13.5 Image Formation and Contrast Agents

There are three components in a signal to a frequency domain:

  1. Amplitude

    This comes from the contrast.

  2. Frequency

    This is the rate at which the proton’s spin.

  3. Phase

    This is the direction of the proton’s spin.

An Inverse Fourier Transform (i.e., IFT) is a mathematical tool for converting data from frequency domain to “image” domain.

13.5.1 k-Spaces

A k-space domain image is a structure that is formed using frequency and phase encoding - this image is turned into an image using a Fourier transform.

The inverse Fourier transform can then be utilized to produce a signal for each individual pixel.

13.5.2 MRI Contrast Agents

MRIs with and without Contarst Agents

Figure 13.20: MRIs with and without Contarst Agents

For more specific kinds of imaging, the most commonly used intravenous contrast agents are gadolinium chelates.

These agents are safer tha iodinated contrast agents used in X-ray or CT scans.

Some types include:

  1. Paramagnetic: Gd and Mn
  2. Superparamagnetic: SPION
  3. Diamagnetic