What is the Isocenter in MRI?
The isocenter is one of the most important areas of the magnetic field produced by a magnetic resonance scanner. Technologically speaking, the isocenter is the center of the magnet.
What are the main components hardware of an MRI machine?
An MRI system consists of four major components: a main magnet formed by superconducting coils, gradient coils, radiofrequency (RF) coils, and computer systems. Each component has safety considerations.
What do magnets do in an MRI?
MRIs employ powerful magnets which produce a strong magnetic field that forces protons in the body to align with that field. When a radiofrequency current is then pulsed through the patient, the protons are stimulated, and spin out of equilibrium, straining against the pull of the magnetic field.
What is the gradient magnetic field in MRI?
A magnetic field gradient refers to a variation in the magnetic field across space. The ability to create magnetic field gradients is essential in MRI, for example, for the purpose of spatial encoding. These variations, superimposed on the main magnetic field, are created by the gradient system.
What is the isocenter in radiation therapy?
The radiation isocenter (in contrast to the mechanical isocenter) is the point in space where radiation beams intersect when the Gantry is rotated during beam-on. This statement is a simplification: gravitation has an influence on the mechanical parts inside the treatment head and therefore on beam direction.
What are coils in MRI?
Radiofrequency coils (RF coils) are the “antennae” of the MRI system, broadcasting the RF signal to the patient and/or receiving the return signal. RF coils can be receive-only, in which case the body coil is used as a transmitter; or transmit and receive (transceiver).
What radio frequencies are used in MRI?
approximately 1MHz to 300MHz
Most modern MRI systems have six or more receivers to process the signals from multiple coils. The signals range from approximately 1MHz to 300MHz, with the frequency range highly dependent on applied-static magnetic field strength.
Does MRI have radio frequency?
A careful analysis of the images by a radiologist will often yield the correct answer. There are no known biological hazards of MRI because, unlike x ray and computed tomography, MRI uses radiation in the radiofrequency range which is found all around us and does not damage tissue as it passes through.
Why do we need gradient in MRI?
The main function of gradients is to allow spatial encoding of the MRI signal, but are also critical for a wide range of physiologic techniques. Examples includes MR angiography, diffusion ad perfusion imaging.
Why gradient coils are used in MRI?
The main function of a gradient coil is to spatially modulate the main magnetic field in a predictable way, thereby causing the Larmor frequency of spins to vary as a function of position. This allows spatial encoding of the MR signal.
Where is the Isocentre?
It is the point on the aerial photo platform that directly falls on a line half-way between the Principal point and the Nadir point. In imaging physics and radiation oncology, the isocenter is termed as the point in space through which the central rays of the radiation beams pass.
What are wedges in radiotherapy?
In radiation oncology, wedge filters are commonly used to improve the dose uniformity in the target volume. They can be used as missing tissue compensators or wedge pairs to alter the shape of isodose curves so that two beams can be angled with a small hinge angle at a target volume without creating a hotspot.
What is the purpose of RF coils in MRI?
The RF coil is the part of the MRI system that excites the aligned spins and receives an RF signal back from the sample. All the components are controlled and interfaced with the user via a console. In general, RF coils act like a broadcasting station: they transmit and receive signals.
What are the different types of coils?
There are 2 different types of ‘coil’; one has copper on it (IUD) and the other contains hormone (Mirena IUS). Both are over 99% effective at protecting against pregnancy. How does it work?