J. Biophotonics 1–19 (2014) / DOI 10.1002/jbio.201400026
REVIEW ARTICLE
Real-time in vivo cancer diagnosis using raman spectroscopy Wenbo Wang1, 2, Jianhua Zhao1, 2, Michael Short1, and Haishan Zeng*, 1, 2 Imaging Unit – Integrative Oncology Department, British Columbia Cancer Agency Research Centre, 675 West 10th Avenue, Vancouver, B.C., V5Z 1L3, Canada 2 Photomedicine Institute, Department of Dermatology and Skin Science, University of British Columbia and Vancouver Coastal Health Research Institute, Vancouver, BC, Canada 1
Received 6 March 2014, revised 25 July 2014, accepted 12 August 2014 Published online 12 September 2014
Key words: Raman spectroscopy, cancer detection, clinical instrumentation, optic fiber probe, spectrometer, chemometrics
Raman spectroscopy has becoming a practical tool for rapid in vivo tissue diagnosis. This paper provides an overview on the latest development of real-time in vivo Raman systems for cancer detection. Instrumentation, data handling, as well as oncology applications of Raman techniques were covered. Optic fiber probes designs for Raman spectroscopy were discussed. Spectral data pre-processing, feature extraction, and classification between normal/benign and malignant tissues were surveyed. Applications of Raman techniques for clinical diagnosis for different types of cancers, including skin cancer, lung cancer, stomach cancer, oesophageal cancer, colorectal cancer, cervical cancer, and breast cancer, were summarized. Schematic of a real-time Raman spectrometer for skin cancer detection. Without correction, the image captured on CCD camera for a straight entrance slit has a curvature. By arranging the optic fiber array in reverse orientation, the curvature could be effectively corrected.
1. Introduction Abnormal alterations in cellular structures and biochemical compositions in tumor stromal microenvironment lead to stipulated tumor growth. The various types of cells within tumor stroma, though not all of them are malignant, have biochemical and physical properties different from normal tissues,
which result in modified tissue optics. Raman spectroscopy measures the fundamental modes of molecular vibrations via light tissue interactions. Most molecular cancer biomarkers, e.g., proteins, nucleic acids, lipids, and carbohydrates, are responsive to Raman scattering process [1]. Raman technique is also sensitive to structural changes such as nuclear enlargement, a histological signature of carcinoma,
* Corresponding author: e-mail: [email protected], Phone: 604-675-8083; Fax: 604-675-8099
© 2014 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
2
W. Wang et al.: Real-time in vivo cancer diagnosis using Raman spectroscopy
and phase transitions [2]. Different imaging and spectroscopy technologies have achieved varying degree of success for early cancer diagnosis. Raman spectroscopy has been heralded as a most promising molecular tool for clinical diagnosis of cancer [3, 4]. The following summarizes the main advantages that enable Raman spectroscopy for real-time tissue characterization in vivo.
1.1 Endogenous molecular specificity Computed tomography (CT) and magnetic resonance imaging (MRI) provide 3-D anatomy images and are good for late stage (large size) tumor detection. Advanced hybrid imaging techniques such as positron emission tomography (PET)/CT can perform molecular imaging using exogenous biomarkers [5]. Magnetic resonance spectroscopy (MRS) provides more detailed information on tissue biochemistry but with limited clinical use. However, these traditional medical imaging modalities are not optimal for the examination of epithelial tissues, where more than 80% of early cancer arises [6, 7]. Optical imaging and spectroscopic techniques have limited penetration, but are ideal for interrogating the surface epithelial tissues for early cancer detection. Optical techniques such as diffuse reflectance spectroscopy (DRS), auto-fluorescence spectroscopy (AFS), and auto-fluorescence imaging provide a non-destructive and exogenous agent-free tissue sensing [8]. While autofluorescence imaging, DRS, and AFS are able to significantly improve sensitivity of intraepithelial neoplasia detection, the diagnostics specificities are mediocre [9]. Spectral similarities between precancerous tissues and benign abnormalities such as inflammation can partially explain the decreased specificity, which could also be a big hurdle to overcome for successful clinical implementation of DRS and AFS [10, 11]. Raman spectroscopy provide high molecular specificity, thus holds the potential to reduce the false positive rates in clinical diagnostics [12].
1.2 Minimally invasive in vivo diagnostics Both Raman and Fourier transform infrared (FTIR) spectroscopy are useful for cancer diagnostics [13]. So far, limited success has achieved using FTIR for in vivo diagnostics of human tissues, mostly on skin [14–17]. The lack of research activities in FT-IR is mainly technical. Strong water absorption in the IR complicates IR measurements of tissue absorption, which has more than 70% water content [18]. Samples need to be either prepared in thin slices (
REVIEW ARTICLE
Real-time in vivo cancer diagnosis using raman spectroscopy Wenbo Wang1, 2, Jianhua Zhao1, 2, Michael Short1, and Haishan Zeng*, 1, 2 Imaging Unit – Integrative Oncology Department, British Columbia Cancer Agency Research Centre, 675 West 10th Avenue, Vancouver, B.C., V5Z 1L3, Canada 2 Photomedicine Institute, Department of Dermatology and Skin Science, University of British Columbia and Vancouver Coastal Health Research Institute, Vancouver, BC, Canada 1
Received 6 March 2014, revised 25 July 2014, accepted 12 August 2014 Published online 12 September 2014
Key words: Raman spectroscopy, cancer detection, clinical instrumentation, optic fiber probe, spectrometer, chemometrics
Raman spectroscopy has becoming a practical tool for rapid in vivo tissue diagnosis. This paper provides an overview on the latest development of real-time in vivo Raman systems for cancer detection. Instrumentation, data handling, as well as oncology applications of Raman techniques were covered. Optic fiber probes designs for Raman spectroscopy were discussed. Spectral data pre-processing, feature extraction, and classification between normal/benign and malignant tissues were surveyed. Applications of Raman techniques for clinical diagnosis for different types of cancers, including skin cancer, lung cancer, stomach cancer, oesophageal cancer, colorectal cancer, cervical cancer, and breast cancer, were summarized. Schematic of a real-time Raman spectrometer for skin cancer detection. Without correction, the image captured on CCD camera for a straight entrance slit has a curvature. By arranging the optic fiber array in reverse orientation, the curvature could be effectively corrected.
1. Introduction Abnormal alterations in cellular structures and biochemical compositions in tumor stromal microenvironment lead to stipulated tumor growth. The various types of cells within tumor stroma, though not all of them are malignant, have biochemical and physical properties different from normal tissues,
which result in modified tissue optics. Raman spectroscopy measures the fundamental modes of molecular vibrations via light tissue interactions. Most molecular cancer biomarkers, e.g., proteins, nucleic acids, lipids, and carbohydrates, are responsive to Raman scattering process [1]. Raman technique is also sensitive to structural changes such as nuclear enlargement, a histological signature of carcinoma,
* Corresponding author: e-mail: [email protected], Phone: 604-675-8083; Fax: 604-675-8099
© 2014 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
2
W. Wang et al.: Real-time in vivo cancer diagnosis using Raman spectroscopy
and phase transitions [2]. Different imaging and spectroscopy technologies have achieved varying degree of success for early cancer diagnosis. Raman spectroscopy has been heralded as a most promising molecular tool for clinical diagnosis of cancer [3, 4]. The following summarizes the main advantages that enable Raman spectroscopy for real-time tissue characterization in vivo.
1.1 Endogenous molecular specificity Computed tomography (CT) and magnetic resonance imaging (MRI) provide 3-D anatomy images and are good for late stage (large size) tumor detection. Advanced hybrid imaging techniques such as positron emission tomography (PET)/CT can perform molecular imaging using exogenous biomarkers [5]. Magnetic resonance spectroscopy (MRS) provides more detailed information on tissue biochemistry but with limited clinical use. However, these traditional medical imaging modalities are not optimal for the examination of epithelial tissues, where more than 80% of early cancer arises [6, 7]. Optical imaging and spectroscopic techniques have limited penetration, but are ideal for interrogating the surface epithelial tissues for early cancer detection. Optical techniques such as diffuse reflectance spectroscopy (DRS), auto-fluorescence spectroscopy (AFS), and auto-fluorescence imaging provide a non-destructive and exogenous agent-free tissue sensing [8]. While autofluorescence imaging, DRS, and AFS are able to significantly improve sensitivity of intraepithelial neoplasia detection, the diagnostics specificities are mediocre [9]. Spectral similarities between precancerous tissues and benign abnormalities such as inflammation can partially explain the decreased specificity, which could also be a big hurdle to overcome for successful clinical implementation of DRS and AFS [10, 11]. Raman spectroscopy provide high molecular specificity, thus holds the potential to reduce the false positive rates in clinical diagnostics [12].
1.2 Minimally invasive in vivo diagnostics Both Raman and Fourier transform infrared (FTIR) spectroscopy are useful for cancer diagnostics [13]. So far, limited success has achieved using FTIR for in vivo diagnostics of human tissues, mostly on skin [14–17]. The lack of research activities in FT-IR is mainly technical. Strong water absorption in the IR complicates IR measurements of tissue absorption, which has more than 70% water content [18]. Samples need to be either prepared in thin slices (
