X-rays are a vital imaging tool utilized around the globe. First used to image bones over 100 years ago, the X-ray has saved countless lives and aided in a myriad of discoveries.
X-rays are a naturally occurring form of electromagnetic radiation; they are produced when charged particles (electrons or ions) of sufficient energy hit a material.
Over the years, scientists have shown concern over the health implications of X-rays; after all, they involve firing radiation at the patient. But, do its benefits outnumber its risks?
In the following article, we will discuss what X-rays are, how they are used in medical science and the level of risk that they pose.
Here are some key points about X-rays. More detail and supporting information is in the main article.
- X-rays are a naturally occurring type of radiation
- Cosmic rays and other natural sources bombard us with radiation daily
- X-rays are classed as a carcinogen
- Different X-ray procedures deliver different amounts of radiation
- The benefits of X-rays far outweigh any potential negative outcomes
- Wilhelm Röntgen is credited with discovering X-rays
- The first X-ray for medical purposes was carried out on a young boy with a broken wrist
- Computed tomography gives the largest dose of X-rays compared to other X-ray procedures
- In X-rays, bones show up white and gasses appear black.
What are X-rays?
The first X-ray was carried out over 100 years ago.
Wilhelm Röntgen is credited with first describing X-rays; just weeks after he discovered that they could help visualize bones, X-rays were being used in a medical setting.
The first person to receive an X-ray for medical purposes was young Eddie McCarthy of Hanover who fell while skating on the Connecticut River in 1896 and fractured his left wrist.1
Everyone on the planet is exposed to a certain amount of radiation as they go about their daily lives. Radioactive material is found naturally in the air, soil, water, rocks and vegetation. The greatest source of natural radiation for most people is radon.2
Additionally, earth is constantly bombarded by cosmic radiation (or cosmic ionizing radiation) which includes X-rays. These rays are not harmless but they are unavoidable, and the radiation is at such low levels that its effects are virtually unnoticed.
Pilots, cabin crew and astronauts are at more risk of higher doses because of the increased exposure to cosmic rays at altitude. But, there have been few studies that have linked an airborne occupation to increased incidence of cancer.3
Types of X-ray
To produce a standard X-ray image, the patient (or part thereof) is placed in front of an X-ray detector and illuminated by short X-ray pulses. Because bones are rich in calcium - which has a high atomic number - the X-rays are absorbed and appear white on the resulting image.
Any trapped gases, for instance, in the lungs, show up as dark patches because of their particularly low absorption rates.
Radiography: this is the most familiar type of X-ray imaging. It is used to image broken bones, teeth and the chest. Radiography also uses the smallest amounts of radiation.
Fluoroscopy: this can be considered the "movie equivalent" of standard X-rays. The radiologist, or radiographer, can watch the X-ray of the patient moving in real-time and take snapshots. This type of X-ray might be used to watch the activity of the gut after a barium meal. Fluoroscopy uses more X-ray radiation than a standard X-ray, but the amounts are still tiny.
Computed tomography (CT): the patient lies on a table and enters a ring-shaped scanner. A fan-shaped beam of X-rays passes through the patient onto a number of detectors. The patient moves slowly into the machine so that a series of "slices" can be taken to build up a 3D image. This procedure uses the highest dose of X-rays because so many images are taken in one sitting.
The risks of X-rays
X-rays can cause mutations in our DNA and, therefore, might lead to cancer later in life. For this reason, X-rays are classified as a carcinogen by both the World Health Organization (WHO) and the US government.4 However, the benefits of X-ray technology far outweigh the potential negative consequences of using them.
It is estimated that 0.4% of cancers in America are caused by CT scans.5 Some scientists expect this level to rise in parallel with the increased usage of CT scans in medical procedures. At least 62 million CT scans were carried out in America in 2007.
According to one study, by the age of 75, X-rays will increase the risk of cancer by 0.6-1.8%.6 In other words, the risks are minimal compared to the benefits of medical imaging.
Each procedure has a different risk associated with it, depending on the type of X-ray and the part of the body being imaged. The list below shows some of the more common imaging procedures and compares the radiation dose to the normal background radiation that we all encounter on a daily basis.
Different X-ray procedures release different quantities of radiation.
- Chest X-ray
Equivalent to 2.4 days of natural background radiation
- Skull X-ray
Equivalent to 12 days of natural background radiation
- Lumbar spine
Equivalent to 182 days of natural background radiation
- IV urogram
Equivalent to 1 year of natural background radiation
- Upper gastrointestinal exam
Equivalent to 2 years of natural background radiation
- Barium enema
Equivalent to 2.7 years of natural background radiation
- CT head
Equivalent to 243 days of natural background radiation
- CT abdomen
Equivalent to 2.7 years of natural background radiation.7
NB - These radiation figures are for adults; children are more susceptible to X-rays.
The benefits of X-rays
The fact that X-rays have been used in medicine for such a significant length of time shows how useful they are considered to be. Although an X-ray alone is not always sufficient to diagnose a problem, they are an essential part of the puzzle-solving exercise.
Some of the main benefits are as follows:
- Noninvasive: without the need to physically enter a patient an X-ray can help diagnose a medical issue or monitor treatment progression
- Guiding: X-rays can help guide medical professionals as they insert catheters, stents or other devices inside the patient. They can also help in the treatment of tumors and remove blood clots or other similar blockages
- Unexpected finds: an X-ray can sometimes show up a feature or pathology that was separate from the initial reason for the imaging. For instance, infections in the bone, gas or fluid in areas where there should be none or some types of tumor.
The X-ray safety debate continues
It is important to keep the risks in perspective. An average CT scan might raise the chance of a fatal cancer by 1 in 2,000. When this figure is compared to the natural incidence of fatal cancer in the US of 1 in 5, it pales in comparison.
Additionally, there is some debate as to whether very low X-ray exposure can cause cancer at all. The most recent report on the matter, published in the American Journal of Clinical Oncology, claims that X-ray procedures carry no risk at all.
The paper argues that the type of radiation experienced in a scan is not enough to cause long-lasting damage. The authors claim that any damage caused by low-dose radiation is repaired by the body, leaving no lasting mutations. It is only when a certain threshold is reached that permanent damage can be produced; this threshold, according to the authors, is well over the standard X-ray dose from any type of scan.
The authors go on to point out that despite being bombarded by cosmic rays and background radiation, the people of America are living longer than ever, partly because of advancements in medical imaging, such as the CT scan.8
Overall, the importance of making the right diagnosis and choosing the correct course of treatment makes X-rays far more beneficial than they are dangerous. Whether there is a small risk or no risk at all, the X-ray is here to stay.
Researchers conclude there is no proof that low-level radiation from medical imaging - such as X-ray and computed tomography scans - causes cancer. They say it is time to throw out an unproven, decades-old theoretical model that has led many people - doctors and regulators included - to believe otherwise.
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