Improved precision of automatic brain volume measurements
By Dr Marcel Warntjes. Published 05.01.2017
In December, the American Journal of NeuroRadiology (AJNR) published an article entitled ’Improved precision of automatic brain volume measurements in patients with clinically isolated syndrome and multiple sclerosis using edema correction’. In the article it is shown that there exists a correlation between brain volume and brain water content.
Figure 1: Left: a synthetic FLAIR image of an axial slice of the brain of an MS patient. Center: automatic segmentation of the intracranial volume (red line) and of cerebrospinal fluid (CSF, in blue color overlay). Right: a proton density map. All images are acquired using SyMRI in the same sequence.
The volume of the brain may change with dehydration or, in case of MS patients, with the presence of edema. When MS disease activity is high, the brain may swell, whereas treatment may reduce edema, resulting in a corresponding decrease in brain volume. It is a well-known phenomenon that early-onset MS patients can show a rapid decrease in brain volume after starting treatment. But for the treating clinician this cannot be distinguished from progressing atrophy, which is also a treat of MS.
In the article SyMRI is used both for measuring brain volume and also for the proton density content of all brain tissue. Finding evidence of a correlation of the two measures implies that brain volume may be corrected for edema, or more general, for the hydration state of the brain. Applying such a correction would improve the precision of automatic brain volume measurements, since the hydration state of the brain is currently entirely ignored. The observed variation on brain volume in the included patient group was about twice as high as normal annual atrophy in a healthy population, showing how important such a correction can be.