This method consists of measuring the area of 3 brain regions on one single MRI slide and then use these data for calculating a simple ratio. First, we take the coronal slide at the level of the interpeduncular fossa on the TIR sequence. Then, regions are traced manually, simply using the pointer-rule tool of any software for visualizing DICOM images. The three areas are: (1) the MTL region (A), defined in a coronal brain slide as the four-sided space bordered in its inferior side by the tentorium cerebelli, in its medial side by the cerebral peduncles, in its upper side by the roof of the temporal horn of the lateral ventricle and in its lateral side by the collateral sulcus and a straight-line linking the collateral sulcus with the lateral edge of the temporal horn of the lateral ventricle; (2) the parenchima within the medial temporal region, that includes the hippocampus and the parahippocampal gyrus—the fimbria taenia and plexus choroideus are excluded—(B); and (3) the body of the ipsilateral lateral ventricle (C).
If we have two MRI studies from different times (1 = first one, 2 = second one), we can also compute the yearly rate of MTA as follows: yrMTA = (A2 − B2) − (A1 − B1) × 120/(#months between MRI studies) and the yearly rate of relative MTA as follows: (yrMTAr) = (A2 − B2) − (A1 − B1) × 120/(C2 − C1) × (#months between MRI studies).
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