In 1895, a physicist named Wilhelm Roentgen was experimenting with a cathode tube, which is a glass container where a beam of electrons lights up a fluorescent screen. He covered the tube with cardboard to block the light, but something unexpected happened: another screen outside the tube started to glow. This meant that invisible rays had passed through the cardboard. Roentgen didn’t know what these rays were, so he called them X-rays. His groundbreaking discovery eventually earned him a Nobel Prize.
Today, we know that when high-energy electrons in a cathode tube hit a metal part, they either slow down and release extra energy or knock electrons out of the atoms they hit. Both actions release energy in the form of X-rays. X-rays are a type of electromagnetic radiation with more energy than visible light but less than gamma rays. They can pass through different materials as if they are semi-transparent, which makes them very useful in medicine for creating images of organs like bones without causing harm. However, there is a small risk of causing mutations in sensitive tissues, which is why lead aprons are often used for protection.
When X-rays hit matter, they collide with electrons. Sometimes, the X-ray is completely absorbed, and other times, it is only partially absorbed and scattered. The chance of these interactions depends on the number of electrons the X-rays encounter. Dense materials or those with elements that have higher atomic numbers, like calcium in bones, are more likely to absorb X-rays. This is why bones appear white on X-ray images. In contrast, soft tissues, which are less dense and made of elements with lower atomic numbers like carbon, hydrogen, and oxygen, allow more X-rays to pass through, resulting in darker areas on the film.
Traditional X-ray images are two-dimensional and have limitations. As X-rays pass through the body, they interact with many atoms along their path, and the image reflects the combined effect of all these interactions. It’s like trying to print 100 pages of a book on a single sheet of paper. To get a clearer picture, multiple X-ray views from different angles are needed. This is where a CT scan, or Computed Tomography scan, comes in, which is another Nobel Prize-winning technology.
Think of CT scans like this: with a single X-ray, you might notice a change in density due to a tumor, but you wouldn’t know how deep it is. By taking X-rays from multiple angles, you can determine the tumor’s position and shape. A CT scanner sends a fan or cone of X-rays through the patient to a set of detectors. The X-ray beam rotates around the patient and often moves down the body in a spiral path. Spiral CT scans create detailed cross-sections that can identify anatomical features, tumors, blood clots, and infections. They can even reveal heart disease and cavities in ancient mummies.
What started as Roentgen’s lucky discovery has become a medical marvel. Today, hospitals and clinics perform over 100 million scans each year worldwide to diagnose diseases and save lives. X-ray technology has revolutionized medicine, allowing doctors to see inside the body without surgery and providing critical information for patient care.
Research the history of X-rays, focusing on Wilhelm Roentgen’s discovery and its impact on science and medicine. Prepare a short presentation to share with the class, highlighting key milestones and advancements in X-ray technology.
Use an online simulation tool to explore how X-rays are produced in a cathode tube. Experiment with different settings to see how changes affect the X-ray output. Write a brief report on your findings and share it with your classmates.
Conduct a simple experiment using materials of varying densities to simulate X-ray absorption. Use a flashlight to represent X-rays and different objects to observe how light passes through or is blocked. Record your observations and discuss how this relates to X-ray imaging in medicine.
Participate in a class debate on the risks and benefits of X-ray technology. Research both sides of the argument, considering the medical advantages and potential health risks. Present your arguments and engage in a discussion with your peers.
Work in groups to create a 3D model of a CT scanner using craft materials. Focus on illustrating how the scanner rotates and captures images from multiple angles. Present your model to the class, explaining the process of CT imaging and its significance in modern medicine.
In 1895, a physicist named Wilhelm Roentgen was conducting experiments with a cathode tube, a glass container where a beam of electrons illuminates a fluorescent window. He had wrapped cardboard around the tube to prevent the fluorescent light from escaping when something unusual occurred: another screen outside the tube began to glow. In other words, invisible rays had passed through the cardboard. Wilhelm was unsure of what these rays were, so he named them X-rays, and his discovery eventually earned him a Nobel Prize.
Here’s what we now understand about the phenomenon. When high-energy electrons in the cathode tube strike a metal component, they either slow down and release extra energy or displace electrons from the atoms they encounter, triggering a reaction that also releases energy. In both scenarios, the energy is emitted in the form of X-rays, which are a type of electromagnetic radiation with higher energy than visible light but lower energy than gamma rays. X-rays are capable of penetrating various types of matter as if they are semi-transparent, making them particularly valuable for medical applications, as they can create images of organs, such as bones, without causing harm. However, there is a small risk of causing mutations in reproductive organs and tissues like the thyroid, which is why lead aprons are commonly used to shield against them.
When X-rays interact with matter, they collide with electrons. Sometimes, the X-ray transfers all of its energy to the matter and is absorbed. Other times, it transfers only some of its energy, with the remainder being scattered. The likelihood of these outcomes depends on the number of electrons the X-rays are likely to encounter. Collisions are more probable if a material is dense or composed of elements with higher atomic numbers, which means more electrons. Bones are dense and rich in calcium, which has a relatively high atomic number, so they absorb X-rays effectively. In contrast, soft tissue is less dense and primarily consists of lower atomic number elements like carbon, hydrogen, and oxygen. As a result, more X-rays penetrate tissues such as lungs and muscles, leading to darker areas on the film.
However, these two-dimensional images have limitations. When X-rays pass through the body, they can interact with numerous atoms along their path. What is captured on the film reflects the cumulative result of all those interactions. It’s akin to trying to print 100 pages of a novel on a single sheet of paper. To gain a clearer understanding of what is happening, multiple X-ray views from various angles around the body are needed to construct a comprehensive internal image. This is a common practice for doctors in a procedure known as a CT scan, or Computed Tomography scan, which is another Nobel Prize-winning innovation.
Consider CT scans in this way: with just one X-ray, you might detect a density change due to a solid tumor in a patient, but you wouldn’t know its depth beneath the surface. However, by taking X-rays from multiple angles, you can determine the tumor’s position and shape. A CT scanner operates by directing a fan or cone of X-rays through a patient to an array of detectors. The X-ray beam rotates around the patient and often moves down the patient’s body, tracing a spiral trajectory. Spiral CT scans generate data that can be processed into detailed cross-sections capable of identifying anatomical features, tumors, blood clots, and infections. CT scans can even reveal heart disease and cavities in mummies buried thousands of years ago.
What began as Roentgen’s fortunate discovery has evolved into a medical marvel. Hospitals and clinics now perform over 100 million scans each year worldwide to diagnose diseases and save lives.
X-rays – Electromagnetic waves with wavelengths shorter than ultraviolet light, used in medical imaging and material analysis. – X-rays are commonly used to view the internal structure of bones in the human body.
Electrons – Subatomic particles with a negative charge, found in all atoms and acting as the primary carrier of electricity in solids. – In a conductor, electrons flow freely, allowing electric current to pass through.
Radiation – The emission of energy as electromagnetic waves or as moving subatomic particles, especially high-energy particles that cause ionization. – Radiation therapy is a common treatment for cancer, using high-energy waves to target and destroy cancer cells.
Matter – Anything that has mass and takes up space, composed of atoms and molecules. – All physical objects, from the smallest particles to the largest galaxies, are made of matter.
Density – The mass of a substance per unit volume, often measured in kilograms per cubic meter (kg/m³). – The density of water is 1,000 kg/m³, which is why ice, with a lower density, floats on water.
Atoms – The basic units of matter and the defining structure of elements, consisting of a nucleus surrounded by electrons. – Atoms combine in various ways to form molecules, which make up the substances we encounter daily.
Images – Visual representations of objects, often created using lenses or mirrors in optical devices. – The microscope uses lenses to magnify images of tiny biological specimens for detailed study.
Mutations – Changes in the DNA sequence of a cell’s genome, which can lead to variations in traits or functions. – Mutations in certain genes can increase the risk of developing hereditary diseases.
Technology – The application of scientific knowledge for practical purposes, especially in industry and medicine. – Advances in technology have led to the development of sophisticated imaging techniques like MRI and CT scans.
Anatomy – The branch of biology concerned with the study of the structure of organisms and their parts. – Understanding human anatomy is essential for medical professionals to diagnose and treat illnesses effectively.
