Contrast Media & Radiopharmaceutical

State the purpose of contrast media

For something to be visualized, the area of interest must differ in radiographic density from surrounding tissues - contrast media makes this possible and allows us to see anatomic structures that are not normally seen on a diagnostic medical image.

Difference between low and high subject contrast

Classified according to tissue atomic number; High contrast (bone) absorb more x-ray photons whereas those with low contrast (GI) scatter and produce images with very few density differences

Compare negative and positive contrast agents

Negative (Radiolucent)

- photons easily pass through tissue

- Low atomic number

- Appears radiolucent (black) on image.

- Decreased attenuation of the x-ray beam.

Positive (Radiopaque)

- absorbs x-ray photons

- High atomic number

- Appears radiopaque (white) on the image.

- Increased attenuation of the x-ray beam.

Name the general types of contrast media used for specific radiographic procedures.

Negative contrast media (AIr)

Physical properties

low-atomic air or gas producing tablets, crystals, or soda water

Specific procedures

laryngopharyngography - air naturally occuring

Adverse reactions

minimal complications; possible emboli (small air masses within circulatory system)

Positive contrast media (Barium Sulfate)

Physical properties

- Inert powder crystal lement with radiopaque number of 56 (BaSO₄)

- Not water soluble; must be mixed into suspension

-requires stabilizing agent (sodium carbonate or sodium citrate)

- vegetable gums, flavoring, and sweeteners also added

Contraindications

perforation in the digestive tract; body can not absorb BaS naturally

Specific procedures

Esophagram, UGI (Stomach), Small bowel, Colon or Barium Enema, CT stomach

Adverse reactions

Constipation (obstruction), extravasation (barium peritonitis), perforation, inflammation, fluid overload (hypervolemia)

List the serious complication of the administration of barium sulfate

Explain the importance of osmosis as it relates to various effects of iodinated ionic contrast media

Advantages of nonionic iodinated contrast media

Differentiate among the major adverse effects of various contrast agents

Recognized clinical symptoms to adverse reactions to iodinated contrast media to the level of treatment required

Relate the patient history to the possibility of adverse reactions

General concerns and issues when using contrast agents in children

Concept of radiopharmaceuticals

Acid group

Contains carbon double bonded to an oxygen, single bonded to another oxygen, and a negative charge at the pH of the body

Anions

negatively charged ions

Amine Group

Contains nitrogen bonded to two hydrogen atoms

Anaphylactoid

resembling an immune system response to foreign material (antigen)

Atomic numbers

Numbers of protons in the nuclei of the different elements

blood urea nitrogen (BUN)

BUN test can reveal whether the urea nitrogen levels are higher than normal, suggesting that the kidneys or liver may not be working properly

bronchospasm

Involuntary muscular contractions in bronchial tubes leading to narrowing of the bronchi.

Cations

positively charged ions

Contraindications

factors of a patient's history or present status that indicate that a medical procedure should not be performed or that a medication should not be given

Creatinine

Nitrogen-containing waste product of muscle metabolism; excreted by the kidney in urine; high blood plasma levels indicate poor filtration by the kidney

Extravasation

leakage from a vessel into the tissue

Gadolinium diethylene triaminepenta-acetic acid (Gadolinium DTPA)

Contrast agent that is a metallic and magnetic agent that will affect the signal intensity during an MRI

Histamine

molecular substance containing an amine group; causes bronchial constriction and a decrease in blood pressure

Hydroxyl

Common chemical group, part of the water molecule, containing one atom of hydrogen and one atom of oxygen; carries a negative charge (anion) when not a part of a molecule

Ionic

atom or molecule having a negative charge (anion) or positive charge (cation)

methyl group

common biochemical groups containing one carbon atom and three hydrogen atoms

Osmolatity

measurement of the number of particles (molecules, ions, or cations) that can crowd out water molecules in a measured mass of water

Osmosis

The movement of water across a selectively permeable membrane from an area of higher concentration to an area of lower concentration.

pH

Relative acidity or basicity (alkalinity) of a solution: pH below 7.0 is acidic and has more hydrogen cations than hydroxyl anions, whereas pH above 7.0 is alkaline and has more hydroxyl anions than hydrogen cations

radiopharmaceutical

pharmaceutical compound that is attached to a radioisotope