Radiology

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Definitions

X-rays
An x-ray (also known as a roentgen ray) is electromagnetic radiation that can be passed through the body to a photographic plate. When used this way it is known as Radiography. The more rays that are absorbed through a tissue the whiter the tissue looks on the film. That is why bones look very white on x-ray as they can absorb more of the rays. Soft tissue such as muscles, ligaments and discs do not absorb they rays as much, so they do not show up as clearly.

A spinal x-ray can show essential information of the spinal bony structure, the overall alignment of the spine and the relationship of one bone to another.

Spine x-rays are usually taken from the front and the side and occasionally at different angles. This is done to obtain all views of the spine. Dynamic x-rays are also required occasionally. This involves the spinal x-ray taken at the limits of spinal motion to assess for any abnormal movements or instability.

CT Scan
Computerized Tomography (CT) is when a series of x-ray beams are passed through the body area of interest, which a computer then transforms into high resolution 2 dimensional images or 'slices' of the area. A CT Scan is useful in viewing the spinal bony structure. It is also performed sometimes after a myelogram to increase the visibility of the spinal cord and nerves in the spinal canal.

Also known as Computerized Axial Tomography (CAT scans) or Computerized Transverse Axial Tomography.

Myelogram
A Myelogram involves injecting a special contrast or dye into the dural sac (the tissue that surrounds the spinal cord and nerves), and then performing an X-ray or CT Scan, which shows the contrast as white. This allows an assessment of the spinal canal dimensions and spinal cord/nerve contours. This test is of particular use to assess a spinal cord or nerve root compression.

MRI
Magnetic Resonance Imaging (MRI) is when a person is placed in a strong magnetic field and then measuring the emitted radiation from the patient as the magnetic filed is turned off. Different tissues give off different signals, which are used to compute an image at almost any required angle. This gives detailed visual information on film about the tissue. The MRI can analyse bony tissue as well as soft tissue such as discs, nerves, ligaments and muscles.

It should be noted that disc bulges are quite commonly found with MRI’s. A recent study demonstrated that 76% of normal, asymptomatic people had a disc bulge on an MRI.

A clinical examination, as conducted by therapists with the same training as Australian Spine Institute Directors has been found to be more accurate than MRI scans in determining painful from non-painful discs in the low back area.

Discogram
A special contrast or dye is injected into a disc which increase pressure within the disc. If the injection reproduces the patient's pain it is considered a positive sign for the cause of pain. The location of the needle is verified by X-ray. 

Following the injection an X-ray or CT Scan is taken which shows up the special contrast or dye inside the disc. This  demonstrates any internal disc damage and can highlight a bulging area.

Bone Scan
A bone scan involves injecting a small amount of radioactive Technetium, a tracer, in to the body. The tracer is rapidly eliminated by the body via the kidneys. Areas of bone that are healing or have abnormal activity can hold on to the tracer in higher amounts. Bony conditions that show an increased uptake of the tracer include fractures, tumors, arthritis, stress injuries and infection

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Last Modified: July 18, 2001