In vivo normative atlas of the hippocampal subfields using multi‐echo susceptibility imaging at 7 Tesla. Issue 8 (13th December 2013)

• Record Type: Journal Article
• Authors: Goubran, Maged; Rudko, David A.; Santyr, Brendan; Gati, Joe; Szekeres, Trevor; Peters, Terry M.; Khan, Ali R.
• Is Part Of: Human brain mapping. Volume 35:Issue 8(2014:Aug.)
• Page Start: 3588
• Page End: 3601
• Publication Date: 2013-12-13
• Subjects: Brain mapping -- Periodicals; 611.81
• DOI: 10.1002/hbm.22423
• Languages: English
• ISSNs: 1065-9471

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>Objectives: To generate a high‐resolution atlas of the hippocampal subfields using images acquired from 7 T, multi‐echo, gradient‐echo MRI for the evaluation of epilepsy and neurodegenerative disorders as well as investigating <inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pghqbc7vnx" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:10659471:media:hbm22423:hbm22423-math-0001" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mi mathvariant="bold-italic">R</mml:mi><mml:mn>2</mml:mn><mml:mo>*</mml:mo></mml:msubsup></mml:mrow></mml:math></alternatives></inline-formula> (apparent transverse relaxation rate) and quantitative volume magnetic susceptibility (QS) of the subfields. Experimental Design: Healthy control subjects (<italic>n</italic> = 17) were scanned at 7 T using a multi‐echo gradient‐echo sequence and susceptibility‐weighted magnitude images, <inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pghqbc7vkw" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:10659471:media:hbm22423:hbm22423-math-0002" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mi mathvariant="bold-italic">R</mml:mi><mml:mn>2</mml:mn><mml:mo>*</mml:mo></mml:msubsup></mml:mrow></mml:math></alternatives></inline-formula> and QS maps were reconstructed. We defined a hippocampal subfield labeling protocol for the magnitude image produced from the average of all echoes and assessed reproducibility through volume and shape metrics. A group‐wise diffeomorphic registration procedure was used to generate an average atlas of the subfields for the whole subject cohort. The quantitative MRI maps and subfield labels were then warped to the average atlas space and used to measure mean values of <inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pghqbc7vpf" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:10659471:media:hbm22423:hbm22423-math-0003" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mi mathvariant="bold-italic">R</mml:mi><mml:mn>2</mml:mn><mml:mo>*</mml:mo></mml:msubsup></mml:mrow></mml:math></alternatives></inline-formula> and QS characterizing each subfield. Principal Observations: We were able to reliably label hippocampal subfields on the multi‐echo susceptibility images. The group‐averaged atlas accurately aligns these structures to produce a high‐resolution depiction of the subfields, allowing assessment of both quantitative susceptibility and <inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pghqbc7vqz" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:10659471:media:hbm22423:hbm22423-math-0004" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mi mathvariant="bold-italic">R</mml:mi><mml:mn>2</mml:mn><mml:mo>*</mml:mo></mml:msubsup></mml:mrow></mml:math></alternatives></inline-formula> across subjects. Our analysis of variance demonstrates that there are more apparent differences between the subfields on these quantitative maps than the normalized magnitude images. Conclusion: We constructed a high‐resolution atlas of the hippocampal subfields for use in voxel‐based studies and demonstrated in vivo quantification of susceptibility and <inline-formula><alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pghqbc7vrg" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math display="inline" altimg="urn:x-wiley:10659471:media:hbm22423:hbm22423-math-0005" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mi mathvariant="bold-italic">R</mml:mi><mml:mn>2</mml:mn><mml:mo>*</mml:mo></mml:msubsup></mml:mrow></mml:math></alternatives></inline-formula> in the subfields. This work is the first in vivo quantification of susceptibility values within the hippocampal subfields at 7 T. <italic>Hum Brain Mapp 35:3588–3601, 2014</italic>. © <bold>2013 Wiley Periodicals, Inc.</bold></p> </abstract>