Effects of Contact Pressure in Reflectance Photoplethysmography in an In Vitro Tissue-Vessel Phantom

With the continued development and rapid growth of wearable technologies, PPG has become increasingly common in everyday consumer devices such as smartphones and watches. There is, however, minimal knowledge on the effect of the contact pressure exerted by the sensor device on the PPG signal and how it might affect its morphology and the parameters being calculated. This study explores a controlled in vitro study to investigate the effect of continually applied contact pressure on PPG signals (signal-to-noise ratio (SNR) and 17 morphological PPG features) from an artificial tissue-vessel phantom across a range of simulated blood pressure values. This experiment confirmed that for reflectance PPG signal measurements for a given anatomical model, there exists an optimum sensor contact pressure (between 35.1 mmHg and 48.1 mmHg). Statistical analysis shows that temporal morphological features are less affected by contact pressure, lending credit to the hypothesis that for some physiological parameters, such as heart rate and respiration rate, the contact pressure of the sensor is of little significance, whereas the amplitude and geometric features can show significant change, and care must be taken when using morphological analysis for parameters such as SpO2 and assessing autonomic responses.

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Morphological Analysis on the Toxic Effect of Manganese on Acanthamoeba sp. Isolated from Setiu Wetland, Terengganu: An in vitro Study

Procedia Environmental Sciences ◽

10.1016/j.proenv.2015.10.003 ◽

2015 ◽

Vol 30 ◽

pp. 15-20 ◽

Cited By ~ 1

Author(s):

Fatimah Hashim ◽

Nur Athirah Abdul Rahman ◽

Nakisah Mat Amin

Keyword(s):

Toxic Effect ◽

Morphological Analysis ◽

In Vitro Study ◽

Vitro Study

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In-vitro Study for Cerenkov Luminescence Imaging Application in Hepatic Metastasectomy

Frontiers in Physics ◽

10.3389/fphy.2021.635540 ◽

2021 ◽

Vol 9 ◽

Author(s):

Esther Ciarrocchi ◽

Sara Saponaro ◽

Francesco Bartoli ◽

Angela Gabriella Cataldi ◽

Sara Vitali ◽

...

Keyword(s):

Signal To Noise Ratio ◽

Detection Limits ◽

In Vitro Study ◽

Surgical Margins ◽

Clinical Protocol ◽

Luminescence Imaging ◽

Cerenkov Luminescence Imaging ◽

Ct Data ◽

The Impact

Cerenkov luminescence imaging (CLI) has been recently proposed as a method to visualize surgical margins in the operating theater, immediately after resection, to allow refining surgery in a single procedure. Our group is preparing a pilot clinical study to evaluate the impact of CLI during hepatic metastasectomy, using 18F-FDG and 68Ga-DOTATOC. Currently, we are optimizing the clinical protocol in terms of patient inclusion criteria, activity to inject, maximum allowed delay for imaging, and radiation monitoring. This paper describes a preliminary study we have performed to define the clinical protocol. The study is composed of two branches: 1) an in-vitro study to predict the typical signals and optical attenuation in the liver with 18F and 68Ga, 2) an analysis of clinical PET/CT data to determine typical values of relevant parameters, such as uptake and lesion dimension. The combined information by these two branches gives us an indication of the feasibility of CLI for margin assessment in liver metastasectomy. For 68Ga, we obtained detection limits ranging from 0.55 to 3.5 kBq/cc, to be compared with minimum and mean clinical uptakes of 1.6 and 7 kBq/cc, respectively. For 18F, the detection limits ranged from 12 to 145 kBq/cc, and the minimum and mean clinical uptakes were 5 and 11 kBq/cc, respectively. From these values, we expect CLI with 68Ga to be able to detect surgical margins in most patients, while with 18F the activities to inject for sufficient signal-to-noise ratio should be larger than standards, or the time delay between injection and imaging largely reduced. The results reported here can be useful also more in general, for studies dedicated to other CLI applications in the liver.

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