MRI Contrast Agent - Types

Types

Most clinically used MRI contrast agents work through shortening the T1 relaxation time of protons located nearby. T1 shortens with an increase in rate of stimulated emission from high energy states (spin anti-aligned with the main field) to low energy states (spin aligned). Thermal vibration of the strongly magnetic metal ions in the contrast agent creates oscillating electromagnetic fields at frequencies corresponding to the energy difference between the spin states (via E = hν), resulting in the requisite stimulation.

MRI contrast agents may be administered by injection into the blood stream or orally, depending on the subject of interest. Oral administration is well suited to G.I. tract scans, while intravascular administration proves more useful for most other scans. A variety of agents of both types enhance scans routinely.

MRI contrast agents can be classified in many ways, including by their:

  1. chemical composition
  2. administration route
  3. magnetic properties
  4. effect on the image
  5. presence and nature of metal atoms
  6. biodistribution and applications:
    1. Extracellular fluid agents (also known as intravenous contrast agents)
    2. Blood pool agents (also known as intravascular contrast agents)
    3. Organ specific agents (i.e.Gastrointestinal contrast agents and hepatobiliary contrast agents)
    4. Active targeting/cell labeling agents (i.e. tumor-specific agents)
    5. Responsive (also known as smart or bioactivated) agents
    6. pH-sensitive agents


Read more about this topic:  MRI Contrast Agent

Famous quotes containing the word types:

    “Science is intimately integrated with the whole social structure and cultural tradition. They mutually support one other—only in certain types of society can science flourish, and conversely without a continuous and healthy development and application of science such a society cannot function properly.”
    —Talcott Parsons (1902–1979)

    “... there are two types of happiness and I have chosen that of the murderers. For I am happy. There was a time when I thought I had reached the limit of distress. Beyond that limit, there is a sterile and magnificent happiness.”
    —Albert Camus (1913–1960)

    “Our major universities are now stuck with an army of pedestrian, toadying careerists, Fifties types who wave around Sixties banners to conceal their record of ruthless, beaverlike tunneling to the top.”
    —Camille Paglia (b. 1947)