Terahertz (THz) pulsed spectroscopy is a convenient instrument for studying the THz dielectric response of healthy and abnormal tissue in a wide spectral range. One of the most promising applications of THz pulsed spectroscopy is associated with non-invasive, least-invasive and intraoperative medical diagnostics of malignancies in various localizations, including the skin, the breast, the colon, and the brain .
In our research, we developed a method for reconstructing the THz dielectric response of biotissues in vitro and in vivo using the THz pulsed spectroscopy [2–5]. We applied this method for studying healthy and pathological tissues of the skin and the brain.
(i) We observed statistical differences between THz dielectric properties of ordinary and dysplastic nevi of the skin in vivo. This highlights an ability for non-invasive early diagnosis of dysplastic nevi and melanomas of the skin using the THz spectroscopy and imaging [3–5].
(ii) By studying the THz dielectric permittivity of non-melanoma skin cancers in vitro (i.e. basal cell carcinoma and squamous cell carcinoma), we justify an ability for discriminating malignant tissues from surrounding normal skin using preoperative and intraoperative THz imaging [6,7].
(iii) Finally, the results of measuring the THz dielectric response of gelatin-fixed malignancies of the brain in vitro allow us to analyze an ability for discriminating brain gliomas from surrounding normal tissues during the neurosurgery using the THz technologies.
The observed results of THz measurements agrees well with the data of biotissues studying using other modern modalities of optical imaging, such as intraoperative exogenous fluorescence imaging and optical coherence tomography, as well as with the data of biotissue histology. These results highlight the prospective of THz spectroscopy, imaging and endoscopy use for non-invasive, least-invasive and intraoperative medical diagnosis of malignancies.
 O.A. Smolyanskaya,·M.M. Nazarov,·O.P. Cherkasova,·J.-P. Guillet,·J.-L. Coutaz, A.A. Konovko, Y.V.Kistenev,·P. Mounaix, I.A. Ozheredov, V.L. Vaks, A. Yaroslavsky,·N.V. Chernomyrdin, K.I. Zaytsev, S.A. Kozlov,·J.-H. Son, V. Wallace,·A.P. Shkurinov, ·V.V. Tuchin, “Terahertz biophotonics as a tool for studies of dielectricand spectral properties of tissues and bioliquids relatedto water content,” Progress in Quantum Electronics (2017, Submitted).
 IEEE Transactions on Terahertz Science and Technology 5(5), 817 (2015).
 Applied Physics Letters 106(5), 053702 (2015)
 European Journal of Cancer 51, S167 (2015).
 Optics and Spectroscopy 119(3), 404 (2015).
 Journal of Physics: Conference Series 486(1), 012014 (2014).
 Journal of Physics: Conference Series 584(1), 012023 (2015).
We have proposed a wavelet-domain de-noising technique for imaging of human brain malignant glioma by optical coherence tomography (OCT). It implies OCT image decomposition using the direct fast wavelet transform, thresholding of the obtained wavelet spectrum and further inverse fast wavelet transform for image reconstruction. By selecting both wavelet basis and thresholding procedure, we have found an optimal wavelet filter, which application improves differentiation of the considered brain tissue classes – i.e. malignant glioma and normal/intact tissue. Namely, it allows reducing the scattering noise in the OCT images and retaining signal decrement for each tissue class. Therefore, the observed results reveals the wavelet-domain de-noising as a prospective tool for improved characterization of biological tissue using the OCT.
We have performed the <i>in vitro</i> terahertz (THz) spectroscopy of human brain tumors. In order to fix tissues for the THz measurements, we have applied the gelatin embedding. It allows for preserving tissues from hydration/dehydration and sustaining their THz response similar to that of the freshly-excised tissues for a long time after resection. We have assembled an experimental setup for the reflection-mode measurements of human brain tissues based on the THz pulsed spectrometer. We have used this setup to study <i>in vitro</i> the refractive index and the amplitude absorption coefficient of 2 samples of malignant glioma (grade IV), 1 sample of meningioma (grade I), and samples of intact tissues. We have observed significant differences between the THz responses of normal and pathological tissues of the brain. The results of this paper highlight the potential of the THz technology in the intraoperative neurodiagnosis of tumors relying on the endogenous labels of tumorous tissues.
We present the nanoparticle-enabled experimentally trained wavelet-domain denoising method for optical coherence tomography (OCT). It employs an experimental training algorithm based on imaging of a test-object, made of the colloidal suspension of the monodisperse nanoparticles and contains the microscale inclusions. The geometry and the scattering properties of the test-object are known a priori allowing us to set the criteria for the training algorithm. Using a wide set of the wavelet kernels and the wavelet-domain filtration approaches, the appropriate filter is constructed based on the test-object imaging. We apply the proposed approach and chose an efficient wavelet denoising procedure by considering the combinations of the decomposition basis from five wavelet families with eight types of the filtration threshold. We demonstrate applicability of the wavelet-filtering for the in vitro OCT image of human brain meningioma. The observed results prove high efficiency of the proposed OCT image denoising technique.