Medical imaging

Doctors use tools to see inside the body.

These tools look past skin and bones. They help find out if someone is sick.

One tool uses X-rays to see bones. Another tool uses big magnets. This magnet tool helps see soft parts. It can make a picture of the brain. These tools help doctors treat people. Many people use these tools every day.

Doctors use special tools to see inside the human body.

These tools help them find sickness or broken bones. Most of these tools are noninvasive. This means they do not put tools inside the body.

One way to see inside is with X-rays. X-rays use a beam of light that we cannot see. This is called radiology. X-rays can show broken bones or parts of the lungs. Some X-ray tools show moving pictures. This is called fluoroscopy.

Another way is magnetic resonance imaging, or MRI.

An MRI scanner uses very strong magnets. It also uses radio waves. These waves talk to the tiny parts of water in your body. This makes a clear picture of soft parts, like the brain. MRI does not use radiation.

There is also CT scanning.

A CT scan uses X-rays to make many views. A computer puts these views together. This makes a picture of a thin slice of the body. This is called tomography. These tools help doctors help people every day.

Doctors use special tools to see inside the human body. This field is called medical imaging.

These tools help find sickness or broken bones. They also show how organs work. This is called physiology. Most imaging is noninvasive. This means no tools are put inside the patient. Imaging helps build a database of normal bodies. This makes it easier to find abnormalities.

One way it works is through X-rays. This is often called radiology. X-rays use a beam of light we cannot see. Some tools use a wide beam for projection radiography. Others use fluoroscopy to make real-time moving pictures.

Doctors can use contrast media like barium or iodine. These substances help see organs like the stomach. Another way is magnetic resonance imaging, or MRI. An MRI scanner uses very strong magnets. It uses radio waves to talk to hydrogen atoms in water. These atoms emit signals that a computer turns into a picture.

History shows how these tools changed medicine. In 1972, an engineer named Godfrey Hounsfield invented a device. He worked for a British company called EMI. He created the X-ray computed tomography device, or CT. It was first used to look at the head. In 1975, EMI made a CT device for the whole body. This was a huge step for doctors. Hounsfield and physicist Allan Cormack won the Nobel Prize in 1979. Later, in 1994, digital image processing joined the Space Technology Hall of Fame.

There are many important facts about these tools. By 2010, people had done 5 billion medical imaging studies. In 2006, imaging caused about 50% of ionizing radiation exposure in the United States.

Making these machines requires many tiny parts. This includes chips from the semiconductor industry. Every year, there are 46 million shipments of medical imaging chips. MRI magnets are very strong, often 1.5 to 3 teslas. These numbers show how big this field has become.

Medical imaging links to many areas of science. It is part of biomedical engineering and medical physics. It also connects to computer science for making images.

Specialists called radiologists look at the pictures. They are trained to find health problems. Other experts like radiographers help take the images. Some tools even use nuclear medicine. This uses tiny particles to see how the body functions. This helps doctors study the heart or the brain.

Medical imaging is a vital scientific process used to view the interior of the human body. This technique allows for clinical analysis and medical intervention by revealing structures hidden by skin and bones.

It also provides a visual representation of physiology, which is the function of organs and tissues. By establishing a database of normal anatomy, imaging helps healthcare professionals identify abnormalities. Most of these procedures are noninvasive, meaning no instruments are introduced into the patient's body. While imaging can be performed on removed tissues, that work is usually classified as pathology rather than medical imaging.

One primary method is radiography, which uses X-rays to create images. There are two main forms: projection radiography and fluoroscopy. Projection radiography uses a wide beam of X-rays to capture still images, such as checking for bone fractures or lung changes.

Fluoroscopy is different because it uses a constant input of X-rays to produce real-time, moving images. This is very useful for guiding catheters or seeing organs as they work. To make certain organs more visible, doctors use contrast media like barium, iodine, or air. Early technology used fluorescing screens to receive radiation, but this evolved into image amplifiers and eventually TV cameras.

Another advanced method is Magnetic Resonance Imaging, commonly known as MRI. This technique does not use ionizing radiation, which makes it safer for repeated use than X-rays.

An MRI scanner uses powerful magnets to polarize hydrogen nuclei, which are single protons found in the water molecules of human tissue. The machine emits a radio frequency (RF) pulse at a specific resonant frequency called the Larmor frequency. When the RF pulse is turned off, the protons "relax" and emit radio waves. These emissions are detected by RF antennas and reconstructed into detailed images. MRI is especially good at showing soft-tissue contrast compared to CT scans.

To create these complex images, MRI uses three distinct electromagnetic fields. First, a very strong static magnetic field, typically between 1.5 and 3 teslas, polarizes the hydrogen nuclei. Second, gradient fields are used for spatial encoding by varying in space and time. Third, a spatially homogeneous radio-frequency field is used to manipulate the nuclei to produce signals. Modern MRI machines can produce 3D blocks of images, whereas older versions focused on 2D "slices" or tomographic images.

While MRI is safe from radiation, doctors must control risks like tissue heating or interference with implanted devices like pacemakers.

The history of medical imaging is marked by massive technological leaps. In 1972, an engineer named Godfrey Hounsfield invented the X-ray computed tomography (CT) device for diagnosing head injuries.

This method involves projecting X-rays through a section of the body and using a computer for image reconstruction. By 1975, EMI developed a CT device capable of imaging the entire body. These breakthroughs were so significant that Hounsfield and physicist Allan Cormack won the Nobel Prize in 1979. Later, in 1994, digital image processing technology was recognized by the Space Technology Hall of Fame.

The scale of medical imaging is enormous. By 2010, over 5 billion medical imaging studies had been conducted worldwide. In 2006, medical imaging accounted for approximately 50% of the total ionizing radiation exposure in the United States. The production of this equipment relies heavily on the semiconductor industry. Manufacturers use CMOS integrated circuit chips, sensors, and various processors like microcontrollers and digital signal processors. The industry is massive, with annual shipments of medical imaging chips reaching 46 million units.

Medical imaging is a multidisciplinary field that connects many areas of science. It is a sub-discipline of biomedical engineering, medical physics, and medicine. Biomedical engineers and computer scientists often work on the research and development of new instrumentation and image acquisition. Meanwhile, specialists like radiologists interpret the images to diagnose diseases. Radiographers, or radiologic technologists, are often responsible for the technical task of acquiring high-quality diagnostic images. Finally, nuclear medicine adds another layer by using isotopes to assess physiology, helping doctors study the heart, brain, and other complex systems.