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Neuroanatomy > Brain Imaging > Flashcards

Brain Imaging Flashcards

1
Q

Which brain imaging modality uses a rotating x-ray beam?

A

Computed Axial Tomography (CAT) Scan

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2
Q

How are attenuation variations in tissue detected in CT Scan?

A

X-ray source and X-ray detector move circularly and the detector picks up radiodensity information from several directions to reconstruct a 3D Image. Patient moving through scanner slowly allows more information to be detected.

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3
Q

CT enhances visualization of what in the brain?

A
  • bony anatomy

- elements with high atomic numbers(Ca, Fe,I, Ba, Pb)

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4
Q

What pathologies are often detected by CT ?

A

Infarction, Tumors, Calcification, hemorrhage, acute stroke, and bone trauma

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5
Q

In a CT Scan Tumor is detected by:

A

swelling and anatomical distortion

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6
Q

In a CT Scan, a hypodense (dark) structure indicates:

A

Edema and infarction (differences in grey matter appear and differences in gray/white differentiation disappear)

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7
Q

In a CT Scan, a hyperdense sturcture (bright) can indicate:

A

calcifications and hemorrhage

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8
Q

Bone trauma is detected in a CT Scan by observation of:

A

bone disjunctions in bone windows

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9
Q

Loss of blood suppply and oxygen to portion of the brain is known as :

A

An Infarct

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10
Q

Spatial Resolution is greater in CT or MRI?

A

CT (several mm); MRI (1mm)

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11
Q

TBI diagnosis and prognosis is significantly affected by what clinical finding?

A

Intracranial bleeding

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12
Q

Heme and other blood products released during trauma lead to what pathologies?

A
  • Subarachnoid Hemorrhages
  • Intraparenchymal Contusion (bruising of brain tissue)
  • Hematomas (bleeding in or around brain)
  • Intrinsic Cellular Injury
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13
Q

Which brain imaging modality uses Nuclear Magnetic Resonance?

A

Magnetic Resonance Imaging (MRI)

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14
Q

What is the advantage of using MRI?

A

No radiation is used; Frequency waves are used instead of X-rays

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15
Q

What are the advantages of using CT scans?

A

It is faster and less expensive than MRI thus can be used as an initial screening and assessment tool

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16
Q

Does a CT Scan or MRI have better contrast difference (high resolotion and detailed visualization) between soft tissues?

A

MRI

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17
Q

What pathologies can best be detected on MRI and why?

A

demyelinating and infectious diseases because MRI has special ability to visualize anatomy- gray, white matter, CSF

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18
Q

What in a proton produces a magnetic field?

A

The Spin

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19
Q

How much of the body is made of hydrogen atoms?

A

63%

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20
Q

Describe the response of a protein spin to an external magnetic field.

A

It aligns against or with the field. It wobbles or “precess” at a frequency proportional to the field. This leads to a net magnetization of the tissue.

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21
Q

What is the purpose of applying the radiofrequency pulse?

A

It tips the protons away from the direction of magnetaization allowing a more readily detection of magnetization. The RF signal is picked up by an antennae and is formed by the energy decay that occurs when a proton realigns with the field when the radiofrequency pulse is turned off. Rate of decay differs by tissue type.

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22
Q

Fourier transform algorithms purpose:

A

to decode RF signal into images.

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23
Q

What does a numerical index represent in Digital Image Construction?

A

Gray-scale level represented by Tissue composition of the particular pixel

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24
Q

Timing of RF pulse can be varied. How and what are the effects/

A

Rapid repetitions of RF pulse enhange gray-white contrast. Infrequent repetitions enhances signal from water which is increased in pathological conditions (like lesions).

25
Q

What are the components of a MRI Scanner?

A

Magnet (Increased strength in Teslans-1.5T is common- high is 7- increases contrast), Gradient Coil, RF Coil. T2 Flair enhances lesion presence

26
Q

Anatomic MRI can be used to diagnose what diseases?

A 
Inflammatory Diesease (Multiple Sclerosis)
Neoplsatic Disease (Tumors)
Epilepsy
Cerebrovascular Disease (stroke)
27
Q

Magnetic Resonance Spectroscopy allows us to study ________

A

chemical structures of brain and derive concentrations and ratios of chemicals.

28
Q

MRS separates out components of the following chemical structures in the brain

A

N-acetylaspartate (neuronal marker located in cell bodies and dendrites)
Choline( demyelination marker; cell membrane synthesis and degradation)
Creatinine (glial marker)
Lactate (found following ischemic events)

29
Q

In MRS, application of a RF pulse causes

A

the emission of a specific frequency by each chemical component (metabolite)

30
Q

What determines the size of the peak produced in the conentration of each metabolite in a MRS?

A

the size of the peak produced from Fourier transforms analysis

31
Q

How can we study a lesion using MRS?

A

Study its evolution and type (discriminate normal tissue from tumor tissue)

32
Q

Diffusion Weighted Imaging and Diffusion Tensor Imaging allows us to …

A

visualize and measure the integrity of white matter tracts in the brain

33
Q

What are three gradient-directions in a DWI? its purpose?

A

alignment of magnetic fielld in 3 different directions to estimate the trace of the diffusion tensor or “average diffusivity” a measure of edema.

34
Q

What reflects the bet estimate of rate of water diffusion at the location in a DWI?

A

Intenstiy of each image element (Voxel)

35
Q

Measurement of water diffusion along different orientations within axons is known as

A

Ansiotropy (Fractional Ansiotropy is calculated based on both axial and radial diffusivity)

36
Q

What restricts the flow of water in an axon?

A

cell membranes and meylin (in the perependicular direction)

37
Q

Measurement of diffusion in a DWI is

A

along length of longitiduinal axis of the axon. the larger the coefficient, the greater diffusion

38
Q

Radial diffusiivity is

A

the diffusion along the perpendicular axes of voxel, in both directions

39
Q

Color Coding DTI:

A

red- transverse- lateral to medial
green-longitudinal-anterior to posterior
blue - horizontal- superior to inferior

40
Q

Functional Magnetic Resonance Imaging allows us to ..

A

acquire images of the brain while patients are performing cognitive tasks in MIR scanner.

41
Q

Clinical advantages of fMRI

A

It shows plasticity in brain . one can understand

  • neural sysgtems that make performance of cognitive tasks possible
  • understand changes in brain function with disorders and aging
  • understand sites of neural reorganization following stroke or injury
42
Q

How is increased neural activity detected in fMRI?

A

INcreased blood flow to region of the brain with increased activity- changes in local cerebral blood volume and oxyhemoglobin (paramagnetic)

43
Q

changes in intensity of values on MR images

A

BOLD signal- measured during baseline and experimental conditions

44
Q

Hemodynamic peak response occurs over what time duration?

A

4-6 s

45
Q

Control condition in fMRI is

A

taks has all features of the experimental task except the specific cognitive variable of interest

46
Q

fMRI experimental condition:

A

TASK IS COMPRISED OF TEH SPECIFIC COGNITIVE VARIABLE OF INTEREST

47
Q

Activation Maps are__________ on brain images

A

superimposed

48
Q

Limitations of fMRI

A
  • limitations of temporal and spatial resolution

- relation between neuronal activity, blood flow and fMRI signals not definitely established

49
Q

This brain imaging modualtiy usees cyclotorn to prepare radioactive isotorpe tracers incorportated int a biolgoically acctive molecule in physiological sites

A

Positron Emission Tomography

50
Q

When does the scannner image postiron-emitting tracer

A

upon its decay

51
Q

Name too findings in fMRI scan for amygdal, prefrontal cortex, and left parietla low grade astroctyoma

A

Amygdala present different in emotions and PFC regions are improtant for memory formation but have prolonged maturational trejectory- mesial temporal lobe/ S[eecj areas areas defined in astrocytoma afftected patient. 2 languages can be in 2 different areas

52
Q

PET applications

A

Blood flow and perfusion
Metabolism (traces glucose and oxygen uptake)
Neurotransmitter Integrity: Ligand/ Neuroreceptor imaging (dopamine synthesis and reuptake- radiotracers bind to rpe and psost synaptic neuroreceptors)

53
Q

PET advantages over CT or MRI:

A

Functional Imaging
Physiologcial variables can be determined

It can distinguish radiation necrosis from tumor recurrence(hypermetabolic) with a high specificity. Radiation necrosis is hypometabolic of FDG-{ET

54
Q

Which matter is lost in Alzheimer’s Disease?

A

Grey; Brain activity correlates with memory decline

55
Q

Which gene and allele carriers increased brain activation during memory tasks in AD?

A

APOE 4gene/ Brain activity correlates with memory decline

56
Q

What disorders can be detected with PET?

A

Psychiatric/ Addictive/ Degenerative Disorders and Epilepsy

It is also useful in grading brain tumors nad determining their progonsis.

57
Q

Measurements provided by MRI

A

Brain structure
Vasculature
Chemical Structure
Fiber Tracts

58
Q

MRI disadvantages

A

Long study duration
No ferromagentic or electronic devices
Clasutrophobic

59
Q

PET disadvantages

A

Ionizing radiation
Costly
limted access
tracer production

Neuroanatomy (6 decks)

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