General Concepts 5 min read
Nuclear Medicine
Nuclear medicine can be defined as the practice of making patients radioactive for diagnostic and therapeutic purposes. The radioactivity is…
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General Concepts 1 min read
Problem and Artifacts in fMRI: The Brain–Vein Problem? The Brain-Inflow Problem?
The artifacts arising from large vessels pose serious problems to the interpretation of oxygenation sensitive fMRI data. It is generally…
General Concepts 5 min read
Mechanism
Flow-sensitive images show increased perfusion with stimulation, while blood oxygenation–sensitive images show changes consistent with an increase in venous blood…
General Concepts 2 min read
Advances in Functional Brain Mapping
The popularity of fMRI is based on many factors. It is safe and totally noninvasive. It can be acquired in…
General Concepts 2 min read
Digital Data Processing
A typical scan protocol calls for a sequence of tailored RF and gradient pulses with duration controlled in steps of…
General Concepts 3 min read
Radiofrequency Coils
Radiofrequency (RF) coils are components of every scanner and are used for two essential purposes — transmitting and receiving signals…
General Concepts 3 min read
Gradient Coils
Three gradient fields, one each for the x, y, and z directions of a Cartesian coordinate system, are used to…
General Concepts 1 min read
Fringing Fields
A large, powerful magnet produces a strong magnetic field in the region surrounding it as well as in its interior.…
General Concepts 2 min read
Magnetic Field Homogeneity
The necessary degree of spatial uniformity of the field can be achieved only by carefully placing the coils at specific…
General Concepts 3 min read
Superconducting Magnets
Since the early 1980s, the use of cryogenically cooled superconducting magnets [Wilson, 1983] has been the most satisfactory solution to…
General Concepts 1 min read
Resistive Magnets
The first whole-body scanners, manufactured in the late 1970s and early 1980s, used four to six large coils of copper…
General Concepts 2 min read
Permanent Magnets and Electromagnets
Both these magnet types use magnetized materials to produce the field that is applied to the patient. In a permanent…
