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 'Respiratory Compensation' 
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Respiratory Compensation
Respiratory compensation reduces motion artifacts due to breathing. The approach is to reassign the echoes that are sensitive to respiratory motion in the central region of k-space. The outer lines of phase encoding normally contain the echoes where the motion from expiration is the greatest. The central portion of k-space will have encoded the echoes where inspiration and expiration are minimal. By a bellows device fixed to the abdomen, monitoring of the diaphragm excursion is possible. Respiratory compensation does not increase scan time with most systems.
An advantage of very fast sequences is the possibility of breath holding during the acquisition to eliminate motion artifacts. Breath hold is commonly used on most abdominal studies where images are acquired using gradient echo-based sequences during a brief inspiratory period (20-30 seconds). To enhance the breath holding endurance of the patient, connecting the patient to oxygen at a 1-liter flow rate via a nasal cannula has been shown to be helpful.
Also called PEAR, Respiratory Trigger, Respiratory Gating, PRIZE, FREEZE, Phase Reordering.
See also Phase Encoding Artifact Reduction, Respiratory Ordered Phase Encoding.
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Further Reading:
  News & More:
Controlling patient's breathing makes cardiac MRI more accurate
Friday, 13 May 2016   by    
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Motion ArtifactInfoSheet: - Artifacts - 
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Reduction Index, 
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 - Artifacts -
Quick Overview
Please note that there are different common names for this artifact.

Artifact Information
NAME Motion, phase encoded motion, instability, smearing
DESCRIPTION Blurring and ghosting
REASON Movement of the imaged object
HELP Compensation techniques, more averages, anti spasmodic

Patient motion is the largest physiological effect that causes artifacts, often resulting from involuntary movements (e.g. respiration, cardiac motion and blood flow, eye movements and swallowing) and minor subject movements.
Movement of the object being imaged during the sequence results in inconsistencies in phase and amplitude, which lead to blurring and ghosting. The nature of the artifact depends on the timing of the motion with respect to the acquisition. Causes of motion artifacts can also be mechanical vibrations, cryogen boiling, large iron objects moving in the fringe field (e.g. an elevator), loose connections anywhere, pulse timing variations, as well as sample motion. These artifacts appear in the phase encoding direction, independent of the direction of the motion.

Image Guidance
Motion artifacts can be flipped 90° by swapping the phase//frequency encoding directions.
The artifacts can be reduced by using breath holding, cardiac synchronization or respiratory compensation techniques: triggering, gating, retrospective triggering or phase encoding artifact reduction. Flow effects can be reduced by using gradient moment nulling of the first order of flow, gradient moment rephasing or flow compensation, depending of the MRI system.
Peristaltic motion can be reduced with the intravenous injection of an anti-spasmodic (e.g. Buscopan).
By using multiple averages, respiratory motion can be reduced in the same way that multiple averages increase the signal to noise ratio. Noticeable motion averaging is seen when four averages are obtained, six averages are often as good as respiratory compensation techniques and higher averages will continue to improve image quality.
In some cases will help a presaturation of the anatomy that was generating the motion.
See also Phase Encoded Motion Artifact.

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Further Reading:
The Effects of Breathing Motion on DCE-MRI Images: Phantom Studies Simulating Respiratory Motion to Compare CAIPIRINHA-VIBE, Radial-VIBE, and Conventional VIBE
Tuesday, 7 February 2017   by    
Scanning the Abdomen
  News & More:
Patient movement during MRI: Additional points to ponder
Tuesday, 5 January 2016   by    
Motion-compensation of Cardiac Perfusion MRI using a Statistical Texture Ensemble(.pdf)
June 2003   by    
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Abdominal ImagingMRI Resource Directory:
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General MRI of the abdomen can consist of T1 or T2 weighted spin echo, fast spin echo (FSE, TSE) or gradient echo sequences with fat suppression and contrast enhanced MRI techniques. The examined organs include liver, pancreas, spleen, kidneys, adrenals as well as parts of the stomach and intestine (see also gastrointestinal imaging). Respiratory compensation and breath hold imaging is mandatory for a good image quality.
T1 weighted sequences are more sensitive for lesion detection than T2 weighted sequences at 0.5 T, while higher field strengths (greater than 1.0 T), T2 weighted and spoiled gradient echo sequences are used for focal lesion detection. Gradient echo in phase T1 breath hold can be performed as a dynamic series with the ability to visualize the blood distribution. Phases of contrast enhancement include the capillary or arterial dominant phase for demonstrating hypervascular lesions, in liver imaging the portal venous phase demonstrates the maximum difference between the liver and hypovascular lesions, while the equilibrium phase demonstrates interstitial disbursement for edematous and malignant tissues.
Out of phase gradient echo imaging for the abdomen is a lipid-type tissue sensitive sequence and is useful for the visualization of focal hepatic lesions, fatty liver (see also Dixon), hemochromatosis, adrenal lesions and renal masses. The standards for abdominal MRI vary according to clinical sites based on sequence availability and MRI equipment. Specific abdominal imaging coils and liver-specific contrast agents targeted to the healthy liver tissue improve the detection and localization of lesions.
See also Hepatobiliary Contrast Agents, Reticuloendothelial Contrast Agents, and Oral Contrast Agents.

For Ultrasound Imaging (USI) see Abdominal Ultrasound at
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Further Reading:
Abdominal MRI at 3.0 T: The Basics Revisited
Wednesday, 20 July 2005   by    
Usefulness of MR Imaging for Diseases of the Small Intestine: Comparison with CT
2000   by    
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Computer-aided detection and diagnosis for prostate cancer based on mono and multi-parametric MRI: A review - Abstract
Tuesday, 28 April 2015   by    
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Wednesday, 29 April 2015   by    
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Tuesday, 27 February 2007   by    
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Thursday, 9 January 2014   by    
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Thursday, 23 April 2009   by    
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ArtifactForum -
related threadsInfoSheet: - Artifacts - 
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 - Artifacts -
An image artifact is a structure not normally present but visible as a result of a limitation or malfunction in the hardware or software of the MRI device, or in other cases a consequence of environmental influences as heat or humidity or it can be caused by the human body (blood flow, implants etc.). The knowledge of MRI artifacts (brit. artefacts) and noise producing factors is important for continuing maintenance of high image quality. Artifacts may be very noticeable or just a few pixels out of balance but can give confusing artifactual appearances with pathology that may be misdiagnosed.
Changes in patient position, different pulse sequences, metallic artifacts, or other imaging variables can cause image distortions, which can be reduced by the operator; artifacts due to the MR system may require a service engineer.
Many types of artifacts may occur in magnetic resonance imaging. Artifacts in magnetic resonance imaging are typically classified as to their basic principles, e.g.:
Physiologic (motion, flow)
Hardware (electromagnetic spikes, ringing)
Inherent physics (chemical shift, susceptibility, metal)

Several techniques are developed to reduce these artifacts (e.g. respiratory compensation, cardiac gating, eddy current compensation) but sometimes these effects can also be exploited, e.g. for flow measurements.

See also the related poll result: 'Most outages of your scanning system are caused by failure of'

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Further Reading:
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Clinical examination or whole-body magnetic resonance imaging: the Holy Grail of spondyloarthritis imaging
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On the Horizon - Next Generation MRI
Wednesday, 23 October 2013   by    
Technical Assessment of Artifact Production from Neuro Endovascular Coil At 3 Tesla MRI: An In Vitro Study
2012   by    
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ENCORE 0.5T™InfoSheet: - Devices -
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From ISOL Technology
'MRI system is not an expensive equipment anymore. ENCORE developed by ISOL Technology is a low cost MRI system with the advantages like of the 1.0T MRI scanner. Developed specially for the overseas market, the ENCORE is gaining popularity in the domestic market by medium sized hospitals.
Due to the optimum RF and Gradient application technology. ENCORE enables to obtain high resolution imaging and 2D/3D Angio images which was only possible in high field MR systems.'
- Less consumption of the helium gas due to the ultra-lightweight magnet specially designed and manufactured for ISOL. - Cost efficiency MR system due to air cooling type (equivalent to permanent magnetic). - Patient processing speed of less than 20 minutes

Device Information and Specification
CONFIGURATION Short bore compact
SURFACE COILS Head, C-spine, L-spine, TMJ, Knee, Shoulder, General purpose, Phased Array System: 4 digital receiver channels (Up to 12 channels)
SYNCHRONIZATION ECG/peripheral: Optional/yes, respiratory gating
PULSE SEQUENCES Spin Echo, Gradient Echo, Fast Spin Echo, Inversion Recovery (STIR, FLAIR), FLASH, FISP, PSIF, Turbo Flash ( MPRAGE ),TOF MR Angiography
IMAGING MODES 2D/3D, Travelling Sat, Multi-Slab 3D, MTC and TONE Pulse Sequence, Fat/Water Suppression, Presaturation (up to 6 bands), Flow Compensation using GMR pulse, Multi-Slice, Multi-Group Imaging
SINGLE/MULTI SLICE Image reconstruction time (2562 ) : 0.02 s
FOV 40 cm
MAGNET TYPE Superconducting
or W x H
58 cm diameter
H*W*D 200 x 168 x 187 cm
COOLING SYSTEM TYPE Air-cooled coil and amplifier
CRYOGEN USE 0.05 L/hr helium
5-GAUSS FRINGE FIELD 2.3 m / 3.1 m
SHIMMING Passive and active


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