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Deformation-based Morphometry of the Human Brain

Deformation field morphometry is a technique which is used to measure structural differences between individual brains. This technique is based on the analysis of images of the human brain, which were acquired by magnetic resonance tomography (MRT). Image registrations techniques are applied to calculate deformation fields, from which maps of local volume differences are derived.
The figure below shows the volume of a certain brain region in the thalamus: Even when healthy subjects are compared, a pronounced volume decline is visible over the range from 20 to 50 years of age. The symbols distinguish the volume of the considered region in the left and right brain hemisphere (rhomb=left, square=right).The lines are calculated by a linear regression of the volume data.

Thalamus, Ncl. ventralis anterior

Besides these “normal” volume declines in the human brain in the course of ageing, volume differences or changes can indicate pathological causes: These could be for example disturbances during brain development, but also neurodegenerative diseases, like Alzheimer’s and Parkinson’s disease. In particular in the latter conditions, neurons in the brain are progressively lost. Such changes are examined by Longitudinal Deformation-based Morphometry. For this purpose, multiple MR images of each subject’s brain are serially aquired with intervals about several months. The follow-up images are registered with the initial image in order to detect the atrophic changes which emerged between the different time-points.

The following example shows the deformation vectors and volume changes in the brain of a patient which suffered from cortico-basal degeneration. These atrophic changes were found after 16 and 26 months, respectively. Note that the deformation vectors are elongated by a factor 4 in this presentation.

DFM_5

The structural changes with occur in the brain are also visualized in the movie cbs_movie_z13.mpg, which shows the actual changes in the MR images along with the calculated deformation fields and volume changes.


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