Final answer:
The medical assistant must inquire about shellfish allergies before administering an iodine-based contrast dye for x-rays, as it may cause allergic reactions in people with shellfish sensitivities.
Step-by-step explanation:
The medical assistant is responsible for giving the patient instructions before the x-ray exam. When using iodine-based contrast dye, the medical assistant must ask if the patient is allergic to shellfish since iodine can cause allergic reactions in individuals sensitive to shellfish. Iodine is concentrated in various organs and is used for imaging because of its radioactive properties. Unlike soluble barium compounds, which are toxic, barium sulfate is used in medical imaging due to its insolubility and inability to be absorbed by tissues, hence preventing toxicity while providing a clear image of the digestive tract. Air contrast mediums and other isotopes such as gadolinium are used as well but have different safety profiles and do not generally require considerations for shellfish allergies.