To a lot of patients getting a CT, MRI, and even an X-Ray can be very intimidating because there is a lot of unknown. To be a great radiologic technologist it is part of our job to ease this uncertainty in the patients. In order to calm these nerves, it is important to get a good understanding of the basics. Such as, what contrast media is, what types of contrast are the most common, and when contrast is used. The rest of this essay is written to help get a better understanding about the basic concepts of contrast media, to help us to be the best radiologic technologist that we can be.
Contrast media is significantly important when it comes to radiology. Contrast is simply defined as “the difference in brightness between an area of interest and its surroundings” (Zaer, Amini, & Elsayes, 2014). It is used to enhance the images taken during the scans in modalities including, but not limited to, computed tomography, magnetic resonance imaging, ultrasound, and x-ray. When contrast is present in the body it gives the tissues a different appearance and can give off a either a brighter whiter look called a positive contrast media, or a darker blacker appearance referred to as a negative contrast agent. Positive and negative contrast mediums are based upon how much of the x-ray beam is being attenuated by these different substances. If contrast agents are used properly than it is perfectly safe and there will not be any adverse effects for the patient.
Doctors order contrast for certain exams for a multitude of reasons such as to help better visualize the size, shape, or position of the tissue structured or to help the radiologist to make a better diagnosis and distinguish any abnormalities within the body. There are three different ways that the patient can receive contrast. It can be injected, ingested, or received through an enema. For the purpose of this paper I am going to strictly talk about the two most common types which is injected contrast and ingested contrast.
Injectable contrast is referred to as anything being injected into a blood vessel such as a vein or artery. When contrast media is injected through a vein it is known as being given intravenously. On the other hand, if the doctor orders the contrast for the exam to be given intra-arterially then the needle must be punctured through an artery. In certain cases, contrast can be injected within the fluid spaces or the fluid spaces of the spine and sometimes even other body cavities as well such as the patient’s shoulder, wrist, or knee.
The most common type of injectable contrast media is iodinated contrast. Iodine has a rather large atomic number. This makes it extremely hard for the x-ray beams to pass through this medium. With that being said iodine is typically used in vascular structures or organs to differentiate them from the surrounding tissues. Doctors like to prescribe scans using iodine mainly because when injected into the vascular structures such as the patient’s veins or arteries, it not only gives the radiologist more of an insight about the inside of the blood vessel, but it can also tell them much about the function of the organs that are supplied by that vascular structure. This mainly happens when scanning the brain, heart, and lungs.
Injectable contrasts are most commonly seen in computed tomography. I had the opportunity to be able to observe this department at Salina Regional Health Center and a good majority of their scans for that day had used a type of iodine-based contrast material. Depending on the exam, this material was used in conjunction with saline. It is said that the patient will likely have a metallic taste in their mouth and this could possibly be combined with a sensation of having to urinate; however, that feeling is simply an effect of the contrast and it generally passes quickly according to Goergen (2017) who is a radiologist and a director of research at Monash University. Injectable contrast agents are not limited just to this modality. We also see the use of injectable contrasts in magnetic resonance imaging and x-ray as well. Gadolinium is the most commonly type of contrast used in magnetic resonance imaging because it changes the magnetic properties of water which in turn enhances the quality of the image. Also gadolinium doesn’t have the same metallic components as iodine so it can be used for patients who may have an iodine related allergy.