皮膚科 王修含醫生

王修含¹²、魏振瑋²、李百祺²³、紀秀華¹  

台大醫院皮膚部¹, 台灣大學生醫電子與資訊學研究所², 台灣大學電機工程學系³

Using Photoacoustic Signal for Temperature Monitoring during Gold Nanoparticles assisted Plasmonic Photothermal Therapy with Laser Irradiation

Shiou-Han Wang¹²,MD; Chen-Wei Wei³,MSE; Pai-Chi Li²³, PhD; Shiou-Hwa Jee¹, MD, PhD

Department of Dermatology¹, National Taiwan University Hospital, Taipei, Taiwan

Institute of Biomedical Electronics and Bioinformatics², National Taiwan University, Taipei, Taiwan

Department of Electrical Engineering³, National Taiwan University, Taipei, Taiwan

王修含¹²、魏振瑋²、李百祺²³、紀秀華¹  

台大醫院皮膚部¹, 台灣大學生醫電子與資訊學研究所², 台灣大學電機工程學系³

 背景：溫度監測對電漿光熱治療（PPTT）的安全與有效性是非常重要的。最準確的測溫法是利用針型熱電偶直接量度，但此法具有高度的侵入性。非侵入式的測量方式具有各自的限制。紅外線熱成像檢測法只能應用於物體表面；超音波測溫法的準確度不高；磁共振測溫法則相當耗時且昂貴。光聲信號(photoacoustic signal)可用來對於真皮層結構進行非侵入性即時造影，且光聲壓力振幅與Grüneisen參數成正比，該參數與溫度具有線性關係。因此，光聲信號具有發展成高準確度且即時非侵入性測量溫度方式的潛力。

左圖：實驗使用之金奈米粒子 (gold nanoparticles)。右圖：光聲實驗雷射架設方式。

目的：利用光聲方式來監測金奈米粒子輔助雷射電漿光熱治療時的溫度。

方法：我們設計一個自製的超音波探頭（中心頻率20百萬赫茲），該探頭具有一條同軸的光纖導管，可發出波長532奈米低功率的脈衝式銣雅各雷射，並同時可接收光聲信號。仿體以另一部連續波銣雅各雷射照射，並浸於熱水浴槽中。在關注區域附近置放針型電熱偶，但雷射光束並未直接照射於該裝置。光聲信號以5077PR前置放大器與取樣頻率200百萬赫茲的類比數位轉換卡收集，並以Matlab^®軟體分析數據（如圖一）。

結果：實驗結果顯示光聲信號與溫度呈現正比例的線性關係，並與連續波雷射之照射具有良好的相關性（如圖二）。

Background: Temperature monitoring is essential to safety and efficacy during plasmonic photothermal therapy (PPTT). Direct measurement with fine needle thermal couple is most accurate but highly invasive. Non-invasive methods have variable limitations. Infrared thermography is limited to superficial surface. Ultrasound suffers from poor accuracy. Magnetic resonance method is time-consuming and expensive. Photoacoustic (PA) signal can approach the dermal structure for real-time image purpose noninvasively, and PA pressure amplitude is proportional to Grüneisen parameter with a linear relationship to temperature. It has potential for real-time measurement of the temperature non-invasively with good accuracy.

Objectives: PA method was used to monitor the temperature during gold nanorods assisted PPTT with laser irradiation.

Methods: We designed a home-made transducer (central frequency 20MHz) with a coaxial optical fiber to emit low power 532 nm pulsed Nd-YAG laser and to receive PA signal simultaneously. The phantoms irradiated with CW mode Nd-YAG laser were immerged in a thermal water tank. A fine-needle thermal couple was placed at the region of interest, but not directly irradiated by the laser beam. The PA signal was collected with a pre-amplifier (5077PR) and an A/D card with sampling rate of 200MHz. The data was analyzed with MATLAB^® software (figure 1).

Results: The result revealed that the PA signal was linearly proportional to the temperature with good correlation to the CW laser irradiation (figure 2).

Conclusions: It showed the potential for temperature measurement during PA image, and this setup was applicable to monitor the temperature in our laser-induced plasmonic photothermal therapy system.