X-Rays are not x-rated
X-rays are almost like magic. It gives veterinarian's special powers, well almost, to get a picture of the inner workings of your pet. The varying shades of grey allow separation of radiographic imprints on a film or digitally similar to a digital camera. The key difference is the image is a "negative". When the film or digital plate is excited by the x-ray generator (tube head), it leaves the tube head and encounters a body or parts. Example: a leg bone. The x-ray gets "blocked" by the bone. This stops exposure of film at that location. The image then shows up white. Most people have seen a radiograph, either in real time or on an ER type TV show. Basic groups of materials that leave a "finger print" type image are air, fat, fluids (actual or fluid enclosed in muscle tissue), bone and metal.
X-rays are electromagnetic waves, much like light, only not in the visible spectrum. X-rays can penetrate body tissues and other things in varying amounts
When taking an X-ray, electrons travel through a patient and are absorbed to varying degrees by the animal. X-ray electrons that complete the journey all the way through hit a film. This provides an image similar to the "negative" mentioned earlier. Where you have more electrons going through an animal, the darker the image will be on the film. Where fewer electrons pass through or are blocked from reaching film will give a lighter image in that area on the film.
When veterinarians look at a radiograph (X-ray), we look for different opacities (shades of dark and light).
Air: allows the most X-rays through the animal, resulting in a dark image. Lungs or the air around a body will show black.
Fat: opacity shows up as separately creating a lighter image than air. Think of the fat around a pork chop, steak or chicken fat on a thigh. This structure is different than muscle or air.
Fluid and soft tissue: The muscle groups can be seen on good quality radiographs. Heart, lung and tumors have their own images.
Bone: Femurs, ribs long bones, vertebrae show almost white. Fractures, arthritis changes are examples of what can be seen.
Metal: It shows up as completely white on a radiograph. Lead letters or numbers for identification of radiographs, or ingested coins, screws, bolts are some examples.
X-ray film is developed much like photographic film in a processor.
Taking X-rays of an animal is different from humans. You may ask a human to hold still. Pets are seldom as cooperative. Pediatricians and x-ray technologist also share these issues.Positioning a pet for an X-ray usually requires sedation to get it to lay still; otherwise it shows up blurry just like an out of focus photograph. Proper positioning is important when taking OFA radiographs (evaluation for hip dysplasia). Films need to be taken efficiently as sedation is short-acting, Less than 30 minutes. X-rays can help veterinarians diagnose internal problems with your pet. When a veterinarian detects a lump or mass in your pet's abdomen, an X-ray can help pinpoint which organ has the mass is in, either spleen or the stomach. If X-rays reveal bunching and irregular gas patterns in the small intestine, your pet may have eaten string or holiday tinsel. A good physical exam and history are needed if the pet is vomiting and off feed. Contrast agents such as air, or barium may be needed to outline a foreign body. Foreign bodies may include scouring pads, plastic toy soldiers, balls, coins towels, other cotton materials.Serious conditions can seen or ruled out with X-rays: gastric dilation volvulus (GDV bloat), broken bones, cancer masses, heart problems, foreign bodies, or even lung fungal diseases. X-rays are very low risk for your pet. There is risk for the people who are involved in taking the X-rays of your pet. Protective lead clothing and dosiomer radiation monitoring badges have to be maintained for personnel safety. There are immediate and long-term effects of X-rays, mutations, birth defects, and radiation induced leukemia.
Even with good radiographs and great images there are times when X-rays (radiograph) gave an indication of a problem, but do not give a solid diagnosis. Then one needs to use ultrasound, or a referral to an ultrasound specialist for a different view. Ultrasound allows veterinarians to see things invisible to X-rays. Ultrasound is high frequency sound waves directed into the body and bounce back off of the organs like sonar. A computer image is generated and you can see the organ or mass on a screen. Ultrasound distinguishes fluid from a soft tissue mass or nonradiopaque stone in an organ like kidney, urinary bladder, or gall bladder. This guides us veterinarians formulate the best treatment recommendation. For further questions about X-rays or ultrasound, consult your veterinarian.
Mike Sweet, DVM
734-439-1112