Irritable bowel syndrome (IBS) is characterized by abdominal pain and abnormal bowel movements and affects an estimated 5–20% of the general population. Although various treatments are available, patient satisfaction remains low, underscoring the unmed need for new therapies. We therefore examined whether photobiomodulation (PBM), reported to suppress the activity of Aδ and C fibers that convey noxious stimuli, could be applied to IBS. Using a restraint stress rat model, we evaluated the effect of PBM on colonic pain hypersensitivity. A semiconductor laser served as the PBM light source. Animals were assigned into three groups (Non stress + Sham, Stress + Sham, and Stress + PBM). In the Stress + PBM group, PBM was percutaneously applied bilaterally to the L6 dorsal root ganglia for 5 min per side. Across two experiments, five PBM conditions were tested, with average output powers of 1,000, 460, 70, 18, and 3.5 mW. After PBM, a barostat catheter was inserted and, following 30 min of acclimation, was maintained at 60 mmHg while abdominal muscle contractions were counted for 5 min. Significant inhibition of contractions was observed at 460, 70, and 18 mW, whereas 1,000 and 3.5 mW had no significant effect. These findings suggest that PBM attenuates restraint stress-induced colonic hypersensitivity and may be a promising therapeutic approach for IBS. PBM has the potential to treat various diseases in which Aδ and C fibers play a role.

The efficacy of skincare products as a measure against dryness during laser hair removal of the lower legs was investigated. A long pulse alexandrite laser was used. Moisturizers were applied to the right lower leg twice daily before irradiation, while the left lower leg was left untreated. At baseline and one and four weeks after irradiation, the skin condition was observed, water content of the stratum corneum was measured, epidermal stratum corneum was evaluated. The moisturized side had lower dryness and itching scores, a significantly higher water content in the stratum corneum, and a significantly lower degree of exfoliation than the unmoisturized side. The use of skincare products during laser hair removal on the lower leg has been suggested as a useful measure against dryness.

Treatment for varicose vein in the lower extremities is mainly classified into treatment for truncal saphenous vein reflux, tributary vein reflux (tributary varicose vein), and incompetent perforator. Among these, the intervention of truncal saphenous reflux is the most promising treatment and the one of most recommended procedure is the endovenous laser ablation (EVLA). EVLA has a less invasive method, is effective in interrupting the saphenous venous reflux, and has a lower rate of severe adverse events. EVLA can also be used to treat tributary venous reflux and incompetent perforator. To achieve better results of EVLA for varicose veins, it is important to determine the correct indication for treatment, to develop a thorough understanding of varicose veins, and to gain proficiency in performing EVLA.

This article describes the historical background and practical techniques of “endovenous laser ablation of tributary varicose veins,” a treatment method approved by the Japanese government’s health insurance system in October 2024. This newly developed technique in Japan uses a slim-type radial fiber inserted through a 16G venule needle for endovenous varicose ablation. It offers excellent cosmetic outcomes with minimal postoperative complications, and it may serve as a promising alternative to the limitations of conventional phlebectomy and sclerotherapy.

Recently, numerical simulations have been increasingly utilized in the development and evaluation of medical devices. In the field of photodynamic therapy (PDT), such simulation can be used to optimize light irradiation conditions to complement experimental data and to enhance development efficiency. This study provides overview of the current applications and advantages of numerical simulations in medical device development. It also provides details on specific examples of their use in the medical device development and evaluation of PDT devices and discusses the validation of simulations and key considerations for their practical implementation.

A wide variety of optical techniques have been developed for the measurement and imaging of morphology, function and dynamics of whole living tissues and cells, and their applications in biology and medicine are being promoted. Most of these techniques are based on tissue optics, which takes into account the interactions between light and biological tissues, such as light absorption and scattering. This article describes several methods for the measurement and imaging of physiological functions using diffuse reflectance spectral analysis based on tissue optics.

Picosecond lasers have been used in plastic surgery, dermatology, and cosmetic surgery. While the appropriate setting of irradiation endpoints is crucial for effective treatment, laser-induced skin reactions vary not only with irradiation parameters but also with skin type and lesion distribution in the skin. In silico evaluation based on tissue optics is effective for analyzing the picosecond laser-skin interactions, taking these factors into account. This article reviews an in silico evaluation based on tissue optics for picosecond laser treatment of pigmented lesions, including an in silico model of picosecond laser treatment, measurement of optical properties of human skin, computational design of an irradiation indicator, and validation of in silico results by comparison with the results from clinical studies.

This study aimed to develop a simulation model for interstitial photodynamic therapy (iPDT) by diffuse irradiation with Laserphyrin for the treatment of malignant brain tumors. A three-dimensional model of subcutaneously implanted tumors was constructed, and light propagation within tumor tissues was analyzed using Monte Carlo simulations. The simulation parameters were calibrated to match experimental measurements obtained from optical phantoms that mimic the optical properties of tumor tissue. The effective therapeutic depth was estimated under various irradiation conditions and compared with reported in vivo experimental results, demonstrating a relative error of approximately 16%, indicating good agreement. This study successfully established a simulation model capable of optimizing probe placement and irradiation parameters to enable safe and effective iPDT for malignant brain tumors.

Upper tract urothelial carcinoma is a malignant tumor that develops in the urothelial mucosa of the renal pelvis and ureters. The standard treatment, total nephroureterectomy, is associated with decreased renal function, high invasiveness, and risk of recurrence and metastasis. In this study, we focused on the potential of photodynamic therapy (PDT) as an organ-sparing treatment for upper tract urothelial carcinoma. As an initial investigation for clinical application, we evaluated the effects of individual differences in PDT irradiation conditions and tissue characteristics on light propagation in the tissue through in silico evaluations. We performed Monte Carlo simulations of light propagation and constructed a tubular model of the ureter using measured optical property values. The inner diameter of the tube, tumor thickness, absorption coefficient, scattering coefficient, light emission length, displacement of the light source from the central axis, and irradiation time were set as evaluation parameters, and the effects of each variation on the optical penetration depth and tumor coverage were analyzed. As a result, it was found that the optical penetration depth depends on the inner diameter of the tube and absorption coefficient, while the tumor coverage depends on the inner diameter of the tube, the tumor thickness, and absorption coefficient. It was also shown that appropriate setting of the light emission length is required for efficient light irradiation of tumor tissue. This study is expected to provide guidance in the design of clinical protocols for PDT for upper tract urothelial carcinoma and to contribute to the development of novel minimally invasive and organ-sparing treatment modalities.