What are x-rays (radiography)?
Radiography is the proper name for x-rays. Radiographic images (x-rays) are created when an electromagnetic beam is directed through a body-part to a plate on the other side. The beam passes easily through some tissues but is partially blocked by more solid tissues. The x-ray plate detects the amount of beam in each area, creating a black and white image. In most veterinary practices, x-ray plates are now digital and produce an image directly on to a computer screen where it can be assessed easily.
What are x-rays used for?
X-rays are very good for looking at:
- The bones and joints
- The skull and teeth
- The chest cavity and lungs
- The abdomen (often used in combination with ultrasound to examine the organs in more detail)
- The spine
The main drawback of radiography is that it produces a 2D image of a 3D structure. This can make it difficult to understand where organs are sitting in relation to each other and can cause them to overlap. To try to avoid this, we often take multiple x-rays in different directions. Advanced imaging, such as a CT scan, eliminates this problem however, CT scans are not as widely available and are significantly more expensive than x-rays.
X-rays require our patient to lie completely still, otherwise we get movement blur which makes the images impossible to understand. To x-ray some body parts, pets would have to sit in an uncomfortable position. For most x-rays, the pet will need to be under anaesthetic. Depending on which part is being imaged, and how unwell the pet is, occasionally light sedation is enough to obtain an image. This is more common in an emergency setting where the patient is very unwell, or the x-ray is being used as a screening tool for more serious injuries.
In most cases, multiple x-ray images are taken during the same procedure. For orthopaedic problems affecting the bones and joints, we often take images of the unaffected limb for comparison. Occasionally, fewer images are needed, though this is most likely where other imaging techniques are being used in combination, such as ultrasound, or if the first x-ray shows a very clear diagnosis.
One advantage of digital x-rays is that the images are available almost instantly. This allows us to immediately screen for serious problems. Often it is helpful to spend time analysing the images after the patient is awake, as this is when subtle changes are seen.
Due to the digital nature of x-rays, they are easy to send to colleagues in other practices, and many specialists will help interpret x-rays if sent them via e-mail. Depending on the case, your vet may be happy to report results within a few hours. Sometimes, if they want a second opinion on interpreting the images, they may get back to you a few days later.
As vets, we never recommend any test unless we think there is a good chance that it will give us a diagnosis. Unfortunately, not every problem can be identified on an x-ray, and sometimes images are more useful for ruling things out than providing a diagnosis. Sometimes x-rays show us that there is something abnormal, but we cannot be certain exactly what is causing the changes. For example, an organ may look larger than normal. The x-ray tells us that there is a structural change but does not tell us whether the organ is working normally, or whether the increase in size is due to swelling, infection, or a mass.
Depending on what is seen on x-ray this may be enough to decide a treatment plan. If x-rays show changes, but are inconclusive, we will need to gather more information. This may involve additional imaging (such as ultrasound), taking a sample of cells, either with a needle or via a surgical biopsy, taking organ-specific blood tests, or even exploratory surgery. Sometimes advanced imaging such as a CT scan is required. This is significantly more expensive, and may require referral to another centre, but gives a much more detailed image.