Observing temporal variation in hemolysis through photoacoustics with a low cost LASER diode based system

Continuous monitoring of total hemoglobin (THb) for the patients suffering from hematological or non-hematological diseases, snake bite, going through surgeries etc., finds immense clinical importance since Hb transports oxygen to the living tissues while being encapsulated within a red blood cell (RBC). Several techniques based on the electrical or chemical and or optical measurements have already been developed to determine total hemoglogin (THb) in blood. Many of them are clinically practiced. But, the very first step of processing which is common to all of them requires extraction of blood sample through venipuncture. That process is invasive, needs trained professional. A non-invasive, real-time, diagnostic tool is rather preferred especially for repeated testing. Having above two capabilities, a photoacoustic (PA) system with near-infrared illumination was previously proposed for THb determination. But a recent study on hemolysis monitoring with a low-cost NIR-PA system suggests that THb determination through NIR-PA requires apriori knowledge of hemolysis status of the sample. The question therefore remains if PA is at all suitable for this purpose. Additionally, in order to become more accessible to the patients, any such device must be portable, ergonomic and cost effective enough, which, in PA, rejects the use of bulky, expensive Nd:YAG or dye LASERs, leaving the power of the optical source limited. The present study reports a high-power LED based low-cost PA system with blue (456.5 nm) illumination that enables PA to determine total hemoglobin in blood irrespective of hemolysis status.

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Quantitative evaluation of the impact of variation of optical parameters on the estimation of blood hematocrit and oxygen saturation for dual-wavelength photoacoustics

Paul,

Patel,

Saha

2024

J. Opt. Soc. Am. A

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Photoacoustic (PA) spectroscopy is considered to be one of the most effective ways to measure the levels of hematocrit (H) and oxygenation saturation (SO2) of blood, which are essential for diagnosing blood-related illnesses. This simulation study aims to investigate the impact of individual optical parameters, i.e., optical absorption coefficient (μ a ), scattering coefficient (μ s ), and anisotropy factor (g), on the accuracy of this technique in estimating the blood properties. We first performed the Monte Carlo simulations, using realistic optical parameters, to obtain the fluence maps for various samples. The wavelengths of the incident light were chosen to be 532, 700, 1000, and 1064 nm. Thereafter, the k-Wave simulations were executed, incorporating those fluence maps to generate the PA signals. The blood properties were obtained using the PA signals. We introduced variations in μ a , μ s , and g ranging from −10% to +10%, −10% to +10%, and −5% to +1%, respectively, at 700 and 1000 nm wavelengths. One parameter, at both wavelengths, was changed at a time, keeping others fixed. Subsequently, we examined how accurately the blood parameters could be determined at physiological hematocrit levels. A 10% variation in μ a induces a 10% change in H estimation but no change in SO2 determination. Almost no change has been seen for μ s variation. However, a 5% (−5% to 0%) variation in the g factor resulted in approximately 160% and 115% changes in the PA signal amplitudes at 700 and 1000 nm, respectively, leading to ≈125% error in hematocrit estimation and ≈14% deviation in SO2 assessment when nominal SO2=70%. It is clear from this study that the scattering anisotropy factor is a very sensitive parameter and a small change in its value can result in large errors in the PA estimation of blood properties. In the future, in vitro experiments with pathological blood (inducing variation in the g parameter) will be performed, and accordingly, the accuracy of the PA technique in quantifying blood H and SO2 will be evaluated.

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Observing temporal variation in hemolysis through photoacoustics with a low cost LASER diode based system

Cited by 3 publications

References 40 publications

Numerical and in vitro experimental studies for assessing the blood hematocrit and oxygenation with the dual-wavelength photoacoustics

Numerical and in vitro experimental studies for assessing the blood hematocrit and oxygenation with the dual-wavelength photoacoustics

Determining total hemoglobin in blood irrespective of hemolysis status using a high-power LED-based low-cost photoacoustic system

Quantitative evaluation of the impact of variation of optical parameters on the estimation of blood hematocrit and oxygen saturation for dual-wavelength photoacoustics

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