Silicon photomultiplier based continuous-wave functional near-infrared spectroscopy module with multi-distance measurements

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Journal Title
Journal ISSN
Volume Title
Perustieteiden korkeakoulu | Master's thesis
Date
2019-05-06
Department
Major/Subject
Biomedical Engineering
Mcode
SCI3059
Degree programme
Master’s Programme in Life Science Technologies
Language
en
Pages
58+21
Series
Abstract
In recent years, there has been growing interest in developing fiberless and wireless functional near-infrared spectroscopy (fNIRS) and diffuse optical tomography (DOT) instruments. However, developing such instruments poses multiple challenges, interms of cost, safety, system complexity and achievable signal quality. One crucial factor in developing wireless and fiberless instruments is the appropriate choice of detectors. Currently, the majority of existing wireless and/or fiberless systems use photodiodes due to their low cost and low power requirements. However, under low-light conditions, the SNR of photodiodes diminishes significantly, making them less effective for measurements with long source–detector separations. The silicon photomultiplier (SiPM) is a relatively new type of detector that contains high internal amplification; this makes SiPMs suitable for low-light applications. Although SiPMs can increase signal quality at long source–detector distances, they cost more and have higher power requirements than photodiodes. This thesis presents the design of a multi-distance, multichannel DOT prototype that uses a hybrid detector arrangement. This arrangement uses photodiodes for short-distance measurements (i.e., 1 cm) and silicon photomultipliers for long-distance measurements (i.e., 3 cm and 4.5 cm). The developed system consists of two printed circuit boards (PCBs): a DOT sensor PCB, a data acquisition and control PCB as well as a graphical user interface. The performance of the developed DOT system prototype was validated using a dynamic optical phantom. The results show that the prototype works as intended.
Description
Supervisor
Ilmoniemi, Risto
Thesis advisor
Nissilä, Ilkka
Keywords
Optical imaging, near-infrared spectroscopy, continuous-wave instrumentation, neuroimaging
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