Contrast media Flashcards
what organs display a low amount of subject contrast? (6)
stomach, kidney, liver, spleen, pancreas, and bowel
what is subject contrast?
is the radiographic contrast caused by the difference in the composition of the patients body tissues
what is subject contrast caused by?
the tissue differences, the anatomic number differences and the thickness of the patients body parts
what 3 organ systems display a low subject contrast?
digestive, urinary and cerebrovascular
what parts of the stomach and intenstine can you see on plain films?
fundus of the stomach due to the gastric bubble and any part in the large intestine that has fecal matter or gas
what is contrast media?
are diagnostic agents that are introduces into the body orifices or injected into the vascular system, joints and ducts to enhance subject contrast in anatomic areas where low subject contrast exists
what does the contrast media depend on? (2)
the anatomic number of the element used in a particular medium and the concentration of atoms of the element per volume of medium
what are the 3 types of contrast media?
- radiolucent (negative) contrast agents
- radiopaque (positive) contrast agents
- speciality contrast agents
what are the MRI contrast agents?
gadolinium diethylenetrianminepentaacetic acid (DTPA)–metalic and magnetic agent that affects signal intensity
how do ultrasound enhance subject contrast?
gas filled microcmubbles that affect the sound wave to enhance ultrasound contrast
what are the physical properties of negative contrast agents?
-composed of elements with low atomic numbers and decrease the attenuation of the x-ray beam
negative contrasts can be administered by 2 way?
gas (air) and carbon dioxide (tablets, crystals, soda water)
what kind of density does the negative contrast agents produce?
increased density, as more x-rays reach the film the structure that is filled with negative contrast agents appear black on the radiograph
what kind of air is the most common negative contrast agent?
room ari- the air in the lungs serve as a negative contrast medium on the chest radiograph
what is a double contrast effect?
when a negative agent may be combined with a positive contrast agent
what kind of agent is barium?
positive contrast agent
what kind of contrast agent must never been injected intravenously? why?
negative, can cause serious or fatal affects
what are positive contrast agents composed of?
elements with high atomic numbers
how do positive contrast agents appear on a radiograph?
absorb more x-rays and appear bright
how much more x-rays do positive agents absorb than bone? soft tissue?
bone about 3 times, and 5 times more than soft tissue
what are 2 types of positive contrast agents?
barium (56) & iodine (53)
what is the atomic number of barium?
56
what is the atomic number of iodine?
53
what is the atomic number of soft tissue?
7.4