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Magnetic Resonance Imaging MRI
(MRI) Magnetic resonance imaging is a noninvasive medical imaging technique that uses the interaction between radio frequency pulses, a strong magnetic field and body tissue to obtain images of slices/planes from inside the body. These magnets generate fields from approx. 2000 times up to 30000 times stronger than that of the Earth. The use of nuclear magnetic resonance principles produces extremely detailed pictures of the body tissue without the need for x-ray exposure and gives diagnostic information of various organs.
Measured are mobile hydrogen nuclei (protons are the hydrogen atoms of water, the 'H' in H20), the majority of elements in the body. Only a small part of them contribute to the measured signal, caused by their different alignment in the magnetic field. Protons are capable of absorbing energy if exposed to short radio wave pulses (electromagnetic energy) at their resonance frequency. After the absorption of this energy, the nuclei release this energy so that they return to their initial state of equilibrium.
This transmission of energy by the nuclei as they return to their initial state is what is observed as the MRI signal. The subtle differing characteristic of that signal from different tissues combined with complex mathematical formulas analyzed on modern computers is what enables MRI imaging to distinguish between various organs. Any imaging plane, or slice, can be projected, and then stored or printed.
The measured signal intensity depends jointly on the spin density and the relaxation times (T1 time and T2 time), with their relative importance depending on the particular imaging technique and choice of interpulse times. Any motion such as blood flow, respiration, etc. also affects the image brightness.
Magnetic resonance imaging is particularly sensitive in assessing anatomical structures, organs and soft tissues for the detection and diagnosis of a broad range of pathological conditions. MRI pictures can provide contrast between benign and pathological tissues and may be used to stage cancers as well as to evaluate the response to treatment of malignancies. The need for biopsy or exploratory surgery can be eliminated in some cases, and can result in earlier diagnosis of many diseases.
See also MRI History and Functional Magnetic Resonance Imaging (fMRI).
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 Anatomic Imaging of the Lumbar Spine  Open this link in a new window

Courtesy of  Robert R. Edelman

 Normal Dual Inversion Fast Spin-echo  Open this link in a new window

Courtesy of  Robert R. Edelman

 Breast MRI Images T2 And T1 Pre - Post Contrast  Open this link in a new window
 Anatomic Imaging of the Shoulder  Open this link in a new window

Courtesy of  Robert R. Edelman

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Further Reading:
A Short History of the Magnetic Resonance Imaging (MRI)
MRI's inside story
Thursday, 4 December 2003   by    
On the Horizon - Next Generation MRI
Wednesday, 23 October 2013   by    
  News & More:
Metamaterials boost sensitivity of MRI machines
Thursday, 14 January 2016   by    
MRI technique allows study of wrist in motion
Monday, 6 January 2014   by    
New imaging technology promising for several types of cancer
Thursday, 29 August 2013   by    
Study Shows MRI Can Be Used for Orthodontic Imaging
Monday, 12 August 2013   by    
MRI method for measuring MS progression validated
Thursday, 19 December 2013   by    
The 2003 Nobel Prize in Physiology or Medicine
2003   by    
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Nuclear Magnetic Resonance ImagingMRI Resource Directory:
 - NMR -
Creation of images of objects such as the body by use of the nuclear magnetic resonance phenomenon. The immediate practical application involves imaging the distribution of hydrogen nuclei (protons) in the body. The image brightness in a given region depends on the spin density and the relaxation times, with their relative importance determined by the particular imaging technique employed. Image brightness is also affected by motion such as blood flow. See also Zeugmatography and Magnetic Resonance Imaging MRI.

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Functional Magnetic Resonance ImagingMRI Resource Directory:
 - Functional MRI -
(fMRI) Functional magnetic resonance imaging is a technique used to determine the dynamic brain function, often based on echo planar imaging, but can also be performed by using contrast agents and observing their first pass effects through brain tissue. Functional magnetic resonance imaging allows insights in a dysfunctional brain as well as into the basic workings of the brain.
The in functional brain MRI most frequently used effect to assess brain function is the blood oxygenation level dependent contrast (BOLD) effect, in which differential changes in brain perfusion and their resultant effect on the regional distribution of oxy- to deoxyhaemoglobin are observable because of the different 'intrinsic contrast media' effects of the two haemoglobin forms. Increased brain activity causes an increased demand for oxygen, and the vascular system actually overcompensates for this, increasing the amount of oxygenated haemoglobin. Because deoxygenated haemoglobin attenuates the MR signal, the vascular response leads to a signal increase that is related to the neural activity.
Functional imaging relates body function or thought to specific locations where the neural activity is taking place. The brain is scanned at low resolution but at a fast rate (typically once every 2-3 seconds). Structural MRI together with fMRI provides an anatomical baseline and best spatial resolution.
Interactions can also be seen from the motor cortex to the cerebellum or basal ganglia in the case of a movement disorder such as ataxia. For example: by a finger movement the briefly increase in the blood circulation of the appropriate part of the brain controlling that movement, can be measured.

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Further Reading:
High-Resolution, Spin-Echo BOLD, and CBF fMRI at 4 and 7 T(.pdf)
October 2002   by    
Vascular Filters of Functional MRI: Spatial Localization Using BOLD and CBV Contrast
  News & More:
Functional MRI may help identify new, effective painkillers for chronic pain sufferers
Thursday, 4 February 2016   by    
Study shows functional MRI differences in working memory in people with primary insomnia
Saturday, 31 August 2013   by    
fMRI leads to mind-reading speller and a way for people in a coma to speak
Sunday, 1 July 2012   by    
Combination of diffusion tensor and functional magnetic resonance imaging during recovery from the vegetative state.
Tuesday, 31 August 2010   by    
Functional magnetic resonance imaging may improve diagnosis of autism
Tuesday, 31 May 2011   by    
Using fMRI to study brain development
Friday, 30 November 2007   by    
Searchterm 'Magnetic Resonance Imaging' was also found in the following services: 
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Intraoperative Magnetic Resonance ImagingMRI Resource Directory:
 - Intraoperative MRI -
With an open configuration MRI system neurosurgical procedures can be performed using image guidance. Open MRI can be used to guide interventional treatments or procedures, such as a biopsy.
Intraoperative MRI allows lesions to be precisely localized and targeted. Constantly updated images, correlated with images obtained pre-operatively, help to eliminate errors that can arise during framed and frameless stereotactic surgery when anatomic structures alter their position due to shifting or displacement of, e.g. brain parenchyma.
Intraoperative MRI can help with the identification of normal structures, such as blood vessels and is helpful in optimizing surgical approaches, achieving complete resection of intracerebral lesions, determining tumor margins and monitoring potential intraoperative complications.

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Further Reading:
Intraoperative MRI in neurosurgery: Technical overkill or the future of brain surgery?
2003   by    
  News & More:
FDA clears ViewRay's next-gen, MRI-guided radiation therapy device
Tuesday, 28 February 2017   by    
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Rapid Excitation Magnetic Resonance ImagingInfoSheet: - Sequences - 
Types of, 
etc.MRI Resource Directory:
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(RE MRI) There are several approaches to speeding up the MRI data acquisition process by repeating the excitation by RF pulses in times short compared to T1, typically using small flip angles and gradient echo refocusing. When TR is also on the order of or shorter than T2, the repeated RF pulses will tend to refocus transverse magnetization remaining from prior excitations, setting up a condition of steady state free precession, and a dependence of signal strength (and image contrast) on both T1 and T2.
This can be modified in various ways, particularly:
1) to spoil the tendency to build up a steady state by reducing coherence between excitations, e.g. by variation of the phase or timing of consecutive RF pulses or of the strength of spoiler gradient pulses, thus increasing the relative dependence of signal strength on T1 or
2) acquire the signal when it is refocusing immediately prior to the next RF pulse, thus increasing the relative dependence of signal strength on T2.
See also Ultrafast Gradient Echo Sequence.

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