Ambulatory diffuse optical tomography and multimodality physiological monitoring system for muscle and exercise applications

Abstract

Ambulatory diffuse optical tomography (aDOT) is based on near-infrared spectroscopy (NIRS) and enables three-dimensional imaging of regional hemodynamics and oxygen consumption during a person’s normal activities. Although NIRS has been previously used for muscle assessment, it has been notably limited in terms of the number of channels measured, the extent to which subjects can be ambulatory, and/or the ability to simultaneously acquire synchronized auxiliary data such as electromyography (EMG) or electrocardiography (ECG). We describe the development of a prototype aDOT system, called NINscan-M, capable of ambulatory tomographic imaging as well as simultaneous auxiliary multimodal physiological monitoring. Powered by four AA size batteries and weighing 577 g, the NINscan-M prototype can synchronously record 64-channel NIRS imaging data, eight channels of EMG, ECG, or other analog signals, plus force, acceleration, rotation, and temperature for 24+ h at up to 250 Hz. We describe the system’s design, characterization, and performance characteristics. We also describe examples of isometric, cycle ergometer, and free-running ambulatory exercise to demonstrate tomographic imaging at 25 Hz. NINscan-M represents a multiuse tool for muscle physiology studies as well as clinical muscle assessment.

Toward mapping spatiotemporal characteristics of muscle oxygenation in different motor modalities by multichannel near‐infrared spectroscopy

“…34 Because the muscle oxygenation/hemodynamic status of a muscle group is not well represented by a single point measurement within that muscle group, 14 the mean values of a multipoint measurement might be more suitable for representing the muscle oxygenation/hemodynamic status of that muscle group. The temporal resolution (23 Hz) of this NIRS system was high enough for characterizing the general muscle oxygenation/hemodynamic response whose time scale was nearly one second.…”

“…10 By utilizing high spatial resolution imaging techniques, such as magnetic resonance spectroscopy (MRS) and positron emission tomography (PET), it can be observed that even in different parts of the same muscle, the oxygen uses varied significantly. 14 Unfortunately, the aforementioned imaging techniques are intrinsically limited by the large size, very high cost, and the strict constraints on the exercise modality. This highlights the importance of spatially resolved measurements, which not only informs basic muscle physiology and potentially helps improve muscle training paradigms, 13 but also supports clinical decision making.…”

“…The NIRS device with more than one source-detector channel is capable of generating two-dimensional (2D) muscle oxygenation images of an entire muscle. Hu et al had developed a portable multichannel NIRS system combined with multimodality physiological monitoring for muscle and exercise applications, 14 and Niwayama et al had developed a 200-channel NIRS system to get images from the quadriceps muscles during isometric knee-extension exercise. 19,20 There existed many commercialized multichannel NIRS devices, such as Hitachi ETG series, 21 Oxymon system, 22 NIRx system, 23 and so on.…”

NIRS-EMG for Clinical Applications: A Systematic Review

“…In 2015, Kimoto et al proposed a new layered sensor for simultaneous measurements of EMG, mechanomyography (MMG), and CW-NIRS, which was tested during a cuff occlusion [88]. In 2016, Hu et al developed an integrated 64-channel portable CW-NIRS instrument with physiological sensors [89]. These sensors were: High-resolution EMG, electrocardiography (ECG), electrooculography (EOG), and electroencephalography (EEG) sensors.…”

Validation of Fabric-Based Thigh-Wearable EMG Sensors and Oximetry for Monitoring Quadriceps Activity during Strength and Endurance Exercises

“…A recent review has nicely summarized the role of the EMG-NIRS combination in clinical practice [ 11 ]. Recently, several prototypes integrating EMG and NIRS have been developed [ 12 , 13 , 14 , 15 , 16 ]. However, those devices presented several limitations; in particular, they did not measure regional muscle O 2 Hb saturation (instead they provided only oxygenation changes) and partially used full textile sensors for EMG.…”