Review of Biomedical Applications of Contactless Imaging of Neonates Using Infrared Thermography and Beyond

Abstract

The sick preterm infant monitoring is an intriguing job that medical staff in Neonatal Intensive Care Units (NICU) must deal with on a daily basis. As a standards monitoring procedure, preterm infants are monitored via sensors and electrodes that are firmly attached to their fragile and delicate skin and connected to processing monitors. However, an alternative exists in contactless imaging to record such physiological signals (we call it as Physio-Markers), detecting superficial changes and internal structures activities which can be used independently of, or aligned with, conventional monitors. Countless advantages can be gained from unobtrusive monitoring not limited to: (1) quick data generation; (2) decreasing physical and direct contact with skin, which reduces skin breakdown and minimizes risk of infection; and (3) reduction of electrodes and probes connected to clinical monitors and attached to the skin, which allows greater body surface-area for better care. This review is an attempt to build a solid ground for and to provide a clear perspective of the potential clinical applications of technologies inside NICUs that use contactless imaging modalities such as Visible Light Imaging (VLI), Near Infrared Spectroscopy (NIRS), and Infrared Thermography (IRT).

Keywords: near-infrared; neonatal imaging; optical coherence tomography; physio-features, infrared thermography; preterm infants, NICU; short-wave infrared; tissue optics; visible light.

Figure 1

Standard monitors for a neonate inside a Neonatal Intensive Care Unit (NICU).

Figure 2

First contactless imaging setup used by Clark in 1980. This setup uses a traditional infrared camera with five frames per second (fps) and 5 ${}^{\circ }$C resolution.

Figure 3

Potential clinical application of contactless imaging techniques, which can be widely used in neonatal intensive care unit (Source: [3]).

Figure 4

Electromagnetic (EM) spectrum showing infrared imaging band (reprinted with permission from one of the authors’ previous works [18]).

Figure 5

Basic mechanism illustration of the light absorption in NIR imaging of biological tissue. CSF: cerebrospinal fluid.

Figure 6

(Left) Diagram of neonatal NIR spectroscopy (NIRS) imaging. A series of photo-emitting diodes and photo-width = 0.9 are integrated to acquire NIRS data from multiple areas of the neonate’s head to reflect blood perfusion in the cerebral cortex. (Right) 2D reconstruction of NIRS images of a neonatal brain.

Figure 7

(Left) example of an SWIR camera used in research and medical applications (courtesy of Stemmer Imaging Inc, Zutphen, The Netherlands); (Right) absorption chart of light in tissue (courtesy of Dr. Dominik J. Naczynski, Stanford University, Stanford, CA, USA, adapted from [47]).

Figure 8

(A) imaging setup of the SWIR with field of view (FOV) set to cover the whole body of the neonate; (B) SWIR image of an adult hand showing the detailed vasculature of the forearm.

Figure 9

Block diagram of Long wave (LWIR)/middle wave infrared (MWIR) and short wave infrared (SWIR) thermography processing in a computer-aided diagnosis system.

Figure 10

(Left) sequence of the neonatal thermograms showing the evolution of temperature distribution over time (photos reprinted from previous work of the author); (Right) typical experimental setup of neonatal infrared thermography (NIRT), including an Long wave infrared (LWIR) camera and associated vital sign monitoring inside an incubator (closed-type).

Figure 11

(Left) extracted gradient movement from defined regions of interest (ROIs) based on color intensity variation in successive video frames; (Right) video frame series of the neonate inside the incubator with three defined ROI profiles over forehead, nose, and shoulder.

Figure 12

Microsoft Kinect experimental setup for mapping a neonate under intensive care, and estimation of behavioral patterns of the global and local body movements.

Figure 13

Experimental setup of a LeapMotion${}^{\circledR }$ unit to monitor body movements of the neonate.

Figure 14

Experimental setup for CGI used in the detection and identification of respiratory and pulmonary functions by using a clinical inductive belt positioned at two levels (upper and lower) to generate several color-coded regions via CGI-vertex meshing colorization to indicate displacement and mechanical distortion due to several physiological- and pathological-related events.

Figure 15

A schematic of neonatal incubator with multiple different embedded contactless imaging modalities for the early detection of various pathologies and neonatal diseases.

Figure 16

Imaging reconstruction of thermal tomography for neonates by using the dynamic thermal tomographic imaging (DYTTI) method; this gives the physician a clear representation of the temperature picture of the neonate’s body.