Hi friends!!!
In our previous blog we have discussed about x ray machine working principle and components of x ray tube. Please check out for the link given below.
x ray machine working principle
In today’s blog, we are going to discuss about radiation safety.
Excessive radiation dose may cause cancer induction, skin burns, genetic defects, sterility, cell killing etc. So radiation protection is a raising concern in radiology. Therefore, radiation safety is a important topic for healthcare professionals working in radiology as well as for the patients.
Let’s get into the topic.
WHAT IS
RADIATION?
The radiation
means energy in motion. There are two types of radiation Ionizing Radiation and
Non Ionizing Radiation. Ionizing radiation has shorter wavelength, higher
frequency and higher energy. Ionizing radiation have energy to eject orbital electrons.
Example: x rays, gamma rays, beta rays. Non ionizing radiation has longer wavelength,
lower frequency and lower energy. Non ionizing radiation does not have energy
to eject orbital electrons. Example: Ultraviolet light, lasers, radio waves,
infrared light, microwaves.
The following image is the radiation warning symbol.
WHAT ARE THE
TYPES
OF
RADIATION
DOSES?
ABSORBED DOSE
Energy deposited
in each tissue as a result of exposure to ionizing radiation. Absorbed dose is
measured in mGy.
EQUIVALENT DOSE
Equivalent dose is
a damaging properties of different types of radiation. Equivalent dose in milliSievert
mSv = Absorbed dose in mGy.
EFFECTIVE DOSE
Effective dose
specifies the long term effects of radiation exposure. It is measured in
millisievert mSv. Factors include absorbed dose to all organs of the body,
relative harm level of the radiation, sensitivities of each organ to radiation.
WHAT ARE THE WAYS
TO
ACHIEVE RADIATION
SAFETY?
TIME DISTANCE
SHIELDING
The radiation safety can be achieved by reducing the time of radiation exposure. Doubling the distance between patient and radiation source decreases
the exposure by 4 times. Tripling the distance between patient and radiation
source decreases the exposure by 4 times. Therefore increase in distance between patient and radiation source increases radiation safety. Exposure varies inversely by the
square of distance from the the x ray tube.
PROPER WORK
PRACTICE
Proper work
practice can improve radiation safety to a great extent. It includes usage of TLD Badges. Scheduled preventive maintenance of the
equipment. Handling by a qualified person. Usage of radiation safety accessories. The radiation protection materials include mobile protective barrier, lead apron, organ shielding.
EQUIPMENT TYPE
APPROVAL
Usage of equipment
type approved by AERB also contributes in radiation safety. Obtain AERB permission prior to installation. Obtain
license for operation.
WHAT ARE THE WAYS
TO
LIMIT RADIATION IN X
RAYS?
BEAM REDUCING
DEVICE
The usage of
following devices limits radiation and improves radiation safety in x ray machine.
APERTURE DIAPHRAGM
Aperture Diaphragm
is a sheet of lead that comes with a circular, square or rectangular openings
to restrict the x ray field size.
CONES
Cones are metal
tubes that comes in different ranges of shapes and sizes. The length of the
cone and size of the opening affects the x ray field size.
VARIABLE APERTURE
Variable apertures
are lead plates or shutters which can be adjusted to change the size of the
beam.
GRIDS
Grids are placed
between patients and x ray film to reduce the scattered radiation reaching the
detector, which greatly improves radiation safety. Grids are parallel strips made up of high attenuating material such
as lead and interspace filled with low attenuating material such as carbon. Grid
ratio is the ratio of height of lead strips to the distance between two lead
strips.
NOTE: High mAs =
High radiation dose, so keep mAs as low as possible. High kVp =low radiation dose. Here usage of high voltage increases radiation safety. Therefore, higher the voltage, shorter the wavelength. Here x rays will have
greater penetrating power and greater intensity.
WHAT ARE THE WAYS
TO
LIMIT RADIATION IN
COMPUTED TOMOGRAPHY?
The following techniques can be used to improve radiation safety in computed tomography.
TUBE CURRENT
MODULATION
Automatic
modulation of x ray tube current (mAs) based on rotational and longitudinal
movement of patient through x ray beam reduces radiation dosage by 40-60%.
BOW TIE FILTER
Usage of Bow tie
filter instead of conventional flat filters can limit lower energy x rays
reaching the patient. Lower energy x rays does not contribute to image
formation. But instead it increases a patient’s radiation dose. Using bow tie
filter can reduce radiation dosage by 50%.
PITCH RATIO
The distance
travelled by CT Table in one 360 degree gantry rotation divided by x ray beam
width. For example, if a table travelled 10mm during one rotation and width of
the x ray beam is 10mm, then the pitch is 10mm/10mm = 1mm.
Two fold increase
in pitch, results in 50% reduction of radiation dose.
WHAT ARE THE RADIATION
PROTECTION
ACCESSORIES?
The usage of following radiation protection materials improves radiation safety to a great extent.
1. Mobile Protective Barrier
(MPB)- 1.5 mm Lead Eqv.
2. Lead Aprons – 0.25
mm Lead Eqv.
3. Thyroid Shield -0.25
mm Lead Eqv.
4. Gonads Shield- 0.25
mm Lead Eqv.
5. Eye Wear (Shield)-
0.25 mm Lead Eqv.
6. Rubber hanging
Flaps (In IR)-0.5 mm Lead Eqv.
7. Hand Gloves -0.25
mm Lead Eqv.
8. Lead Glass window-
1.5 mm Lead Eqv.
9. Door (Lead Lined)-1.7
mm Lead Eqv.
Now I hope you have acquired some knowledge about radiation safety. We will discuss in detail about a topic related to Biomedical Engineering in our next blog.
NOTE: Dear friends!!! …Please do comment a topic related to Biomedical, so that we can discuss it in future blogs.
Check out for this blog about Computed Tomography
COMPUTED TOMOGRAPHY|TECHNOLOGY|ARTIFACTS
DON’T FORGET TO FOLLOW THIS BLOG PAGE
DROP YOUR MAIL ID TO GET IMMEDIATE UPDATES
If you find this blog post knowledgeable, comment & share it with a friend!
So clear and neat explanation