CT scanning is the basic procedure to identify malfunctioning or working of inner body parts which was prescribed by the doctors for diagnostic purposes. Especially for the case of acute chronic diseases like heart disorders, spinal disorders, renal issues, cancers and emergency situations like accidents.
Lot of discussion went on in the scientific community as to whether radiation from CT scan will have a risk towards cancer. First we have to know the basic details of CT scan.
What is CT Scan?
CT scan, Computer Tomography is a type of imaging technique widely used in medicine. It helps us to obtain detailed images of the body or parts of the body that are imaged by using X-rays
The procedure of CT is non-invasive and multiple X-ray measurements are taken from various angles and are runthrough reconstructed algorithms to obtain an accurate cross sectional image of the body. Image obtained here is called Tomographic image
Advantages of CT over MRI
- CT can be taken in patients with rods or metal implants or pacemakers unlike in MRI these are not allowed as it has powerful magnets.
- CT scan is so quick as it helps with patients having severe pain.
Who invented CT scan?
British electrical engineer Godfrey Hounsfield and South African physicist Dr Alan Cormack developed CT in 1972. They received the Nobel prize in physiology and medicine in 1979. Initially it is called CAT scan, computer axial tomography and later it is changed to CT scan.
How does CT scan work?
CT machine has a doughnut-shaped tube that rotates the X-ray generator which emits X-ray 360 degrees around a patient body and X ray detectors are placed opposite to the generator.
Multiple images are recorded of a particular part of the body as multiple X-rays are projected onto the body. These raw images are called sinogram and are constructed to give a 3D view of the inside of the body. Sometimes, a radio contrast of Iodine is injected into the body before a CT scan for better visualisation of blood vessels.
Ionising X-rays are used in the CT scan like Gamma rays, X-rays, and UV rays as they are highly ionising and may have a risk of skin cancer. Prolonged exposure to the ionising radiation in CT scan may lead to the Radiation induced cancer
Tissues of Breast, thyroid, lung and bone marrow are sensitive to the CT scan radiation. Lead is used to shield or protect the scattered radiation
Uses
CT is used to produce images of any part of the body such as bones, muscles. fat, organs and blood vessels. Recently in COVID-19 situation, CT scans play a key role in identifying false negative Covid-19 cases, lung damage and some conditions such as pulmonary embolism, pneumomediastinum (presence of air in heart and lung blood vessels), and fungi diseases associated with COVID-19, mucormycosis.
Types of radiation dose in CT scan
- Absorbed dose is measured by taking the amount of energy deposited by radiation in a mass like water. rock, air and people. It is expressed in milligrays (mGy)
- Equivalent dose is calculated for individual organs. It is based on the absorbed dose to an organ that is adjusted to type of radiation. It is expressed as millisieverts (mSv) to an organ.
- Effective dose is calculated for the whole body. It is the addition of all equivalent doses to all organs and is adjusted to sensitivity of the organ to radiation. It is expressed as millisieverts (mSv) to an organ.
Common CT scans radiation doses:
Most common CT scan and its amount of radiation absorbed are included as follows;
For Head : 2 millisieverts (mSv) of radiation which is equal to 8 months of background radiation.
For Abdomen : 10 mSv of radiation which is equal to 3 years of background radiation.
For Spine: 6 mSv of radiation which is equal to 2 years of background radiation.
For Chest: 7 mSv of radiation which is equal to 2 years of background radiation.
For Coronary angiography : 12 mSv of radiation which is equal to 4 years of background radiation.
For Lung cancer : 1.5 mSv of radiation which is equal to 6 months of background radiation.
For Cardiac (calcium scoring): 3 mSv of radiation which is equal to 1 year of background radiation.
For Colonography: 6 mSv of radiation which is equal to 2 years of background radiation.
Incase of the Contrast CT scan,
- For Head: 4 mSv of radiation which is equal to 1.4 years of background radiation.
- For Abdomen : 20 mSv of radiation which is equal to 7 years of background radiation.
Normal background radiation present in India is 0.734 mSv per year whereas worldwide is 2.4mSv a year due to scattered gamma radiation from space and human activities.
Recent data from the International Atomic Energy Agency makes us surprised that one chest CT scan might equal 300 normal X-ray. Childrens are ten times more sensitive and susceptible to the radiation especially female childrens are more sensitive.
FDA reports that 30-50% CT scans are medically unnecessary and it can be altered with MRI.
Link of radiation to cancer
Constantly in the human body precancerous lesions are developed and are gradually removed by the natural immune responses. If these high dose radiation are exposed to humans especially children, it may have a chance for DNA mutations that results in cancer development.
A Recent study in 2023 revealed that high dose CT scan radiation to bone marrow resulting in haematological malignancies in children.
Preventive steps
- CT scan has to be prescribed in the rightful needs based on the condition of patients especially in children and women and no CT scan has to be done without doctors advice.
- Modern low dose scanners are working effectively in low dose radiation and hospital management has to be thoroughly updated with the modern equipment to prevent collateral damage.
- Every CT Scan equipment has good performance when it is scanned for 8,00,000 to 16,00,000 scan seconds and is approximately for a period of 7 years.
How to reduce damage from radiation
It’s not CT radiation, even though we have normal radiation which is present in our surroundings and we can reduce the radiation damage by adding some ingredients in our daily diet are;
- Sea kelp
- Spirulina and chlorella
- Wheatgrass juice
- Green Tea
- Sprouts especially Cruciferous Sprouts, and
- Curcumine (Turmeric)
We know the fact, ‘Our Diet Is Our Medicine’ so by taking required amounts of fruits and vegetables, we can restore our health and make our society a healthy one.