WK 1 Contrast media

What is contrast media

• Substance to help visualise anatomical structures and passages within the human body during medical imaging

• Used to differentiate pathology

• Identify vessels

• Joints

• Natural cavities

• Make hollow passages more visible

How it works in x-ray

can increase or decrease the attenuation characteristics

• Natural contrast: very similar attenuation characteristics to soft tissue - doesn’t increase or decrease radiographic appearance but fills the space - doesn’t outline structures eg. water

• Negative contrast: decreases the attenuation characteristics and appears radiolucent on imaging eg. air

• Positive contrast: increases the attenuation characteristic and makes structures appear more radio-opaque eg. iodinated LOCM, barium, gastrograffin

Postive contrast media

Barium sulphate

• Needs to be mixed - alters density

• High kvp of 100

• Not water soluble - contraindications - risk of obstruction - can cause barium peritonitis

• Used for:

• Ba swallow - oesophagus

• Ba meal - stomach

• Ba follow through - small bowel

• Ba enema - large bowel

• Excretion through faeces

Gastrograffin

• iodinated ionic HOCM - draws water in

• Water soluble

• diluted with water

• 80-90 kVp used

• Administered; orally, enema or feeding tube

• Advantages: processes through small bowel faster than barium

• Disadvantages: doesnt coat mucosa, dont use for risk of aspiration

• Used when barium cannot be used

• Contraindication; risk of aspiration - hyperosomolarity can cause acute pulmonary oedema, risk of allergy

• Excreted through faeces

Iodinated LOCM

• water soluble

• low osmolar and non ionic - most common contrast media

• used all over the body

• genitourinary, hepatobiliary, sialography, dacrocystography

• excetion through kidneys and urine - lots of water after the examination

• EGFR needs to be determined before