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Prepared for : En. Syed Zulkarnain bin Syed Idrus

Prepared by : Farid Nurulhaq bin Awg. Matsni @ Ali

School of Microelectronic

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What Is MRI????

Magnetic resonance imaging (MRI) is a non-invasive imaging method that uses radio waves and a powerful magnetic field to produce clear and detailed images of virtually any part of the body. This procedure has greatly improved the ability to see normal and diseased tissue. It is vital for the patient to be able to remain still in one position during the MRI scan. It is because most of MRI scans take about 30 minutes. Because MRI uses a powerful magnet, metallic objects are prohibited during the scan.

What does an MRI look like?

The MRI scanner is essentially a large tunnel that is open on each end. The body part being imaged must be placed in the center of the scanner’s bore. This typically leaves some portion of the patient’s body outside of the bore.

Wha is BOLD??

The brain is the largest consumer of oxygenated blood in the human body. When neural activity increases in certain areas of the brain, during talking or pondering a problem for example, perfusion of those areas are hence increased. This change in blood supply can be detected by fMRI or functional magnetic resonance imaging thanks to two phenomena:

• the different signals of oxyhemoglobin and deoxyhemoglobin,
• and the increased local perfusion.

With the BOLD (blood oxygen level dependent) technique it is possible to map a patient’s brain before a risky surgery so that important areas such as Broca’s or Wernicke’s can be spared.

Just recently, in a research paper published in Nature, scientists at The University of California at Berkeley claim to have figured out a way to predict the image that their subject is looking at.

Their experiement consisted of two phases. In the first phase the subjects were asked to view 1750 images and their brain activity was monitored with fMRI. This means that every 4 seconds a MRI scan was obtained. During the second phase the subjects were shown 120 novel images, and the software, based on previous experience, “guessed” what image the subjects were looking at.

Technique

BOLD effects are measured using rapid volumetric acquisition of images with contrast weighed by. Such images can be acquired with moderately good spatial and temporal resolution; images are usually taken every 1–4 seconds, and the voxels in the resulting image typically represent cubes of tissue about 2–4 millimeters on each side in humans. Recent technical advancements, such as the use of high magnetic fields and multichannel RF reception, have advanced spatial resolution to the millimeter scale. Although responses to stimuli presented as close together as one or two seconds can be distinguished from one another, using a method known as event-related fMRI, the full time course of a BOLD response to a briefly presented stimulus lasts about 15 seconds for the robust positive response.