Convolution differentiation is a method of suppressing broad underlying spectral lines in order to emphasize narrower spectral lines. Strong smoothing of the spectrum (e.g., by severe negative exponential weighting of the time data) will suppress the narrow lines but minimally affect very broad ones; subtracting such a smoothed spectrum from the original will largely remove the contributions from the broad lines. This provides a means of baseline correction.

(fMRI) Functional magnetic resonance imaging is a technique used to determine the dynamic brain function, often based on echo planar imaging, but can also be performed by using contrast agents and observing their first pass effects through brain tissue. Functional magnetic resonance imaging allows insights in a dysfunctional brain as well as into the basic workings of the brain.
The in functional brain MRI most frequently used effect to assess brain function is the blood oxygenation level dependent contrast (BOLD) effect, in which differential changes in brain perfusion and their resultant effect on the regional distribution of oxy- to deoxyhaemoglobin are observable because of the different 'intrinsic contrast media' effects of the two haemoglobin forms. Increased brain activity causes an increased demand for oxygen, and the vascular system actually overcompensates for this, increasing the amount of oxygenated haemoglobin. Because deoxygenated haemoglobin attenuates the MR signal, the vascular response leads to a signal increase that is related to the neural activity.
Functional imaging relates body function or thought to specific locations where the neural activity is taking place. The brain is scanned at low resolution but at a fast rate (typically once every 2-3 seconds). Structural MRI together with fMRI provides an anatomical baseline and best spatial resolution.
Interactions can also be seen from the motor cortex to the cerebellum or basal ganglia in the case of a movement disorder such as ataxia. For example: by a finger movement the briefly increase in the blood circulation of the appropriate part of the brain controlling that movement, can be measured.

Keyhole imaging is used for dynamic imaging with contrast medium. The advantage is that the keyhole technique increases temporal resolution without a loss of spatial resolution by limited data acquisition. Keyhole Fourier imaging updates the low spatial frequencies of the original full, high-resolution data set. The high spatial frequency content of the image is constant in time so that its updating would be unnecessary. The high spatial frequency data is acquired from a baseline image, for example, before injection of a contrast agent.
After contrast injection, only the lower spatial frequency data is acquired because, there is no change in the tissue that is responsible for the higher frequency spatial variation in the image.

The planned sequence of the functional imaging measurement. This can for example look like: 10 non-activated images (baseline) and then 10 activated images.