Low-level laser therapy (LLLT) has been employed to alleviate pain resulting from chronic non-infectious inflammation in muscles and joints. One of the challenges of LLLT is that a consistent understanding of mechanism of action remains elusive. The spinal dorsal horn, a key site where sensory signals (pain, touch, etc.) are densely conveyed, offers a significant point of study for understanding the analgesic mechanism of LLLT. In this study, we developed establishment of electrophysiological analysis by using animals. However, there are few reports on the effectiveness of LLLT. As results, 15 minutes post-laser irradiation, von Frey filaments (vFF, especially 26.0 g)-evoked superficial spinal dorsal horn neuron firing frequencies were selectively inhibited. However, the vFF-evoked deep spinal dorsal horn neuron firing frequencies were not altered after the laser irradiation for any of the vFFs. Sham irradiation showed no changes in firing frequency. Our results suggest that laser irradiation selectively inhibits neuronal firing triggered by pain. This hints at the inhibition of neural activities in either or both Aδ and C fibers. In conclusion, we could develop establishment of electrophysiological analysis the effect of laser irradiation on the sciatic nerve and the resultant firing of spinal dorsal horn neurons—triggered by mechanical skin stimulation—was investigated using in vivo extracellular recording.

Head and neck aluminox therapy (photoimmunotherapy) is a treatment that combines cetuximab, an EGFR monoclonal antibody, and IR700, a light-sensitive substance, injected intravenously and irradiated with a 690 nm laser light. This treatment destroys cells to which the drug has adhered specifically. Based on the results of clinical trials in the U.S. and Japan, this treatment has been covered by insurance since January 2021 for unresectable locally advanced or locally recurrent head and neck cancer.

Photoimmunotherapy is a novel treatment approach combining the administration of a cancer-specific antibody–photosensitizer conjugate with laser light illumination. Pioneering globally, it has been approved for insurance coverage for head and neck cancer in Japan and is available for clinical use. Owing to its novelty, determining its applicability can often be challenging. It is crucial to make decisions regarding its suitability by considering the patient’s risks and benefits as well as insurance coverage, contraindications, treatment methods, and potential adverse events.

Photoimmunotherapy is a new cancer treatment that is distinct from surgery, chemotherapy, and radiation therapy, with adverse events that differ from those of other treatments. The adverse events of photoimmunotherapy include pain, photosensitivity, effects on nearby organs, bleeding, and airway edema. It is regrettable that patients refuse to undergo photoimmunotherapy because of these adverse events, despite its potential beneficial effects. Addressing these adverse events is important in order to promote the provision of photoimmunotherapy.

The head and neck region contains important organs that influence patient quality of life (QOL) by facilitating mastication, swallowing, breathing, and speech. Local control of head and neck cancer in these areas can maintain QOL while prolonging survival. It also has a significant cosmetic impact. Inability to address a cancer by local control alone may decrease QOL. We conducted a retrospective study of patients at our institution to assess the impact of Alluminox treatment for head and neck cancer on QOL. This article describes our study and presents our conclusions regarding the impact of Alluminox treatment on QOL. In nine patients treated with Alluminox, no significant changes were observed in any QOL endpoints before or after treatment. For unresectable head and neck cancer, Alluminox treatment did not decrease QOL and was associated with a good local disease control rate. Safety was also acceptable. Aggressive use of Alluminox treatment as an option may prolong survival in head and neck cancer.

Photoimmunotherapy is a treatment modality that selectively binds light-activated molecular target drugs to the cell membranes of tumor cells and illuminates the target lesions with light to induce the destruction of the cell membranes and cell death of the tumor cells. Due to its therapeutic characteristics, appropriate light illumination to the lesion is needed, and the strategy of light illumination must be planned based on enough understanding of the characteristics of the laser light and illumiation device. This article describes the types of light illumination devices, their characteristics, and challenges in light illumination. We also the innovative approaches for appropriate light illumination, including the development of treatment planning and simulation software specialized to photoimmunotherapy, the application of a surgical navigation system, and the manufacture of a puncture guideplate that enables high-precision light illumination.

Diffuse optical imaging can evaluate biological functions by extracting light absorption and scattering information from in vivo living tissues and organs. Among them, imaging with white LED light source and RGB color video camera can be constructed with simple and inexpensive measurement system, and easily used to support medical imaging diagnosis such as rigid endoscopic imaging systems. This article describes an intraoperative real-time imaging method for monitoring spatial and temporal hemodynamics in intraperitoneal organs using a commercially available laparoscopic imaging system. Monte Carlo simulation of light transport in biological tissues was used to establish relationships between RGB values and oxygenated and deoxygenated hemoglobin concentrations. In vivo animal experiments with rats demonstrated the ability of the method to evaluate the volume fraction of total hemoglobin and its oxygen saturation of intraperitoneal organs in real time.

When circularly polarized light irradiates biological tissues, it undergoes gradual depolarization via multiple scattering, and finally emits outward as scattered light. Resultant polarization state of the scattered light provides structural characteristics such as the size, distribution, anisotropy and density of scatterers. Since the degree of depolarization strongly depends on the ratio between the size of scatterers and the wavelength of incident light, the difference in size of cell nuclei derived from nuclear atypia can be detected by using scattering of circularly polarized light with appropriate wavelengths. Introduced in this paper are the principle of this technique based on physics and optics, the experimental and computational demonstrations, the depth estimation of tumor invasion in early-staged cancer, and the detection of scirrhous gastric cancer. Also the circularly polarized light emitting diodes are introduced as a device materialized this technique.

A study was conducted on the mechanism of dentin hardness measurement using a tooth hardness measuring device with a light-emitting diode, which is being developed as a new method for diagnosing root caries. The theoretical formulas for the dark area (the projected area of contact between the indenter and the dentin when the indenter is pressed into the dentin), the measured values and the indentation area were compared, and the physical interpretation of the dark area was performed. The results showed that the actual dark areas included the effect of exuded water from dentin in addition to the dentin deformation. Furthermore, it was noted that the result indicated that the indentation areas were smaller compared to the dark areas due to the elastic recovery.

Photoacoustic imaging is expected to be a next-generation diagnostic modality in medical imaging due to its ability to determine oxygen saturation of veins and blood in real-time. The current systems which use a solid-state-laser (SSL) are expensive, large in size, have probes with poor operability, and require the use of protective goggles due to the laser light. However, four technologies can be combined which improve the signal-to-noise-ratio (SNR) of the LED-based system from 1/2.3 million of the SSL to the equivalent level with SSL, to create a small, affordable and easy to-operate device that provides a real time functional imaging. The four technologies applied to the LED photoacoustic imaging system are; a) High power and high density LED array technology, b) Giant and ultra-short-pulse LED drive circuit technology, c) Optical pulse generation technology optimum for the frequency response characteristics of an Ultrasound Probe, d) Noise reduction technology for faint signals using ultra-amplification. In order to use LED-based photoacoustic imaging system, the ultra-amplification over 80 dB and SNR over 4 are required for real-time imaging when using a biological phantom. Based on the human in-vivo real-time functional imaging using a dual-wavelength of both 820 nm and 940 nm, the trial proved that the LED-based system can be used clinically.

Inverted OLEDs, which are stable to water and oxygen, can simplify the protective/barrier layer in its structure, making it possible to make the total film thickness of the OLED device thinner than paper, and also because it simplifies the process, and is expected to reduce total process costs. Nippon Shokubai considers its thinness and flexibility to be a major strength. And we are working toward bringing it to market under the development name “iOLED^TM Film Light Source.” “iOLED^TM film light source” is the thinnest in the industry at 0.07 mm, has excellent flexibility, and has the ability to fit to various curved surfaces. For example, it can be used in places and situations where conventional organic OLEDs have been difficult to apply, such as applying it directly to the skin or wrapping it around a rod-shaped object, and we believe that it is highly compatible with applications in the medical field. In this article, we will explain the background and issues of OLEDs, the technical features of “iOLED^TM film light source”, and application examples.

Photodynamic therapy (PDT) is a promising technique for the treatment of skin ulcers infected with multidrug-resistant bacteria because of its ability to prevent the emergence of new multidrug-resistant bacteria. We aim to use portable and disposable organic light-emitting diodes (OLEDs) as a PDT light source for home treatment of infected skin ulcers. OLEDs, as flexible surface light sources, provide uniform and widespread light delivery by adhering to the skin. However, OLEDs emit lower light intensity than traditional, relatively larger PDT light sources, which requires evaluation of differences in treatment effects due to variations in irradiation conditions. In this paper, we review the bactericidal and antitumor effects of low-intensity and prolonged illumination PDT and compare these effects with those of traditional PDT. In addition, we discuss the trend in the development of optical devices and introduce 5-aminolevulinic acid-mediated PDT using OLED light with low-intensity and prolonged illumination against methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa.

This review provides an overview of the inactivation of pathogenic microorganisms using deep-UV light. Specifically, it discusses bacteria and viruses, presenting inactivation mechanisms and outlining key considerations for evaluating the effectiveness of inactivation. In addition, it also presents the actual inactivation effect of viruses using deep-UV LEDs, which have garnered significant attention in recent years.

Extensive, irreversible skin damage must be treated by transplantation. Cultured skin with vascular networks is a useful skin substitute because it enables rapid reperfusion after transplantation. However, nutrient delivery from the surrounding medium to the thick skin tissue is often insufficient during cultivation, resulting in decreased viability. To solve this problem, we applied photobiomodulation (PBM). This article describes our cultured skin model and the investigation of its activation by PBM using a light-emitting diode (LED) array.

Acquired dermal melanocytosis (ADM) is a skin condition that can be effectively treated with Q-switched lasers. However, post-inflammatory hyperpigmentation, a common side effect of irradiation, can be problematic. The use of Q-switched ruby laser irradiation with a fractional handpiece can mitigate post-inflammatory hyperpigmentation, resulting in a shorter downtime compared to conventional treatments. However, it is important to note that the number of treatments required for colour improvement may increase with this approach.

To achieve low fluence, the nanosecond alexandrite laser with a wavelength of 755 nm is applied at a specific distance. The entire face is irradiated for the treatment of pigmented lesions and skin rejuvenation. While several sessions may be required, it is of significance that this laser treatment can be performed without downtime and without causing post-inflammatory hyperpigmentation. No complications such as depigmentation or scarring have been observed, making this treatment safe and effective.

Studies have reported on combined laser treatment for congenital pigmented nevus, wherein epidermal exfoliation is first performed with a long pulsed laser followed by irradiation with Q-switched ruby laser. Based on this technique, we administered simultaneous surgical procedures comprising excision and skin abrasion, and laser treatment in difficult-to-excise cases on back. The treatment must be initiated in the early stages to take advantage of the skin abration, which results in a reduction of the nevus area and improvement in the color tone before group living.

The introduction of selective photothermolysis in 1980’ was considered a landmark in the laser treatment of cutaneous pigmented lesions, by allowing for precise targeting of the abnormal pigment, while sparing surrounding normal tissue. Especially in treating the dermal melanocytosis, such as nevus of Ota, Mongolian spot, and aberrant Mongolian spot, Q-switched lasers have been a standard treatment method. Since 2013, novel picosecond lasers (ps-laser) have become available and the subsequent clinical trials have reported the safety and efficacy in treating multicolored tattoos and benign cutaneous pigmented lesions. It is considered that irradiation of targets with the ultra-short picosecond pulses can induce almost instantaneous heating of chromophores in the skin and greater fragmentation of the targets in an almost nonlinear fashion. These laser-tissue interaction caused by ps-laser irradiation is named photomechanical effect, not photothermal effect. Application of the ps-laser for the treatment of multicolored tattoos and epidermal or dermal benign pigmented lesions was started in authors’ clinic from December 2013. In this manuscript we present our clinical experience of treatment for dermal pigmented lesion with pico-second domain lasers. These novel laser devices, which have been developed based on the theory of ps-laser tissue interaction, might set the option for the new approach to treat dermal melanocytosis in Asians.

The activities of Social Insurance Committee of the Japan Society for Laser Surgery and Medicine for medical fee revision in 2024 and the results were described. In addition, the summary of the laser equipment that have been approved by government and the present insurance coverage for laser treatment were described in detail.