Low-cost, smartphone-based instant three-dimensional registration system for infant functional near-infrared spectroscopy applications

Abstract

To effectively apply functional near-infrared spectroscopy (fNIRS)/ diffuse optical tomography (DOT) devices, a three-dimensional (3D) model of the position of each optode on a subject's scalp and the positions of that subject's cranial landmarks are critical. Obtaining this information accurately in infants, who rarely stop moving, is an ongoing challenge.Aim: We propose a smartphone-based registration system that can potentially achieve a full-head 3D scan of a 6-month-old infant instantly.Approach: The proposed system is remotely controlled by a custom-designed Bluetooth controller. The scanned images can either be manually or automatically aligned to generate a 3D head surface model.Results: A full-head 3D scan of a 6-month-old infant can be achieved within 2 s via this system. In testing on a realistic but static infant head model, the average Euclidean error of optode position using this device was 1.8 mm.Conclusions: This low-cost 3D registration system therefore has the potential to permit accurate and near-instant fNIRS/DOT spatial registration.

Three-dimensional infrared scanning: an enhanced approach for spatial registration of probes for neuroimaging

“…It is also simple and easy to use, allowing 3D models of objects to be captured by simply walking around them, with an acquisition time of 2 min and almost instant reconstruction of a single 3D mesh. 6 , 17 …”

“…However, this approach requires additional cap preparation time for marker placement, and due to the photogrammetric approach, the reconstruction time constrains the immediate feedback of the recording. 6 The advantage of our method is the immediate reconstruction and the use of visible landmarks on the head, eliminating the need for any additional markers. Notably, the SD of our method’s accuracy (1.73 mm) was lower than expected with the standard EEG cap (5.5 mm, as per Ref.…”

“…This approach was intended to eliminate the influence of anatomical landmark positioning and provide system-specific details. 6 …”

“…However, their drawbacks include high costs, time-consuming consecutive probe registration, interference with medical implants (e.g., cochlear implants), and impracticality in certain populations. 6 , 7 To address these limitations, less cost-intensive photogrammetric approaches gained popularity, utilizing a single camera for video recording around the head, enabling parallel acquisition of multiple probes and faster data collection. 7 , 8 Yet, the computationally expensive and time-consuming reconstruction of 3D shapes from two-dimensional video frames poses challenges, limiting immediate assessment after recording.…”

“… 7 , 8 Yet, the computationally expensive and time-consuming reconstruction of 3D shapes from two-dimensional video frames poses challenges, limiting immediate assessment after recording. 6 Adding a depth-sensing instrument (e.g., an infrared camera) to the setup offers multiple advantages. It facilitates quick 3D reconstruction, allowing immediate evaluation of the 3D mesh and avoiding additional experimental time due to lengthy reconstruction processes.…”