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Hippocampal layers on high resolution magnetic resonance images: real or imaginary?

Published online by Cambridge University Press:  01 July 1999

U. C. WIESHMANN ,
M. R. SYMMS ,
J. P. MOTTERSHEAD ,
D. G. MACMANUS ,
G. J. BARKER ,
P. S. TOFTS ,
T. REVESZ ,
J. M. STEVENS  and
S. D. SHORVON
U. C. WIESHMANN
Affiliation:
NSE Epilepsy Research MRI Unit, Chalfont St Peter, UK Epilepsy Research Group, University Department of Clinical Neurology, London, UK
M. R. SYMMS
Affiliation:
NSE Epilepsy Research MRI Unit, Chalfont St Peter, UK Epilepsy Research Group, University Department of Clinical Neurology, London, UK
J. P. MOTTERSHEAD
Affiliation:
NMR Research Unit, London, UK
D. G. MACMANUS
Affiliation:
NMR Research Unit, London, UK
G. J. BARKER
Affiliation:
NMR Research Unit, London, UK
P. S. TOFTS
Affiliation:
NMR Research Unit, London, UK
T. REVESZ
Affiliation:
University Department of Neuropathology, Institute of Neurology, UCL, London, UK
J. M. STEVENS
Affiliation:
Department of Neuroradiology, National Hospital for Neurology and Neurosurgery, London, UK
S. D. SHORVON
Affiliation:
NSE Epilepsy Research MRI Unit, Chalfont St Peter, UK Epilepsy Research Group, University Department of Clinical Neurology, London, UK
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Abstract

To evaluate whether the lines occasionally detected on clinical magnetic resonance (MR) images are genuine hippocampal layers, a formalin fixed hippocampal specimen was scanned using T2 weighted sequences at 7 Tesla (voxel dimensions 0.064×0.064×1 mm) and at 1.5 Tesla (voxel dimensions: 0.156×0.156×1 mm) and compared with the results of histological examination. In addition, a healthy volunteer was scanned with a T2 weighted sequence at 1.5 Tesla (voxel dimensions: 0.469×0.469×2 mm). On 7 Tesla images hippocampal layers and the granule cell layer of the dentate were visible. On 1.5 Tesla images of the specimen, the hippocampal layers were again identified, but the granule cell layer of the dentate was not detectable. On 1.5 Tesla images of the hippocampus in vivo, 3 layers could be distinguished in the hippocampus on some slices. These mainly represented the alveus, pyramidal cell layer and stratum radiatum. A dark line consisting of a few pixels possibly represented the dentate gyrus. Our results show that the lines occasionally detected on clinical MR images are likely to be real hippocampal layers. However, the resolution currently used in clinical imaging (typically 0.469×0.469×2 mm or lower) is not sufficient for the detection of all hippocampal layers. For the reliable detection of all hippocampal layers on MR images an increase by a factor of approximately 20 would be necessary.

Keywords

Neuroimaginghippocampal formation
Type
Research Article
Information
The Journal of Anatomy , Volume 195 , Issue 1 , July 1999 , pp. 131 - 135
Copyright
© Anatomical Society of Great Britain and Ireland 1999

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