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Imaging

X-Ray

Introduction Doctors have used x-rays in medicine for a long period of time. An x-ray is a type of radiation and a specific portion of the electromagnetic spectrum. More specifically, an x-ray is a stream of protons with short wavelengths, which means x-rays are high-energy particles. With the advent of the newer imaging techniques with ultrasound, nuclear medicine and MRI, the use of x-rays is now limited to the initial screening. A chest x-ray is still the most common type of imaging. It gives the overall general view of the heart and lungs. It can detect heart disease such as cardiomegaly and congestive heart failure.

X-rays are utilized for their high energy. X-rays are able to penetrate the human skin, organs, and other body parts. But different parts of the body have different densities. For instance, an x-ray would have a harder time penetrating a solid metal block than penetrating a piece of paper. The paper can’t absorb as many of the high-energy protons as the metal block. So more of the x-rays would go through the paper than the metal block. Similarly, the x-rays have an easy time penetrating skin and fat but have a harder time penetrating more dense parts like bone.

X-ray machines generate a stream of x-rays that penetrate the body. Depending on the densities of the body parts, the remaining x-rays will strike a film. Black parts of the film have little density. The gray parts of the film are somewhat dense. The white parts of the film are what the x-rays had a hard time penetrating and are extremely dense.

The x-ray is a basic cardiac imaging technique often used before any kind of surgery to screen for abnormalities. X-rays give a general sense of health of the organs in the chest. X-rays are inexpensive, painless, and fast.

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In the lab...
Radiation Amount: Very little. The radiation amount can be less than the radiation emitting from natural sources.

Safety Precautions: An x-ray gown is worn. Any metallic objects, such as jewelry, are removed. No discomfort is felt during the test.

Orientation of Patient: The patient can stand, sit, or lie down in front of the x-ray plate. The x-ray camera is suspended from the ceiling so that different angles can be taken. The patient is told to stand still, because like a camera taking a shot, any movement can make the x-ray blurry. The patient is also told to breathe in and hold his or her breath until the x-ray is done. This make the lungs and the heart show up clearly on the image.

Length of Scan: A few minutes. If a patient moved or didn’t breathe in enough, the length of the scan may change. Top

History Timeline

1876: Eugen Goldstein coined the term "cathode rays" to describe tubes that use a negative electrode to emit a stream of particles which glow on the glass of the tubes. Cathode ray tubes were crucial to the development of x-rays.

1887: Physicist Nikola Telsa used the Crookes tube and and his own tubes to experiment with x-rays. Tesla did not know that he was working with x-rays, but classified it as “radiant energy”. Tesla also cautioned the dangers of x-rays.

1892: Heinrich Hertz investigated x-rays. He penetrated thin metal foil, such as aluminum, using x-rays. His student, Philipp Lenard, also studied the penetration of different materials using x-rays. These two scientists used cathode ray tubes to generate x-rays.

1895: X-rays discovered by scientist Wilhelm Roentgen. While working with cathode ray tubes, he noticed a glow on a wall. Roentgen saw that the cathode rays were traveling through solid material. When he put his hand in front of the cathode tube, he saw the bones of his hand. One of the first pictures taken with x-rays was when Roentgen told his wife to place her hand in front of the x-ray emissions. The outline of her hand, her bones, and her wedding ring can be seen in the photograph.

1896: Roentgen published his paper “On a new kind of ray: preliminary communication” in a scientific journal and the public became aware of the topic, but Roentgen received greater attention in the scientific community than throughout the general public. Roentgen called the radiation emission “x-ray” where ‘x’ stood for something unknown. His friends tried to persuade Roentgen to call them Roentgen rays. The term “Roentgen rays” is used in some Germanic countries today.

1896: Thomas Edison perfected the x-ray machine and called it a fluoroscope. The fluoroscope included a screen made of tungstate of calcium. These screens made brighter x-ray images.

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Pathologies Detected by EKG The chest x-ray shows the shape and size of the heart and can detect any excess fluid build-up. This is important in the following pathologies that can be detected by a chest x-ray.

Congenital Heart Disease – Congenital means existing since birth. Congenital heart disease affects 1% of all babies. Chest x-rays are still common tools used to diagnose congenital heart disease.

Congestive Heart Failure – Congestive heart failure causes fluid build up in the lungs and other tissues. Chest x-rays enable the doctor to visualize these build-ups as fluid levels in the lungs.

Enlarged Heart – Enlarged hearts are easily seen on x-ray images.

Pericarditis – Pericarditis is noted by excess fluid in pericardium, the lining around the heart. Chest x-rays allow the doctor to see the fluid build-up.

Aortic Aneurysm – The x-rays image shows a wider aorta.

Aortic Dissection - About 12 % of the people with an aortic dissection can have a normal chest x-ray. Statistically, chest x-rays have a high sensitivity but a low specificity. A diagnosis of an aortic dissection is hard because many different heart diseases can cause a widening of the mediastinum.


Drawbacks Any exposure to radiation is not good for the body. The penetrating x-rays that are absorbed can break cells. Doctors tend to limit the radiation a patient is exposed to. The fetus of a pregnant woman is more susceptible to x-rays. Commonly, the benefit information gained from an x-ray image outweighs the risks associated with radiation.



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