Diagnostic Techniques

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Diagnostic Techniques

Post by Admin on Sun Dec 09, 2007 9:10 pm

Ultrasonography

Ultrasonography or ultrasound scans are produced via ultrasonic waves being passed through tissues. The waves that are reflected back are recorded on screen enabling direct viewing of the affected areas. However the waves do not penetrate bone very well and hence ultrasound is most useful for diagnosing soft tissue problems such as tendon injuries.



Biopsy

When a biopsy is performed, a piece of tissue is removed from the animal and examined under a microscope. The tissue undergoes a special process where it is stained and cut into very thin sections to enable visualisation beneath the microscope. Biopsies are performed regularly to aid the diagnosis of a wide range of conditions. It is most commonly used for diagnosing skin diseases in horses.

Blood Tests

Blood tests are samples of blood that are taken, typically from the jugular vein in the neck and analysed by a variety of different methods. There are two main types of blood test the first is where the actual constituents of the blood are examined i.e. the cells and proteins present. The second type of blood test that is performed is the biochemistry test which looks for different chemicals present in the blood. Blood tests are also used to identify the presence of antibodies as well as viruses and bacteria.

CT (computed tomography)

CT or computed tomography is where X-rays are passed through the affected area but are interpreted by a computer to provide a 3-dimensional image of the region. This enables a more accurate picture of the affected area thus aiding diagnosis.



Endoscopy

This is another form of diagnostic imaging but the actual area of interest is directly viewed via small cameras. An endoscope is a long thin tube containing both a light source as well as a fibre optic camera. They can be up to 3 metres in length to enable viewing of the stomach and the small intestine of a horse. They can aid the diagnosis of all sorts of conditions including roaring, gastric ulcers and nasal tumours.



MRI

MRI (magnetic resonance imaging) relies on the principle that the different tissues within the body respond differently when exposed to a magnetic field. Strong electromagnets are placed close to the area of interest and the response of the tissues is detected to produce a detailed image.



Nerve Blocks

Nerve blocks are used to isolate a source of pain that may be resulting in, for example lameness. Local anaesthetic is injected into various areas and which are then "numbed". These specific regions may include joints or where nerves lie close to the skin. Based on the horse's response to this numbing it can be ascertained whether the horse was painful or not before the injection and therefore whether that area is injured. For example during an examination of a lame horse, nerve blocks may be used to numb the foot. If the horse subsequently trots up sound then it can be said that the area of injury is in the foot. Typically the blocks are started at the lowest points, working up the limb to isolate the area of pain.



Nuclear Scintigraphy

Scintigraphy or Nuclear Scintigraphy is commonly referred to as a "bone scan". When the cause of pain or lameness cannot be readily identified scintigraphy is used to aid their discovery. A radioactive dye is injected into the vein of the horse and its uptake measured and compared. The radioactive dye will become concentrated in areas of inflammation. The horse is scanned using a gamma camera that is sensitive to the radioactivity of the dye. The image is fed through to a computer that displays the image of the uptake. Areas where the uptake is increased are easily visible (termed "hotspots") and are a likely source of pain.

Radiography

Radiography (or X-rays) is the most common form of diagnostic imaging available. The principal benefit is that it is a relatively cheap process and the bones of the horse can be easily visualised. Radiography can also be used to identify areas of soft tissue as well but typically denser objects show up most clearly. Once an area has been isolated as a site of injury, it will be radiographed (or X-rayed) to aid further diagnosis. Radiographs are produced by passing X-rays through the body onto an X-ray sensitive film. Dense objects prevent x-rays passing through them and, consequently, they cast a shadow onto the film. This film is then developed to produce an image of the region. Digital radiography is now becoming more common in veterinary practices. The difference is that the film is replaced by a sensor that generates a digital image on a computer. This change is very similar to the change to digital cameras away from traditional film cameras.

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