ABHI Contrast Media Special Interest Section (Contrast in
Radiology)
The Contrast Media Special Interest Section of the Association
of British Healthcare Industries (ABHI) represents the
manufacturers of contrast media in the United Kingdom.
This technology is used by radiologists, radiographers and
radiology nurses in radiology and cardiology departments to enhance
images obtained by x-ray, CT [computed tomography], MRI [magnetic
resonance imaging] and ultrasound.
Overview of Technology and diagnostic
procedures
Contrast can be divided into two types, negative and positive
contrast:
Negative contrasts describe those X-ray contrast media that
absorb X-rays less than the soft tissues of the body. Gases like
air, and carbon dioxide are example of X-ray contrast media as most
of the X-rays pass through them to blacken the film. The contrast
provided by gases is insufficient for visualising fine structures,
but suitable for imaging relatively large cavities.
Positive contrast utilises a molecule that absorbs X-rays more
than surrounding tissue. Opacification the fineness of the vessel
is dependent on the formulation of the molecule:
Barium Contrast
Barium has been known as a positive X-ray contrast medium since as
long ago as 1910. Barium sulphate (BaSO4) is still used today to
visualise the upper, middle and lower parts of the gastrointestinal
tract – barium meals, swallows, follow through, small bowel enemas
and colon enema, respectively. However, barium is only suitable for
visualising the GI tract. Consequently, other organs or blood
vessels cannot be visualised using this contrast medium.
Iodinated Contrast
Contrast containing iodine has been used for over 100 years.
In 1919, Dünner and Calm used water-soluble sodium iodide (NaI) to
visualise the lesser circulatory system. It was the first time that
iodine was used for this purpose. However, sodium iodide was
unsuitable for widespread use because it could only be administered
in very small doses owing to its toxicity.
Many transformations of the contrast molecule have occurred over
the century, resulting today in a contrast medium formulation that
provides a much lower toxicity and much greater patient
tolerability. Monomeric iodinated contrast now accounts for roughly
90% of the market for contrast enhanced imaging, such as CT
scanning, angiography and intravenous urography.
Magnetic Resonance
Contrast
Around 1980 MRI was 1st used for chemical
diagnosis in patients in the UK. This development was rapidly
followed by the commercialisation of MRI contrast media allowing
improved diagnostic capability.
Magnetic Resonance Imaging (MRI) utilises the ability of the
water molecules in the body, when placed in a strong magnetic
field, to generate detectable electromagnetic radiation (EMR).
Using extremely complex and powerful computer algorithms, this EMR
can provide images of soft tissue structures in the body.
MRI contrast enhances the EMR produced to allow visualisation of
blood vessels and soft tissue structures more clearly.
Ultrasound Contrast
Ultrasound has provided a non-hazardous method of visualising soft
tissue structures since it’s first use in 1960. Ultrasound contrast
uses micro bubbles of a gas to create an environment highly
reflective to ultrasound. This gas, when present in tissue e.g. the
ventricle of the heart, will provide a very bright and
well-delineated ultrasound echo. The image can be dramatically
improved and ultimately the diagnosis is made more
uncomplicated.
Companies
The ABHI Contrast Media SIS is interested in supporting patients
and legislation that involves radiology diagnosis and
treatment.
The following 6 contrast media manufacturers are represented:
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Bracco UK Ltd
EZEM Ltd
Guerbet Laboratories Ltd
Sanochemia
Schering
Tyco
The group meets quarterly.