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13DEVELOPMENT OF A MULTIMODAL APPROACH TO THE DIAGNOSIS OF HUMAN SKIN CANCER IN VIVO
ISABELLA A. SEREBRYAKOVA12, YURY I. SURKOV1,2, YANA K. KUZINOVA3, OLGA M.
KONOPATSKOVA3, VALERY V. TUCHIN1,2,4, ELINA A. GENINA1,2
1Science Medical Center, Saratov State University, 83 Astrakhanskaya str., Saratov 410012, Russia 2Laboratory of Laser Molecular Imaging and Machine Learning, Tomsk State University, 36 Lenin's av., Tomsk 634050, Russia 3Pathological Department, State Healthcare Institution "Saratov City Clinical Hospital No. 1 named after Yu.Ya. Gordeev", 19
Kholzunova st., Saratov 410017, Russia 4A.N. Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Moscow, 33Leninsky
Prospect, building 2, Moscow 119071, Russia
ABSTRACT
This work describes a newly developed multimodal method that has the potential to differentiate various types of basal cell carcinoma (BCC), a type of skin cancer, and benign neoplasms. The method includes: high-frequency ultrasound, optical coherence tomography (OCT), backscattering and Raman spectroscopy. Specific spectral markers are proposed. In addition, the possibility of increasing the depth of OCT imaging using skin optical clearing technique was tested. This diagnostic method allows also for postoperative monitoring to detect recurrence, and provides additional information useful for determining treatment tactics.
BCC is the most common non-melanocytic malignant epithelial skin tumor, accounting for more than 80% of all non-melanocytic malignant skin tumors. [1, 2]. These statistical indicators are a stimulus for the development of a multimodal approach that allows for monitoring the skin in vivo, as well as monitoring the progression of the tumor process and the outcome of treatment. BCC grows from epidermal cells called keratinocytes, which are located near the basal layer of the dermis. The initial stage of BCC is characterized by a varied clinical picture. There are several forms of basal cell skin cancer: for example, superficial, exophytic, scleroderm - like, nodular, infiltrative, eczema - like, pigmented forms, and others.
Visual checkup of skin neoplasms remains an absolutely subjective diagnostic method and requires confirmation by instrumental methods, for example, histological expertise of an invasive excisional biopsy of a tumor tissue sample. However, the biopsy has potential complications such as increased sensitivity to anesthesia, bleeding, scarring, and infection. [3] In practice, the histological process takes a long time. Obviously, new methods and approaches are needed to quickly and reliably obtain diagnostically significant information. [4]
In recent years, optical methods have become effective diagnostic tools that allow obtaining information about the structural and biochemical changes that accompany the development of pathology in skin tissues, which is necessary for the timely diagnosis and treatment of neoplasms in clinical conditions [5]. The purpose of this study is to increase the information content by combining several optical methods and high-frequency ultrasound of the skin.
The study involved 20 volunteers (42 - 80 years old) of both sexes with poorly pigmented skin diagnosed with BCC, including ulcerative, infiltrative, superficial, eczema - like, and pigmented forms, or a benign neoplasm (BN), including nevus, angioma, and fibroma, who signed an informed consent to the study. Areas with neoplasms and nearby healthy and/or symmetrically located skin areas were selected as the object of the study for subsequent comparison and assessment of deviations from the norm. A visually healthy area of the skin was taken as the norm. Comparison of data obtained from a neoplasm and from a healthy area of the skin makes it possible not to take into account the individual characteristics of the patients' skin. Two of the volunteers were examined before and after radiation therapy (RT) for BCC (Wolf T-200 apparatus).
At the beginning of the study, a visual examination of the volunteer was carried out by an oncologist at the Public Health Institution "Clinical Hospital "RZD-Medicine" in Saratov. The final diagnosis was made by a doctor based on the results of a cytological examination at the Regional Oncological Dispensary No. 2. Macro-photos of the lesions were made using a digital video polarizing dermatoscope DE300 (Firefly Global, USA) with magnification 35*. High-frequency ultrasound (US) was performed using a DUB Skin Scanner (TPM Tabernapromedicum GmbH, Germany) with two probes operating at central frequencies of 33 and 75 MHz with depth OCT B-scans were obtained using a GAN930V2-BU spectral OCT (Thorlabs, USA) operating at a central wavelength of 930 nm with axial and lateral resolution 5.3 and 7.3 ^m. Using USB4000-UV-VIS spectrometer and QR400-7-VIS-NIR fiber optic probes (Ocean Optics, USA), diffuse reflectance was measured in the wavelength range of 400-900 nm on the skin areas under study/
On OCT of significant values of BCC and BN in detection with a healthy disease (Fig. 1), there is an inhomogeneous increase in the number of epidermis up to two times, the boundaries of the epidermis-dermis manifestations, in some cases, between the epidermis and dermis are indistinguishable, in addition, there is an increase in the number of optical inhomogeneous some of which can manifest themselves in blood and lymph microvessels, and the other part in areas of necrosis and, possibly, a local area of dissociated collagen causes increased activity of collagenase. The diameter of the vessel can increase several times compared to the intact disease. There is heterogeneity in the scattering coefficient and the structure of the epidermis and dermis in terms of the volume of the lesion. The border of the neoplasm most often appears below the OCT probing depth. Often loose, often crusty, especially common in case of BCC. The lateral borders of the neoplasm are often well distinguishable from healthy skin.
Macro-photo
The red arrow OCT image
corresponds to the
probing plane
Nevus
J
US image
33 MHz
75 MHz
BCC
Angioma
Visually healthy skin area
J
^ • - ' ' Err .
J
Figure 1: Macrophotographs, OCT and US images of neoplasms and healthy skin Specific differences between OCT images of BCC and BN were not observed, however, it can be noted that the overall homogeneity of the signal of BN is higher than BCC, but lower compared to healthy skin. The hallmark of angioma on OCT and US images is a greater number of large vessels located close to the surface of the skin. According to US images of BCC and BN, in comparison with healthy skin, the echogenicity in the area of education is evenly reduced, the structure is acoustically homogeneous, the boundaries are often determined. There were no specific differences on US images between BN and BCC, but even and clear boundaries were more often observed.
In Fig. 2 macro-photos, US, and OCT scans of BCC before and 3 months after RT are presented. Acoustic inhomogeneities associated with the neoplasm are not observed. In OCT scans, an increase in the contrast between the epidermis and dermis is observed, the thickness of the epidermis in the area under study varies within the normal range for a healthy area, and the dermis has a more ordered structure with fewer optical inhomogeneities.
Macro-photo
OCT image
US image (75 MHz)
BCC before RT
3 months after RT
Figure 2: Macrophotographs, OCT and US images ofBCC of a volunteer before RT and 3 months after RT For each neoplasm under study, the effective coefficients of melanin pigmentation, erythema, and the slope coefficient of the effective diffuse reflection spectrum in the wavelength range from 400 to 900 nm were calculated. For each diagnosis, these coefficients were averaged and the standard deviation was found.
R E = R cancer ,#(1)
R healthy
where RE is the effective reflection spectrum; R cancer and R k eaith y are the spectra of reflection of neoplasm and visually healthy skin, respectively.
M = 100(OD620 -OD700),#(2) where M is the effective coefficient of melanin pigmentation; ODx is the effective optical density at a particular wavelength X;
E = 100 [OD56o + 1.5 (OD545 + OD575) - 2 (ODsw + OD6W)],#(3)
where Fis the effective coefficient of erythema
R =
R healthy 500 X R
lesion 700
Rhealthy 700 X R
,# (4)
lesion 500
where R is the coefficient of malignancy, the values of the ratio between normal and lesion reflectance intensity at 500 and 700 nm [6]; R h eaith y 500; R lesion 500; R k eaitk y 700; R lesion 700 are the diffuse reflection coefficient of visually healthy human skin and lesions at wavelengths of 500 and 700 nm, respectively.
Figure 3 shows the values of the coefficients. One can observe the changes in pigmentation, blood oxygen saturation, a decrease in the diffuse scattering coefficient of the skin in the area under study and change in the slope of the spectrum, compared with visually healthy skin. For BCC, a characteristic feature was a low content of lipids and keratin. In the area of benign neoplasms, increased content of proteins, nucleic acids, lipids, and keratin was observed.
50 40 30 20
m 10 0 -10 -20
Figure 3: Effective coefficients of melanin pigmentation (M), erythema (E), the slope coefficient of the effective diffuse reflection spectrum (k), and malignancy (R) in the wavelength range from 400 to 900 nm for different forms of BCC and fibroma (BN).
Thus, a multimodal approach to the study of skin neoplasms made it possible to obtain comprehensive information on BCC and BN: the boundaries of neoplasm, tissue microarchitecture, effective coefficients of melanin pigmentation and erythema, coefficient of spectral slope k, and coefficient of malignancy R, calculated from backscattering spectra. A multimodal approach to the diagnosis of BCC and BN may have greater sensitivity and specificity than each method to the study of skin neoplasms separately.
The reported study was funded by the grant of RFBR (#20-52-56005) and the grant under the Degree of the Government of the Russian Federation No. 220 of 09 April 2010 (Agreement No. 075-15-2021-615 of 04 June 2021).
REFERENCES
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[4] Y. P. Sinichkin et al., In vivo fluorescence spectroscopy of the human skin: experiments and models, Journal of Biomedical Optics, V. 3, p. 201-211, 1998.
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