MAGNETIC RESONANCE IMAGING (MRI) Flashcards
______ associated with atoms and nuclei were first described in the ___ (year).
Magnetic fields; 1930s
____ and ___ each received a Nobel Prize in physics for their work on atomic and nuclear magnetism. Rabi coined the term ____.
Otto Stern and Isador Rabi; nuclear magnetic resonance (NMR)
In (year), ____ and ____ at Harvard independently described NMR in a solid. They shared the 1952 Nobel Prize in physics for this work. Bloch continued extensive studies with the ___ , thereby laying the groundwork for later developments that led to MR
1946; Felix Bloch at Stanford and Edward Purcell ; NMR of water
is known as the father of MRI
Felix Bloch
He proposed some novel properties for the atomic nucleus, including that the nucleus behaves like a small magnet. He described this nuclear magnetism by what are now called
Bloch equations
He explain that a nucleus, because it spins on an imaginary axis, has an associated _____ This field is called a ____. Nucleons that have charge (e.g., protons) and that spin have even stronger magnetic fields.
magnetic field; magnetic moment
In the late (year)s engineer-physician ____, while working with NMR spectroscopy, showed that malignant tissue has a different _____ spectrum from normal tissue.
1960s; Raymond Damadian ; NMR (relaxation time of water)
This finding suggested that images of the body might be obtained by producing _____.
maps of relaxation rates.
He produced a crude NMR image of a __ tumor in ___ and the first body image in ___ . That image took almost (how long) to produce.
rat ;1974 ; 1976; 4 hours
_____, an NMR chemist at State University of New York in Stony Brook, developed the first imaging method using NMR that is similar to what is used today. He called this method ____, which was sort of Greek for saying that this imaging method requires a whole bunch of magnetic fields whizzing and buzzing around. I
Paul Lauterbur; zeugmatography
In (year) Lauterbur published the first cross-sectional images of objects obtained with MRI techniques. These first images were crude, and only ___ objects could be distinguished.
1973; large
Meanwhile in Nottingham, England, ____, a solid-state physicist, was engaged in similar research and eventually developed the ____method that is used for functional MR neuro imaging today.
Peter Mansfield; echoplanar MRI method
The basic principle of MRI is that protons in certain atomic nuclei, if placed in a ____, can be stimulated by (absorb energy from) ____ of the correct frequency. After this stimulation the protons ___ while energy is induced into a receiver antenna (the MRI signal), which is then digitized into a viewable image.
magnetic field; radio waves. relax;
____ represent the rates of signal decay and the return of protons to equilibrium.
Relaxation times
The earliest magnets were described ___ years ago as naturally occurring ___ stones that attracted iron. These “leading stones,” or lodestones, were thought to be magic by the natives in a region of present-day ___ , then known as ___ in the Greek language
2000; black ; western Turkey; Magnesia
A magnet is a material or object that produces a magnetic field. Magnets used for MRI are of three types:
permanent, resistive and superconductive.
In the space between the poles, the ____ is uniform enough for imaging.
magnetic field
A ____ is generated by a moving charge (electrical current). The direction of the magnetic field can either be ___ with respect to the direction of flow of the current.
magnetic field ; clockwise or counter-clockwise
___ or ___ determines the magnitude and direction of the magnetic field due to a current
Ampere’s law or Fleming’s right-hand rule
When a magnet is moved in and out of a closed circuit, an ___ current is produced, which ceases the moment the magnet stops moving. Such a current is called an ___ .
oscillating; induced electric current
___ explains the phenomenon of an induced current.
Faraday’s law of induction
____ is defined as the energy available from a unit of charge travelling once around a loop of wire. The ___ drives a current in the circuit and is the result of a changing magnetic field inducing an electric field.
electromotive force (emf)
formula for magnetic field
B=F/p, where B-field strength in tesla (T), F is force in newton (N), and p is pole strength in ampere meter (Am)
The tesla (T) is the standard international (SI) unit for the magnetic field. An older unit still very much in use is the gauss (G); 1 T equals ___ G.
10,000 G.
