Transmutation of the nucleus from one element to another is associated with radioactivity.
When radium emits an alpha particle, the nucleus is transformed into the element radon.
Most physics texts discuss the details of the process.
A random event is the decay or transmutation of a radioactive nucleus.
Some nuclei decay sooner than others.
The laws of probability can be used to predict the decay rate for the aggregate if we deal with a large number of radioactive nuclei.
The half-life is the time interval for half of the original nucleus to be transliterated.
The half-life of radioactive elements varies greatly.
Some decay very quickly and have a half-life of less than a few microseconds.
Others have a half-life of thousands of years.
The Earth's crust is home to the very long-lived radioactive elements.
The short-lived radioactive isotopes can be produced by bombarding certain stable elements with high-energy particles.
The nucleus of naturally occurring phosphorus has 15 protons and 16 neutrons.
A half-life of 14 days is what this radioactive phosphorus has.
Radioactive elements can be produced in a similar way.
In biological and clinical work, many of these isotopes have been very useful.
The shapes of internal organs can be seen with a computerized X-ray tomography.
Information about the internal structure of tissue is not provided by X-rays.
Changes in tissue structure and pathological alterations inside internal organs can be missed by CT scans.
This technique uses the magnetic properties of the nucleus to provide images of internal body organs with information about soft-tissue structure.
The techniques we have discussed so far are relatively easy to use.
They use reflected or transmitted energy to see internal structures.
The principles are relatively easy to explain, but a detailed description is beyond the scope of this text.
An introduction to the principles of nuclear magnetic resonance is what begins the discussion.
The quantum mechanical property of spin is found in the nucleus of atomic nuclei.
As if they were small spinning tops, we can imagine these particles.
Small bar magnets are created by the spin of the nuclear particles.
The small magnets associated with the nucleons line up inside the nucleus to cancel each other's magnetic fields.
The nucleus has a net magnetic moment if the number of nucleons is odd.
Tiny magnets are created by nuclei with an odd number of nucleons.
Hydrogen has a nucleus with a single protons and has a nuclear magnetic moment.
The human body is made of mostly water and hydrogen.
Magnetic resonance images of structures within the body can be produced using the magnetic properties of the hydrogen nucleus.
Nuclear magnetic properties of hydrogen will be the focus of our discussion.
Small arrows are represented by the nuclear magnets.
The situation is changed by an external magnetic field.
The parallel configuration has a lower energy.
The Mag netic fields can be found in the range 1 to 4 T.
The Larmor Frequency is given by Eq.
The population of the spin up and spin down states is equalized by a displacement of 90*.
An external source of energy is needed to reverse the alignment of antiparallel spins.
The magnetic moment is displaced from the direction of the external field by the use of a short radio Frequency driving pulse at the Larmor Frequency.
The magnetic moment from the external magnetic field is displaced by an angle determined by the strength and duration of the driving pulse.
The magnetic moment is displaced from the external magnetic field by an angle determined by the strength and duration of the driving pulse.
The displaced magnetic moment produced by the radio Frequency driving pulse, precesses around the external magnetic field and itself produces a radio Frequency signal at the Larmor Frequency of rotation.
The signal can be detected by a separate coil or the driving coil.