Hippocampal spatial position evaluation on MRI for research and clinical practice

Area of Science:

• Neuroimaging
• Radiology
• Medical Image Analysis

Background:

• Magnetic Resonance Imaging (MRI) is crucial for volumetric studies.
• Brain reorientation on MRI scans is common in clinical practice and research.
• The impact of different reorientation planes on hippocampal measurements is not fully understood.

Purpose of the Study:

• To investigate the effect of different brain reorientation planes on 2D hippocampal area measurements.
• To compare measurements from native MRI scans with those reoriented to the anterior commissure-posterior commissure (AC-PC) and hippocampal horizontal long axis (hipp) planes.
• To assess rotation variability in Alzheimer's disease patients and healthy controls.

Main Methods:

• Manual measurement of hippocampal area and temporal horn using ImageJ software.
• Reorientation of native MRI scans into AC-PC and hipp planes.
• Comparison of area measurements across different reorientation planes in 23 Alzheimer's patients and 31 healthy controls.

Main Results:

• Hippocampal area was largest in native (nat) scans, smaller in AC-PC reoriented scans, and smallest in hipp reoriented scans.
• Area measurements including the temporal horn showed similar trends: nat > AC-PC > hipp.
• Significant rotation variability (up to 35°) was observed in both AC-PC and hipp axes, as well as skull rotation.

Conclusions:

• The measured hippocampal area in native MRI is comparable to that reoriented to the AC-PC axis.
• For 2D hippocampal area studies and clinical practice, using native MRI or AC-PC reoriented scans is recommended.
• Brain and skull rotation variability is substantial and independent of the chosen reorientation plane.