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The Medial Temporal-Lobe ratio (MTLr) compares the volume of the MTL with the whole hemispheric volume. To find out the MTLr we need 1. the volume of the hippocampus (A); the volume of the parahippocampal gyrus (B); 3. the volume of the whole brain hemisphere (C). We can compute the ratio “Medial Temporal Lobe ratio” as follows: MTLr = (A+B)2 / C. Low values are suggestive of MTL atrophy, and therefore the pattern of atrophy matches the expected in typical AD.
If we have 2 MRI studies from different times (1= first one, 2=second one), we can also compute the yearly rate of MTL atrophy (yrMTL) =(A1+B1)-(A2+B2) x 1200 / (#months between MRI studies) and the yearly rate of relative MTL atrophy (yrMTLr) as follows: (A1+B1)-(A2+B2) x 1200 / (C2-C1) x (#months between MRI studies).
The Hippocampus ratio (Hr) compares the volume of the hippocampus with the whole hemispheric volume. To find out the Hr we need 1. the volume of the hippocampus (A); 2. the volume of the ipsilateral brain hemisphere (B). We can compute the ratio “Hippocampus ratio” as follows: Hr= A2 / B. Low values are suggestive of hippocampus atrophy, and therefore the pattern of atrophy matches the expected in typical AD.
If we have 2 MRI studies from different times (1= first one, 2=second one), we can also compute the yearly rate of Hippocampus Atrophy (yrHA)= (A1-A2) x 1200 / (#months between MRI studies) and the yearly rate of relative Hippocampus atrophy as follows: (yrHAr)= (A1-A2) x 1200 / (B1-B2) x (#months between MRI studies).
The Hippocampus-Ventricle index (HVi) is the addition of the volume of the hippocampus plus the tenth part of the volume of the the lateral ventricle. Then, to find out the HVi we need 1. the normalized volume of the hippocampus (A); 2. the normalized volume of the the lateral ventricle (B). We can compute the ratio “Hippocampus-Ventricle index” as follows: HVi = A+(B/10). Low HVi values are suggestive of AD pathology in incipient stages, while high HVi values are suggestive of global brain atrophy due to aging or any neurodegenerative disease other than AD. Intermediate values are not informative.
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Title Volumetric indices and rates of atrophy for the assessment of atrophy in the medial temporal lobe
The Medial Temporal-Lobe ratio (MTLr) compares the volume of the MTL with the whole hemispheric volume. To find out the MTLr we need 1. the volume of the hippocampus (A); the volume of the parahippocampal gyrus (B); 3. the volume of the whole brain hemisphere (C). We can compute the ratio “Medial Temporal Lobe ratio” as follows: MTLr = (A+B)2 / C. Low values are suggestive of MTL atrophy, and therefore the pattern of atrophy matches the expected in typical AD.
If we have 2 MRI studies from different times (1= first one, 2=second one), we can also compute the yearly rate of MTL atrophy (yrMTL) =(A1+B1)-(A2+B2) x 1200 / (#months between MRI studies) and the yearly rate of relative MTL atrophy (yrMTLr) as follows: (A1+B1)-(A2+B2) x 1200 / (C2-C1) x (#months between MRI studies).
The Hippocampus ratio (Hr) compares the volume of the hippocampus with the whole hemispheric volume. To find out the Hr we need 1. the volume of the hippocampus (A); 2. the volume of the ipsilateral brain hemisphere (B). We can compute the ratio “Hippocampus ratio” as follows: Hr= A2 / B. Low values are suggestive of hippocampus atrophy, and therefore the pattern of atrophy matches the expected in typical AD.
If we have 2 MRI studies from different times (1= first one, 2=second one), we can also compute the yearly rate of Hippocampus Atrophy (yrHA)= (A1-A2) x 1200 / (#months between MRI studies) and the yearly rate of relative Hippocampus atrophy as follows: (yrHAr)= (A1-A2) x 1200 / (B1-B2) x (#months between MRI studies).
The Hippocampus-Ventricle index (HVi) is the addition of the volume of the hippocampus plus the tenth part of the volume of the the lateral ventricle. Then, to find out the HVi we need 1. the normalized volume of the hippocampus (A); 2. the normalized volume of the the lateral ventricle (B). We can compute the ratio “Hippocampus-Ventricle index” as follows: HVi = A+(B/10). Low HVi values are suggestive of AD pathology in incipient stages, while high HVi values are suggestive of global brain atrophy due to aging or any neurodegenerative disease other than AD. Intermediate values are not informative.
Work type Article
Tags mild cognitive impairment, mtai, medial temporal lobe, neuroimaging, alzheimer
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Author. Holder Manuel Menendez Gonzalez. Date Nov 9, 2013.
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