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mri Flashcards

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1
Q

What imaging modality is contraindicated for patients with metal implants?

A

MRI

MRI can pose risks to patients with metal implants due to the strong magnetic fields.

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2
Q

What occurs only if the Larmor frequency is equal to radio frequency?

A

Resonance

This phenomenon is essential for the functioning of MRI technology.

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3
Q

Which imaging modality does not require contrast media and is relatively safer than iodinated contrast media?

A

MRI

MRI uses magnetic fields and radio waves for imaging without the need for iodinated contrast.

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4
Q

What causes protons to precess?

A

Magnetic field

The presence of a magnetic field influences the behavior of protons.

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5
Q

What determines how many times the protons precess per second?

A

Precession frequency

It depends on the strength of the external magnetic field.

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6
Q

Who discovered the properties of magnetic resonance?

A

Bloch and Purcell

Their work laid the foundation for MRI technology.

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7
Q

Who is known for the discovery of gradient echo relative to multiecho train imaging?

A

Peter Mansfield

Mansfield’s contributions significantly advanced MRI techniques.

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8
Q

Which imaging modalities can be performed in patients with metal implants?

A

CT Scan, Ultrasound, X-rays

Unlike MRI, these modalities do not pose risks related to metal implants.

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9
Q

What is the wobble of the rotational axis of a spinning body about a stationary axis called?

A

Precession

This concept is crucial in understanding how protons behave in a magnetic field.

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10
Q

What is the term for the magnetic moments of individual hydrogen nuclei aligned in the external magnetic field?

A

Net magnetization

Net magnetization is key to producing MRI signals.

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11
Q

The hydrogen nucleus has a net _______ charge.

A

Positive

This positive charge is fundamental to its behavior in magnetic fields.

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12
Q

What theory uses the direction of magnetic moments to illustrate alignment?

A

Classical theory

This theory contrasts with quantum theory, which uses energy levels.

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13
Q

What theory uses the energy level of nuclei to illustrate alignment?

A

Quantum theory

Quantum theory provides a deeper understanding of atomic behavior in magnetic fields.

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14
Q

What can precessing protons absorb energy from?

A

RF pulse

RF pulses are essential for exciting protons in MRI.

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15
Q

What is the hydrogen precession frequency at 1.5 Tesla?

A

63 MHz

This frequency is standard for many clinical MRI scanners.

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16
Q

What refers to the position of the magnetic moments on their circular precessional path?

A

Phase

Phase is important for the timing of signal acquisition in MRI.

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17
Q

What is used for transmitting RF signals and receiving MR signals?

A

RF coils

RF coils play a crucial role in the functioning of MRI machines.

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18
Q

What is the return of excited nuclei from the high energy state to the low energy state associated with?

A

T1 relaxation time

T1 relaxation is crucial for image contrast in MRI.

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19
Q

What is the gyromagnetic ratio of hydrogen at 1.5 Tesla?

A

63.86 MHz

This value is critical for calculating precession frequencies.

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20
Q

What occurs when an object is exposed to an oscillating perturbation close to its own natural frequency?

A

Resonance

This principle is fundamental in various imaging techniques.

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21
Q

What is a loop of current-carrying wire placed in the area of inhomogeneity called?

A

Shim coil

Shim coils help improve image quality by correcting magnetic field inhomogeneities.

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22
Q

What are current-carrying coils designed to produce a desired gradient magnetic field used for?

A

Slice selection

Gradient coils are essential for obtaining images of specific anatomical slices.

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23
Q

What intrinsic parameter is related to the density of protons in the tissue?

A

Proton density

This parameter influences the brightness of images in MRI.

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24
Q

What has a long T1 relaxation time?

A

Water

Water’s long T1 value is significant for imaging applications.

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25
What are a series of radio wave pulses designed to excite nuclei called?
Pulse sequences ## Footnote Pulse sequences are tailored to optimize image quality and contrast.
26
What type of images visualize pathology such as inflammation and tumors?
T2 weighted images ## Footnote T2 weighted images are particularly sensitive to fluid content in tissues.
27
What type of images best demonstrate anatomy?
T1 weighted images ## Footnote T1 weighted images provide clear anatomical details.
28
What is the return of excited nuclei to their normal state by the release of energy called?
Relaxation ## Footnote Relaxation processes are key to generating MRI signals.
29
What refers to inhomogeneities of the external and internal magnetic field?
T2 relaxation time ## Footnote T2 relaxation time is influenced by tissue characteristics and magnetic field uniformity.
30
What depends on surroundings, tissue composition, and structure?
Spin lattice relaxation time ## Footnote This time varies based on the environment of the nuclei.
31
What is decreased in a signal by 37%?
T2 relaxation time ## Footnote This decrease affects image quality and contrast.
32
What is parallel with the external magnetic field?
T1 relaxation time ## Footnote This relationship influences the behavior of spins in the magnetic field.
33
What is the angle through which the NMV is moved as a result of an RF excitation?
Flip angle ## Footnote The flip angle is crucial for determining the resulting signal strength.
34
What affects the length of a relaxation period after the application of one RF excitation pulse?
Repetition time ## Footnote Repetition time is significant for determining image contrast.
35
What affects the length of the relaxation period after the removal of the RF excitation pulse?
Time to echo ## Footnote Time to echo is critical for signal acquisition timing.
36
What is the extrinsic parameter that affects image quality?
Flip angle ## Footnote The flip angle is controlled by the operator and affects image contrast.
37
What parameters are inherent to tissue and do not come under the operator's control?
Intrinsic contrast parameters ## Footnote These parameters are determined by the tissue's physical properties.
38
What is the time from the application of one RF pulse to another RF pulse called?
Repetition time ## Footnote This timing is essential for optimizing image acquisition.
39
What comprises hydrogen atoms linked to oxygen, consisting of small molecules with high molecular motion?
Water ## Footnote Water's properties are crucial for MRI imaging due to its high proton density.
40
What has high signal intensities seen in T1 weighted images?
Fat ## Footnote Fat appears bright in T1 weighted images due to its short T1 relaxation time.
41
What has high signal intensities seen in T2 weighted images?
Synovial fluid ## Footnote Synovial fluid is prominently visible in T2 weighted images due to its fluid content.
42
What has low signal intensity seen in T2 weighted images?
Cortical bone ## Footnote Cortical bone appears dark in T2 weighted images due to low proton density.
43
What has low signal intensity seen in T1 weighted images?
Calcification ## Footnote Calcification appears dark in T1 weighted images.
44
What is an approximate T1 value of adipose tissue in ms?
240-250 ## Footnote This value is important for differentiating adipose tissue in MRI.
45
What is the approximate T2 value of adipose tissues in ms?
60-80 ## Footnote This T2 value helps in assessing fat content in tissues.
46
What initiates the appropriate radiowave transmission?
Operators console ## Footnote The console controls the MRI system and manages the imaging process.
47
What produces a magnetic field by passing electric current through a coil of wire?
Resistive magnet ## Footnote This type of magnet is commonly used in MRI machines.
48
What bathes the wires of the magnet in liquid helium to maintain superconductive properties?
Superconducting electromagnet ## Footnote Superconducting magnets are essential for high-field MRI systems.
49
What is a double-walled flask of metal with a vacuum between the walls called?
Dewar ## Footnote Dewars are used to store liquid helium for superconducting magnets.
50
What produces a magnetic field without requiring an external electricity supply?
Permanent magnet ## Footnote Permanent magnets are used in specific MRI applications.
51
Along TR and long TE will result in _______ proton density weighted images.
T2 weighted images ## Footnote T2 weighted images provide contrast based on proton density.
52
What demonstrates anatomy and pathology in MRI?
Proton density weighted images ## Footnote These images are particularly useful for visualizing anatomical structures.
53
Tissues with a low proton density appear ______.
Dark ## Footnote Low proton density tissues do not produce strong MRI signals.
54
Tissues with a high proton density appear ______.
Bright ## Footnote High proton density tissues produce strong MRI signals.
55
Tissues with a short T2 decay time such as fat appear ______.
Dark ## Footnote Fat has a rapid decay time, making it less visible in T2 weighted images.
56
In T1 weighted images, tissues with short T1 relaxation times such as fat appear ______.
Bright ## Footnote Fat appears bright due to its short T1 relaxation characteristics.
57
What comprises hydrogen atoms mainly linked to carbon, making up large molecules?
Fat ## Footnote Fat molecules are significant for MRI due to their high proton content.
58
True or False: PARAMAGNETIC refers to materials that alter the magnetic field or nearby nuclei.
TRUE ## Footnote Paramagnetic materials can enhance MR signals.
59
True or False: Diffusion means spontaneous random motion of molecules in a medium.
TRUE ## Footnote Diffusion is an important concept in understanding the behavior of molecules in tissues.
60
True or False: Perfusion describes the flow of blood through the vessels of an organ or anatomic structure.
TRUE ## Footnote Perfusion is critical for assessing tissue viability in imaging.
61
True or False: Relaxation time is a measure of the rate at which nuclei, after stimulation, release their extra energy.
TRUE ## Footnote Understanding relaxation times is essential for MRI image contrast.
62
True or False: Resonance is a process of energy absorption by an object that is turned to absorb energy of a specific frequency only.
TRUE ## Footnote Resonance is fundamental to MRI operation.
63
True or False: Spectroscopy is the science of analyzing the components of an electromagnetic wave, usually after its interaction with some substance.
TRUE ## Footnote Spectroscopy can provide additional information about tissue composition.
64
True or False: T1 relaxation is also known as spin lattice relaxation.
TRUE ## Footnote This term describes the process of energy transfer to the surrounding lattice.
65
True or False: Spin spin relaxation is the release of energy by excited nuclei to their general environment.
TRUE ## Footnote Spin spin relaxation is important for understanding T2 relaxation.
66
True or False: Specific absorption rate (SAR) is used to calculate an expected increase in body temperature during an average MR examination.
TRUE ## Footnote SAR is a critical safety parameter in MRI.
67
True or False: Stray field is a portion of the magnetic field extending away from the confines of the magnet that cannot be used for imaging but can affect nearby equipment or personnel.
TRUE ## Footnote Managing stray fields is important for safety in MRI environments.

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