ASIAN JOURNAL OF PHYSICS

Optical Diagnostics: Bench to Bedside

Guest Editorial

            Optical diagnostics, also variously and interchangeably referred to as optical pathology, optical diagnosis, optical biopsy, spectral diagnosis, spectromics, describe applications of spectroscopic and/or optical based methods in disease diagnosis- one of the highly attractive, active and vigorously  pursued areas of biomedical applications of spectroscopy and optical methods. Conventionally, diseases are diagnosed by clinical examination followed by relevant biochemical/micorobiological/pathological/imaging investigations. Such approaches, relying on symptoms, are considered to diagnose an existing disease, could be a late diagnosis which often lead to  poor prognosis. Early stage diagnosis can almost always provide better prognosis. Since morphological changes could be rather late, diagnostics should be sensitive to biochemical changes happening much earlier, for early diagnosis. In this context, opical spectroscopy methods are being pursued as potential alternatives/adjuncts, mainly due to the attributes such as sensitivity to biochemical composition, less time consuming, no external labeling or sample processing, more objective, and most importantly feasible in vivo/in situ on line diagnosis. Laser-induced-fluorescene, FTIR, FT-Raman and diffuse reflectance are some of the most widely pursued optical methods. In the present issue articles are selected to showcase some of the latest development in disease diagnosis by optical spectroscopy methods – otpical diagnostics.

            As discussed earlier, objective diagnosis is one of the major attributes of optical diagnostics, besides noninvasive/in vivo/in situ applications. As spectral data are amenable mathematical data processing, multivariate analyses offer a suitable approach through various unsupervised and supervised methods in achieving objective and on line decision making. The opening paper ‘Disease diagnosis by optical spectroscopy: Role of multivariate analysis’ by N Tayal et al  reviews several data processing and preprocessing tools that are being widely employed, and also presents typical optical diagnostics protocols. This could be useful starting step for enthusiasts who like to venture into this promising field. Conventionally, experimental models, mostly rodents, have been used for development of diagnostics and therapeutics, especially in early phases or more commonly known as Proof-of-Concepts studies. In the case of optical diagnosis, ex vivo samples, tissues, or body fluids are also investigated to develop proof of concept. This can be attributed to the fact that spectral investigations are mostly non-interventional, unlike drug or other clinical trials. Accessibility, both ethical and practical point of view, of these samples could be other driving point. Nevertheless, there have been several pioneering spectroscopy based disease diagnosis studies on animal models. Therefore, it is pertinent to present the role of animal models in development of spectral diagnosis.  Hence the article entitled ‘Animal models in disease diagnosis: Raman spectroscopic explorations, by P Kumar and Murali Krishna  presents an overview, though limited to Raman spectroscopic studies, of this field. The ultimate aim/goal of optical pathology is noninvasive screening and diagnosis. Screening of oral cancer, most common among Indian and south Asian population, is a daunting task, from the logistic point of view. Higher incidence, large population, coupled with lack of reliable early diagnosis and screening, are known reasons for high mortality. In view of this, several groups have actively pursued spectral diagnostics using laser-induced-fluorscence, Raman and many other methods. The Manipal Group (India) of  Laser Spectroscopy, established by Prof  V B  Kartha, presently lead by Prof  C Santosh, is one of the pioneers in optical diagnostics applications, especially towards oral cancer screening and diagnosis. In their article, entitled ‘Optical Biopsy: Journey from laboratory system to rural health-care’, they share their observations and experiences in bench to bed-side translation towards rural set up. Another poineering laser spectroscopy group is one lead by Dr R Jaysree at Sree Chitra Tirunal Institute for Medical Sciences & Technology, Thiruvananthapuram, India. This group has been actively pursuing spectral diagnostic applications in several cancers, including oral, liver and brain. In the article ‘Pathological fingerprinting of tissue observed through the window of fluorescence spectroscopy’,  they overview cancer diagnosis using home-built fluorescence spectrometer, besides lucid description of fundamentals of spectroscopy. Raman spectroscopy is the other widely explored optical spectroscopy technique in disease diagnosis. Among cancers, treatment (surgery) of brain cancer is very critical and often tricky. As majority of these tumors are highly infiltrative gliomas, wherein demarcation of surgical margins are very crucial for better prognosis. Keeping importance of brain, conservative surgeries are often carried out leaving residual tumor, hence recurrence. There have been several Raman spectroscopic investigations reporting its utility. The article entitled ‘Raman spectroscopy in biomedical diagnosis: Brain cancers’ by Hole and Murali Krishna  summarizes  the literature on Raman spectroscopic explorations in brain cancers. Radiotherapy is the choice of treatment for many cancers such cervix and laropharynx, usually combination of surgery, radiotherapy, chemotherapy employed in a typical cancer thereapetuic regimen. Unfortuately radiation resistance is a major hurdle in radiotherapy. In the next article, Goyal et al describe basic mechanisms involved in radioresistance, assays to predict tumor radioresponse. Authors also provide insights on  emerging  optical based technologies in the article entitled ‘Mechanistics of tumour radioresistance and predictive techniques to assess tumour response’. Mutlimodal approach, i.e., two or more optical methods, is the other widely pursued approach in disease (cancer) diagnosis. Most commonly employed methods are combination of Raman + IR- complementary vibrational spectroscopy methods, fluorescence + diffused reflectance. There also exist several reports exploring combination of opical imaging tools such as OCT with spectroscopy tools.  In this context, the paper entitled ‘Multimodal spectroscopic applications in cancer diagnosis: Combined Raman spectroscopy and optical coherence tomography’, by P Kumar et al provides insights on combined Raman + OCT explorations in cancer diagnosis. These  authors also describe some of  their findings on hamster buccal pouch models. As mentioned earlier, there have been significant advancements in spectral diagnosis using less invasive samples such bodyfluids –plasma, serum, CSF, semen- and exfoliated cells. These explorations were  necessitated due to the fact that, though in vivo/in situ applications are very attractive and useful, they are limited by on-site instrumentation and rather stringent experimental requirements – controlled environment and a dark room. Such facilities may be difficult in rural areas of under developed and developing countries. On the other hand, body fluids such as serum and plasma are more easily accessible and transferable to centralized facilities. The article entitled ‘Serum Raman spectroscopy and applications in disease diagnosis by Sahu and Murali Krishna summarizes advancements in this area of research.

We would like to acknowledge the whole-hearted cooperation from all the authors who have contributed to this issue. Special mention goes to Prof V B Kartha for his suggestions. We gratefully acknowledge the help of Dr Dominque Bertrand, France, for his valuable suggestions and ideas in preparing the article entitled, ‘Disease Diagnosis by optical spectroscopy: Role of multivariate analysis’.

We would also like to express our sincere thanks to the Editor in Chief  of Asian journal of Physics, Prof Vinod Rastogi for giving me the opportunity to edit and his  enthusiasm in presenting this special issue to the scientific community during International Year of Light. Finally, thanks are due to Er Manoj Kumar, Managing Editor AJP, for preparing the Press Copy of the articles.

June 30, 2015

C Murali Krishna