Medical physics applications
Unit 21 Aim A+B
Introduction:
In this assignment, I will be talking about ionising and non-ionising radiations.
Non- ionising radiation:
Non-ionising radiation is the radiation of electromagnetics that do not carry enough energy to ionise
atoms. This type of radiation has a low energy radiation which means it's not able to ionise an atom or
molecule. So, it cannot completely remove an electron from an atom or molecule. Non- ionising
radiation has enough energy only for excitation- excitation is when an electron moves from a low
energy state to a higher energy state. So, because non-ionising radiation only has low frequency, it has
no harm on the human health and body. Examples of non- ionising radiation could be UV, visible light,
infrared and microwave. They all have a low frequency with a long wavelength.
Magnetic resonance imaging (MRI):
In general, atomic nuclei behave like small bar magnets. These tiny bar magnets have the same
tendency to line up with magnetic fields in magnetic fie lds as a compass needle must line up with the
magnetic field of the earth.
A powerful magnetic field and radio waves are used in the medical
imaging procedure known as magnetic resonance imaging (MRI) to
provide precise images of the inside organs of the body. The
fundamental idea behind MRI is that because the human body is made
up of atoms, many of them have a quality known as spin. These atoms
line up with the magnetic field when a magnetic field is introduced to
the body.
An extremely powerful magnet is used in an MRI machine to provide a
powerful and consistent magnetic field. A radio wave is then applied while the patient is still inside the
magnet, causing some of the paired atoms to absorb energy and shift their direction. These atoms
release the absorbed energy when the radio wave is switched off, and sensors in the MRI scanner can
pick up this energy. The NMR phenomenon occurs when the nuclei are thrown out of alignment with
the field by the radio frequency pulse that the MRI machine transmits into the body. The nuclei will
produce their own radio frequency signal as they spin around the magnetic field. The scanner picks up
on this. However, the RF signal from the nuclei fades away after a while. various body tissues require
various amounts of time for the signal to stop working. T2 relaxation is the term for this action.
Finally, the nuclei will re-align with the magnetic field; this process, known as T1, takes a varied
amount of time for different tissues.
Water and other molecules are distributed differently in the body's tissues, and they interact with the
magnetic field in various ways. An MRI machine may provide images of the body's internal structures,
including the brain, organs, and bones, by measuring the energy produced by the atoms inside the
body.
The frequency at which a charged particle with a particular charge and mass precesses around the
direction of an external magnetic field is known as the Larmor frequency (). The Larmor frequency is
determined mathematically by: ω = γ * B. The magnetic field density B is inversely proportional to the
precession frequency. This is how the magnetic field density and RF interact. Then, a gradient field is
included, aiding in 3D spatial resolution. With the use of these gradient coils, we will be able to
, pinpoint the source of the RF signals and create 3D images of tissue. The protons flip as a result of
resonance occurring and microtesla-scale RF signals being sent by the RF coils. A specific slice of the
body is recognised by the scanner because the frequency of the RF signals from the RF coils matches
with the larmor frequency RF signals produced by the processing nuclei.
The MRI scanner uses a set of radio wave pulses and monitors the energy
generated at various periods to produce an entire image. Following a
computer's processing of these signals, a detailed picture of the body's internal
structure is produced. Because it is non-invasive and does not use ionising
radiation, which can be damaging to the body, MRI is a great tool for medical
diagnostics. MRI is a useful tool in the diagnosis and treatment of many medical
disorders because it can identify a wide variety of tissue anomalies, including
tumours, infections, and injuries.
MRI is frequently used to diagnose traumas or strokes in the brain and spinal cord. That is only if the
injury is severe, then it would show but if it is a mild severe it does not show on MRI.
Infrared:
Infrared is known as a non-ionising electromagnetic radiation, which means it does not cause cancer. It
has a wavelength between 760nm and 100,000nm. Because nerve cells can respond well with IR, it is
used in neurostimulation. Applications for infrared radiation include heating, communication, imaging,
and medical diagnosis and treatment.
Infrared is produced by the thermal motion of atoms and molecules. The basis for infrared production
is the generation of heat, which causes materials to emit infrared radiation. Thermal radiation is what
this is. An object's temperature and material composition affect the amount and type of radiation it
emits. An object emits more radiation the hotter it is, and the type of radiation it emits is determined by
the composition of the thing.
Because infrared radiation may penetrate deeply into the body, it is useful for both diagnosis and
treatment. Infrared radiation raises tissue temperature when it interacts with the body's tissues, which
can promote blood flow and relieve discomfort. Many illnesses, such as joint pain, muscle stiffness, and
inflammation, are treated using infrared treatment.
Also utilised for diagnostic purposes is infrared imaging. The radiation that the body emits is picked up
by infrared cameras, which then use the variations in temperature to build
an image. This can assist in locating body parts with unusual temperature
patterns, which may be a sign of a more serious problem. Laser therapy also
use infrared radiation. A laser releases infrared radiation at a particular
wavelength during this form of treatment, and the tissues absorb it. This
may help in promoting tissue repair and increasing the body's own healing
processes.
Infrared cameras: It is possible to observe the heat signatures of objects and surfaces with infrared
cameras, which are specialised cameras that detect and display infrared radiation. Common uses for
infrared cameras include thermography in medicine, industrial, military, and scientific settings.
Using infrared spectroscopy, chemical substances can be recognised and examined depending on how
well they absorb infrared light. A light source, a sample holder, and a detector are commonly used in
infrared spectroscopy apparatus to measure the radiation absorption by the sample.
