Research Projects

Ultrashort-pulsed laser skin treatment (超短パルスレーザーによる皮膚疾患治療)

Birthmarks and blemishes are symptoms in which melanin pigment is deposited excessively in parts of the skin tissue. Laser irradiation is the most common treatment, and in recent years, picosecond lasers, which emit laser pulses in units of 1 to 10 billionths of a second, have been attracting attention. Many clinical studies have reported that picosecond laser treatment has fewer complications such as post-inflammatory hyperpigmentation, but the setting of irradiation conditions, which is an essential factor in treatment efficacy, is often based on the surgeon's empirical rule, and there is no objective indicator. In this study, I am developing a technique for laser irradiation with optimal conditions and high reproducibility by elucidating the picosecond laser-tissue interactions and constructing a treatment model based on the physical phenomena.

アザやシミは，皮膚組織の一部にメラニン色素が過剰に沈着する症状です．レーザー照射による治療が主流で，近年では10億～100億分の1秒の時間単位でレーザーを照射するピコ秒レーザーが注目されています．ピコ秒レーザー治療では，炎症後色素沈着等の合併症が少ないと報告されていますが，治療効果に最も重要となる照射条件の設定は，術者の経験則に基づくことが多く，客観的な指標がありません．本研究では，ピコ秒レーザーによる生体反応を解明し，それに基づく治療モデルを構築することで，一人ひとりの肌質や病変の状態に合わせて，最適な条件で再現性高くレーザー照射する技術を開発しています．

Development of minimally-invasive laser treatment technique (超低侵襲な疾患選択的レーザー治療技術の開発)

Lasers can be used to treat birthmarks, moles, and cancers in a minimally invasive way, but the irradiated light undergoes multiple scattering by the skin, and is absorbed by the target as well as by normal blood vessels and melanocytes. Because the energy of the laser used in treatment is extremely high, the absorbed light can cause thermal damage to normal tissue, leading to complications. In this study, I am developing a treatment technique that is noninvasive to normal tissues by efficiently delivering the laser to the target and improving the selectivity of the lesion's response to the laser.

レーザーは，シミ・あざ，がんを低侵襲に治療することができますが，レーザーが生体組織に散乱されて拡がることで，血管等の標的以外の正常組織に吸収されてしまいます．治療で使用するレーザーのエネルギーは極めて高いため，正常組織に熱傷を誘発し合併症を生じる可能性があります．本研究では，レーザーを標的に効率良く照射し，レーザーによる生体反応の病変選択性を向上させることで，正常組織に非侵襲な治療技術を開発しています．

Related papers: Sci. Rep. 14, 20112 (2024).

Measurement of optical properties of biological tissues (生体組織の光学特性値計測)

For light-based diagnostic and therapeutic techniques, which are attractive due to the minimally invasive nature to biological tissue, understanding the light distribution within the tissue is important to achieve accurate and safe diagnosis and treatment by quantitatively assessing the area to be diagnosed or treated. The light distribution within the tissue is determined by the optical properties of the biological tissue (absorption coefficient, scattering coefficient). In this study, I develope a measurement system and analysis algorithm to measure the optical properties, and measure various human and animal tissues. I have reported on the optical properties of Asian human skin for the first time in the world and am currently working on creating a database.

生体組織に対する非侵襲・低侵襲性が魅力である光診断・治療技術において，生体組織内の光分布を理解することは，診断や治療している領域を定量的に把握し，正確かつ安全な診断・治療を実現するうえで非常に重要です．組織内光分布は，生体組織の光学特性値（吸収係数，換算散乱係数）より決まります．本研究では，光学特性値を計測する測定システムや解析アルゴリズムを開発し，ヒトや動物の様々な組織を測定しています．これまでに世界で初めてアジア地域のヒト皮膚光学特性値を報告しており，現在はデータベース化も進めています．

In silico trial method (計算機臨床試験法)

Improving the sophistication of optical devices that emit light and lasers is important for expanding the clinical application of optical diagnosis and treatment technology, but the time and cost of clinical trials is a constraint. In this study, I am developing computational modelling and simulation for the physicochemical reactions that occur in biological tissues when exposed to laser light, and I am developing a new testing method called 'in silico trials,' which will allow us to replicate on the computer the tests that have previously been carried out in the physical world. Complementing or partially replacing preclinical and clinical trials could lead to new optical devices being brought into clinical use quickly and at low cost.

光診断・治療技術の臨床応用の拡大には，光・レーザーを照射する光学機器の高度化が重要ですが，臨床試験等にかかる時間・費用が制約となっています．本研究では，レーザー照射によって生体組織に生じる物理化学反応のモデリング・計算機シミュレーション技術を開発し，これまで物理空間で行われていた試験を計算機上で再現する，計算機臨床試験という新たな試験法を開発しています．これまでの前臨床試験・臨床試験を補完・一部代替することで，新規光学機器が迅速かつ低コストに臨床応用されることが期待されます．

Photodynamic therapy for cancer and bacteria

Photodynamic therapy (PDT) is a minimally invasive treatment that produces anti-tumour and sterilising effects by irradiating photosensitizers accumulated in the target with low-intensity light, causing the production of reactive oxygen species. In this study, I am developing an antimicrobial PDT using a portable, wearable, and disposable OLED film for home treatment, and a computational simulator based on measured optical properties of normal and tumour tissues to control the light irradiation in PDT.

光線力学治療 (Photodynamic therapy; PDT) は，標的に蓄積させた光感受性薬剤へ低強度の光を照射し，活性酸素種を生成させることで抗腫瘍効果・殺菌効果をもたらす低侵襲な治療法です．本研究では，在宅治療に向けた，貼付け式の有機ELフィルムを用いた細菌PDTの開発や，がんPDTの光照射管理に向けた，正常組織と腫瘍組織の実測した光学特性値に基づく治療シミュレータを開発しています．