Development of a methodology for the volume estimation of the prefrontal cortical subfields in very pre-term infants using magnetic resonance imaging and stereology

Abstract

Background: The prefrontal cortex (PFC) is vital for cognitive and emotional functions and is vulnerable to disruptions in preterm infants. Reliable volume estimation methods are needed to study its development.

Objective: To develop and validate a novel method for estimating the volume of PFC subfields in very preterm infants using magnetic resonance imaging (MRI) combined with stereological techniques. The method was designed to achieve a coefficient of error (CE) below 5%.

Methods: Five preterm infants born before 28 weeks of gestation were scanned using a 1.5-Tesla MRI scanner. The points of intersection between the grid and structure boundaries, in addition to the points in each slice, were counted using in-house software (Easy Measure).

Results: The shape coefficient for each subfield of the prefrontal cortex was calculated, which yielded coefficients of 4.5, 6.1, 6.4, and 6.5 for dorsolateral, dorsomedial, orbitolateral, and orbitomedial PFC regions, respectively. For the dorsolateral prefrontal cortex, a grid size of 4 × 4 pixels and a 0.2 cm slice gap for the dorsomedial prefrontal cortex (DMPFC), a grid size of 5 × 5 pixels and a 0.1 cm slice gap for the orbitolateral PFC, a grid size of 5 × 5 pixels and a 0.3 cm slice gap, and a grid size of 5 × 5 pixels and 0.1 cm slice gap for the DMPFC resulted in <5% CE.

Conclusion: This methodology offers new insights into the neurodevelopmental effects of preterm birth and has potential applications in the early detection of neurodevelopmental disorders. Its precision, reliability, and non-invasive nature make it suitable for longitudinal studies and contribute to neonatal neuroimaging and neurodevelopmental research.

Keywords: PFC; grey matter; magnetic resonance imaging; stereology; volume estimation.

Figure 1.

Cross-sectional area point counting (points removed) for the DL PFC and OL PFC (the upper and lower left frames, respectively). Boundary length estimation for the DL PFC and OL PFC (the upper and lower right frames, respectively). The stereological grids appear as red crosses in the cross-sectional area point counting, and as red lines in the boundary length estimation. The yellow crosses indicated demonstrate the intersections between the structure boundaries and the grid. DL, dorsolateral; OL, orbitolateral; PFC, prefrontal cortex.