Age-related Changes in Diffuse Optical Tomography Sensitivity to the Cortex in Infancy

• In Event: Poster Session 14
  In Poster Session: PS 14 Topic - Biological Processes: Neuroscience and Genetics

Abstract

Diffuse optical tomography (DOT) uses near-infrared light spectroscopy (NIRS) to measure changes in cerebral hemoglobin concentration. Anatomical interpretations of the location that generates the hemodynamic signal requires accurate descriptions of the cranio-cerebral relations and DOT sensitivity to the underlying cortical structures. Such information is limited for pediatric populations because they undergo rapid head and brain development.

The present study used spatial scalp projection and photon propagation simulation methods to examine scalp-to-cortex distance, the mapping between scalp locations and underlying brain atlas regions of interest (ROIs), and DOT sensitivity profiles in realistic head models based on MRIs (Figure 1). We investigated age-related differences in these measures among infants ranging from 2 weeks to 24 months with narrow age bins, children (4 and 12 years) and adults (20 to 24 years). MRIs from a total of 1058 individuals were obtained from open-access databases and a local scanning facility.

We found age-related differences in scalp-to-cortex distance, cranio-cerebral correspondence, and DOT sensitivity profiles. Figure 2A shows that there were considerable variations in the scalp-to-cortex distances among the infant age groups. The developmental increase was magnified in children and adults. The probabilistic mappings between scalp locations and cortical lobes were relatively stable across development. However, the mappings between scalp locations and cortical ROIs in sub-lobar atlas parcellations showed greater age-related variations. For example, channel TP7 was sensitive to both the inferior and middle temporal gyrus in the LPBA40 atlas for age 2 weeks through 12 years whereas it was mapped to only the middle temporal gyrus for 20-24-year-olds. Figure 2B reveals that the DOT sensitivity profiles had a common shape across source-detector separation and ages. There were expected differences in the depth sensitivity for source-detector separations, with larger separations being more sensitivity to greater cortical depths but showing decreasing signal strength with source-detector distances. There were age-related differences in the DOT sensitivity profiles across separations. A noticeable age-group difference was that the fluence distribution penetrated greater depth with the same level of signal loss in the younger infant (2 weeks to 4.5months) than the rest of the infant age groups.

Our findings have important implications in the design of sensor placement and DOT image reconstruction in NIRS and fNIRS research. Age-appropriate realistic head models should be used to provide anatomical guidance for standalone DOT data in infants.

Authors

• Xiaoxue Fu, University of South Carolina
  Presenting Author

• John E Richards, University of South Carolina
  Non-Presenting Author