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What does fMRI stand for and how does it work?
fMRI stands for Functional Magnetic Resonance Imaging (fMRI).It is a non-invasive imaging technique used for detecting, localizing and quantifying brain activity.
fMRI is based on the detection of temporal changes in blood oxygenation and blood flow, which occurs in response to activity in specific neural networks. fMRI can be used to produce activation maps showing which parts of the neuronal network are involved in a particular task.
Why am I having an fMRI scan?
In clinical practice, mapping of eloquent cortical networks is vital to assess:
1. Feasibility and possible risk associated with surgical resection
2. Determine hemispheric dominance of language (laterality index).
3. Brain plasticity.
Who can have the fMRI scan?
Patients who need pre-surgical evaluation of brain tumor and epilepsy surgeries.
How fMRI helps?
1. Detecting, localizing & quantifying brain activity.
2. To produce activation maps showing which neural networks are involved in particular tasks.
3. A part of the pre-surgical work-up, in patients with epilepsy & brain neoplasm to identify eloquent cortical areas.
Why fMRI is a preferred diagnostic tool?
The alternative method for localizing eloquent cortex including cortical stimulation are invasive hence fMRI is the preferred non- invasive method.
What is the injection that I may receive?
If necessary you may be injected with a gladonium based dye to see blood vessels and blood supply better.
What therefore are the instructions that the patient should follow?
- Patient should get all X-rays, Sonography, CT and MR films along with other papers, operative notes, discharge cards etc. This will help in more accurate analysis of the new scans.
- There should preferably be an accompanying friend/relative.
- Please inform the doctor/nurse/receptionist if you have any metallic or electromagnetic items in or on your body.
- Please inform the doctor/nurse/receptionist if you are pregnant or think you may be.
- The patient may be called a day prior for counseling session with the doctor including a Neuropsychologist in order to explain to him the procedure.
- The patient is instructed not to have stimulants like tea and coffee etc.
Clinical Case:
65 year old man, a religious teacher by profession presented with seizures since 4-5 years. Episodes of speech arrest lasting for 1-2 min without loss of consciousness.
Routine MRI scan done earlier showed a focal lesion with infiltrative margins within the left frontal lobe near the Sylvian fissure.
Purpose of fMRI:
- To lateralize the language networks.
- To assess proximity to Brocca’s area.
- Preoperative risk assessment.
- Whether safe surgical margin can be achieved to prevent speech impairment.
fMRI Study:
fMRI showed lateralization of language in the left hemisphere. Brocca’s area (Expressive
Speech Area) in the Left frontal lobe is shifted superiorly and anteriorly in relationship to mass. The Brocca’s area is in close proximity to the lesion.
Additional Diffusion Tensor Imaging performed along with the fMRI study shows the
Arcuate fasciculus (subcortical white matter bundle connecting the Brocca and Wernicke areas) in close proximity with the medical margin of the tumor.
Conclusion Drawn from f M R I Study:
There is a significant potential risk associated with tumor excision due to its close proximity with Brocca’s area which is in the left frontal lobe.
When will I know the results of my scan?
The scans need to be carefully analyzed and interpreted by our experienced Radiologists (scan doctors) team. The report and the scans will be given to you at the reception after printing the films and reports signed by our Radiologists.