Digital x-ray, contrast studies

In conventional way the x-ray image is processed so that the x-ray film is put in to the cassette, the cassette is placed in to the x-ray table and x-ray is taken. Than the x-ray film is taken out of the cassette in the dark room and placed in to the developing machine and the x-ray picture is born. Once exposed and developed the image can not be changed any more.

What is different in digital radiography? Digital radiography is not using x-ray films. The x-ray is taken not on the conventional x-ray screen but on the special so called phosphor plate. The phosphor plate is than put in to the phosphor plate reader and the reader is producing the image to the computer screen. The image can be stored in computer hard disk and printed later if needed. What is most important in digital radiography is that the image can be manipulated, that means contrast can be added or removed, shades of grey made more dark or light and the image can be enlarged or decreased in size. These extra tools are adding to the interpretation possibilities of the x-rays. In addition, all the data can be stored on hard or computer disks.

Radiography is the most frequently used diagnostic tool currently in veterinary medicine. Native x-rays are always taken first in Aisti (unless they have been taken already) in every patient with the back problems. It is cheap and gives important information about the back bones, intervertebral disks and adjacent soft tissues. The nervous tissue has the same radiographic density as other soft tissues; therefore, brain and spinal cord are not visible in native radiographs. That is the main reason why so frequently in neurology the advanced diagnostic imaging is necessary.

Most important indications for radiography are examination of bone tissues of skull or spine. Usually the images are taken when the animal is lying on the side or on the back.

Positioning of the patient is very important in order to obtain good quality images and therefore the deep sedation of the patient or narcosis is almost always necessary. Dog and cat has 7 neck, 13 thoracic, 7 lumbar, 3 sacral and different number of tail vertebras depending on the breed.

Myelography

As it was mentioned before the spinal cord is not visible in the conventional x-rays. Therefore different contrast procedures have been developed in the past to visualize the spinal cord (myelography), the epidural space – space around the spinal cord (epidurography) and the intervertebral disk (discography). The procedure is performed on the patient in narcosis (does not feel injection or puncture) and the needle is inserted in to the spinal canal (or other space) and the contrast is injected.

After the injection is completed the normal x-rays are taken again and the image evaluated. From the mentioned procedures, the myelography is the most frequently used. It is mainly indicated when the bigger areas of the spine need to be examined as in patient with the back pain where the localization of the pain area is not possible or where the signs of paralysis can be caused by a lesion somewhere in the thoracic or lumbar spine. The myelography in the mentioned patients is frequently quicker than MRI and so the duration of narcosis can be shortened.

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