Review of Contrast Media and Sterile Techniques

Contrast Media in Medical Imaging

• Introduction to Contrast Media

  • Contrast agents are substances used in imaging techniques to enhance the visibility of internal structures.
  • There are positive contrast (high atomic number) and negative contrast (low atomic number).

• Types of Contrast

  • Positive Contrast Media:
  • Example: Barium (Ba) has an atomic number of 56, used for its radiopaque properties.
  • Appearance on images: Bright white areas, indicating high attenuation.
  • Used in various imaging studies including X-rays to highlight the gastrointestinal tract.
  • Negative Contrast Media:
  • Example: Air or Carbon Dioxide; lower density causes areas to appear darker on images.
  • Introduced during studies like double-contrast Barium Enemas (BE) for better visualization.

• Absorption and Attenuation Characteristics

  • Contrast media alter the absorption of X-rays in the body.
  • Enhancements in imaging are achieved by varying the attenuation of beams due to different contrast materials.

• Application Examples

  • Double Contrast BE:
  • A combination of barium and air to highlight the bowel structure.
  • The air expands the structure enhancing visibility for potential abnormalities such as diverticula or polyps.
  • Upper GI Studies:
  • Crystals (e.g. effervescent) are used to create expansion in the stomach for better imaging.

• Diverticula vs. Polyps

  • Diverticula: Outpouches in the bowel wall.
  • Conditions: Diverticulosis (presence of diverticula) and Diverticulitis (inflamed diverticula).
  • Polyps: Growths within the intestinal lumen that may be stalked or sessile (attached without a stalk).

• Procedure Considerations

  • Barium Studies:
  • Barium sulfate is used in a suspension, requires careful preparation to prevent flocculation (separation).
  • Critical to avoid administration if there is a perforation in the GI tract due to risk of complications like peritonitis.
  • Iodinated Contrast:
  • Iodine, with an atomic number of 53, is used predominantly in CT scans and angiography.
  • Monitored for renal function as it can affect kidney function and lead to contrast-induced nephropathy.

• Contraindications for Contrast Media

  • Barium:
  • Contraindicated in cases of perforation, recent surgery, or certain biopsy procedures due to risk of complications.
  • Iodinated Contrast:
  • Allergic reactions, especially in patients with a history of anaphylaxis.
  • Creatinine levels must be low (typically <1.4-1.6) for safe administration.
  • Consideration needed for patients on medications such as metformin, which should be temporarily withheld.

• Patient Care

  • Importance of thorough patient history and consent.
  • Ensure hydration to help flush out contrast.
  • Continuous monitoring before, during, and after procedures for safety.

• Radiopharmaceuticals

  • Radionuclides like Technetium-99 are used in nuclear medicine for imaging and therapeutic purposes.
  • Specific biodistribution patterns can indicate disease states (e.g., areas with increased metabolic activity in cancer).

• Sterile Techniques in Procedures

  • Understanding the aseptic technique is crucial for procedures involving catheters and injections.
  • Maintain a sterile field to prevent infections during procedures, including gowning and gloving techniques.
  • Importance of proper training in sterile field management and communication within surgical teams.

• Conclusion

  • Knowledge of contrast media properties and contraindications is essential for safe and effective imaging practices.
  • Continuous learning and protocol adherence are critical in handling various patient scenarios in imaging.