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Sequences - Implant and Prosthesis pool - Stent - Contrast Enhanced MRI - Pacemaker - Claustrophobia
 
Transmit Receive CoilInfoSheet: - Coils - 
Intro, 
Overview, 
etc.MRI Resource Directory:
 - Coils -
 
(T/R) Also called transceiver coil. An RF coil that acts as a transmitter (T) producing the B1 excitation field and as a receiver (R) of the MRI signal. Such a coil requires a T/R switching circuit to switch between the two modes. A body coil is typically a T/R coil, but smaller volume T/R coils (head/extremities) are often used at high field as a possibility of reducing RF power absorption (SAR).
 
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• Related Searches:
    • Receiver
    • Signal Intensity
    • Bird Cage Coil
    • Radio Frequency Coil
    • Magnetic Resonance
 
Further Reading:
  Basics:
System Architecture
2003   by www.revisemri.com    
Electrical eddy currents in the human body: MRI scans and medical implants
   by www.phy.olemiss.edu    
MRI Resources 
DICOM - Used and Refurbished MRI Equipment - Stimulator pool - Stent - Liver Imaging - Education
 
Bird Cage CoilInfoSheet: - Coils - 
Intro, 
Overview, 
etc.MRI Resource Directory:
 - Coils -
 
A RF coil, often a transmit receive coil with a number of wires running along the z-direction, arranged to give a cosine current variation around the circumference of the coil, which looks like a bird cage. The bird cage coil works on a different principle to conventionally tuned local and surround coils in that it behaves like a tuned transmission line with one complete cycle of standing wave around the circumference. The frequency supply is generated by an oscillator, which is modulated to form a shaped pulse by a product detector controlled by the waveform generator. The signal must be amplified to 1000's of watts. This can be done using either solid state electronics, valves or a combination of both.
The bird cage coil design provides the best field homogeneity of all RF imaging coils.
One advantage is that it is simple to produce an exceedingly uniform B1 radio frequency field over most of the coil's volume, with the result of images with a high degree of uniformity.
A second advantage is that nodes with zero voltage occur 90° away from the driven part of the coil, thus facilitating the introduction of a second signal in quadrature, which produces a circularly polarized radio frequency field.
This type of volume coil is used for brain (head) MRI, or MR imaging of joints, such as the wrist or knees.

See also the related poll result: '3rd party coils are better than the original manufacturer coils'
 
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• View the DATABASE results for 'Bird Cage Coil' (4).Open this link in a new window

 
Further Reading:
  Basics:
HEAD AND NECK MRI GRADIENT COIL DESIGN
Thursday, 26 August 1999   by www.imaging.robarts.ca    
System Architecture
2003   by www.revisemri.com    
  News & More:
On the Horizon - Next Generation MRI
Wednesday, 23 October 2013   by thefutureofthings.com    
TOSHIBA INTRODUCES 32 ELEMENT COILS FOR ITS VANTAGE TITAN MR SYSTEMS
Tuesday, 9 November 2010   by medical.toshiba.com    
MRI Resources 
Veterinary MRI - Knee MRI - Mass Spectrometry - Pacemaker - Fluorescence - Contrast Enhanced MRI
 
Cardiac PacemakerMRI Resource Directory:
 - Safety -
 
A pacemaker is a device for internal or external battery-operated cardiac pacing to overcome cardiac arrhythmias or heart block. All implanted electronic devices are susceptible to the electromagnetic fields used in magnetic resonance imaging. Therefore, the main magnetic field, the gradient field, and the radio frequency (RF) field are potential hazards for cardiac pacemaker patients.
The pacemaker's susceptibility to static field and its critical role in life support have warranted special consideration. The static magnetic field applies force to magnetic materials. This force and torque effects rise linearly with the field strength of the MRI machines. Both, RF fields and pulsed gradients can induce voltages in circuits or on the pacing lead, which will heat up the tissue around e.g. the lead tip, with a potential risk of thermal injury.
Regulations for pacemakers provide that they have to switch to the magnet mode in static magnetic fields above 1.0 mT. In MR imaging, the gradient and RF fields may mimic signals from the heart with inhibition or fast pacing of the heart. In the magnet mode, most of the current pacemakers will pace with a fix pulse rate because they do not accept the heartsignals. However, the state of an implanted pacemaker will be unpredictable inside a strong magnetic field. Transcutaneous controller adjustment of pacing rate is a feature of many units. Some achieve this control using switches activated by the external application of a magnet to open/close the switch. Others use rotation of an external magnet to turn internal controls. The fringe field around the MRI magnet can activate such switches or controls. Such activations are a safety risk.
Areas with fields higher than 0.5 mT (5 Gauss Limit) commonly have restricted access and/or are posted as a safety risk to persons with pacemakers.
mri safety guidance
MRI Safety Guidance
A Cardiac pacemaker is because the risks, under normal circumstances an absolute contraindication for MRI procedures.
Nevertheless, with special precaution the risks can be lowered. Reprogramming the pacemaker to an asynchronous mode with fix pacing rate or turning off will reduce the risk of fast pacing or inhibition. Reducing the SAR value reduces the potential MRI risks of heating. For MRI scans of the head and the lower extremities, tissue heating also seems to be a smaller problem. If a transmit receive coil is used to scan the head or the feet, the cardiac pacemaker is outside the sending coil and possible heating is very limited.
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• View the DATABASE results for 'Cardiac Pacemaker' (6).Open this link in a new window

 
Further Reading:
  Basics:
MRI in Patients with Implanted Devices: Current Controversies
Monday, 1 August 2016   by www.acc.org    
Magnetic resonance imaging in patients with cardiac pacemakers: era of MR Conditional designs
Thursday, 27 October 2011   by 7thspace.com    
  News & More:
Newer Heart Devices Safe During MRI
Monday, 23 August 2004   by www.hospimedica.com    
BIOTRONIK debuts pacemaker with continuous MRI sensor
Wednesday, 30 August 2023   by www.medicaldevice-network.com    
Patients with standard pacemakers, ICDs may safely undergo MRIs
Friday, 24 February 2017   by www.cardiovascularbusiness.com    
ITOCHU Named the Exclusive Distributor for ViewRay's MRI-Guided Radiation Therapy System in Japan
Thursday, 22 January 2015   by www.prnewswire.com    
Modern Implantable Heart Devices Safe For Use In MRI Scans
Wednesday, 16 March 2005   by www.sciencedaily.com    
MRI Resources 
Homepages - Directories - Abdominal Imaging - Education - MR Guided Interventions - Movies
 
Radio Frequency CoilInfoSheet: - Coils - 
Intro, 
Overview, 
etc.MRI Resource Directory:
 - Coils -
 
A coil is a large inductor with a considerable dimension and a defined wavelength, commonly used in configurations for MR imaging. The frequency of the radio frequency coil is defined by the Larmor relationship.
The MRI image quality depends on the signal to noise ratio (SNR) of the acquired signal from the patient. Several MR imaging coils are necessary to handle the diversity of applications. Large coils have a large measurement field, but low signal intensity and vice versa (see also coil diameter). The closer the coil to the object, the stronger the signal - the smaller the volume, the higher the SNR. SNR is very important in obtaining clear images of the human body. The shape of the coil depends on the image sampling. The best available homogeneity can be reached by choice of the appropriate coil type and correct coil positioning. Orientation is critical to the sensitivity of the RF coil and therefore the coil should be perpendicular to the static magnetic field.

RF coils can be differentiated by there function into three general categories:
The RF signal is in the range of 10 to 100 MHz. During a typical set of clinical image measurements, the entire frequency spectrum of interest is of the order 10 kHz, which is an extremely narrow band, considering that the center frequency is about 100 MHz. This allows the use of single-frequency matching techniques for coils because their inherent bandwidth always exceeds the image bandwidth. The multi turn solenoid, bird cage coil, single turn solenoid, and saddle coil are typically operated as the transmitter and receiver of RF energy. The surface and phased array coils are typically operated as a receive only coil.

See also the related poll result: '3rd party coils are better than the original manufacturer coils'
 
Images, Movies, Sliders:
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• View the DATABASE results for 'Radio Frequency Coil' (9).Open this link in a new window

 
Further Reading:
  Basics:
Radio-frequency Coil Selection for MR Imaging of the Brain and Skull Base1
   by radiology.rsnajnls.org    
  News & More:
High-field MRI Coils – that work, superbly, even at 750 MHz
   by www.dotynmr.com    
Magnetic resonance-guided motorized transcranial ultrasound system for blood-brain barrier permeabilization along arbitrary trajectories in rodents
Thursday, 24 December 2015   by www.ncbi.nlm.nih.gov    
MRI Resources 
Movies - Implant and Prosthesis - MRA - - Calculation - MR Guided Interventions
 
Signa SP 0.5T™ Open ConfigurationInfoSheet: - Devices -
Intro, 
Types of Magnets, 
Overview, 
etc.MRI Resource Directory:
 - Devices -
 
www.gehealthcare.com/usen/mr/index.html From GE Healthcare;
The Signa SP 0.5T™ is an open MRI magnet that is designed for use in interventional radiology and intra-operative imaging. The vertical gap configuration increases patient positioning options, improves patient observation, and allows continuous access to the patient during imaging. The magnet enclosure also incorporates an intercom, patient observation video camera, laser patient alignment lights, and task lighting in the imaging volume.
Device Information and Specification
CLINICAL APPLICATION
Whole body
CONFIGURATION
Open
Integrated transmit and receive body coil; optional rotational body coil, head; other coils optional; open architecture makes system compatible with a wide selection of coilsarray
SYNCHRONIZATION
Standard cardiac gating, ECG/peripheral, respiratory gating
PULSE SEQUENCES
Standard: SE, IR, 2D/3D GRE and SPGR, 2D/3D TOF, 2D/3D FSE, 2D/3D FGRE and FSPGR, SSFP, FLAIR, EPI, optional: 2D/3D Fiesta, true chem sat, fat/water separation, single shot diffusion EPI
IMAGING MODES
Localizer, single slice, multislice, volume, fast, POMP, multi slab, cine, slice and frequency zip, extended dynamic range, tailored RF
TR
1.3 to 12000 msec in increments of 1 msec
TE
0.4 to 2000 msec in increments of 1 msec
3cm to 40 cm continuous
2D: 1.4mm - 20mm 3D: 0.2mm - 20mm
1280 x 1024
MEASURING MATRIX
128x512 steps 32 phase//freq.
PIXEL INTENSITY
256 gray levels
60 x 58 cm
POWER REQUIREMENTS
200 - 480, 3-phase
COOLING SYSTEM TYPE
Liquid helium
0.03 L/hr, holds 300 L
STRENGTH
12 mT/m
Active
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• View the DATABASE results for 'Signa SP 0.5T™ Open Configuration' (2).Open this link in a new window

 
Further Reading:
  News & More:
MR Surgical Suite, Improving surgical procedure quality (.pdf)
   by www3.gehealthcare.com    
MRI Resources 
Spectroscopy pool - Fluorescence - Spine MRI - MRI Technician and Technologist Schools - Nerve Stimulator - Shielding
 
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