X-ray, X-ray, Read All About It!
Greetings once again, Bored Surfer and welcome to November!
While 2020 has not featured a particularly festive vibe overall, there still some occasions that will hopefully bring you at least a little joy. November 10 marks the anniversary of the debut of Sesame Street in 1969. If you don’t know how many years ago that was, Count von Count is compelled (according to old Eastern European folklore) to tally it for you.
Friday the 13th is World Kindness Day. Fingers crossed that the world will be kind to you on that day (and every other day).
I would be remiss if I did not wish you a Dill-lightful National Pickle Day on Nov 14.
Nov 17 is Unfriend Day. It is also Take A Hike Day, so you can selectively tell people to celebrate that.
Most importantly, for BLOG blog purposes, is November 8, the International Day of Radiology, aka X-ray Day. On this date in 1895, while working at the University of Würzburg, Wilhelm Röntgen discovered the X-ray (woo hoo - two umlauts in one sentence!). While investigating cathode rays from a Crookes tube (a glass bulb used to study the conduction of electricity through gases at low pressure), he noticed that a nearby fluorescent screen glowed. Since the cathode rays were known not to travel that far, he came to the conclusion that some other form of energy was present. Due to the unknown nature of this phenomena, he dubbed them X-rays (in some places, however, they are referred to as Röntgen rays). Further experiments showed that if an object was placed between the source of the rays and a photographic plate, the resulting image displayed different transparencies of different materials. After weeks of experimenting on inanimate objects, he X-rayed the hand of his wife, Bertha. The results of this work, including copies of the X-ray image of Bertha’s hand, were made public at the end of December, 1895. It is interesting to note that Röntgen did not try to patent the generation of X-rays, because he wanted it to benefit medicine and research to be freely available. He also received the first Nobel Prize for Physics in 1901 and donated the prize money to the university where he performed his research.
Within a matter of weeks after their discovery, X-rays were being used for medical purposes such as localizing foreign bodies (a needle in a person’s hand) and evaluating broken bones. The first hospital X-ray department opened in March of 1896 in Glasgow, Scotland. This medical breakthrough even saw combat as early as 1897, on the battlefield of the Greco-Turkish War.
X-rays also captured the imagination of the general population. Since the ability to see the inner workings of a living organism is inarguably utterly fascinating, X-ray machines appeared at carnivals and fairs (like the Trans- Mississippi Exposition in Omaha in 1898), allowing people to see inside objects and themselves. In fact, X-rays were so trendy, companies used the name for non- related products including headache pills, liniment for rheumatism, antiseptic ointment, razor blades, batteries, furniture polish, raisin seeders, a Waltz and a “scientific, substantial, beneficial” whiskey.
The power of X-rays is not limited to the medical arena. They are used to inspect industrial parts and airport luggage. They can be used to look beneath the layers of a painting or a mummy without causing damage. They also play a part in the detonation of a Hydrogen bomb. There are telescopes that detect X- rays from black holes, neutron stars and other celestial objects. There are X-ray microscopes and a process called crystallography that is used to analyze the arrangement of atoms. Work in this area performed by a British biophysicist named Rosalind Franklin contributed to the discovery of the double helix structure of DNA; she did not live to see Crick and Watson get all the credit (and the Nobel Prize).
At this point, I need to issue my own terminology disclaimer. Technically, the images produced from X-rays are called radiographs. Personally, I prefer the term X-rays for both the method of production as well as the result. X-ray is a more interesting word, and unless you use the phonetic alphabet, you probably don’t have much occasion to use it. I will also unashamedly refer to X-ray generated pictures using the somewhat antiquated term “films”, even though they are very often digital in this day and age. Gone is the era when the physical X-ray films could be turned into records (which started in Hungary during the 1940s before its spread to USSR, where it continued until the late 70s). I also need to mention that while the majority of this blog entry is based on human medical procedures, most of the information applies to animals as well.
Originally, the “x” symbolized an unknown factor (feel free to reminisce fondly about algebra, or be relieved you don’t have to take any more math classes, as you see fit). We now know that x-rays are, in fact, electromagnetic waves, similar to light but of a much shorter wavelength, below the visible spectrum. While they are not visible in conventional sense, some early researchers reported seeing a faint blue-gray glow. It is said to be possible to see ionization of air molecules if the intensity of an X-ray beam is high enough, but it would be very unwise to expose yourself to the level of radiation required to witness it.
Due to their high energy level, X-rays are able to pass through many seemingly solid objects. The denser an object (or type of tissue) is, the more X- rays get absorbed, and the lighter it will appear on the image. Less dense materials allow more rays to pass through and expose the film or sensor. This shows up as a dark area on the picture. When you look at an X-ray, the densest materials (metal or bone) appear the lightest, while the least dense (air) shows up the darkest. Materials of intermediate density (water, soft tissue etc.) are visualized in various shades of gray (please refrain from asking that arithmomaniac muppet to count them). Variations in density in a tissue that is normally uniform could be a manifestation of disease (such as an unusual spot on a skull film that marks the remnants of your unabsorbed twin in your pre-frontal lobe).
At this point, I need to express appreciation for those who perform X-ray exams. In most veterinary practices, this task is performed by Veterinary Technicians (in addition to their many, many other job duties). In a people hospital, there is a dedicated X-ray department staffed by specialized staff. They are officially called Radiologic Technologists, sometimes called radiographers, but I shall affectionately call them X-ray techs. There are some places that have personnel certified to perform certain radiologic exams (limited radiographer), but they do not have the breadth of knowledge (and the minimum of a 2-year degree) of a true X-ray tech.
Traditional X-ray exams (plain films) entail placing the body part to be examined between the X-ray source (tube) and the receptor/sensor/film. Most radiologic exams also require 2 or more different positions to demonstrate the anatomy from different angles. Many conscious human patients will remain in the proper position for optimal imaging; animals, as a rule, do not. Pets require a person (or two) to hold them in place during the exam. Depending on the patient’s stress level, sedation is also frequently necessary. The person performing the exam pushes a button that causes the machine to generate X-rays for a fraction of a second. (Note that the X-ray machine is only making waves when the button is pushed. The X-rays come from electricity passing through it. There is not a block of Uranium or Plutonium generating radioactivity when the machine is not on.) Most of the X-rays travel from the source, through the patient and out the other side to expose the film or sensor and create the image. The image is then developed (usually in minutes for actual films, seconds for digital) so it can be displayed.
There is a technique called fluoroscopy that uses luminescent screens to allow the image to be displayed in “real time” during the x-ray exposure. This technology dates back to experiments performed by Röntgen himself, and was first made commercially available by one Thomas Edison. Between the 1930s and 1950s, fluoroscopes were commonly featured in shoe stores, so you could see how well your footwear fit. These days, fluoroscopy is limited Radiology Departments and Cardiac Catheterization Labs.
While bony structures are quite distinct from the surrounding tissues, other body systems are more difficult to visualize on regular X-ray views. In these cases, denser materials can be utilized to provide contrast. Contrast materials vary with the system being evaluated. Barium sulfate (hereafter known simply as Barium – pure Barium does not occur in nature and other Barium compounds can be toxic, so I will not be referring to them) is used for studies of the gastro- intestinal tract. When swallowed, it allows for radiography of the esophagus, stomach and small intestines. In the human radiology department, a radiologist performs fluoroscopy while the patient drinks the Barium, followed by standard static views taken by the X-ray tech. In some cases, follow-up films are taken at timed intervals to monitor the progression of the Barium through the small bowel. Animals rarely drink the Barium on command, so we usually resort to squirting the liquid in their mouth and convincing them to swallow. The pet is then held in one or two different positions for X-rays. This process is repeated several times over the course of the day to monitor the passage of the Barium through the GI tract. Thankfully, pets are not subjected to the most dreaded (by patients and X-ray techs alike) of Barium studies, the double contrast (Barium + air) Barium Enema. If you have the misfortune of personal experience with this procedure (either giving or receiving), you have my most sincere sympathy.
For examinations of other body systems, a clear, colorless liquid containing iodine can be used. Although the contrast material is sometimes referred to as “dye”, it works by increasing the density of the anatomy in question, not by changing color. It can be administered through a variety of routes, depending on the objective of the exam. For example, intravenous administration allows radiologic visualization of blood vessels and injection through the urethra can be used to demonstrate the bladder. Other imaging techniques include an injection into the joint space (intraarticular) or in the space around the spinal cord (intrathecal) to enhance MRI or CAT scans (yes, CT is the proper terminology, but cats are truly remarkable creatures) of those areas. While not uncommon in the realm of human medicine, tests of these types are usually only performed in the most specialized of veterinary facilities.
As awesome and intriguing as X-rays are, they are not harmless. X-rays are a type of ionizing radiation, which means they can break molecular bonds and displace or remove electrons. This, in turn, can cause damage to living cells. Short term side effects of high doses include cataracts, burns and hair loss. This revelation actually led to salons using X-ray machines removing unwanted hair in the 1920s. The skin damage also led to the use of radiation treatments to treat cancer.
The primary long-term effect is an increased cancer risk. This was exemplified in the case of Clarence Dally, a glass blower by trade, who worked extensively with X-rays at Edison’s lab in New Jersey. In the course of eight years, his initial symptoms of degenerative skin conditions, hair loss, pain and swelling of the hands progressed to cancer. After having both arms amputated, he eventually succumbed to metastatic cancer in 1904.
While most of the detrimental effects are dose dependent (more X-rays = more damage), there is no level that is deemed completely safe. It is not possible to completely avoid exposure to all radiation - we are constantly exposed to the small percentage of cosmic rays that penetrate the atmosphere and radioactive materials that exist naturally in the soil, water and air – but safety measures should be taken when possible.
The basic principles of radiation protection are time, distance and shielding. “Time” means minimizing how long you are in contact (or in close proximity) to the threat. The only people in the room when X-rays are being taken are the patient and any personnel required to keep the patient still. Minimizing repeat exposures (to patient and tech) is accomplished by good positioning and proper settings on the X-ray machine. “Distance” means just that – staying as far away from the X-ray beam as possible without compromising the exam. The preferred minimum distance is 6 feet from the X-ray source. “Shielding” refers to the lead apron worn by everyone (including parts of the human patient that are not in the area of interest) in the room during an X-ray exam. Shielding also covers the wall the X-ray tech runs behind before they take your picture, and the lead-lined door they close so the X-rays don’t escape and wander the halls. Please note that these principles can apply to other invisible threats. For example, during an outbreak of a contagious disease, you should lessen your chance of exposure by minimizing your time in a potentially infectious environment, maintain distance from possible vectors and shield yourself from the secretions of others and you from theirs.
Thank you for joining me for this month’s ramblings, Bored Surfer. I hope you have enjoyed this brief overview of the wonders of radiology as much as I did.
Until next time, be excellent to each other.
Dr. Debbie Appleby