In the field of clinical instrumentation and life science research, sensing and optical spectroscopy perform vital roles in a range of applications. Optical spectroscopy offers an optimal method for real-time analysis and non-destructive sampling in vivo or in the laboratory.
For these applications, the instrumentation requirements have quickly progressed in recent years with the increase in demand for lower and lower detection-limit systems, the advent of wearable diagnostic systems, and the development of point of care devices.
The performance, cost, and size of instruments are of significant importance for these areas, commonly with mutually exclusive specifications. The significance of the enabling fiber optic technologies, which offer micro-scale sampling on synthesized matrices, tissues, and bodily fluids employed in life sciences cannot be overlooked.
This article outlines human life science applications for optical spectroscopy with a focus on biotechnology, clinical care, and research.
Clinical Care Optical Spectroscopy
Smart Biopsy/Endoscopy
The concept of a smart endoscopy or biopsy today may refer to the use of an endoscopy or biopsy procedure to acquire more detailed information from these invasive practices, which can support diagnostic procedures.
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The smart biopsy of the future aims to design a minimally-invasive and fast diagnostic tool that, when used in a clinical environment, can decrease the amount of unnecessary conventional invasive biopsies and can enhance the treatment and early detection of a range of conditions in the developing world.
Smart endoscopies and biopsies may integrate fluorescence or tissue reflection measurements with the hardware employed to carry out these procedures. The acquisition of the spectroscopic data during the procedure heavily relies on fiber optics.
The demands of this application are complex, usually requiring both high sensitivity and high speed. The AvaSpec-HS2048XL-EVO from Avantes has been effectively used to support these applications.
High-speed sampling capabilities and high sensitivity detection are both offered by this instrument. The instrument’s high sensitivity 0.22 numerical aperture optical bench is integrated with cutting-edge electronics that provide the acquisition of samples in as little as a few milliseconds.
Real-World Application Development for Smart Biopsy Technology
Cancer treatment outcomes across the globe are frequently related to early treatment and detection. Cancers like oral cancers, cervical cancer, colorectal cancer, and prostate cancer have all been the focus of research into the utilization of diffuse reflectance spectroscopy (DRS) for the accurate and rapid identification of cancer.
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Early treatment and detection in the developed world have led to a reduction in fatality rates for epithelial cancers, but current diagnostic equipment for carrying out DRS is bulky, expensive, and requires a high power output. Highly trained personnel are also required.
These challenges mean that low to middle-income countries has excessively high mortality rates for these cancers because of the scarcity of diagnostic instrumentation. The production of an easy-to-use, inexpensive, portable, and most crucially, effective diagnostic tool for the detection of epithelial cancers, would save lives internationally.
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In the last few years, research has focused on solving the challenges encountered when designing a dependable portable DRS system.
Two of those issues are the lack of a reliable way to perform a real-time calibration in the field and the inability to standardize the pressure applied to the probe when manually performing tests. These are two possible sources for serious user error, which increase the risk of test results being highly variable.
One possible solution is to integrate a self-calibrating channel with a unique probe design that furnishes the probe tip with an optical pressure sensor which only facilitates data acquisition when the pressure of the probe falls within a predetermined range.
The self-calibration and pressure sensor elements increase the efficacy and accuracy of clinical deployment and decrease the requirement for advanced operator training (Yu et al. 2014).
The system developed for this research includes the smart fiber-optic probe with a pressure sensor that combines a self-calibration channel and a tissue-sensing channel.
This is coupled to 850 nm LED light sources and a high-powered white LED, along with a three-channel AvaSpec-2048 series array spectrometer and a computer with the Matlab and LabView software programs installed for analysis.
Two visible channels (A & B) with a resolution of 1.8 nm and spanning a wavelength range 400-635 nm are coupled to the white LED and deployed for self-calibration (SC) and Diffuse Reflection Spectroscopy (DRS). The optical pressure sensor uses channel C, with a 0.23 nm resolution and covering the NIR range from 750-932 nm range, which was coupled to the 850 nm LED.
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The traditional technique for the identification and detection of colorectal cancer is visual inspection through endoscopy utilizing white light. Colorectal carcinoma usually follows predictable phases of neoplastic transformation which, in turn, results in variations to the optical features of transformed cells.
The early phases of cellular defects in mucosal linings cannot be detected using conventional white-light endoscopy, while fluorescence spectroscopy provides a highly sensitive tool to identify early modifications to the physical characteristics of abnormal cells (Horak 2006).
According to the cellular environment, spectral features may display an autofluorescence response, ranging from 510-560 nm in healthy cells toward the red at 630-690 nm, in relation to the number of abnormal tissues.
The AvaSpec-2048 (now replaced by the AvaSpec-ULS2048CL-EVO) is the ideal system constructed for this research application, detecting 560-800 nm with a direct attach filter holder.
Additional studies have applied NIR spectroscopy by utilizing a dual-channel spectrometer system including the AvaSpec-NIR256-2.5-HSC NIRLine and the AvaSpec-ULS2048L spectrometers for the identification of oral cancer biomarkers in saliva (Hurskainen 2019).
In a further study, research partners in the Netherlands and Iran used the AvaLight-Hal-S halogen light source with the AvaSpec-2048-USB2 (now replaced by the AvaSpec-ULS2048CL-EVO) spectrometer to apply single fiber reflectance spectroscopy for the identification of cervical premalignancy. The possibility to decrease the number of unnecessary biopsies is realized by this non-invasive technique (Tabrizi 2013).
Blood Perfusion
The volume of blood flowing through a mass or given volume of tissue is described by the term blood perfusion. It can be quantified in units of ml/ml/sec or ml/100 g/min which signifies the amount of local blood flowing through extracellular spaces in the tissue and the capillary network.
This parameter is a crucial medical diagnostic procedure for the determination of pathological and normal physiologies. For example, sufficient post-operative blood perfusion is required to determine the viability of a tissue transplant.
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Blood perfusion is measured using a technique known as Diffuse Correlation Spectroscopy (DCS) where the scatter of emitted photons is treated as a function of the motion of cells inside a target volume (Bi et al. 2015).
This technique appears to be promising for wearable spectroscopy systems that enable real-time monitoring of tissue health. The AvaSpec-Mini2048CL is the optimal component for such a system.
Pulse Oximetry
Anyone who has visited a medical facility will have experienced pulse oximetry technology, which delivers a real-time, painless, accurate measurement of pulsatile arterial blood levels from a fingertip measurement.
The majority of these devices comprise of two LEDs, one at 950 nm (near-infrared) and the other at 650 nm (visible), and two sensors which combine to quantify the oxygen absorbance (SPO2) from the ratios of deoxyhemoglobin and oxyhemoglobin.
While complete spectroscopic analysis and sampling are not needed, spectrometers are commonly employed in the qualification and validation of these tools and their subcomponents.
The AvaSpec-ULS2048Cl-EVO is perfectly suited to the application with its 2kHz sampling rates and 30 microsecond integration times, given the high-speed sampling requirements of this measurement.
Blood Gas Analysis – Co-Oximetry
Co-oximetry is the term for the spectroscopic method which facilitates the quantitative measurement of the blood parameters methemoglobin (MetHb), carboxyhemoglobin (COHb), deoxygenated hemoglobin (deoxy-Hb), and oxygenated hemoglobin (oxyHb) as a percentage of the total concentration of hemoglobin in a sample of blood.
While pulse oximetry measures oxygenated hemoglobin as a percentage of total hemoglobin, Co-oximetry divides and measures all of the hemoglobin types. A spectrometer with transmission or absorbance from 380 to 780 nm is traditionally used to measure these blood gas parameters.
Thermal stability and a significantly low stray light are required as specifications for the instrumentation in this application. Avantes has effectively deployed the AvaSpec-ULS2048CL-EVO and its subcomponent optical bench, the Avabench-75-ULS2048CL-U3, into clinical equipment for this application. For this purpose, the new AvaSpec-Mini2048CL is also an optimal choice.
Medical Research
Diffuse Reflection
At the Irvine Beckman Laser Institute, University of CA, researchers have utilized near-infrared spectroscopy not only to monitor and identify the reduction in cancer mass during chemotherapy treatments but also to characterize distinct histological features to predict the treatment response.
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Diffuse reflection spectroscopy measurements are inherently demanding of sensitivity and Avantes designed the AvaSpec-HS2048XL-EVO high sensitivity spectrometer specifically for this application type.
A large pixel detector and a 0.22 numerical aperture (NA) optical bench are featured on this instrument, facilitating the complete collection of the light received by a fiber optic of the same NA.
References and Further Reading
- Bi, Renzhe, et al. "Optical methods for blood perfusion measurement—theoretical comparison among four different modalities." JOSA A 32.5 (2015): 860-866.
- Horak, L., et al. "Auto-fluorescence spectroscopy of colorectal carcinoma: ex vivo study." Journal of Optoelectronics and Advanced Materials 8.1 (2006): 396.
- Hurskainen, Miia. "Attempt to Reliably Identify Oral Cancer Salivary Biomarkers Using Near-Infrared Spectroscopy and Savitzky-Golay Algorithm." DEStech Transactions on Engineering and Technology Research icicr (2019).
- Santoro, Ylenia, et al. "Breast cancer spatial heterogeneity in near-infrared spectra and the prediction of neoadjuvant chemotherapy response." Journal of biomedical optics 16.9 (2011): 097007.
- Tabrizi, Sanaz Hariri, et al. "Single fiber reflectance spectroscopy on cervical premalignancies: the potential for reduction of the number of unnecessary biopsies." Journal of biomedical optics 18.1 (2013): 017002.
- Yu, Bing, et al. "Diffuse reflectance spectroscopy of epithelial tissue with a smart fiber-optic probe." Biomedical optics express 5.3 (2014): 675-689.
About Avantes BV
Avantes is a leading innovator in the development and application of miniature spectrometers. To meet our customer’s application needs, Avantes continues to develop and introduce new instruments for fiber optic spectroscopy. Avantes instruments and accessories are also deployed in a variety of OEM applications and a variety of industries in markets throughout the world. With more than 18 years of experience in fiber optic spectroscopy and thousands of instruments in the field, Avantes is eager to help our customers find their Solutions in Spectroscopy®.
Techniques supported
- UV-VIS/NIR spectroscopy
- Process control
- Absorbance/transmittance/reflectance
- Laser-induced breakdown spectroscopy
- CIE color spectroscopy
- Portable spectrometers
- Fluorescence spectroscopy
- Custom applications
- lrradiance
- Raman spectroscopy
- OEM application development
Major products/services
Low-cost. high-resolution, miniature fiber optic spectrometers: System solutions and OEM instruments for applications from 185 nm to 2500 nm. Detector choices: PDA, CMOS, CCD, back-thinned CCD, and lnGaAs.
Optical benches with focal lengths of 45, SO or 75 mm; revolutionary new ultra-low straylight optimized optical bench (ULS) and a new high sensitivity optical bench.
Other features
- 14 and 16 bit AID converters
- TE cooling
- multi-channel instrument configurations enabling simultaneous signal acquisition
- USB2 communication support for multiple instruments from a single computer
- 14 programmable digital I/O ports
Standard application solutions
- lrradiance and LED measurements
- gemology
- hemometric analysis
- thin-film measurement
- color
- fluorescence
- laser-induced breakdown spectroscopy (LIBS)
- Raman spectroscopy
- process control
Light sources
- Tungsten-halogen
- Deuterium
- LED
- Xenon calibration sources for wavelength and irradiance
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