Chemical imaging of human teeth by a time-resolved Raman spectrometer based on a CMOS single-photon avalanche diode line sensor

Kekkonen, Jere; Finnilä, Mikko A. J.; Heikkilä, Jarkko; Anttonen, Vuokko; Nissinen, Ilkka

doi:10.1039/c9an01136f

Cited by 17 publications

(20 citation statements)

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“…Time-gated SPAD Raman acquisition times of 29 s using pulsed laser repetition rates of 350 kHz compared with 0.17 s using a conventional CW Raman system have been reported [7]. CW Raman spectrum acquisition times of less than 10 ms have been reported with high quantum efficiency electron multiplying charge coupled device detectors [8,9].…”

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confidence: 99%

Time-correlated single photon Raman spectroscopy at megahertz repetition rates

et al. 2021

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Significant improvements in time-correlated single photon counting (TCSPC) Raman spectroscopy acquisition times can be achieved through exploitation of megahertz (MHz) laser repetition rates. We have developed a TCSPC Raman spectroscopy system based on a high peak power ( > 40 W ) pulsed laser, a high pulse repetition rate (40 MHz), a custom f / 1.5 spectrometer, and a 512 spectral channel × 16 time bin single photon avalanche diode line sensor. We report millisecond Raman spectrum acquisition times, a peak Raman count rate of 104 kcps, and a linewidth aggregated count rate of 440 kcps with a diamond sample. This represents a three-order-of-magnitude increase in measured Raman count rate in comparison with a 104 kHz pulsed laser operating at 300 W and a four-order-of-magnitude increase over a 0.1 W pulsed laser operating at 40 MHz. A Raman-to-fluorescence ratio of 4.76 is achieved with a sesame oil sample at a 20 MHz repetition rate. Achieving high count rates and Raman-to-fluorescence ratios unlocks the potential of combined Raman/fluorescence lifetime spectroscopy for imaging and other short acquisition time applications.

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confidence: 99%

Time-correlated single photon Raman spectroscopy at megahertz repetition rates

et al. 2021

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“…CMOS SPAD based time-resolved Raman spectrometers have already been successfully applied to mineral identification and chemical imaging of human teeth, for example. In both cases, fluorescence suppression due to time gating has been appropriate, but the timing skew of the line sensor has been one of the main factors limiting the performance of the spectrometer [28], [45]. The obtained results are important, because they show that with a well-designed line sensor and suitable postprocessing steps, the effective timing skew can be pushed from tens of picoseconds to picosecond level.…”

Section: Discussionmentioning

confidence: 99%

Time-Resolved Raman Spectrometer With High Fluorescence Rejection Based on a CMOS SPAD Line Sensor and a 573-nm Pulsed Laser

Talala

Kaikkonen

Keränen

et al. 2021

IEEE Trans. Instrum. Meas.

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A time-resolved Raman spectrometer is demonstrated based on a 256×8 CMOS SPAD line sensor and a 573 nm fiber-coupled diamond Raman laser delivering pulses with duration below 100 ps FWHM. The collected back scattered light from the sample is dispersed on the line sensor using a custom volume holographic grating having 1800 lines/mm. Efficient fluorescence rejection in the Raman measurements is achieved due to a combination of time gating on sub-100 ps-time scale and a 573 nm excitation wavelength. To demonstrate the performance of the spectrometer, fluorescent oil samples were measured. For organic sesame seed oil having a continuous wave mode fluorescence-to-Raman ratio of 10.5 and a fluorescence lifetime of 2.7 ns, a signal-to-distortion value of 76.2 was achieved. For roasted sesame seed oil having a continuous wave mode fluorescence-to-Raman ratio of 82 and a fluorescence lifetime of 2.2 ns, a signal-to-distortion value of 28.2 was achieved. In both cases, the fluorescence-to-Raman ratio was reduced by a factor of 24-25 owing to time gating. For organic oil, spectral distortion was dominated by dark counts while for the more fluorescent roasted oil, the main source of spectral distortion was timing skew of the sensor. With the presented post-processing techniques, the level of distortion could be reduced by 88-89 % for both samples. Compared to common 532 nm excitation, approximately 73 % lower fluorescence-to-Raman ratio was observed for 573 nm excitation when analyzing the organic sesame seed oil. Index Terms-Fluorescence rejection, Raman laser, Raman spectrometer, Raman spectroscopy, SPAD sensor, time-correlated single photon counting, time gating, timing skew I. INTRODUCTION AMAN spectroscopy is used in a wide range of fields including food and oil industries, mining industry, medical diagnostics, pharmacy, forensic science and archaeometry [1]

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“…Since previous literature on enamel mineralization is contradictory, our results provide much-needed validity to these observations. In our proof-of-concept study, we imaged human teeth using a time-resolved CMOS SPAD-based Raman spectrometer and analyzed Raman chemical image maps (step size: 250 μm) 19 . The fluorescence suppressed time-resolved Raman spectrometer can be used to rapidly acquire comparable spectra with the continuous wave Raman spectroscopy.…”

Section: Discussionmentioning

confidence: 99%

“…This method utilized the fact that there is a reduction in polarization anisotropy of certain peaks in the Raman spectra from the caries lesion. In our previous proof-of-concept study with a time-resolved complementary-metal-oxide-semiconductor (CMOS) singlephoton-avalanche-diodes (SPADs) based Raman spectrometer, we have demonstrated that the fluorescence-suppressed Raman spectrometers have the potential to be used in the clinical settings 19 . Although the time-resolved Raman spectroscopy holds great potential, detailed mapping has remained challenging.…”

Section: Introductionmentioning

confidence: 99%

Mineralization of dental tissues and caries lesions detailed with Raman microspectroscopic imaging

Killenberger

Tanner

et al. 2021

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Chemical imaging of human teeth by a time-resolved Raman spectrometer based on a CMOS single-photon avalanche diode line sensor

Abstract: Improvement to the spectral quality of Rama images of human teeth were achieved with a time-resolved CMOS SPAD-based Raman spectrometer.

Cited by 17 publications

References 36 publications

Time-correlated single photon Raman spectroscopy at megahertz repetition rates

Time-correlated single photon Raman spectroscopy at megahertz repetition rates

Time-Resolved Raman Spectrometer With High Fluorescence Rejection Based on a CMOS SPAD Line Sensor and a 573-nm Pulsed Laser

Mineralization of dental tissues and caries lesions detailed with Raman microspectroscopic imaging

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