Contrast Media Part 1 (RADS 210)

PDART

Right patient, documentation & drug, amount (dose), route, time

range from most dense to least dense tissue is:

tooth enamel, bone, hollow organs filled, solid organs, muscles, hollow organs empty, cartilage, fat, gas (air)

Contrast Media

an agent that wherever localized in a particular organ will enable that area to be recorded on the image receptor by adding contrast to the normal general characteristics

General characteristics of all contrast media

-must show structure clearly

-no toxicity to patient

-physiologically inert (should not alter appearance or function of the organs)

-media should be eliminated unchanged or if not eliminated cannot be harmful

3 types of contrast media

Positive, negative, radionuclides

Positive contrast media

radiopaque, hard to penetrate, bright areas on the radiograph, high atomic weight

negative contrast media

radiolucent, easily penetrated by xrays, appears dark on image, low atomic weight

Radionuclides

emit radiation, mainly used in nuclear medicine creating hot spots

-not dangerous to pt.

Radiopaque (positive)

relatively non toxic, hard to penetrate, positive images or light areas on the radiographs, decreased image density, increase organ density by absorbing more x-rays

Do radiopaque CM have high or low atomic number?

high and is rapidly extcreted uncheanged by the body (water soluble)

Types of radiopaque contrast media

inert compounds, organic iodides, inorganic iodides, iodized oils, radioactive

inert compounds (metallic salts) of radiopaque contrast media

used in gastrointestinal studies

-cannot be soluble in water and cannot be absorbed by the body (highly toxic)

Barium Sulfate

a type of inert compound that is an insoluble salt of Barium which if it were soluble (to dissolve) in water is poisonous

-most popular

Barium Particles may be...

iodized, charged with like charges so that they will repel each other and stay in suspension longer

Organic Iodides

water soluble salts of iodinated organic acids, should have low toxicity, reactions may occure since they contain iodine

What is the largest group of radiopaque media

organic iodides

Iodine atomic number

53

What are the two categories of organic iodide contrast media?

ionic and non-ionic

When are organic iodides most effectively opacified with what kVp?

65-80 kVp

Osmosis

the diffusion of a liquid through a membrane into another liquid

osmolarity

a measure of the total number of particles in solution per kilogram of water

The body maintains osmolarity at about...

300 mosm/kgH2O

Most adverse reactions to iodinated contrast media (CM) are related to the...

osmolarity of the CM

osmotic pressure

controls the movement of water in the body, determined by the osmolarity of a solution

The higher the osmolality of extracellular fluids, ____ of an adverse CM induced reaction

the greater the risk

osmotic diuresis

an increased secretion of urine leading to dehydration

Osmotic effects are presumed to cause an increase in the amount of molecular substances that cannot be reabsorbed by the renal tubules. this results in?

osmotic diuresis, leading to dehydration

An increased creatine level indicates:

that the patient may have renal disease a good indicator for possible contrast media induced renal effects

normal range for creatinine

0.6-1.2 mg/dL

ionization

the addition or removal of an electron from the orbital shell of an atom

Ionic contrast media

contains enough iodine to give adequate radiopacity of a structure (high contrast, structure will be white on image)

When in solution, ionic CM can seperate into 2 ions:

cation & anion

Cation

a non radiopaque, positively charged particle

Anion

radiopaque, negatively charged particle (structure will appear bright on the image)

High-osmolar contrast media (HOCM)

ionic contrast media is hyperosmolar meaning the CM changes the osmolarity by increasing extracellular fluid molecules causing physiological changes

To inject enough iodinated CM to give the desired opacity for viewing the osmolarity would need to be...

4-8 times the osmolarity of normal body fluids (1200-1800 mosm/kg H2O)

Non-ionic contrast media

does not dissociate (seperate) in solution creating an anion and cation, therefore providing for greater patient comfort and fewer adverse reactions

Non ionic contrast media is also reffered to as:

Low osmolarity contrast media (LOCM)

Which organic iodide CM is more expensive?

Non ionic CM

Inorganic compunds are used only for...

retrograde studies, never injected intravenously

-must be diluted to less than 15%

Systemic routes of administration of contrast media

oral, rectal, tube/catheter (can be reffered to as enteral)

Parenteral

anything other than by mouth and alimentary canal

Parenteral routes of administration of CM examples

intravenous, intra-arterial, intrathecal, intramuscular, subcutaneous

Disadvantages of using oral hypaque and Gastrografin for GI studies

more expensive, poor contrast, bad taste

Inert compounds (Barium Sulfate) should not be used in cases of:

-perforated ulcers

-appendicitis

-intestinal obstruction

in these cases, organic iodides are used because they are absorbed by the body safely

Exams using radiolucent contrast media

pheumonencephalogram & arthrography

Types of radiolucent contrast media:

air, carbon dioxide (used in radiology), helium, oxygen, nitrous oxide, nitrogen

inorganic compounds are slowly being replaced by:

organic iodides

Iodized oil

made from iodine and poppy seed oil and will not mix with body oils used whenever increased radiographic contrast was required

-must not be absorbed (had to be removed), no longer used

Types of iodized oil:

-pantopaque (myelograms, sialograms)

-visciodol (bronchograms)

-lipoidol (fistulagrams, sialograms)

-ethiodol (lymphangiograms, hysterosalpingograms)

-dionosil (bronchograms)

Radioactive radiopaque contrast media

Thorastast once used but was absorbed by the liver and bone marrow and deaths were reported containing thorium dioxide emiting alpha radiation

-not used anymore

Radiolucent (negative)

easily penetrated by x-rays, will appear dark, decreases organ density by allowing passage of x-rays, rapidly absorbed by the body, and has a low atomic number

Barium Sulfate: Esophagus use

to check swallowing mechanism and for foreign bodies

-puts it on food like marshmallows, cookies, fudge, cotton ball, burgers (BaSO4)

Barium Sulfate: Stomach use

los viscosity contrast medium, shows double contrast (radiopaque barium & radiolucent air)- citrocarbonate

-similar to pop rocks

The advanatages of using oral Hypaque and Gastrografin for GI studies: (contain iodine)

- are absorbed by the GI tract

- goes through the system faster than barium

- can be easily removed from the patient

- if it escapes into the abdominal cavity, it will be filtered by the kidneys and excreted out the body

The disadvantages of using oral hypaque and Gastrografin for GI studies: (iodinated CM)

- more expensive

- poor contrast

- bad taste