Noninvasive hemoglobin sensing and imaging: optical tools for disease diagnosis

Abstract

. Significance: Measurement and imaging of hemoglobin oxygenation are used extensively in the detection and diagnosis of disease; however, the applied instruments vary widely in their depth of imaging, spatiotemporal resolution, sensitivity, accuracy, complexity, physical size, and cost. The wide variation in available instrumentation can make it challenging for end users to select the appropriate tools for their application and to understand the relative limitations of different methods. Aim: We aim to provide a systematic overview of the field of hemoglobin imaging and sensing. Approach: We reviewed the sensing and imaging methods used to analyze hemoglobin oxygenation, including pulse oximetry, spectral reflectance imaging, diffuse optical imaging, spectroscopic optical coherence tomography, photoacoustic imaging, and diffuse correlation spectroscopy. Results: We compared and contrasted the ability of different methods to determine hemoglobin biomarkers such as oxygenation while considering factors that influence their practical application. Conclusions: We highlight key limitations in the current state-of-the-art and make suggestions for routes to advance the clinical use and interpretation of hemoglobin oxygenation information.

Periodic-net: an end-to-end data driven framework for diffuse optical imaging of breast cancer from noisy boundary data

“…Due to the excellent imaging capabilities, optical imaging (OI) techniques have been developed and employed to restore, segment, classify, and identify tissue properties 1 – 4 Diffuse optical imaging (DOI) is the one for being used in the reconstruction of optical properties of the brain and breast. Due to the growing power of artificial intelligence, many inverse problems in DOI are solved in deep learning-based algorithms to improve image reconstruction quality 5 …”

Multispectral imaging of nailfold capillaries using light-emitting diode illumination

“…Hemoglobin, the protein that binds and transports oxygen around the body, is the primary optical absorber in blood. 11 , 12 Hemoglobin exhibits distinct spectral absorption characteristics depending on its oxygenation state, 13 hence measurement of the relative oxygenated ( ) and deoxygenated (Hb) hemoglobin concentrations can be used to calculate blood oxygen saturation ( ). Oxygen saturation can be optically measured in the finger using well-established pulse oximetry; 14 – 16 however, oximetry relies on pulsatile blood flow and does not allow for visualization of the oxygenation dynamics in combination with morphological deformations or perfusion measurements.…”

“…To gain a greater understanding of the interplay between microvascular deformation and oxygen saturation, a spatial mapping of the oxygenation information is necessary, which can be achieved using spectral imaging methods. 12 , 17 , 18 …”

“… 20 Spectral imaging hardware can be broadly classified into spatial-scanning, spectral-scanning, and snapshot methods. 12 , 22 Spatial-scanning methods are impractical in capillaroscopy, given the requirement for video-rate measurement and the challenging topology of the finger.…”

“… 24 , 25 Spectral-scanning methods can vary in complexity can cost, employing either tunable illumination or imaging filters, however, such systems can be large and expensive. 22 Alternatives, such as Fourier transform spectroscopy and optical coherence tomography (OCT), are also capable of measuring optical absorption, 12 , 26 however, increased complexity hampers rollout and integration in a clinical setting. 27 …”