Nuclear Medicine combines Physics and Medicine in a very strong way.
Nuclear Medicine uses non-invasive methods to image the physiology of human body by detecting the radiation emitted by radiopharmaceuticals inside the body.
Understanding how radiation is detected is important in order to use optimally Nuclear Medicine detectors.
In the following hour we hope to describe in sufficient detail the basics of the phenomena of the emission of radiation and its detection.
Characterized by wavelength.
Wavelength related to frequency and energy:
1 ev = 1.6 x 10e-19 joules
1 kev = 1000ev ; 1 Mev = 1000000 ev
wavelength frequency Energy Comments
[m] [Hz] [eV]
3.0e+03 1.0e+05 6.6e-11 LF, MF
3.0e+00 1.0e+08 6.6e-08 VHF,UHF,FM
3.0e-03 1.0e+11 6.6e-05 m-wave,radar
3.0e-06 1.0e+14 6.6e-02 IR,Light, UV
3.0e-09 1.0e+17 6.6e+01 UV, X-ray
3.0e-12 1.0e+20 6.6e+04 X-ray,gamma
3.0e-15 1.0e+23 6.6e+07 gamma
The Atom can be divided into the nucleus and the electron envelope.
The electrons generate all chemistry (and biology) and are in large responsible for interaction between radiation and matter.
All radiation detectors are mainly based on the interaction between radiation and the electron envelope.
The electrons are arranged in “layers” (or “shells”) each with its binding energy.
(For each layer n there 2n-1 sublayers , and 2 electrons sit in each sublayer) .
The innermost layer has an index of 1 and is called the K layer. The next layer is called L layer and so on.
L K “ Free” Electrons 4-5 keV 33.2 keV Binding Energy
The electrons tend to fill the atomic layers from the bottom up, i.e. if a K shell electron is kicked out , an outer shell electron will move to take its place, releasing energy. This energy can be released in two ways:
Characteristic X-ray photons E=B K -B L
Auger electrons E=B K -2B L
L Nucleus K-shell Vacancy Auger Electron K Characteristic X-ray