Veterinary X-Ray Positioning - A Helpful Guide

Buying a good veterinary x-ray machine is one thing. However, for taking high-quality images, you’ll also need to know the proper techniques regarding the patient's position and the direction of light from the device. 

This article discusses some of the most important principles and protocols of veterinary x-ray positioning for small animals. 

X-Ray Positioning for Small Animals

Small animals include house pets like dogs, cats, rabbits, hedgehogs, etc. 

Sedation Requirements

Chemical Sedation may be required if the animal is restless or is in pain. Sedation will also help ​make more accurate images since it ​relaxes muscles and keeps the animal still.

On the other hand, physical restraint should be enough to calm patients. You’ll need two people; one to hold the head and forelimbs and another on the hind position. Extra personnel may be needed for larger or more anxious animals.

You can also use positioning aids and devices such as V troughs, cotton, tape, foam wedges, and sandbags, along with physical and chemical restraint.

Positioning for Different Organs

Now, let’s look at how you can position your patient while taking x-rays of different body parts.

Exposure Guideline

First, you’ll need to use the correct exposure to ensure patient safety and high-quality images. For this, you need to consider the thickness of the part you’re measuring and the patient’s weight. The distance between the patient and the x-ray beams also matters.

Always measure the thickness from the thickest part of the organ.

Nowadays, with most veterinary professionals using digital systems, you can easily find presets on the software. You may need to play around with the settings to get an accurate image.

Thorax Views

The most commonly used views for the thorax include the right lateral and dorsoventral views. In some cases, you can do a left lateral or ventrodorsal view.

Thorax Lateral View Guidelines

1. The front legs should be pulled away from the thorax's cranial part and taped if required.

2. The hind limbs should also be extended, but be careful not to rotate the patient.

3. The collimated light field should start from the shoulder and end at the top of the last rib. 

4. Finally, make the exposure at peak inspiration (the highest pressure during the respiratory cycle).

Tip: Using a foam wedge under the sternum can help keep the sternum and the thoracic spine in the same plane.

Thorax Ventrodorsal View Guidelines

1. You need to place the patient in dorsal recumbency.

2. Align the patient's spine and sternum in the same line using a  V-trough. 

3. Tape the thoracic limbs evenly and pull them forward.

4. Pull and secure the pelvic limbs caudally.

5. The vertical line of the collimator light should be at the caudal border of the scapula. Similarly, the horizontal line should be directly over the sternum.

6. And finally, the exposure should also be at the peak inspiratory phase.

Thorax Dorsoventral View Guidelines

1. The dorsoventral view is generally only used when fluid blocks the heart and lungs or to visualize the lesions in the caudodorsal long lobes.

2. Depending on the patient's comfort, it should be placed in ventral recumbency without the legs taped. 

3. Pull and abduct the thoracic limbs.

4. The settings for the exposure and the direction of the beams are similar to the Ventrodorsal view.

Abdominal Views

Right lateral and ventrodorsal views are preferred for a clear view of the abdomen. 

Abdominal Lateral View Guidelines

1. For the abdominal lateral view, the patient's position should be similar to that of the thorax lateral view, i.e., the front and the hind limbs extended. 

2. But in this case, the center should be in the middle of the last rib. 

3. The center can be kept just behind the last rib for cats and other small animals.

4. Take the images during the expiratory breathing phase when there's less movement on the abdomen.

Abdominal Ventrodorsal View Guidelines

• For ventrodorsal view, you can simply follow the positioning instruction for the thorax ventrodorsal. 

• In this case, the light beam center should start behind the last rib and cover the entire diaphragm.  

• Again, the images must be taken during the expiratory phase of the breathing.

Skull Views

For the skull, the lateral and the ventral views should be simple since there are few distractions. However, the real challenge lies in taking images when the mouth is open:

Ventrodorsal Maxilla (Open Mouth) Guidelines

1. Open the mouth of the patient in a way the hard palate is straight and parallel to the table surface.

2. Pull the mandible away from the head and secure it.

3. Either secure the endotracheal tube and tongue in the center or pull them to one side of the mandible.

4. The best angle for the x-ray beams is 20 degrees from perpendicular.

Frontal Sinus View Guidelines

1. For the frontal sinus view, lay the animal on its back in a way the hard palate is perpendicular to the table surface.

2. The mandible should be secured, but the nostrils should point straight up.

Note: Anesthesia is required whenever the mouth is open.

Pelvis Views

For the pelvis as well, the standard views are lateral and ventrodorsal.

Pelvis Lateral View Guidelines

1. Scissor the legs, placing the down leg forward and the back leg back and parallel to the table.

2. Center the beam on the greater trochanter and collimate the field to the pelvis, femur, and lumbosacral spine.

Pelvis Ventrodorsal View Guidelines

1. For the ventrodorsal view, you can choose a physical restraint with two people or put the patient in a frog leg position.

2. Grip the back legs at the Tauras and pull the legs forward with the femur parallel to the table.

3. Rotate the stiflers to make the patella point up.

4. The center of the light beam should be on the center of the pelvis and collimated between the top of the pelvis and right below the stifles.

Extremities

For extremities, you can use lateral, posteroanterior, or anteroposterior positions. The most important thing here is to center on the joint you want to study.

Conclusion

X-ray positioning for animals boils down to this; the patient should be comfortable, and you should center the beams in the organ you want to analyze. At the same time, the beam should be collimated appropriately so that the image is accurate in the center and the sides.