Introduction to Cat X-ray Imaging: Importance and Basics

Radiography is one of the most common diagnostic tools utilized in veterinary clinics. It can provide vital information about structures inside the body and can be used to identify pathologies in both bone and soft tissues.

Cats differ from dogs and other pets in many ways, including their propensity to hide pain and illness. As a result, radiographs can be an excellent method of collecting vital diagnostic information for these patients in a non-invasive manner. 

Techniques

Safety for both patient and veterinary staff should be paramount when using X-rays. Veterinary clinics and hospitals should have effective radiation safety protocols in place and clinical staff should wear monitoring equipment.

Radiographs also need to be of good diagnostic quality to allow for accurate interpretation of injury and disease for cats presented to the veterinary clinic. 

When a feline patient requires X-rays, certain procedures should be followed.

Be cat-friendly!

Taking X-rays of a fractious cat is no veterinarian’s idea of a good time! Keep these feline-centric principles in mind to reduce stress for all involved:

• Quiet areas

• Calm handling

• Pheromone sprays/diffusers
  
  
  

  Restraint

Cats must be adequately restrained for radiographs, to ensure correct positioning and to minimize motion blur. Even small movements can cause unacceptable blurring in the X-ray.

This can be minimized by adjustments to the exposure time and mA settings, but sufficient restraint is still the most desirable. 

Sedation or brief anesthesia is usually required, but physical restraint using equipment such as sandbags and tape is also possible if necessary.

There are various sedation and anesthesia protocols that are suitable for cats, including cardiac-friendly combinations and short-acting sedatives.

Wherever possible, chemical restraint is preferred to physical in fractious animals.

Positioning

Depending on the body area requiring radiographic examination, the cat will need to be carefully positioned. Proper positioning is necessary to achieve X-rays of diagnostic quality in your veterinary clinic. 

Take more than one radiograph

Multiple views are always necessary for radiography! A good example of this is in thoracic radiographs in cats: when in lateral recumbency, fluid accumulates in the down-side lung, and there is a degree of atelectasis (lung collapse).

This leads to an increased opacity of this lower lung field, which can obscure soft tissue nodules. Orthogonal views are also needed, as X-rays are two-dimensional images of a three-dimensional patient, therefore opposing views are needed to visualize the patient as a whole. 

Interpretation

Radiographs require expertise and attention to detail for accurate interpretation. In a veterinary hospital, veterinarians should be encouraged to view X-rays in a quiet, darkened room and should not be rushed for a diagnosis. 

When interpreting feline X-rays, it is best to proceed in a logical and step-wise manner, to avoid anything being missed.

Assess positioning and exposure

Before leaping to any diagnostic conclusions, first, evaluate the basics. 

Is the X-ray:

• Of the correct patient?

• Clearly marked as to the positioning of the animal and the area exposed (i.e., left vs right markers)?

• Is the X-ray well positioned and collimated correctly, and is the exposure adequate? A cat X-ray that is improperly positioned or exposed is difficult to interpret and reduces the amount of available information.

• Are there orthogonal views available? X-ray images are two-dimensional representations of a three-dimensional subject (the patient), requiring some mental reconstruction of an anatomical image, using two radiographs taken at right angles to each other.

• Are any exposure, positioning, or rendering artifacts visible? If so, note them at this point so as not to be distracted by pseudopathological changes later.

Assess the X-ray

A logical and systematic approach should be used to evaluate X-rays in a veterinary clinic. Clinicians should choose an approach that works for them – for example, evaluate from outside in, or from left to right, or whatever system suits them and allows a thorough assessment of the whole radiographic area. 

All organs and structures should be assessed, and findings should be categorized by radiologic (or Roentgen) signs:

• Number

• Size

• Shape

• Position

• Opacity/architecture

• Margination

If possible, normal function can also be assessed, for example through contrast studies or through the use of physiological changes such as inspiratory vs expiratory thoracic radiographs. 

Evaluate the X-ray

Once the radiograph has been thoroughly assessed and described, the findings can be evaluated for abnormalities and a radiographic diagnosis.

There is a wide range of ‘normal’, which can make this assessment of pathologies more difficult, and X-rays should be used alongside other clinical findings when making a list of differential diagnoses. 

Radiography is a commonly utilized tool in veterinary clinics and has a wide range of indications in cats. However, taking good radiographs – and interpreting them correctly – is indeed an art form, requiring practical skills, study, and experience.