A radiograph, or X-ray, is a two-dimensional image of a three-dimensional body part. A single image has limitations, as it cannot fully represent a 3D structure. To overcome this, a standard approach called orthogonal radiographs is used. This technique involves capturing at least two images of the same area from different orientations, usually at a right angle to each other. This practice is standard in both human and veterinary medicine.
The Principle of Orthogonal Views
The term “orthogonal” refers to views positioned at a right angle (90 degrees) to one another. A single radiograph is a flat projection where all anatomical structures in the X-ray beam’s path are superimposed. This superimposition makes it impossible to determine the precise location of an object or abnormality from one image. For instance, a lesion on the skin, within the muscle, or deep inside a bone might look identical on a single X-ray.
Imagine looking at a shoebox from directly above. You can see its length and width, but not its height. If you then view the box from the side—a 90-degree angle from your first view—you can see its height and length. This second perspective provides the missing dimension.
By taking a second X-ray at a right angle to the first, medical professionals gain the depth and spatial information absent in a single image. A common combination is a ventrodorsal (VD) view, with the patient on their back, and a lateral view, with the patient on their side. This pairing allows for a more accurate three-dimensional assessment of the anatomy.
Diagnostic Advantages and Applications
Two views taken at right angles are necessary for localizing abnormalities and understanding their relationship to surrounding structures. For a bone fracture, a single X-ray might show the break but not the degree of displacement or alignment of the fragments. An orthogonal view clarifies the fracture’s complexity, showing if bone ends are shifted, angled, or rotated, which informs the treatment plan.
The technique is also used for locating foreign bodies. A single image might show a swallowed or embedded object but won’t pinpoint its exact location. An orthogonal view can reveal if an object, like a nail, is in soft tissue or has penetrated a bone. In chest radiographs, a second view helps separate the layered structures of the heart, lungs, and spine, making it possible to locate otherwise obscured lesions.
Orthogonal views are standard for evaluating joints in both human and veterinary medicine. They allow for assessing joint spaces to check for issues like cartilage loss in arthritis or to confirm the severity of a dislocation. Because of this, imaging in an emergency setting is rarely done with a single projection. Even when a perfect 90-degree angle isn’t possible, a second view from a different angle is better than one image alone.
The Patient Experience
The process begins with the patient being positioned for the first X-ray. Depending on the body part being examined, this may involve lying on a table, standing, or sitting. The radiographer positions the area of interest to capture a clear image.
After the first exposure, the patient or the specific body part is repositioned for the second view. For example, if the first image of a limb was taken from the front (an anteroposterior view), the second is taken from the side (a lateral view). The patient must remain as still as possible during each exposure to prevent blurring the image.
Positioning aids like foam wedges or sandbags may be used to help the patient hold the correct position. This is common in veterinary medicine to help keep an animal stationary. The process is quick and painless, with repositioning taking only a few moments between exposures.