Haishan Zeng

Rapid near-infrared Raman spectroscopy system for real-time in vivo skin measurements.

A rapid dispersive-type near-infrared (NIR) Raman spectroscopy system and a Raman probe were developed to facilitate real-time, noninvasive, in vivo human skin measurements. Spectrograph image aberration was corrected by a parabolic-line fiber array, permitting complete CCD vertical binning, thereby yielding a 3.3-16-fold improvement in signal-to-noise ratio. Good quality in vivo cutaneous NIR Raman spectra free of interference from fiber fluorescence and silica Raman scattering can be acquired in less than 1 s, which greatly facilitates practical noninvasive tissue characterization and clinical diagnosis.

Integrated endoscopy system for simultaneous imaging and spectroscopy for early lung cancer detection.

An integrated endoscopy system for simultaneous imaging and spectroscopy was developed to facilitate more accurate and convenient detection of early lung cancers. A specially designed three-CCD camera in combination with a dedicated light source permits capture of both white-light color images and tissue autofluorescence images without the need to switch between two different cameras. A mirror with an optical fiber at its center, placed at an interim imaging plane inside the camera unit, facilitates simultaneous imaging and spectroscopy measurements in either white-light reflectance mode or fluorescence mode. The system has been successfully tested in a clinic, demonstrating a practical approach to improve both diagnostic sensitivity and specificity at the same time.

In vivo assessment and evaluation of lung tissue morphologic and physiological changes from non-contact endoscopic reflectance spectroscopy for improving lung cancer detection

We present a method for lung cancer detection exploiting reflectance spectra measured in vivo during endoscopic imaging of the lung. The measured reflectance spectra were analyzed using a specially developed light-transport model to obtain quantitative information about cancer-related, physiological, and morphologic changes in the superficial bronchial mucosa layers. The light-transport model allowed us to obtain the absorption coefficient (mua) and further to derive the micro-vascular blood volume fraction in tissue and the tissue blood oxygen saturation. The model also allowed us to obtain the scattering coefficient (mus) and the anisotropy coefficient (g) and further to derive the tissue scattering micro-particle volume fraction and size distribution. The specular component of the reflectance signal and the instrument response were accounted for during the analysis. The method was validated using 100 reflectance spectra measured in vivo in a noncontact fashion from 22 lung patients (50 normal tissue/benign lesion sites and 50 malignant lesion sites). The classification between normal tissue/benign lesions and malignant lesions was further investigated using the derived quantitative parameters and discriminant function analysis. The results demonstrated significant differences between the normal tissue/benign lesions and the malignant lesions in terms of tissue blood volume fraction, blood oxygen saturation, tissue scatterer volume fractions, and size distribution. The results also showed that the malignant lung lesions can be differentiated from normal tissue/benign lesions with both diagnostic sensitivity and specificity of better than 80%.

Autofluorescence properties of skin and applications in dermatology

Skin autofluorescence was observed as early as 1908. Its applications in dermatology was first reported in 1925- the use of Woods lamp for the detection of fungal infection. In the first part of the paper, a historical review was presented on skin autofluorescence properties. In the second part, systematic research done in out laboratory on autofluorescence properties of normal and diseased skin was summarized. We developed three tools for the study: 1) a compact fiber optic spectrometer for in vivo macroscopic fluorescence spectral measurements on volunteers and patients; 2) a CCD camera based fluorescence imaging for in vivo macroscopic imaging of 2D fluorescence intensity distributions over various skin diseases; 3) a fiber optic microspectrophotometer (MSP) system for in vitro microscopic fluorescence spectral measurements and fluorescence imaging of frozen tissue sections. With these tools, we obtained the excitation-emission matrices (EEMs) of in vivo normal skin, the temporal dynamics of skin autofluorescence decay under continuous wave laser exposure, and fluorescence spectra of 1500 lesions from 600 patients spanning 35 disease types. Monte Carlo simulation has been employed to explain the autofluorescence decay dynamics and to reconstruct the in vivo spectra from in vitro microscopic fluorophore distribution and intrinsic fluorescence spectra of various skin structures. Spectral feature based linear discrimination function analysis and principal components decomposition analysis are performed to assess the potential of autofluorescence spectroscopy for skin cancer detection. Clinical test of a fluorescence scope system for skin cancer margin delineation is under way.

Intrinsic fluorescence spectroscopy for endoscopic detection and localization of the endobronchial cancerous lesions.

Fluorescence spectroscopy contains diagnostic information about the lung biochemistry and morphology, including tissue optical properties and fluorophores. However, the fluorophore information is generally masked by the optical properties of the tissue, which complicates the evaluation of their role in lung-cancer detection. In this work, we have developed a method for extracting the intrinsic fluorescence spectra from the endoscopic measurements of the combined fluorescence and reflectance spectra. Principle components and classification analysis was performed to evaluate the diagnostic potential of the extracted intrinsic fluorescence spectra from in vivo combined fluorescence and reflectance spectral measurements. We evaluated the diagnostic sensitivity and specificity of both the intrinsic fluorescence and the fluorescence spectra. The results showed that the intrinsic fluorescence spectra contain significant diagnostic information that had been masked by the lung optical properties. We have also found that the intrinsic fluorescence has improved the specificity for endobronchial-cancer detection, although with a slight decrease in the detection sensitivity, when compared to the fluorescence spectra. This may indicate that intrinsic fluorescence analysis could be used to improve the diagnostic specificity of fluorescence spectroscopy and imaging.

Characterization and application of chirped photonic crystal fiber in multiphoton imaging

Fiber delivery of ultrashort pulses is important for multiphoton endoscopy. A chirped photonic crystal fiber (CPCF) is first characterized for its transmission bandwidth, propagation loss, and dispersion properties. Its extremely low dispersion (~150u2009fs(2)/m) enables the delivery of sub-30 fs pulses through a ~1 m-long CPCF. The CPCF is then incorporated into a multiphoton imaging system and its performance is demonstrated by imaging various biological samples including yew leaf, mouse tendon, and human skin. The imaging quality is further compared with images acquired by a multiphoton imaging system with free-space or hollow-core photonic band-gap fiber (PBF) delivery of pulses. Compared with free-space system, the CPCF delivered system maintains the same ultrashort pulsewidth and the image qualities are comparable. Compared with the PBF delivery, CPCF provides a 35 times shorter pulsewidth at the sample location, which results in a ~12 and 50 times improvement in two-photon excitation fluorescence (TPEF) and second harmonic generation (SHG) signals respectively. Our results show that CPCF has great potential for fiber delivery of ultrashort pulses for multiphoton endoscopy.

Aggregation of nanoparticles in endosomes and lysosomes produces surface-enhanced Raman spectroscopy

Abstract. The purpose of this study was to explore the use of surface-enhanced Raman spectroscopy (SERS) to image the distribution of epidermal growth factor receptor (EGFR) in cells. To accomplish this task, 30-nm gold nanoparticles (AuNPs) tagged with antibodies to EGFR (1012u2009u2009peru2009mL) were incubated with cells (106u2009u2009peru2009mL) of the A431 human epidermoid carcinoma and normal human bronchial epithelial cell lines. Using the 632.8-nm excitation line of a He-Ne laser, Raman spectroscopy measurements were performed using a point mapping scheme. Normal cells show little to no enhancement. SERS signals were observed inside the cytoplasm of A431 cells with an overall enhancement of 4 to 7 orders of magnitude. Raman intensity maps of the 1450 and 1583u2009u2009cm−1 peaks correlate well with the expected distribution of EGFR and AuNPs, aggregated following uptake by endosomes and lysosomes. Spectral features from tyrosine and tryptophan residues dominate the SERS signals.

Improvements to a laser Raman spectroscopy system for reducing the false positives of autofluorescence bronchoscopies

Preneoplastic lesions of the bronchial tree have a high probability of developing into malignant tumours. Currently the best method for localizing them for further treatment is a combined white light and autofluorescence bronchoscopy (WLB+AFB). Unfortunately the average specificity from large clinical trials for this combined detection method is low at around 60%, which can result in many false positives. However a recent pilot study showed that adding a point laser Raman spectroscopy (LRS) measurement improved the specificity of detecting lesions with high grade dysplasia or carcinoma in situ to 91% with a sensitivity of 96% compared to WLB+AFB alone. Despite this success, there is still room for much improvement. One constant need is to find better ways to measure the inherently weak Raman emissions in vivo which will result in even better diagnostic sensitivity and specificity. With this aim in mind a new generation Raman system was developed. The system uses the latest charge coupled device (CCD) with low noise, and fast cool down times. A spectrometer was incorporated that was able to measure both the low and high frequency Raman emissions with high resolution. The Raman catheter was also redesigned to include a visible light channel to facilitate the accurate indication of the area being measured. Here the benefits in the adjunct use of LRS to WLB + AFB are presented, and description of the new system and the improvements it offers over the old system are shown.

Recent Advances in Real-Time Raman Spectroscopy for In Vivo Skin Cancer Diagnosis

A large-scale clinical study established that real-time Raman spectroscopy n could distinguish malignant from benign skin lesions with good diagnostic accuracy. n Recent independent skin cancer Raman measurement validated previous n findings.

In Vivo Real-time Endoscopic Raman Spectroscopy for Improving Early Lung Cancer Detection

A real-time endoscopic Raman spectroscopy system has been developed that takes 1 second to obtain a spectrum from the human lung in vivo. The system was tested on 80 patients, achieved high diagnostic sensitivity (90%) and good specificity (65%) for lung cancer/precancer detection.