Anatomy and Contrast Media Chapter 23

Contrast Media Overview

• Contrast materials enhance the visibility of anatomical structures by improving low subject contrast.
• Contrast agents are classified into positive and negative types.

Radiographic Densities

• Radiographic images result from varying absorption of x-ray photons based on tissue density and thickness.
• The five radiographic densities are air or gas, water, fat, mineral, and metal.
• The lowest subject contrast exists between water and fat.

Negative and Positive Contrast Agents

• Negative contrast agents possess low atomic numbers.
• Positive contrast agents have high atomic numbers, appear white on radiographs, and significantly absorb x-ray energy.

Air-Contrast Studies

• An air-contrast colon study exemplifies a high-contrast exam utilizing both negative and positive contrast agents, such as barium sulfate and air.

Common Contrast Agents

• Gadolinium-DTPA is widely used for MRI examinations.
• Double-contrast studies utilize both air (negative contrast) and radiopaque contrast to outline mucosal linings and interspaces.

Barium Sulfate Characteristics

• Barium sulfate does not dissolve completely when mixed with water, contradicting a common misconception.
• It is contraindicated for patients who cannot tolerate its properties.

Patient Risks with Barium Sulfate

• Stomach exams using barium sulfate pose risks for patients who are sedated, mentally handicapped, or hypovolemic.

Adverse Reactions to Ionic Agents

• Most adverse reactions to ionic iodinated contrast agents arise from their osmolality, causing fluid shifts in the body.
• Ionic agents dissociate into cations and anions in plasma.

Nonionic Contrast Agents

• Nonionic iodine contrast agents do not dissociate and generally present a lower risk profile compared to ionic agents.
• The ideal iodinated contrast agent has low osmolality, nonionic structure, high water solubility, and contains multiple iodine atoms.

Osmotic Effects

• The effects of ionic contrast agents can increase blood volume and pressure due to water moving from cells into the bloodstream.

Patient Monitoring After Contrast Injection

• Patients exhibiting warm sensations and itching after receiving ionic iodinated contrast should be closely monitored for severe reactions, including anaphylaxis.

Renal Function Assessment

• BUN and creatinine tests assess renal function, crucial for patients receiving high osmolality contrast media.

Vulnerable Patient Populations

• Patients with compromised renal function include diabetics, the elderly, and renal dialysis patients, making them particularly at risk from high osmolality contrast agents.

Safety of Nonionic Contrast Agents

• Despite being a safer choice, nonionic low-osmolality contrast agents can still pose risks to renal function.

Importance of Medical History

• A comprehensive medical history assessment is essential before using any contrast agent for radiographic examinations.

Radiopharmaceuticals

• Radiopharmaceuticals are agents used in nuclear medicine for imaging and treatment, containing radioactive material.

Test your knowledge on the use of contrast media in visualizing human anatomy with these flashcards. This quiz covers key terminology and classifications related to contrast agents in radiography. Enhance your understanding of how these agents impact image quality.