Date: 10/30/13

Magnetic Resonance ImagingBy: Lillian Xue and Stephanie Ganzeveld

MRI Machine

Various shapes of MRI machines

Closed MRI

The traditional closed MRI machine is cylinder-shaped and possesses movable bed slides which patients rest on in order to enter the inner magnetic tube.

Open MRI

The open MRI machine is ring-shaped (instead of cylinder-shaped) and encloses only the region of the body under inspection.

Upright MRI

The upright MRI machine allows patients to either sit or stand inside of the relatively open vertical scanner.

The difference between closed MRI machines and open MRI machines

Upright MRI machine

Practical Uses

Diagnosis of brain tumors

Identification of hemorrhage

Recognition of abnormal brain development

Discernment of lesions connected with multiple sclerosis

Diagnosis of hormonal instability

Possible locations for malignant brain tumors Identification of hemorrhageAbnormal brain development in young children

Method

To begin, MRI machines focus primarily on the nuclei of hydrogen atoms in polar water molecules.

Hydrogen protons, under normal circumstances, spin arbitrarily with their “axises” pointing in various directions.

When the body is placed under a magnetic current (as issued by the MRI Machine), all of the protons line up to face in the same direction.

The alignment of positive subatomic particles creates a magnetic vector which is consequently identified by the MRI scanner.

Radio waves are then added in concurrence with the magnetic current to deflect the original magnetic vector.

When the radio waves are turned off, the magnetic vector returns to its initial state, causing another radio wave signal to be produced.

This signal is what MRI machines translate to produce accurate scans.

Protons of Hydrogen spinning in arbitrary directions

Protons of Hydrogen spinning in the same direction

Method Continued

Receiver coils are placed around the part of the body being inspected to improve signal emission

How long it takes protons to return to their resting state can be evaluated in two ways:

Time taken for the magnetic vector to return to its initial state (T1 relaxation)

Time needed for the axial spin to return to its resting state (T2 relaxation)

In essence, MRI scans are composed of a series of pulse patterns.

Since different tissues have different relaxation states they can thus be distinguished from one another.

In this respect, diseases can be identified by increased water content.

Receiver coils in MRI machines

T1 and T2 relaxation

Advantages of MRI

Does not involve x- or exposure to radiation and is not invasive.

Provides clear images of soft tissue structures such as grey matter.

Provides images of the brain at any direction, or slice.

Provides information on the blood moving through areas of the body.

The difference between white and grey matter

Various brain slice angles

Disadvantages of MRI

Can be very expensive and unaffordable

Can be dangerous for patients with metallic devices placed within the body such as pacemakers

Performed in small spaces which will be difficult to be performed on claustrophobic patients

Movement during scanning may cause blurry images, so the patient must lie still during the scan.

RF transmitters can cause severe burns if misused or mishandled.

Claustrophobia as a result of closed MRI machines Pacemakers and other metallic devices are not permitted RF (radio frequency) power should be used with caution

Advantages of fMRI

non-invasive and effective

no exposure to radiation, unlike CT, X-Rays, and PET scans

high resolution images (1mm)

signals can be recorded from all regions in the brain, unlike EEG scans

more precise than PET scans

Example of functional MRI scans High resolution images fMRI scans are able to show the brain from all regions

Disadvantages of fMRI

can only examine the blood flow in the brain (cannot detect activities of neurons)

results may be difficult to interpret (cannot specify emotions or feelings)

Unfortunately, fMRI scans can only examine blood flow in the brain

Results may be difficult to interpret or analuze

Difference between MRI and fMRI Magnetic Resonance Imaging (MRI)

views anatomical structure

focuses on protons in hydrogen nuclei

high, spatial resolution

utilized for experimental purposes

Functional Magnetic Resonance Imaging (fMRI)

views metabolic function

calculates oxygen levels

long-distance resolution

utilized for diagnostic purposes

MRI scan

fMRI scan

Maguire and MRI

Used fMRI to locate blood flow in the brain

"FMRI can tell you which brain areas are involved in memory but you are never sure which ones are really necessary. That is where the study of patients comes in."

Used to see which areas were active when participants were trying to locate a specific region from spatial memory

The hippocampus was not the only active region of the brain

Used MRI to compare the structures of the brain

Hippocampus

Hippocampus as shown on the fMRI scan

Identification of spatial navigation

References (Sources)

Tilakaratna, P. (n.d.). Magnetic Resonance Imaging : Basic principles of how it works. Retrieved November 4, 2013 from http://www.howequipmentworks.com/physics/medical_imaging/mri/magnetic_resonance_imaging.html

Berger, A. (January, 2002). Magnetic Resonance Imaging. Retrieved November 2, 2013 from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1121941/#!po=16.6667

Blake, L. (2013). What does MRI equipment look like? Retrieved November 4, 2013 from: http://www.ehow.com/facts_5499464_mri-equipment-look-like.html

Smith, A. (2013). Reasons for an MRI of the brain. Retrieved November 4, 2013 from: http://www.ehow.com/facts_5499464_mri-equipment-look-like.html

Kalapurayil, M. (2013, July). What is MRI? How does MRI work? Retrieved November 4, 2013 from: http://www.medicalnewstoday.com/articles/146309.php

Seven Counties Services Inc. (n.d.). Functional Magnetic Resonance Imaging. Retrieved November 4, 2013 from http://www.sevencounties.org/poc/view_doc.php?type=doc&id=8947&cn=18

CancerQuest (2011, October). Benefits and Disadvantages of MRI. Retrieved November 4, 2013, from http://www.cancerquest.org/mri-advantages-and-disadvantages.html

Schwartz., A. (n.d.). MRI: Advantages and Disadvantages. MRI: Advantages and Disadvantages. Retrieved November 4, 2013, from http://www.anapolschwartz.com/practices/gadolinium-nsf/blog/mri-side-effects.html

Health information you can trust. (n.d.). MRI scan. Retrieved November 4, 2013, from http://www.nhsinform.com/health-library/articles/m/mri-scan/advantages

Chudler, E. (2013). Brain imaging. Retrieved November 4, 2013 from: http://faculty.washington.edu/chudler/image.html

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References (Images) Continued

http://medcastaway.edublogs.org/files/2011/03/cerebral-hemorrhage-mjkqx4.JPG

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References (Images) Continued

http://www.nih.gov/news/pr/dec2005/nimh_07.jpg

http://www.brianjogrady.com/images/fmri.jpg

http://www.med.nyu.edu/thesenlab/group/images/fmri1.jpg

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http://morphonix.com/software/education/science/brain/game/specimens/images/hippocampus.gif

http://www.neuro24.de/hip0006.jpg