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Result : Searchterm 'Bird Cage Coil' found in 1 term [] and 4 definitions []
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Bird Cage Coil | |
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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' | | | | | | | • Share the entry 'Bird Cage Coil': | | | | | | | | Further Reading: | | Basics:
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Brain imaging, magnetic resonance imaging of the head or skull, cranial magnetic resonance tomography (MRT), neurological MRI - they describe all the same radiological imaging technique for medical diagnostic.
Magnetic resonance imaging of the human brain includes the anatomic description and the detection of lesions. Special techniques like diffusion weighted imaging, functional magnetic resonance imaging ( fMRI) and spectroscopy provide also information about the function and chemical metabolites of the brain.
MRI provides detailed pictures of brain and nerve tissues in multiple planes without obstruction by overlying bones. Brain MRI is the procedure of choice for most brain disorders. It provides clear images of the brainstem and posterior brain, which are difficult to view on a CT scan. It is also useful for the diagnosis of demyelinating disorders (disorders such as multiple sclerosis (MS) that cause destruction of the myelin sheath of the nerve).
With this noninvasive procedure also the evaluation of blood flow and the flow of cerebrospinal fluid (CSF) is possible. Different MRA methods, also without contrast agents can show a venous or arterial angiogram. MRI can distinguish tumors, inflammatory lesions, and other pathologies from the normal brain anatomy. However, MRI scans are also used instead other methods to avoid the dangers of interventional procedures like angiography (DSA - digital subtraction angiography) as well as of repeated exposure to radiation as required for computed tomography (CT) and other X-ray examinations.
A ( birdcage) bird cage coil achieves uniform excitation and reception and is commonly used to study the brain. Usually a brain MRI procedure includes FLAIR, T2 weighted and T1 weighted sequences in two or three planes. See also Fetal MRI, Fluid Attenuation Inversion Recovery ( FLAIR), Perfusion Imaging and High Field MRI. See also Arterial Spin Labeling. | | | | | | | | • View the DATABASE results for 'Brain MRI' (14).
| | | • View the NEWS results for 'Brain MRI' (32).
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MRI Reveals Significant Brain Abnormalities Post-COVID Monday, 21 November 2022 by neurosciencenews.com | | |
Combining genetics and brain MRI can aid in predicting chances of Alzheimer's disease Wednesday, 29 June 2022 by www.sciencedaily.com | | |
Roundup: How Even Mild COVID Can Affect the Brain; This Many Daily Steps Improves Longevity; and More Friday, 11 March 2022 by baptisthealth.net | | |
A low-cost and shielding-free ultra-low-field brain MRI scanner Tuesday, 14 December 2021 by www.nature.com | | |
Large International Study Reveals Spectrum of COVID-19 Brain Complications Tuesday, 9 November 2021 by www.itnonline.com | | |
Brain MRI-Based Subtypes of MS Predict Disability Progression, Treatment Response Thursday, 13 May 2021 by www.neurologyadvisor.com | | |
New MRI method improves detection of disease changes in the brain's network Thursday, 11 June 2020 by www.compute.dtu.dk | | |
New NeuroCOVID Classification System Uses MRI to Categorize Patients Friday, 12 June 2020 by www.diagnosticimaging.com | | |
New MRI technique can 'see' molecular changes in the brain Thursday, 5 September 2019 by medicalxpress.com | | |
Talking therapy or medication for depression: Brain scan may help suggest better treatment Monday, 27 March 2017 by www.newsnation.in | | |
MRI identifies brain abnormalities in chronic fatigue syndrome patients Wednesday, 29 October 2014 by www.eurekalert.org | | |
MRIs Useful in Tracking Depression in MS Patients Tuesday, 1 July 2014 by www.hcplive.com | | |
Contrast agent linked with brain abnormalities on MRI Tuesday, 17 December 2013 by www.sciencecodex.com | | |
MRIs Reveal Signs of Brain Injuries Not Seen in CT Scans Tuesday, 18 December 2012 by www.sciencedaily.com | | |
Iron Deposits in the Brain May Be Early Indicator of MS Wednesday, 13 November 2013 by www.healthline.com | | |
Migraine Sufferers Have Thicker Brain Cortex Tuesday, 20 November 2007 by www.medicalnewstoday.com |
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| | | | • View the DATABASE results for 'Imaging Coil' (7).
| | | • View the NEWS results for 'Imaging Coil' (9).
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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' | | | | | | • View the DATABASE results for 'Radio Frequency Coil' (9).
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| | | | • View the DATABASE results for 'Volume Coil' (5).
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