The histological validation of post mortem magnetic resonance imaging-determined hippocampal volume in Alzheimer's disease

For 11 AD cases and four normal elderly controls, post mortem volumes of th e hippocampal subdivisions were calculated by using magnetic resonance imag ing and histological sections. After at least six weeks of fixation in form alin, brains were examined on a 1.5-T Philips Gyroscan imager producing T-1 -weighted coronal images with a 3-mm slice thickness. Brains were then proc essed and embedded in paraffin. Serial coronal sections, 3 mm apart and sta ined with Cresyl Violet, were used for the planimetry and unbiased estimati on of the total numbers of neurons in the hippocampal subdivisions. For all 15 cases, magnetic resonance imaging- and histology-based measurements wer e performed along the whole rostrocaudal extent of the hippocampal formatio n and included three subvolumes: (i) the hippocampus (CA1-CA4 and the denta te gyrus); (ii) hippocampus/subiculum; and (iii) hippocampus/parahippocampa l gyrus. After controlling for shrinkage, strong correlations were found be tween magnetic resonance imaging and histological measurements for the hipp ocampus (r = 0.97, P < 0.001), hippocampus/subiculum (r = 0.95, P < 0.001) and hippocampus/parahippocampal gyrus (r = 0.89, P < 0.001). We also calcul ated the total number of neurons in the hippocampus and hippocampus/subicul um subvolumes. Strong correlations between the magnetic resonance imaging s ubvolumes and neuronal counts were found for the hippocampus (r = 0.90, P < 0.001) and the hippocampus/subiculum subvolume (r = 0.84, P < 0.001). We conclude that very accurate volumetric measurements of the whole hippoca mpal formation can be obtained by using a magnetic resonance imaging protoc ol. Moreover, the strong correlations between magnetic resonance imaging-ba sed hippocampal volumes and neuronal numbers suggest the anatomical validit y of magnetic resonance imaging volume measurements. (C) 1999 IBRO. Publish ed by Elsevier Science Ltd.