Construction and validation of a database of head models for functional imaging of the neonatal brain.

Liam H Collins‐Jones,Tomoki Arichi,Tanya Poppe,Lorenzo Fabrizi,Jeremy C Hebden,Robert J Cooper,Jiaxin Xiao,Addison Billing,Clare E Elwell,Sabrina Brigadoi

doi:10.1002/hbm.25242

Abstract

The neonatal brain undergoes dramatic structural and functional changes over the last trimester of gestation. The accuracy of source localisation of brain activity recorded from the scalp therefore relies on accurate age‐specific head models. Although an age‐appropriate population‐level atlas could be used, detail is lost in the construction of such atlases, in particular with regard to the smoothing of the cortical surface, and so such a model is not representative of anatomy at an individual level. In this work, we describe the construction of a database of individual structural priors of the neonatal head using 215 individual‐level datasets at ages 29–44 weeks postmenstrual age from the Developing Human Connectome Project. We have validated a method to segment the extra‐cerebral tissue against manual segmentation. We have also conducted a leave‐one‐out analysis to quantify the expected spatial error incurred with regard to localising functional activation when using a best‐matching individual from the database in place of a subject‐specific model; the median error was calculated to be 8.3 mm (median absolute deviation 3.8 mm). The database can be applied for any functional neuroimaging modality which requires structural data whereby the physical parameters associated with that modality vary with tissue type and is freely available at www.ucl.ac.uk/dot-hub.

Highlights

A structural prior is a model of structural anatomy that delineates the different tissues within a particular anatomical region
Such constraints can be overcome by using other more motion tolerant functional imaging techniques to collect functional data, such as fNIRS, an optical imaging technique whereby the head is interrogated with near-infrared light via an array of sources and detectors placed on the scalp (Lee, Cooper, & Austin, 2017; White, 2010)
A structural prior would be derived from an individual's own magnetic resonance imaging (MRI) scan; this is often not available and requiring each individual to undergo an MRI scan undermines the benefits of many functional imaging techniques that enable neonates to be studied at the cot-side

Summary

Introduction

A structural prior is a model of structural anatomy that delineates the different tissues within a particular anatomical region. Given the requirement that subjects remain still, fMRI cannot be used to study the awake infant, which limits fMRI data acquisition to infants who are either asleep or sedated Such constraints can be overcome by using other more motion tolerant functional imaging techniques to collect functional data, such as fNIRS, an optical imaging technique whereby the head is interrogated with near-infrared light via an array of sources and detectors placed on the scalp (Lee, Cooper, & Austin, 2017; White, 2010). Advantages of fNIRS include the fact that it is silent, non-invasive, portable, and relatively tolerant of motion (Eggebrecht et al, 2014; Ferradal et al, 2016; Lee et al, 2017) Techniques such as fNIRS conventionally offer limited spatial resolution (Lloyd-Fox, Blasi, & Elwell, 2010), but can be extended to produce three-dimensional images with the use of a structural prior

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