Functional MRI

Functional magnetic resonance imaging (fMRI) is a technique used to obtain functional information by visualising cortical activity. fMRI detects subtle alteration in blood flow in response to stimuli or actions. It is used in two broad ways:

  1. clinical practice
    • typically in pre-surgical patients 
  2. research 
    • often cohort of patients (often normals)
    • aimed at elucidating novel neural networks

fMRI is technically challenging to perform as the techniques used to visualise cortical activity (typically BOLD imaging) rely on minute changes in a low signal-to-noise ratio (SNR) environment. 

  • 1.5 T or higher MRI
  • excellent quality assurance
  • appropriate software
  • appropriate paradigms and ability to deliver visual and auditory stimuli and record motor response
  • co-operative patients

Two testing designs are employed most commonly:

Block design uses repeated blocks of activity (paradigm) separated by blocks of inactivity or alternative activity. This is by far the most frequently used study design in clinical fMRI.

Event-related design involves individual events rather than blocks, and can be randomly distributed during the study. 

The activity performed or stimulus received by the patient is termed a paradigm, and each is designed to elicit a specific cortical response. Numerous paradigms have been developed of various complexity. In the clinical setting four paradigms (with modifications according to the clinical situation) suffice for most indications. 

  • visual paradigm
  • motor paradigm
  • speech paradigm
  • memory paradigm
Physics and Imaging Technology: MRI

Factors affecting T1

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Article information

rID: 12364
Section: Physics
Tag: fmri, refs
Synonyms or Alternate Spellings:
  • fMRI
  • Functional magnetic resonance imaging (fMRI)

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Cases and figures

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     Figure 2: motor paradigm
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    Figure 2: language paradigm
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    Figure 3: fMRI block design
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    Results on Activa...
    Case 1: low grade astrocytoma
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