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P3 Physical > Multi-Modal Imaging - Motivation, Synchronicity, Instrumentation & Data Quality Issues > Flashcards

Multi-Modal Imaging - Motivation, Synchronicity, Instrumentation & Data Quality Issues Flashcards

1
Q

What is multi-modal imaging?

A

Simultaneous production of signals got more than one imaging technique

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2
Q

What is an example of multi- moral imaging?

A

One could combine using optical, magnetic and radioactive reporters to be detected by SPECT, MRI and PET

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3
Q

Who undergoes multiple imaging for any given condition?

A

Most (all?) patients in tertiary medical centres

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4
Q

What is multi-modal imaging used for?

A

Visualise various aspects of the patients condition:

  • Brain morphology and pathology
  • Brain metabolism
  • Brain’s electrical activity
  • Skull (for surgery)

Optimal use of this information can be achieved through multi-modal data fusion

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5
Q

What does multimodal imaging enable?

A

Examining more than one molecule at a time, so that cellular events may be examined simultaneously or the progression of these events can be followed in real time

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6
Q

What is multi-moral imaging a combination of?

A

Images or maps

  • from different sources (instruments) or from the same scanners but using different sequences
  • that show different aspect of the body’s structure or function (e.g. MR contrasts)
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7
Q

What is the fundamental assumption of multi-modal imaging?

A

All measurements (images) relate your the same phenomenon

  • if you bring all of the data together and show it is in a fused image - co-registered side by side
  • there is no time difference between the two
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8
Q

What are the two crucial consideration of multi-modal imaging?

A
  1. Space

2. Time

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9
Q

What is an example of multi-modal imaging?

A
  1. EEG-fMRI
    - these are fMRI statistical maps superimposed on the structural scans showing both changes, fMRI changes into an EEG pattern showing patients with generalised epilepsy
  • BOLD changes are correlated with the amount of generalised spike waves
  • All the images are co-registered
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10
Q

What is a holding structure for surgical instrument?

A

The skull

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11
Q

Why is it difficult to segment the skull from fMRI?

A

Because CSF is quite dark - you can’t tell the difference between bone and CSF

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12
Q

What is fMRI and structural MRI?

A
  1. fMRI maps are always superimposed on structural MRI - done in SPM
  2. It is easy to believe the blob is exactly there
  3. This is the result of an operation that can fail - superimposition of 2 images can fail
  4. If the blob is off by 3cm - it can end up in The air, in the eye but if it is closer to where it should be
  5. A software always produces an answer
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13
Q

What is PET-CT?

A
  1. This is a merged instrument
  2. This is good for abdominals
  3. Abdominal imaging is difficult - the head doesn’t move but the abdomen always moves
  4. Big efforts to have two images acquired at the same time
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14
Q

What is the principle and aim of multi-modal imaging data

A

Ensure that all data is comparable

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15
Q

What are two equivalent ways of looking at multi-modal imaging?

A

All the information to be shown must…

  • relate to the phenomenon of interest
  • Be up to date
  • Accuracy - being true to the reality
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16
Q

What are two considerations of multi-modal imaging data?

A
  1. Acquisition co-localisation

2. Acquisition synchrony

17
Q

What are the fundamental underlying problem with multi-nodal imaging data?

A
  1. Images are powerful
  2. We tend to believe what we see
  3. Need to carefully consider how the multi-modal data is acquired, processed and displayed
  4. Most fused images are the result of lot of processing
18
Q

What are examples of acquisition co-localisation?

A
  1. Same field of view or built-in co-registration: ‘PET-CT’
    - post-acquisition co-registration unnecessary
  2. Different fields of view: MRI & CT
    - post-acquisition co-registration necessary
19
Q

What is same fields of view or built-in co-registration: PET-CT?

A
  1. The subject doesn’t move, you acquire two images at the same time it is built in
  2. It is acquired at the same time at the same space
  3. It produced co-registered images by design
20
Q

Different fields of view: MRI + CT

A

Co-registrations are required

21
Q

What are the key operational questions of co-localisation?

A
  1. How precisely must the data be co-registered
    (Often. Neglected consideration)
    - aswell As possible given available means
  2. Are the data from the same image space or not?
    - decide on co-registration strategy
22
Q

What are examples of same acquisition sessions ?

A
  1. Maintain field of view
    - Subject immobilisation
    - Sale scanning matrix
  2. Change field of view

Different acquisition sessions

  1. Maintain field of view
    - subject re-positioning
    - recall scanning matrix (MRI)
  2. Change field of view
23
Q

What are the key operational questions for acquisition synchrony?

A
  1. What is the tome scale of the phenomenon in relation to data acquisition time’s?
    - is the date ‘accurate’: is it up to dates
  2. Are we interested in individual or averaged events
24
Q

What is Acquisition synchrony?

A
  1. This is about what is happening in the subjects brain, are all my images up to date
  2. Or how quickly are things changing - can I use the structural MRI from a month ago to do surgery
  3. If I am to use the lesion in MRI -can I use that scan in the operating theatre to target lesion
  4. You might have some relevant information because you have analysed their old scan much more time to analyse the old scan
25
Q

What is linearly related?

A

Neuronal response and BOLD response

26
Q

What is an example study for the acquisition synchrony?

A

The Neuronal basis of BOLD decreases

Technique: simultaneous BOLD and micro-electrode neurophysiology in primates

27
Q

What are the phenomena of interest and acquisition synchrony?

A
  1. Reproducible or slow events (e.g. evokes responses, brain structure/function)
    - different data acquisition sessions - allow study of averaged, typical or slow effects
  2. Simultaneous (synchronous) data acquisitions
    - allow study of individual event
    - possible dada degradation
  3. Unpredictable (spontaneous), brief, unique events (e.g. epileptic spikes, seizures)

Simultaneous acquisition are necessary

  • averaged effects and single realisations (individual events)
  • possible data degradation
28
Q

What is a downside; inference of synchronous multi-model acquisitions?

A

The combined instruments might interact
- possible interferences

  1. The introduction of a modality in the environment of another can lead to undesirable effects:
    - performance degradation (data quality degradation)
    - additional safety risks
  2. Modifications or remedial post-hoc measures may be required
    - hardware modifications
    - acquisition protocol modifications
    - additional data processing
29
Q

What are example applications of multi-modal imaging?

A
  1. CT & MRI
  2. PET-CT
  3. FMRI & structural MRI
  4. FMRI & MRI: application in neuro-navigation
  5. EEG-fMRI
30
Q

What is CT & MRI?

A
  1. Instrumentation: MR and CT scanners used in separate sessions
  2. Application: visualise soft tissue in relation to radio-opaque structures
    - Brain vs. Bone or implanted objects
  3. Synchrony requirement; low to medium, depending on the precise circumstances
  4. Co-localisation: post-hoc registration
    - data quality issue: different geometric distortion between CT and MR
31
Q

What is ‘PET-CT’?

A

Instrumentation: combined PET-CT instrumentation

Application: measure glucose intake in organs in oncology

Synchrony requirement: high in abdominal application

Co-localisation: same space
Motivation: perfect registration of moving tissues

Data quality issues: not the the best PET not CT but adequate for purpose

32
Q

What is fMRI & structural MRI?

A

Instrumentation: MR scanner

Application: measure brain activity (haemodynamic) in relation to brain structure for functional mApping for neurosurgery

synchrony requirement; low to medium

Co-localisation: post-hoc registration
Data quality issue: different geometric distortion between MRI sequences

33
Q

What is fMRI & MRI: application in neuro-navigation?

A

Additional considerations:
Synchrony requirement: low-Hugh
Co-localisation: co-registration of instruments with images
Data quality issue: image update

34
Q

What is EEG-fMRI?

A

Instrumentation: combined EEG system - MR scanner

Application, measure haemodynamic of brain activity identified on EEG and in relation to brain structure: BOLD mapping and epileptic activity

Synchrony requirement: Hugh

Co-localisation requirement: low-medium; post-hoc registration

Data quality issue: interference between EEG and MR Systems

P3 Physical (21 decks)

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