Contrast Media types

 Contrast media is and the types of contrast media in the  radiographic contrast in our radiographic imaging series we learned the differences in tissue thickness and other characteristics of tissues determine how much radiographic contrast is produced this means that when there is a high difference in the structure of tissues like how bones and fat are different great contrast is recorded on the image a great difference in densities on the image now what happens when there is a low difference between different anatomical structures and you need an image contrast media is employed contrast media or artificial media that are used in delineating or outlining tissues that naturally have a low subject contrast this implies body parts with structures that are similar in appearance

Contrast media increases the subject contrast in these body parts examples of parts that we commonly use contrast media for include the digestive system the urinary system the reproductive system and the biliary system there are many ways you can classify contrast media

 start out by grouping them based on their atomic weight under this classification, we have the positive and negative contrast media the positive contrast media has its name because it possesses a higher atomic weight than the tissue it is introduced into this means that it will absorb more photons than the tissue that surrounds it and would produce a lower radiographic density than this tissue that surrounds it examples of positive contrast media include barium sulfate and organic iodine as for the negative contrast media its atomic weight is lower than that of the tissue that it is introduced into this means that it would absorb fewer photons and would produce greater radiographic density than the tissue surrounding.

 Examples include gases like air oxygen and carbon dioxide

take note that imaging modalities like

computed tomography and magnetic

resonance imaging has greatly reduced

the need for solubility is a measure of how much one

the substance dissolves in another

the positive contrast media barium

sulfate and organic iodine

are further classified based on their

solubility in water

the first group under this is the water

insoluble contrast media

barium sulfate is usually

produced in a powder or semi-solid

colloidal suspension

as a syrup, it is not soluble in water

the human body is made up of a lot of

water this means that when barium

sulfate

which is not soluble in water is

introduced into the body

it is not readily absorbed and excreted

by the body

this means that it will stay in the body

for a long period of time.

you will find water insoluble contrast media like barium sulfate used majorly in investigations of the

gastrointestinal tract examples of these investigations include barium swallow investigations of the

esophagus barium meal investigations of the stomach small bowel enema investigations and barium enema investigations of the large intestine depending on the examination the barium sulfate are either taken orally or through the rectum, as an enema now because it is water-insoluble it will stay within the body system long enough for the examination to be completed before it is adjusted as part of the feces we should also point out that there are precautions with the use of barium sulfate as we have stated barium sulfate is water-insoluble and is therefore not readily absorbed and excreted by the body, for this reason, it is not used when investigating patients who are suspected to be suffering from perforation or obstruction if barium sulfate is used in cases of perforation it could leak through the perforation and get to the peritoneal cavity this would cause an irritation of the peritoneal cavity is known as barium peritonitis and barium peritonitis can lead to death in cases of obstruction the blockage makes the barium sulfate unable to leave the body system through ingestion as feces this causes further abdominal distension in both cases of perforation and obstruction.

Water-soluble contrast media is used instead next is the water-soluble contrast media the organic iodines fall under this group this type of contrast media usually exists in a liquid form that is soluble in water what this means is that when it is introduced into the body it is rapidly absorbed into the body's water and excreted by the kidneys thus it does not stay within the region of interest for long this is why speed is important in investigations where this type of contrast media is used in investigations of the urinary system the biliary system the central nervous system the cardiovascular system and in some gastrointestinal system exams.

A suspected case of perforation or obstruction of organic iodines are further classified

into highest molar contrast media and lowest molar contrast media to better understand these two we need to talk about a phenomenon known as osmolality is simply the concentration of dissolved particles in a solution how many dissolved particles are in a solution with a high osmolality will induce the greatest modic pressure this osmotic pressure causes more fluid to flow into the solution what this means is that when contrast media that has an osmolality greater than that of the body, fluids is introduced into the body the contrast media will induce an osmotic pressure that would cause water to flow into it and this water that flows into the contrast media where is it coming from it comes from the body fluid which is a lower osmolality this movement of water from the body fluid will cause the patient to be dehydrated and this increases the likelihood of being physiologically intolerant to the contrast media.

which sets the stage for many contrast media reactions this implies that the greater the osmolality of contrast media used the greater the chances of contrast media reactions occurring to emphasize further if contrast media that has an osmolality near the osmolality of the body fluid is used there is a low chance of contrast media reactions occurring compared to when contrast media with osmolality far greater than the body fluid is used which is a higher chance of leading to contrasting media reactions that take us to the highest molar contrast media these were the first type of organic iodine contrast media to be produced