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What is Diagnostic Radiology? Understanding its Tests and Procedures

Importance of Diagnostic Radiology in Healthcare

Diagnostic radiology involves using imaging procedures to take pictures of the body’s internal organs and structures. It is usually ordered by healthcare practitioners to detect injuries or specific illnesses. For example, an X-ray is a classic example of diagnostic radiology, which is used to confirm bone fractures after an injury. Without X-rays, fractures are difficult to detect just by physical observation. Similarly, an ultrasound (US) is commonly used for studying foetal health and growth throughout the pregnancy.

Diagnostic imaging services are an integral part of any healthcare setting and are widely used nowadays by physicians to not only establish an accurate diagnosis but to monitor treatment and understand the outcome of such treatment precisely. Technological advances in the field of radiology have now enabled improved image clarity, tissue differentiation and a deep understanding of our body’s internal structures leading to faster diagnosis without the need for complicated and invasive procedures in many cases. Moreover, these images can be stored digitally, can be manipulated as needed and can be transmitted quickly with just a click of the mouse globally for future reference or a second opinion. 

Tests and Procedure

There are several diagnostic procedures, the most commonly used being the X-rays, computed tomography (CT) scan, magnetic resonance imaging (MRI), US, Positron emission tomography (PET) scan, etc. 


X-rays are generally used to diagnose tumours or bone injuries. The procedure involves passing invisible electromagnetic beams through the body to produce images on a specially-treated plate, known as X-ray film. When X-rays is passed through the body, the different body tissues, such as the blood, fat, muscles, bone etc allow light to pass through it in varying amount. Bones, tumours and denser structures allow very few X-rays to pass through them and thus appear white on an X-ray film. A fracture can be detected as a dark line in the white bones on the X-ray film. 

During the X-ray procedure, the patient is asked to remove jewellery or clothing that may interfere with the results and the body parts not being imaged are covered with a shield to avoid unnecessary exposure. He/She is then positioned on a table between the X-ray beam and the X-ray film. The patient is required to hold his/her breath and stay very still for a good-quality image. X-rays should be avoided in pregnancy to avoid birth defects.


Fluoroscopy is a special type of X-ray that involves the passing of a continuous X-ray beam through the body to study moving body structures. This is commonly used to study the functioning of bone joints, heart, lungs, etc. For example, in a barium X-ray, the patient is made to drink a liquid containing barium and then fluoroscopy is used to see the movement of the barium in the intestine to diagnose abnormalities such as tumours, ulcers, hernias, etc.

CT scan

This scanning method makes use of a series of X-rays and a computer to create cross-sectional images of the internal body parts. As compared to an X-ray which creates a 2D image, a CT scanner revolves around the patient taking hundreds of images of the body to create a more detailed and clearer image. A CT scan is most commonly ordered to diagnose tumours, fractures, heart diseases, internal bleeding, etc. 

The patient is required to fast overnight and allowed to drink only clear liquids before the scan. Sometimes, the doctor may inject a contrast or ask the patient to drink an oral contrast solution before the scan starts. This improves the visibility of the specific organ or tissue under investigation. During the test, the patient is asked to lie down on a table which slowly moves inside a circular scanner. The patient is required to stay still and hold his breath briefly. Once the scanner finishes taking pictures of the area of interest, the table moves back out of the scanner. 


An MRI procedure uses a strong magnetic field and radio waves to create detailed images of the internal body organs. It is employed for examining the brain, spinal cord, liver, prostate gland, bones, joints, breasts, heart, blood vessels, etc. The procedure is very similar to the CT scan procedure, except that the MRI scanner makes loud noises during the procedure and the patient is required to wear earplugs or headphones. 

Our body is made up of hydrogen and oxygen atoms. The centre of each hydrogen atom contains a smaller particle called a proton. When a strong magnetic field is created, these protons are aligned in the same direction. When radio waves are sent through the body, these protons are knocked out of alignment. They return to their original position when the radio waves are turned off. This creates radio signals which are picked up by the receiver and recreated as a detailed image of the structure of interest. 


The US procedure makes use of high-frequency sound waves to pass through the body. The body structures reflect off the sound waves which are received by a computer to generate images of the internal organs. The US scan is used to identify problems involving the blood vessels, gastrointestinal tract, breast, etc or to monitor healthy pregnancy. The patient is made to lie down on the table and a clear gel is applied to the skin covering the area of interest. This gel helps in the transmission of radio waves. The doctor moves a device known as a transducer over the area to be examined.


A PET scan involves using a radioactive drug known as a tracer to detect abnormal metabolic activities inside the body. A PET scan helps detect cancers, heart diseases, and brain ailments at an early stage even before it is identified through other imaging procedures such as a CT or MRI scan. The tracer is injected in the vein which circulates via the blood and gets collected in those areas with high metabolic activities. This helps to identify the disease location. The PET images can be combined with CT or MRI scans and are known as PET_CT or PET-MRI scans. The PET-CT or PET-MRI procedure is similar to the CT or MRI procedure and takes about 30-45 minutes


What is diagnostic radiology?

When imaging techniques such as X-rays, CT, MRI, US, etc are used to have a detailed view of the body’s internal organs and structures to aid diagnosis or monitor treatment, it is known as diagnostic radiology. Diagnostic radiology is also employed for screening cancers and heart conditions. 


What is interventional radiology?

When imaging techniques are used to guide procedure, it is known as interventional radiology. For example, a biopsy procedure guided by the US technique or an angioplasty guided by the CT technique.

How is nuclear medicine different from normal X-ray and CT examinations?

Nuclear medicine involves giving the patient a radioactive medication and detecting the radiation that is released by the body to create images of the organ of interest. Whereas, in normal X-ray and CT scan procedures X-ray beams are passed through the body to create images of the internal organs. A nuclear medicine study generally gives information about the normal or abnormal activities of an organ whereas an X-ray or CT scan shows structural abnormality or defect.

What is Tomosynthesis (3D mammography)?

Tomosynthesis is an advanced diagnostic procedure to detect breast cancer at an early stage. This technique makes use of low-dose X-rays to create 2D and 3D images of the breast tissues. These images are very detailed and can detect abnormal tissues better as compared to a standard mammogram.

What is angiography?

Angiography is a type of invasive diagnostic procedure that makes use of X-rays and a special dye known as a contrast agent to check abnormalities in the blood vessels. The X-ray images created during the procedure are known as an angiogram. It is useful for identifying blockage in blood flow due to clot formation or fat deposition.

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