Ancillary Electronic Equipment for Detection
The detectors used in nuclear medicine are attached to preamplifiers, amplifiers, and pulse shapers to form a signal that can be examined for information about the energy of the detected…
Various Detector Configurations
The detectors in clinical nuclear medicine are NaI(TI) crystals. In research applications, other substances are employed, but the engineering considerations for the use of other detectors are more complex and…
Detection of Photon Radiation
Gamma rays are detected when atoms in a detector are ionized and the ions are collected either directly as in gaseous or semiconductor systems or by first conversion of the…
Nuclear Medicine
Nuclear medicine can be defined as the practice of making patients radioactive for diagnostic and therapeutic purposes. The radioactivity is injected intravenously, rebreathed, or ingested. It is the internal circulation…
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 believed that microvascular changes are specific to the underlying region…
Mechanism
Flow-sensitive images show increased perfusion with stimulation, while blood oxygenation–sensitive images show changes consistent with an increase in venous blood oxygenation. Although the precise biophysical mechanisms responsible for the signal…
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 single subjects for a scanning duration of several minutes, and…
Digital Data Processing
A typical scan protocol calls for a sequence of tailored RF and gradient pulses with duration controlled in steps of 0.1 msec. To achieve sufficient dynamic range in control of…
Radiofrequency Coils
Radiofrequency (RF) coils are components of every scanner and are used for two essential purposes — transmitting and receiving signals at the resonant frequency of the protons within the patient…
Gradient Coils
Three gradient fields, one each for the x, y, and z directions of a Cartesian coordinate system, are used to code position information into the MRI signal and to permit…
