256 x 192; the second number determines the number of RF pulses (or TR's) that happen. 192 TR, gives an indication of scan time. A T1 weighted scan will have a shorter scan time. (T1 = 300ms x 192 = shorter scan time; T2 = 3000ms x 192 longer scan time).
Decreasing matrix will decrease scan time but also decreases spatial resolution.
High resolution = high matrix = smaller pixels
Pulse sequences are operator controlled.
Series of RF pulses and recovery times.
Proton density images are based on hydrogen concentration. Some structures have more or less hydrogen. Bones minus marrow typically have little hydrogen. Bone marrow generally gives a signal on T1 due to fat. Bones show up as bright on a T1 due to fat within. CSF is rich in hydrogen causing a good signal to differentiate gray and white matter. Good for multiple sclerosis and to visualize structures in the brain.
Always include sagittal proton density for MS and corpus collosum. The axial plane is generally best for imaging the brain, along with the corpus callosum.
T1: short TR and short TE; T2: long TR and long TE. Never short TR and long TE.
Premature dephasing (T2*) is from inhomogeneities within the magnet, leading to faster dephasing.
Spin echo and gradients include 90° and 180° pulses. First RF pulse is the FID. Acts like a wall that bounces back and speeds up the slow to read the signal. The 180 degree pulse from one side to the other helps to get the nuclei phase to be the same.
Gradient echo and pulse sequences do not have an 180° pulse but use bipolar gradients to reverse and rephase the process. This technique allows for shorter scan times in T2*; but is susceptible to metal artifacts.
Scan time is estimated as TR x phase encoding (second number of matrix) x number of excitations.
Compensates for premature dephasing; gradients cause loud noises, not the RF pulses.
Short flip angle for T1 and PD, allows quick recovery with no 180 degree pulse.
T1 weighted: larger flip angle, short TR. T2 weighted: long TR, small flip angle.

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Description

Test your knowledge of T1 and T2 weighted MRI images with this quiz. Learn about the differences in appearance between fatty structures, fluid, and various types of brain matter. Explore key concepts related to TR and TE, and their effects on image quality and diagnostic value.