Introduction To Radiologic Sciences And Patient Care Ch. 21

Front 1

Types of Contrast Media

Back 1

Negative contrast: Decrease attenuation of xrays and produce areas of increased density
Positive Contrast: Increases the attenuation of xrays and produce areas of decreased density on the radiograph

Front 2

Radiolucent (Negative)

Back 2

Xrays are easily transmitted through radiolucent media. Anatomic areas filled with this media appear dark (increased density) they are called negative

Front 3

Radiopaque (Positive)

Back 3

Xrays are absorbed by radiopaque media. Appears white (decreased density) on radiographs so they are called positive media.

Front 4

Specialty Contrast Agents

Back 4

A common intravenous contrast used in MRI is gadolinium-DTPA. Its a metallic and magnetic agent that will affect the signal intensity used to image the area of interest.

Hint 4

Ultrasound contrast agents are generally gas-filled microbubbles that affect the sound wave to enhance US contrast.

Front 5

Physical Properties of Negative Contrast

Back 5

Low atomic number, either gas(air) or gas producing crystals (CO2). Because cells absorb O2 quickly, this gas is rarely used alone as a contrast agent.

Front 6

Specific Procedures for Negative Contrast

Back 6

Air alone provides negative contrast for Laryngopharynography. Otherwise radiopaque contrast is combined to view lumens of body structures

Front 7

Common double contrast studies

Back 7

Stomach: Barium Sulfate & Crystals, Oral
Large Intestine: Barium Sulfate and Air, Rectal
Arthrography (Shoulder, knee, wrist, hip): Water soluble iodine & air, Injection into join space

Front 8

Adverse Reaction to Negative Contrast

Back 8

Usually Minimal although air can cause Emboli. These small air masses can enter the circulatory system and become lodged in blood vessels, causing pain and loss of oxygen to the area.

Hint 8

Drink lots of water if barium sulfate is used.

Front 9

Positive Contrast Media- Barium Sulfate Physical Properties

Back 9

Atomic number of 56, inert powder composed of crystals. Chemical formula BaSO4. Its a compound. Not water soluble must be made into a suspension.

Hint 9

Flocculation-Tendency of barium to clump in acidic environments.
For small intestine studies, methylcellulose(non-digestible starch) with BaSO4 gives see through effect and shows lesions.
For Lower GI mix with cold tap water to reduce irritation to colon, reduces spasms and cramping.

Front 10

Hypervolemia

Back 10

Excess fluid entering the circulatory system, serious situation. 2 teaspoons of salt in the suspension can reduce risk of hypervolemia.

Front 11

Specific Procedures for BaSO4

Back 11

Esophagus: esophogram, 30-50% Concentration, oral
Stomach: Upper GI, 30-50%
Small Intestine: Small Bowel Series, 40-60 if included iwth stomach
Large Intestine: Colon or BE, 12-25%, Rectal
Stomach:CT 12-25%

Front 12

Adverse Reactions with BaSO4

Back 12

Constipation
Perforation of the colon with extravasation during Lower GI exam, can cause barium peritonitis, older patients have higher risk b/c their tissue is atrophic(lost elasticity),
Inflammation and degradation of colon tissue due to history of diverticulitis and ulcerative colitis
Avoid BE after Biopsy

Hint 12

Vaginal rupture from misplacement of catheter before BE
Hypervolemia-causes fluid in lungs, seizures, coma, and death- Signs are drowsiness and apathy, don't do a BE on a sedated patient

Front 13

Water-Soluble Iodine Contrast Media-Physical Properties of Ionic Iodine

Back 13

Atomic Number 53, These media are ionic because one particle called anion has a negative charge and the other particle (cation) has a positive charge. Results 3 different classes of ionic media: diatrizoate, metrizoate, and iothalamate.

Hint 13

Most ionic contrast media are identified as high-osmolality contrast media because of their osmotic effects. Higher the osmolality the higher the osmotic pressure. This pulls water to the contrast media. Not good!

Front 14

Water-Soluble Iodine Contrast Media-Physical Properties of NonIonic Iodine

Back 14

Don't dissociate into anions and cations, Lower-osmolality contrast media. Ioxaglate(Hexabrix) is a nonionic media. More hydrophilic so less likely to trigger allergic reactions.

Front 15

Water-Soluble Iodine Contrast Media- General Effects

Back 15

Higher-Osmolality media cause the most effects. Also, heating the contrast to body temp decreases friction/viscosity and allows for better injection.

Front 16

Water-Soluble Iodine Contrast Media-Osmotic Effects

Back 16

Ionic Media causes Hypervolemia due to osmosis. In dehydrated patients, the osmotic effect can further reduce body cell volume and result in shock.

Front 17

Water-Soluble Iodine Contrast Media-Allergic Reactions

Back 17

May be minor such as urticaria(hives). Edema in throat with bronchospasms. Nausea and vomting can happen but are thought to be caused by the release of histamine. Premedication with steroids and antihistamines can prevent that.

Front 18

Water-Soluble Iodine Contrast Media-Renal Effects

Back 18

High osmolality contrast media can cause constriction of the renal arteries and result in diminished blood supply to the kidneys

Hint 18

Also can cause osmotic diuresis(increased secretion of urine) and dehydration, increased blood urea nitrogen levels and creatinine.

Front 19

Water-Soluble Iodine Contrast Media-Other effects

Back 19

Patients with sickle cell anemia can be affect by high osmolality contrast which causes the red blood cells to shrink and sickle.

Front 20

Water-Soluble Iodine Contrast Media-Drug Interactions

Back 20

Beta-adrenergic blockers used to treat hypertension can increase risk for anaphylactoid reactions with iodine contrast
Calcium channel blockers are at risk for heart block and abrupt decrease in blood pressure with ionic contrast

Front 21

Water-Soluble Iodine Contrast Media-Considerations in use of nonionic contrast

Back 21

Most adverse reactions are limited but kidney toxicity hasn't been therefore the patients BUN and Creatinine level is important.

Hint 21

Use nonionic contrast on Patients with:
history of adverse reactions to contrast
history of asthma or allergies
cardiac problems
generalized severe debilitation conditions
who will under go helical CT
diabetes mellitus, renal disease, sickle cell

Front 22

Oil-Based Iodine Contrast Media

Back 22

Use is rare in radiography. Used mainly in lymphangiography

Front 23

Oil-Based Iodine Contrast Media- Physical Properties

Back 23

Made of fatty acids found in plants and animals. Very viscous. Don't use if darkend from original color. Don't use with plastic syringes. Main disadvantage is that they persist in the body because they are insoluble in water

Front 24

Oil-Based Iodine Contrast Media-Specific Procedures

Back 24

Bronchography, dacryocystography, sialgraphy and lymphography. Most of these are replaced by nonionic contrast.

Front 25

Oil-Based Iodine Contrast Media-Adverse Reactions

Back 25

Anything with iodine can cause anaphylaxis.

Front 26

Radiopharmaceutical

Back 26

Radionuclide that is attached to a pharmaceutical that has a specific biodistribution in the human body.