What Is Radiology? What Is Nuclear Medicine?

Date: Aug-07-2012Radiology is a specialty of medicine that uses ionizing and nonionizing radiation for the diagnosis and treatment of disease. Radiology uses imaging technologies, such as X-ray radiography, magnetic resonance imaging (MRI), nuclear medicine, ultrasound, computed tomography (CT), and positron emission tomography (PET) to see within the human body in order to diagnose disease and abnormalities.

Imaging means creating a picture of the inner configuration of a dense object, which in radiology usually means a part of the human body with the use of radiation.

Radiology is sometimes referred to as radioscopy or clinical radiology. Clinical radiology refers to the use of radiology to diagnose and/or treat injury or disease.

Radiology is a key part of clinical practice across a wide range of medical disciplines. It is usually the best, minimally invasive way of diagnosing, treating or monitoring disease and injury. Over the last 20 years clinical imaging has become much more sophisticated.

According to Medilexicon's medical dictionary, Radiology is:

"1. The science of high-energy radiation and of the sources and the chemical, physical, and biologic effects of such radiation; the term usually refers to the diagnosis and treatment of disease.

2. The scientific discipline of medical imaging using ionizing radiation, radionuclides, nuclear magnetic resonance, and ultrasound."
What is the difference between a radiologist and a radiographer?
A specialist in radiology is a radiologist; a doctor who then specializes in radiology. To become a radiologist you must first complete your training at medical or osteopathic school to become a doctor, and then train for an additional five to six years.

A radiographer, or radiologic technician is a person who performs the radiography imaging scans, such as X-rays - they operate the imaging machines. A radiographer is not a doctor, while a radiologist is.

The radiologist looks at the images and interprets them. He/she pinpoints an injury or abnormality, determines what it is and possibly how severe the abnormality is. The radiologist will typically consult with the patient's doctor when interpreting the results of an imaging scan.

A radiologist is a qualified doctor who then specializes in radiology
What is Projection (plain) Radiography?
This is the most commonly encountered type of radiological investigation. Projection radiography is the practice of creating two-dimensional images (radiographs) using X-ray radiation.

Radiographs, also known as roentgenographs (named after Wilhelm Conrad Röntgen), are created by beaming X-rays through the patient. The insides of the patient absorb radiation at varying levels, depending on their densities; for example, bones are denser than surrounding tissue, so bones show up more on the images because they have absorbed (attenuated) more radiation. A capture device converts all the data into visible light and then creates an image.

For the fifty years following the invention of radiology, plain radiography was the only imaging modality possible. Plain radiography is still the most widely available modality worldwide; is relatively fast and cheap, compared to other forms of imaging, making it the first-line test of choice in radiologic diagnosis in most cases.
What is Fluoroscopy?
This is a type of medical imaging that displays a continuous X-ray image on a screen - a bit like an X-ray movie. It displays the movement of a body part or of an instrument or contrast agent (dye) through the human body.

In this procedure, an X-ray beam passes through the body, the image is transmitted to a screen so that a specific body part and its motion can be viewed in fine detail.

Fluoroscopy may be used in several different types of examinations and procedures, such as:

To see movement through the gastrointestinal tract, using Barium X-rays and enemas

An angioplasty or angiography procedure, to direct the placement of a catheter

To be able to see how blood flows through specific organs

To look at fractures or fracture treatments following orthopedic surgery

What is Interventional Radiology?
This is a rapidly expanding field of medicine. Interventional radiology is minimally invasive, targeted treatments which are performed using imaging guidance. These procedures are often carried out instead of open surgery. They are less risky, involve no large incisions, and are less painful, compared to surgical procedures. Patients who undergo interventional radiologic procedures usually recover faster.

Some interventional procedures, such as angiograms, are done for just diagnostic purposes, while others, for example angioplasty, are treatment procedures.

Somebody who works in this field is called an interventional radiologist. They can diagnose and treat several different types of diseases and disorders, including hepatic interventions, gastrostomy tube placements, inferior vena cava filter placements, renal artery stenosis, and peripheral vascular disease.

The main purpose of using images in interventional radiology is for guidance - the images help the surgeon use his/her instruments accurately and precisely. The main instruments used are needles and catheters.

With the guidance of images, the interventional radiologist can thread the instruments through the body to wherever the disease or injury is located. Interventional radiology involved much less physical trauma to the patient, compared to other procedures.
What is Computed Tomography?
A Computed Tomography scan, also known as a CT scan or CAT (Computer Axial Tomography) scan, is a type of medical imaging that uses tomography.

Tomography is a process whereby a two-dimensional image of a slice or section through a tomogram (3-dimensional object) is generated. The device is called a CTG scanner; it is a large device which uses X-rays.

The CT scanner, through the use of digital geometry processing, generates a 3-D image of the inside of the human body. Several 2-D X-ray images are taken around a single axis rotation to make the 3-D image. Put simply, several pictures of the same area are taken from different angles, then put together to create a three-dimensional (3-D) image.

Unlike the X-ray machine, which sends just one beam of radiation, the CT scanner sends a series of narrow beams into human body as it moves through an arc. The final CT image is a much more detailed one, compared to the simple X-ray picture.

There is an X-ray detector within the CT scanner which can see hundreds of varying levels of density. With a CT scanner you can see tissues within a solid organ. The data is transmitted to a computer, which then creates a 3-D cross-sectional image and displays it on a monitor.

The radiologist may use a contrast dye so that whatever he/she wants to look at shows up more. If the target area is the GI tract, the patient may be asked to drink a barium meal. Barium shows up white on the scan as it moves through the gut. For images, say in the rectum, the patient may be given a barium enema. Barium may be injected into veins too.

Spiral CT may improve the accuracy and speed of the scan. During the scanning, the X-ray beams take a spiral path, and data is gathered with no gaps in between the images.

CT scans are useful if you want detailed 3-D images of specific parts of the body, such as blood vessels, the lungs, brain, abdomen, bones, pelvis, and soft tissues. It is useful for diagnosing some cancers, especially pancreatic, liver and lung cancers, as it is often easier for the doctor to identify a tumor.

Health care professionals tend to prefer using CT scans when diagnosing urgent and emergent conditions, such as pulmonary embolism, aortic dissection, cerebral hemorrhage, obstructing kidney stones, diverticulitis, and appendicitis.

Researchers from UCLA showed that low-dose helical computed tomography (CT) scanning resulted in a 20% lower death rate in lung cancer compared to chest X-ray screening.

Sir Godfrey Hounsfield, at EMI, UK, invented the first commercially viable CT scanner in 1972. EMI used their distribution rights income from the Beatles music to fund the research. Sir Hounsfield, along with Alan McLeod McCormick were awarded the Nobel Prize for Medicine in 1979 for inventing the CT scanner.
What is Ultrasound (Ultrasonography)?
An ultrasound scan is a medical device that utilizes high frequency sound waves to create an imagine (sonogram) of the inside of the human body, such as blood vessels, muscle, joints, the stomach, liver, tendons, or the heart.

Many believe that ultrasound is safer than other forms of imaging because it uses sound waves rather than radiation.

Apart from helping detect problems in certain parts of the body, ultrasonography can also help guide surgeons when they carry out biopsies.

Higher sound frequencies produce better images but cannot penetrate as deeply as lower frequencies.

Ultrasound travels through fluids and soft tissues and bounces off denser surfaces. For example, when looking at the heart and blood vessels around it, ultrasound will travel through the blood, and bounce back off the heart valve.

In a report published in the BMJ (British Medical Journal), researchers from the University of Brest in France showed that compression ultrasonography can safely rule out a diagnosis of DVT (deep vein thrombosis) in pregnant women.

The data of ultrasound bouncing back is processed in a computer, which then creates image on a monitor. If the doctor is viewing the gallbladder and there are no gallstone, the ultrasound with travel straight through, but will bounce back when there are stones.

The denser an object is, the harder the ultrasound bounces back. This echo (bouncing back) is what gives the ultrasound images their features - they can be seen on the screen as varying shades of gray.

Anesthetists sometimes use ultrasound for guidance when injecting anesthetics near nerves. Cardiac ultrasound refers to the creation of 2-D images of the heart. Some more modern machines can produce 3-D images.

Ultrasound can also be used to see how fast blood flows, or the state of cardiac tissue at specific points, by using pulses or continuous wave Doppler ultrasound.

Arterial sonography has many uses, such as diagnosing possible blockages.

Obstetrical imaging - because it uses no radiation, ultrasound is used to check fetal anatomic development.
What is Magnetic Resonance Imaging (MRI)?
Magnetic Resonance Imagine is usually referred to as MRI. MRI devices are large machines which look like large tubes; they have a big magnet in the circular area. The patient is laid down on a table, which then moves into the tube.

Extremely powerful radio waves, between 10,000 and 30,000 times stronger than earth's magnetic field are sent through the body. They force the nuclei of the body's atoms into a new position. As they move back into their original place they emit radio waves. A scanner gathers these signals, sends them to a computer which turns them into an image on a screen. The images are based on where the incoming signals are coming from and how strong they are.

The human body is made up mostly of water - H2O. Water has hydrogen atoms. That is why hydrogen atoms are most commonly used to create an MRI scan.

MRI scanners can create pictures of nearly any part of the body. Bones have the least number of hydrogen atoms, so they come out dark in the pictures, while blood or tissue (especially fatty tissue) look much brighter.

The timing of the radiowave pulses may be altered so that more data may be gathered on the different tissues being scanned.

Even parts of the body that are surrounded by bone can be clearly seen with an MRI scan, making it an ideal device for examining the spinal cord and brain.

MRI scans are helpful for finding tumors in the brain, as well as determining whether the cancer has spread beyond its place of origin. Many different studies on the brain can be done with MRI.

The heart and blood vessels show up clearly on MRI scans. Doctors often order these types of scans to determine whether there are any heart defects, as well as helping them work out whether they are new or long-term problems.

Scientists at Edinburgh University, Scotland, developed an MRI technique that can track cells in the bloodstream. They added that their technique could eventually be developed to measure how effective stem cell treatments are.
MRI scans take pictures from nearly every angle, while CT scans only show images horizontally. MRI scans use no ionizing radiation. Overall, MRIs offer more detailed pictures than CT scans.

Up to 5% of patients cannot cope with the claustrophobia they feel when placed for long periods in the noisy and cramped tube of the MRI device. New technological advances are coming through which will mean scans may be completed more rapidly.
What is Nuclear Medicine?
Nuclear medicine refers to medications that are attached to a radioisotope (radioactive material); the drug is called a radiopharmaceutical. Several different radiopharmaceuticals are available today to study various parts of the body and treat some conditions and diseases.

The radioisotope which is attached to the drug is usually called a "tracer". The most common tracers used in nuclear medicine are thallium-201 and fludeoxyglucose (18F) (18F-FDG), gallium-67, indium-111), iodine-131, iodine-123, and technetium-99m.

The radiopharmaceutical is administered either by injection, orally (swallowing) or as an inhalation. It is designed to target a specific part of the body where there might be some abnormality or disease. The radioactive part of the drug emits gamma rays which are detected using a gamma camera. The doctor can then see what is happening inside the body.

Nuclear medicine is commonly used to evaluate the gallbladder, liver, thyroid, lungs and heart. Physiological function can be determined well using nuclear medicine, rather than anatomical detail.

Nuclear medicine can, for example, be used to identify lesions deep inside the body without having to open up with patient (surgery). It can also determine whether certain organs are working properly; it can determine whether the heart is pumping blood adequately, or whether the brain is getting enough blood, and whether the brain cells are functioning properly.

After having a heart attack, nuclear medicine procedures can help accurately assess the damage to the patient's heart.

Nuclear medicine is useful in locating the brain sites of seizures (epilepsy), Parkinson's disease and Alzheimer's disease.

Nuclear medicine can also be used to treat patients. Thousands of people with hyperthyroidism are treated every year using radioactive iodine. Certain types of cancers, as well as bone pain resulting from cancer can also be treated.

With the most advanced equipment, nuclear medicine images can be used almost simultaneously with CT scans, making detailed anatomical studies possible.

Written by Christian Nordqvist

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