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A contrast agent usually shortens, but in some instances increases, the value of T1 of nearby water protons thereby altering the contrast in the image. Most clinically used MRI contrast agents work by shortening the T1 relaxation time of protons inside tissues via interactions with the nearby contrast agent.
Iodinated contrast contains iodine.It is the main type of radiocontrast used for intravenous administration.Iodine has a particular advantage as a contrast agent for radiography because its innermost electron ("k-shell") binding energy is 33.2 keV, similar to the average energy of x-rays used in diagnostic radiography.
Therefore, they are often now replaced by ultrasonography and magnetic resonance imaging (MRI). Also, the iodinated contrast medium used in contrast CT and contrast radiography can cause allergic reactions, including severe ones. [5] The contrast dye may also be toxic to the kidneys. [7]
A contrast agent (or contrast medium) is a substance used to increase the contrast of structures or fluids within the body in medical imaging. [1] Contrast agents absorb or alter external electromagnetism or ultrasound , which is different from radiopharmaceuticals , which emit radiation themselves.
Contrast CT of a patient with brain metastases from breast cancer, before (left) and after (right) injection of iodinated contrast.. Iodinated contrast is a form of water-soluble, intravenous radiocontrast agent containing iodine, which enhances the visibility of vascular structures and organs during radiographic procedures.
A meta-analysis revealed 3.6 times greater odds (OR = 3.6) of pregnancy with oil-based contrast compared to no hysterosalpingography. [5] This effect is thought to be due to the flushing action of the contrast into the uterus that causes dislodgement of mucus plug, debris, or opening of mild adhesions in the fallopian tubes. [6]
Abdominal imaging is associated with many potential uses for the different phases of contrast CT.The majority of abdominal and pelvic CT's can be performed using a single-phase, but the evaluation of some tumor types (hepatic/pancreatic/renal), the urinary collecting system, and trauma patients among others, may be best performed with multiple phases.
The most common example of molecular imaging used clinically today is to inject a contrast agent (e.g., a microbubble, metal ion, or radioactive isotope) into a patient's bloodstream and to use an imaging modality (e.g., ultrasound, MRI, CT, PET) to track its movement in the body.