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Spectrometer
 
The part of the NMR system that actually produce the NMR phenomenon and acquire the signals, including the magnet, the probe, the RF circuitry, the gradient coils, etc. The spectrometer is controlled via the interface.
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Radiology  (1) Open this link in a new window
Computer
 
MRI computer can be divided into central processing unit (CPU), consisting of instruction, interpretation and arithmetic unit plus fast access memory, and peripheral devices such as bulk data storage and input and output devices (including, via the interface, the spectrometer). The computer controls the RF pulses and gradients necessary to acquire data, and process the data to produce spectra or images. (Devices such as the spectrometer may themselves incorporate small computers.)

See also Digital to Analog Converter, Analog to Digital Converter, Transformer, Pulse Programmer, Array Processor, Detector.

See also the related poll result: 'Most outages of your scanning system are caused by failure of'
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Further Reading:
  News & More:
University of Texas supercomputer speeds real-time MRI analysis
Thursday, 2 March 2017   by www.information-management.com    
Superhuman 20 second AI heart tool begins NHS roll-out
Friday, 11 March 2022   by www.bhf.org.uk    
Computer tool maps ridges on brain's bumpy surface
Tuesday, 1 August 2017   by spectrumnews.org    
MRI Resources 
MRI Reimbursement - Collections - Education - Breast MRI - Contrast Agents - Safety pool
 
Machine Imperfection ArtifactInfoSheet: - Artifacts - 
Case Studies, 
Reduction Index, 
etc.MRI Resource Directory:
 - Artifacts -
 
Quick Overview
Please note that there are different common names for this artifact.
Artifact Information
NAME
Machine imperfection, data error
DESCRIPTION
Striped ghosts with a shift of half the field of view
REASON
Non-uniform sampling, phase differences
HELP
Data correction
Machine imperfection-based artifacts manifest themselves due to the fact that the odd k-space lines are acquired in a different direction than the even k-space lines. Slight differences in timing result in shifts of the echo in the acquisition window. By the shift theorem, such shifts in the time domain data then produce linear phase differences in the frequency domain data.
Without correction, such phase differences in every second line produce striped ghosts with a shift of half the field of view, so-called Nyquist ghosts. Shifts in the applied magnetic field can also produce similar (but constant in amplitude) ghosts.
This artifact is commonly seen in an EPI image and can arise from both, hardware and sample imperfections.
A further source of machine-based artifact arises from the need to acquire the signal as quickly as possible. For this reason the EPI signal is often acquired during times when the gradients are being switched. Such sampling effectively means that the k-space sampling is not uniform, resulting in ringing artifacts in the image.
mri safety guidance
Image Guidance
Such artifacts can be minimized by careful setup of the spectrometer and/or correction of the data. For this reasons reference data are often collected, either as a separate scan or embedded in the imaging data. The non-uniform sampling can be removed by knowing the form of the gradient switching. It is possible to regrid the data onto a uniform k-space grid.
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Further Reading:
  Basics:
MRI Artifact Gallery
   by chickscope.beckman.uiuc.edu    
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Multiple Sensitive Point
 
Sequential line imaging technique utilizing two orthogonal oscillating magnetic field gradients, a SFP pulse sequence, and signal averaging to isolate the NMR spectrometer sensitivity to a desired line in the body.
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ProbeForum -
related threads
 
The portion of a MR spectrometer comprising the sample container and the RF coils, with some associated electronics. The RF coils may consist of separate receiver and transmitter coils in a crossed coil configuration, or, alternatively, a single coil to perform both functions.
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