LVTNKHẢO SÁT TÁC ĐỘNG CỦA ÁNH SÁNG HỒNG NGOẠI GẦN CHIẾU TỪ BỀ MẶT DA LÊN ĐỐT SỐNG CỔ

Tìm hiểu về giải phẫu và sinh lý bệnh thoái hóa đốt sống cổ. Tìm hiểu về sự tương tác giữa ánh sáng và mô sinh học. Tìm hiểu các thông số quang học mô. Tìm hiểu cơ sở lý thuyết về mô phỏng lan truyền của photon trong mô sinh học bằng phương pháp Monte Carlo. Mô phỏng sự lan truyền và khảo sát tác động của ánh sáng hồng ngoại gần chiếu từ bề mặt da lên đốt sống cổ.

ĐẠI HỌC QUỐC GIA TP HỒ CHÍ MINH TRƯỜNG ĐẠI HỌC BÁCH KHOA KHOA KHOA HỌC ỨNG DỤNG LUẬN VĂN TỐT NGHIỆP KHẢO SÁT TÁC ĐỘNG CỦA ÁNH SÁNG HỒNG NGOẠI GẦN CHIẾU TỪ BỀ MẶT DA LÊN ĐỐT SỐNG CỔ NGUYỄN HỮU NHẤT THỐNG TP HCM, 01/2023 ĐẠI HỌC QUỐC GIA TP HỒ CHÍ MINH TRƯỜNG ĐẠI HỌC BÁCH KHOA KHOA KHOA HỌC ỨNG DỤNG LUẬN VĂN TỐT NGHIỆP ĐẠI HỌC KHẢO SÁT TÁC ĐỘNG CỦA ÁNH SÁNG HỒNG NGOẠI GẦN CHIẾU TỪ BỀ MẶT DA LÊN ĐỐT SỐNG CỔ Ngành: Vật lý kỹ thuật Sinh viên: Nguyễn Hữu Nhất Thống MSSV: 1810560 GVHD: TS Trịnh Trần Hồng Duyên TP HCM, 01/2023 ĐẠI HỌC QUỐC GIA TP.HCM TRƯỜNG ĐẠI HỌC BÁCH KHOA KHOA KHOA HỌC ỨNG DỤNG CỘNG HÒA XÃ HỘI CHỦ NGHĨA VIỆT NAM Độc lập – Tự – Hạnh phúc TP Hồ Chí Minh, ngày tháng năm 2022 NHIỆM VỤ LUẬN VĂN TỐT NGHIỆP HỌ VÀ TÊN: NGUYỄN HỮU NHẤT THỐNG MSSV: 1810560 NGÀNH: Vật lý kỹ thuật LỚP: KU18VLY Đầu đề luận văn: KHẢO SÁT TÁC ĐỘNG CỦA ÁNH SÁNG HỒNG NGOẠI GẦN CHIẾU TỪ BỀ MẶT DA LÊN ĐỐT SỐNG CỔ Nhiệm vụ: - Tìm hiểu giải phẫu sinh lý bệnh thối hóa đốt sống cổ - Tìm hiểu tương tác ánh sáng mô sinh học - Tìm hiểu thơng số quang học mơ - Tìm hiểu sở lý thuyết mơ lan truyền photon mô sinh học phương pháp Monte Carlo - Mô lan truyền khảo sát tác động ánh sáng hồng ngoại gần chiếu từ bề mặt da lên đốt sống cổ Ngày giao nhiệm vụ luận văn: Ngày hoàn thành nhiệm vụ: Họ tên người hướng dẫn: 31/08/2022 23/12/2022 TS Trịnh Trần Hồng Duyên Tên đề tài nội dung LVTN thông qua Bộ môn NGƯỜI HƯỚNG DẪN (Ký ghi rõ họ tên) CHỦ NHIỆM BỘ MÔN (Ký ghi rõ họ tên) LỜI CẢM ƠN Lời em xin chân thành cảm ơn sâu sắc đến cô TS Trịnh Trần Hồng Duyên định hướng đề tài, tận tâm hướng dẫn, góp ý, đánh giá mặt chuyên môn động viên tinh thần cho em suốt thời gian vừa qua Nhờ mà em giải vấn đề, sửa chữa hoàn thiện đề tài luận văn Em xin gửi lời cảm ơn sâu sắc đến tất thầy cô giảng dạy suốt thời gian học tập trường cung cấp tảng khơng mặt chun mơn mà cịn kỹ để em hoàn thiện đề tài luận văn Em xin cảm ơn trường Đại học Bách khoa – ĐHQG HCM nói chung khoa Khoa học ứng dụng nói riêng tạo mơi trường thật động cho sinh viên học tập nghiên cứu, từ bước đệm làm tảng phát triển thân tương lai Đồng thời, em xin gửi lời cảm ơn chân thành đến anh chị khóa trên, bạn KU18VLY gia đình ln hỗ trợ, động viên, góp ý, đóng góp ý tưởng suốt thời gian vừa qua Em cố gắng hồn thành khơng thể tránh khỏi thiếu sót hạn chế Rất mong quý thầy đóng góp ý kiến giúp đỡ để đề tài hoàn thiện Sau cùng, em xin kính chúc thầy có thật nhiều sức khỏe giữ nhiệt huyết với sứ mệnh truyền đạt kiến thức, hướng dẫn tuổi trẻ hoàn thành ước mơ tương lai Sinh viên thực NGUYỄN HỮU NHẤT THỐNG i TĨM TẮT LUẬN VĂN Ngày nay, thối hóa đốt sống cổ bệnh lý xương khớp ngày phổ biến xã hội đại Hiện nay, có nhiều phương pháp để giải vấn đề như: sử dụng thuốc, phẫu thuật vật lý trị liệu Trong mảng vật lý trị liệu, liệu pháp laser công suất thấp bật khả ứng dụng chẩn đoán điều trị Nhưng phương pháp gặp nhiều vấn đề khó khăn đối tượng sử dụng đa dạng, việc lựa chọn thông số vật lý cho thiết bị liều chiếu thích hợp cho đối tượng,… Bài luận văn giải vấn đề dựa phương pháp mô Monte Carlo (MCML) tích chập CONV Bên cạnh đó, xây dựng mơ lan truyền ánh sáng mơ hình 3D thơng qua chương trình MOSE Kết khảo sát lan truyền từ bề mặt da đến đốt sống cổ với mật độ lượng, mật độ công suất khác bốn bước sóng (633 nm, 780 nm, 850 nm 940 nm) Từ đó, xây dựng đường đặc tuyến mối liên hệ mật độ lượng đầu vào so với “độ xuyên sâu” “bán kính tác dụng” Các kết đạt độ xác 0,1% Từ kết làm sở phát triển thiết bị trị liệu laser công suất thấp dùng lâm sàng để điều trị thối hóa cột sống ii ABSTRACT Nowadays, cervical spondylosis is an increasingly common musculoskeletal disease in modern society Currently, we have many methods to solve that problem, such as using drugs, surgery, and physical therapy In the field of physical therapy, low-power laser therapy is even more prominent in terms of its applicability in diagnosis and treatment But this method faces many difficulties when the target audience is diverse, as well as the selection of physical parameters for the device and the appropriate dose for each object, etc The thesis solves the above problem based on the Monte Carlo simulation method (MCML) and convolution (CONV) Besides, building simulation of light propagation on 3D model through MOSE program The results investigated the propagation from the skin surface to the cervical vertebrae with different energies and power densities for four wavelengths (633 nm, 780 nm, 850 nm, and 940 nm) From there, a curve representing the relationship between the input energy density and the "penetrating depth" and "radius of action" is built The above results have an accuracy of 0,1% These simulation results are the basis for analyzing the impact of near-infrared light and developing a low-level laser therapy device that could be used in clinical settings for treating the degenerative spine iii MỤC LỤC Trang LỜI CẢM ƠN i TÓM TẮT LUẬN VĂN ii ABSTRACT iii MỤC LỤC iv DANH MỤC HÌNH ẢNH vi DANH MỤC BẢNG BIỂU viii DANH MỤC CÁC THUẬT NGỮ VIẾT TẮT ix CHƯƠNG TỔNG QUAN 1.1 Đặt vấn đề 1.2 Mục tiêu nhiệm vụ đề tài 1.2.1 Mục tiêu đề tài 1.2.2 Nhiệm vụ đề tài 1.3 Bệnh thối hóa đốt sống cổ 1.3.1 Giải phẫu đốt sống cổ 1.3.2 Chức đốt sống cổ 1.3.3 Thối hóa đốt sống cổ 1.4 Các tượng xảy ánh sáng tác động vào mô 1.4.1 Hấp thụ 1.4.2 Tán xạ hệ số bất đẳng hướng 10 1.4.3 Phản xạ khúc xạ 13 1.5 Ứng dụng laser công suất thấp điều trị 14 1.5.1 Lịch sử phát triển định hướng laser y học 14 1.5.2 Các chế tương tác laser công suất thấp 15 1.5.3 Các thông số trị liệu laser công suất thấp 18 1.5.4 Đáp ứng liều hai pha 19 1.5.5 Các tác động laser công suất thấp 20 CHƯƠNG PHƯƠNG PHÁP VÀ MƠ HÌNH MƠ PHỎNG 2.1 Mô lan truyền ánh sáng mô phương pháp Monte Carlo iv 23 23 2.1.1 Tạo biến số ngẫu nhiên 23 2.1.2 Quy tắc lan truyền photon 25 2.1.3 Thuật tốn chương trình MCML 32 2.2 Chương trình tích chập CONV 35 2.3 Chương trình MOSE 36 2.4 Thực mô 36 2.4.1 Xây dựng mơ hình 36 2.4.2 Chuẩn bị tệp đầu vào 38 2.4.3 Mơ chương trình MCML 38 2.4.4 Mơ chương trình CONV 39 2.4.5 Mơ chương trình MOSE 40 CHƯƠNG KẾT QUẢ VÀ BÀN LUẬN 42 3.1 Kết mô MCML 42 3.2 Kết chương trình CONV 52 3.3 Khảo sát đánh giá liều tác dụng 53 3.3.1 Bước sóng 633 nm 54 3.3.2 Bước sóng 780 nm 57 3.3.3 Bước sóng 850 nm 60 3.3.4 Bước sóng 940 nm 63 3.4 Kết chương trình MOSE 65 3.4.1 Mật độ lượng 1J 67 3.4.2 Mật độ lượng 4J 68 CHƯƠNG KẾT LUẬN VÀ HƯỚNG PHÁT TRIỂN 70 4.1 Kết luận 70 4.2 Hướng phát triển 71 TÀI LIỆU THAM KHẢO 73 PHỤ LỤC 77 v DANH MỤC HÌNH ẢNH Hình 1.1 Giải phẫu cột sống cổ Hình 1.2 Các q trình tương tác ánh sáng với mơ Hình 1.3 Cửa sổ quang học bước sóng vùng hồng ngoại gần Hình 1.4 Sơ đồ tán xạ ánh sáng hạt nằm gốc tọa độ O 12 Hình 1.5 Cơ chế tế bào LLLT 16 Hình 1.6 Đường cong Arndt-Schultz 19 Hình 2.1 Mô tả lấy mẫu biến số ngẫu nhiên χ dựa vào số ngẫu nhiên phân bố ξ 25 Hình 2.2 Lưu đồ mơ chương trình Monte Carlo 34 Hình 2.3 Vị trí chiếu laser từ bề mặt da lớp thang đến đốt sống cổ 37 Hình 3.1 Phân bố mật độ lượng hấp thụ theo độ sâu z (cm) bán kính r (cm) bước sóng 633 nm 42 Hình 3.2 Phân bố thông lượng theo độ sâu z (cm) bán kính tác dụng r (cm) 43 Hình 3.3 Phân bố mật độ lượng hấp thụ theo độ sâu z (cm) bán kính r (cm) bước sóng 780 nm 44 Hình 3.4 Phân bố thông lượng theo độ sâu z (cm) bán kính tác dụng r (cm) 45 Hình 3.5 Phân bố mật độ lượng hấp thụ theo độ sâu z (cm) bán kính r (cm) bước sóng 850 nm 46 Hình 3.6 Phân bố thông lượng theo độ sâu z (cm) bán kính tác dụng r (cm) 47 Hình 3.7 Phân bố mật độ lượng hấp thụ theo độ sâu z (cm) bán kính r (cm) bước sóng 940 nm 48 Hình 3.8 Phân bố thơng lượng theo độ sâu z (cm) bán kính tác dụng r (cm) 49 Hình 3.9 Biểu đồ mật độ lượng hấp thu theo độ sâu bước sóng 50 Hình 3.10 Biểu đồ thông lượng phân bố theo độ sâu bước sóng 51 Hình 3.11 Khả xuyên sâu mật độ công suất 10-4 W/cm2 tổng lượng đầu vào J 52 Hình 3.12 Tác động lượng đầu vào bán kính tác dụng độ xuyên sâu bước sóng 633 nm 54 Hình 3.13 Đường cong dự đoán thay đổi bán kính tác dụng phụ thuộc tổng vi lượng đầu vào bước sóng 633 nm 55 Hình 3.14 Đường cong dự đoán thay đổi độ xuyên sâu phụ thuộc tổng lượng đầu vào bước sóng 633 nm 56 Hình 3.15 Tác động lượng đầu vào bán kính tác dụng độ xuyên sâu bước sóng 780 nm 57 Hình 3.16 Đường cong dự đoán thay đổi bán kính tác dụng phụ thuộc tổng lượng đầu vào bước sóng 780 nm 58 Hình 3.17 Đường cong dự đoán thay đổi độ xuyên sâu phụ thuộc tổng lượng đầu vào bước sóng 780 nm 59 Hình 3.18 Tác động lượng đầu vào bán kính tác dụng độ xuyên sâu bước sóng 850 nm 60 Hình 3.19 Đường cong dự đoán thay đổi bán kính tác dụng phụ thuộc tổng lượng đầu vào bước sóng 850 nm 61 Hình 3.20 Đường cong dự đoán thay đổi độ xuyên sâu theo tổng lượng đầu vào bước sóng 850 nm 62 Hình 3.21 Tác động lượng đầu vào bán kính tác dụng độ xuyên sâu bước sóng 940 nm 63 Hình 3.22 Đường cong dự đoán thay đổi bán kính tác dụng phụ thuộc tổng lượng đầu vào bước sóng 940 nm 64 Hình 3.23 Đường cong dự đoán thay đổi độ xuyên sâu theo tổng lượng đầu vào bước sóng 940 nm 65 Hình 3.24 Mơ hình xây dựng chương trình MOSE 66 Hình 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University of Technology (HCMUT), 286 Ly Thuong Kiet Street, District 10, Ho Chi Minh City, Vietnam Vietnam National University Ho Chi Minh City, Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Vietnam thong.nguyenaka@hcmut.edu.vn, tt_hd2005@hcmut.edu.vn Abstract In the musculoskeletal system, the spine determines the life and movement of humans as well as that of all other vertebrates The degenerative spine usually begins with damaged joints of the vertebral bodies, neck herniated disc, ligament, and then gradually occurs degeneration of the vertebrae, causing neck pain, especially when moving the neck area Nowadays, along with the development of the biomedical field, low-power laser therapy is more prominent in its applicability in diagnosis and treatment This paper describes the simulation results of low-level laser propagation from the skin surface to the cervical vertebrae with four wavelengths (633 nm, 780 nm, 850 nm, and 940 nm) by the Monte Carlo method These simulation results are the base for analyzing the impact of near-infrared light and developing a low-level laser therapy device, that could be used clinically for treating the degenerative spine Author keys: Monte Carlo simulation; low-level laser therapy LLLT; cervical vertebrae; degenerative spine Introduction The term "cervical spondylosis" refers to a variety of gradually developing degenerative alterations that affect every part of the cervical spine (i.e., intervertebral discs, facet joints, joints of the Luschka, the ligamenta flava, and the laminae) The majority of people begin to experience it after their fifth decade of life, and it is a natural part of aging [1] When neural structures are compressed, cervical spondylosis symptoms such as neck pain and stiffness may be accompanied by radicular symptoms [2] The majority of adults with spondylotic alterations of the cervical spine on radiographic imaging are asymptomatic, with degenerative changes being evident in 25% of people under the age of 40, 50% of people over the age of 40, and 85% of those over the age of 60 C6-C7 and C5-C6 are the levels that are most commonly impacted The most typical symptom of symptomatic cervical spondylosis is neck pain The point prevalence of neck discomfort in the general population ranges from 0.4% to 41.5%, 1-year incidence from 4.8% to 79.5%, and lifetime prevalence up to 86.8% [3] Low-Level Laser Therapy (LLLT) is an application developed and applied widespread in the field of medicine in today’s world which stimulates tissue regeneration, relieves pain and inflammation Unlike any other medical laser applications, the LLLT does not have mechanism of ablation or thermal, but a photochemical effect meaning light is absorbed resulting in photochemical reaction inside the biological tissues This paper depicts the model construction and the propagation of the low-level laser from the skin surface layer to the cervical vertebrae layer through the Monte Carlo method This Monte Carlo-based simulation mimics the light propagation inside the multi-layered tissue, the anatomical structure in the human body, and the optical parameters of the biological tissues The results show that the power density ranging from (1.0 - 10-4 W/cm2) of the specific wavelengths (633 nm, 780 nm, 850 nm, and 940 nm) which exhibit the “effective operating area” of the lowlevel laser beam on the tissue being treated The fact ultimately states that the choice of wavelength, power density, and appropriate dosage affect the treatment process Materials and Methods 2.1 Monte Carlo method The Monte Carlo method is the main technique used to describe the simulation of light transmission in biological tissues in this paper [4] The mentioned method is applied to simulate the propagation of light in biological tissues based on the Radiative transport equation (RTE) and simulated calculations, calculating the propagation of photons in the absorption and scattering medium [5-11] The radiative transport equation (RTE) is a popular equation for describing particle propagation in the complex structure of tissues [5] A photon is a unit of light The wave properties of a photon are ignored in this paper, it only deals with the properties of the particle Therefore, the phase and polarization parameters of the light are not taken into account In the simple case, the photon is introduced into an independent medium and its motion is recorded until it is absorbed or scattered out of the field of view Although the results are highly accurate, this method demands repeated computations to achieve the desired accuracy, resulting in the simulation implementation being time consuming For example, to achieve 0.1% accuracy, the movement of 1000000 photons must be performed A Monte Carlo simulating method described by Prahl [6] and programmed by Wang and Jacques [7] employs the technique of capturing the hidden photon called "existing weights" Photons have their “initial weight” and will decrease with each move until scattered without a stop for each photon in the scattering process until they are finished by an absorption one By that, the statistics would be more effective and efficient skipping the computational process of the movement of the photons which takes plethora steps until the end in the absorption process 2.2 Simulation models The structure from the skin surface to the cervical vertebrae is classified into layers: human skin ~ 0.3 cm, subcutaneous fat ~ 1.0 cm, musculus trapezius ~ 2.0 cm; and cervical vertebrae ~ 2.0 cm Human skin consists of stratum-cormeum, epidermis, demis with the thickness approximately (0.06 – 0.1 cm), (0.0006 – 0.015 cm), (0.06 – 0.3 cm) [14-16] In this paper, we focus on the model with a thickness of 0.3 cm The aborted coefficient μa and the scattered coefficient μs are the probability density functions whose reciprocals can be interpreted as the average mean distances for the absorption and scattering The sum of them is called the total attenuation characterizing the reaction of the photon’s mean per unit of path length Anisotropy coefficient g is the value of the cosine of angle average deviation scattering θ of the angle between the direction of the photons being scattered and incident photons, characterizes the isotropy of the medium These aforementioned parameters characterize the properties of the tissue layers and are published internationally with credibility which is present in Table Table 1: The optical parameters of the tissues Tissue Skin [17-19] Subcutaneous fat [8] Musculus trapezius [8] Cervical vertebrae [8]  (nm) 633 780 850 940 633 780 850 940 633 780 850 940 633 780 850 940 n 1.4 1.44 1.37 1.4 µa (cm-1) 0.334 0.142 0.1223 0.1905 0.128 0.0846 0.086 0.168 1.32 0.331 0.295 0.401 0.122 0.073 0.092 0.172 µs (cm-1) 272.9 197.3 175.73 156.7 125.5 114.67 110.9 108.6 89.6 71.2 66.0 58.1 106.66 88 82 79.33 g 0.9 0.9 0.9 0.9 0.91 0.91 0.91 0.91 0.93 0.93 0.93 0.93 0.85 0.85 0.85 0.85 The simulated result is performed under the precision value of 0.1% being calculated with 1000000 photons based on the Monte Carlo Multi-Layered (MCLC) program [7] in unison with its companion called CONV [9] to optimize the performance and reduce the simulation Laser power would change complying with the required position for the desired results continuously, with the Gaussian-shaped spatial beam profile (radius 1/e2 is 0.14 cm) The simulated results display the distribution of power density of 10-4 W/cm2 at which laser beam can cause biological effects on the tissue stimulation Results 3.1 MCML program We measure the light density distribution along the horizontal axis by using the cm intervals for the reflective and transmitted edges The MCML program would be executed under the file named “file.mci” inputting the data prepared, when the calculation is finished, the output result would be performed under the “file.mco” using the MATLAB machine language which is usually used to launch the “.m” files These simulation results show the distribution of power density of 10-4 W/cm2 - at which the laser beam causes the stimulation biological effect on tissue The output file of MCML is handled by the program named “conv.exe” to respond to an infinite photon beam and to compute the finite size beams of photon Initial beams mostly propagate along the vertical axis then gradually disperse over different directions After the program being invoked, the menu system will direct the data input, output, or process – “file.iso” We used Excel software to produce publication-quality graphs and fit data with arbitrary curves Figure 1: Absorbed energy distribution and incident flux distribution at 633 nm Figure describe the absorbed energy density distribution and the photon flux distribution at 633 nm according to the depth z (cm) and radius r (cm) from the MCML program The light source is defined as the point of the laser beam at 𝑟 = 0, z = at the neck skin surface Regarding the power density distribution, the MCML program results in the absorbed energy density per unit of time The power density distribution is plotted in log form representing the color scale The discontinuity at the intervals between tissue layers is due to differences in absorption coefficients owing to the occurrence of non-absorption scattering at the boundary During the propagation of photons from the skin surface to the cervical vertebrae at 633 nm, there is a 10 − 10-4 W/cm2 power density photon deposition Thus, photon propagation with absorbed power density of 10-4 W/cm2 at 633 nm exists only in the dermal layer, subcutaneous fat layer, and muscle layer (reaching ~2.2 cm depth) and the largest radius of action in the muscle layer (~2.2 cm wide) – Figure 1a Regarding the photon flux distribution, the flux distribution with a power density of 104 W/cm2 for tissue layers has a continuum, the radius of effect gradually increases to a width of ~2.2 cm as the photon propagates from the surface skin surface into adipose tissue At a depth of approximately ~1.0 cm, the flux distribution with a power density of 10-4 W/cm2 according to the radius of action does not continue to increase but gradually decreases and ends in the muscle layer – Figure 1b Figure 2: Absorbed energy distribution and incident flux distribution at 780 nm Figure describe the absorbed energy density distribution and the photon flux distribution at 780 nm according to the depth z (cm) and radius r (cm) from the MCML program Regarding the power density distribution, the photon propagation with absorbed power density of 10-4 W/cm2 at 780 nm exists only in the dermal layer, subcutaneous fat layer, and muscle layer (reaching ~3.2 cm depth) and the largest radius of action in the muscle layer (~2.7 cm wide) – Figure 2a Regarding the photon flux distribution, the flux distribution with a power density of 10-4 W/cm2 for tissue layers has a continuum, the radius of effect gradually increases to a width of ~2.5 cm as the photon propagates from the surface skin surface into adipose tissue At a depth of approximately ~1.4 cm, the flux distribution with a power density of 10-4 W/cm2 according to the radius of action does not continue to increase but gradually decreases and ends in the muscle layer – Figure 2b Figure 3: Absorbed energy distribution and incident flux distribution at 850 nm Figure describe the absorbed energy density distribution and the photon flux distribution at 850 nm according to the depth z (cm) and radius r (cm) from the MCML program Regarding the power density distribution, the photon propagation with an absorbed power density of 10-4 W/cm2 at 850 nm exists only in the dermal layer, subcutaneous fat layer, and muscle layer (reaching ~3.2 cm depth), and the largest radius of action in the muscle layer (~2.6 cm wide) – Figure 3a Regarding the photon flux distribution, the flux distribution with a power density of 10-4 W/cm2 for tissue layers has a continuum, the radius of effect gradually increases to a width of ~2.5 cm as the photon propagates from the surface skin surface into adipose tissue At a depth of approximately ~1.5 cm, the flux distribution with a power density of 10-4 W/cm2 according to the radius of action does not continue to increase but gradually decreases and ends in the muscle layer – Figure 3b Figure 4: Absorbed energy distribution and incident flux distribution at 940 nm Figure describe the absorbed energy density distribution and the photon flux distribution at 940 nm according to the depth z (cm) and radius r (cm) from the MCML program Regarding the power density distribution, the photon propagation with absorbed power density of 10-4 W/cm2 at 940 nm exists only in the dermal layer, subcutaneous fat layer, and muscle layer (reaching ~3 cm depth) and the largest radius of action in the muscle layer (~2.4 cm wide) – Figure 4a Regarding the photon flux distribution, the flux distribution with a power density of 10-4 W/cm2 for tissue layers has a continuum, the radius of effect gradually increases to a width of ~2.4 cm as the photon propagates from the surface skin surface into adipose tissue At a depth of approximately ~1.0 cm, the flux distribution with a power density of 10-4 W/cm2 according to the radius of action does not continue to increase but gradually decreases and ends in the muscle layer – Figure 4b Figure 5: The penetrating ability of wavelengths (633 nm, 780 nm, 850 nm, and 940 nm) from the skin surface to cervical vertebrae at 10-4 W/cm2 of power density The simulation result is shown in Figure from the skin's surface to the cervical vertebrae, using a 1J total energy for the Gaussian laser beam In comparison to 940 nm (~3.7 cm), the penetration depth into tissue of 780 nm and 850 nm is relatively comparable (~4.2 cm) Less tissue may be penetrated by the 633 nm wavelength (~2.3 cm) The "depth of penetration" and "impact radius" of the beam, on the other hand, both considerably rise as the irradiation period increases 3.2 MOSE program The model of layers from the skin to the cervical vertebrae is built based on the computed tomography image data set from the Carver College of Medicine, the University of Iowa (USA) Then use Materialize Mimics software to build 3D and mesh the model The model is then fed into the MOSE program to simulate the propagation of photons in tissue from the skin surface to the cervical vertebrae [10, 11] Figure 6: Absorption capacity with a total energy input of 1J from the MOSE program Figure depicts the results of absorption ability from the skin surface to the cervical vertebrae when irradiating a laser source with input energy of 1J from the MOSE program at four wavelengths of interest 633 nm, 780 nm, 850 nm, and 940 nm (in order a, b, c, d) At 633 nm, photon absorption only reaches the muscle layer surface and has not reached the cervical vertebrae surface With the remaining three wavelengths, the photon absorption capacity reaches the surface of the cervical vertebrae In which, the wavelength of 850 nm gives the best absorption results compared to the remaining wavelengths Figure 7: Absorption capacity with a total energy input of 4J from the MOSE program Figure depicts the results of absorption ability from the skin surface to the cervical vertebrae when irradiating a laser source with input energy of 4J from the MOSE program at four wavelengths of interest 633 nm, 780 nm, 850 nm, and 940 nm (in order a, b, c, d) At 633 nm, photon absorption only reaches the muscle layer surface and has not reached the cervical vertebrae surface The photon absorption capacity reaches the cervical vertebral surface with the remaining three wavelengths and spreads to the occipital bone surface In which, the wavelength of 850 nm gives the best absorption results compared to the remaining wavelengths The simulation results of the light propagation in the 3D model of the MOSE program are consistent with the results from the MCML program From this result will help us to see an intuitive view of light propagation in the model of tissues with complex surfaces Conclusions With the implementation of the low-level laser therapy (LLLT) and the use of the Monte Carlo method to simulate the propagation of the laser beam into the biological tissue, this paper state that the low-level laser of 780 nm, 850 nm, and 940 nm wavelength have significant impact to the tissue layers from the skin surface to the cervical vertebrae in which the 780nm and 850nm wavelength are the two best in the perspective of penetrating ability The mentioned ones are best suited to develop the LLLT devices The irradiation time and the penetration depth and impact radius of the beams are directly proportional to each other, meaning that when the irradiation time increases, the "depth of penetration" and "impact radius" of the beam also increase Although out of the four, the 633 nm wavelength can reach the lowest depth compared to the other two, it can be used for skin treatment equipment or 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