許多重要疾病如腫瘤的研究，皆與血管有著密切的關係。在此研究中，我們基於非聚焦式超音波換能 器，建立一套可應用於活體小動物微細血管脈絡造影之光學解析度光聲顯微影像系統 (optical resolution photoacoustic micro-imaging system, OR-PAM)。光聲造影 (photoacoustic imaging) 為一種基於光聲效應之 新穎生醫造影技術，對於微細血管造影來說，此技術最大優點為不需標定的高光學吸收對比，且為非侵入 式的成像技術，同時可進行血液相關重要參數，如血紅素濃度及血氧飽和濃度的功能性造影。傳統的光學 解析度光聲顯微影像系統，使用機械式掃描及聚焦式超音波換能器來提升系統之訊雜比，但機械式掃描會 增加系統成像時間。光學式掃描可以解決此問題，但系統的光學物鏡與聚焦式超音波換能器會限制系統之 視野，本系統選用非聚焦式超音波換能器增加系統之視野，並針對非聚焦式超音波換能器所造成之空間脈 衝響應優化超音波換能器中心頻率、尺寸及成像距離的選擇，以改進訊雜比。實驗結果證實本系統之於影 像平面空間解析度可達 13.5 微米，並可用於活體微細血管脈絡造影。未來工作重點將放在系統掃描速度 的提升、空間解析度的改進及多波長功能性血管造影上。

Blood vessels play an important role in many significant disease researches such as cancer study. In this study, we developed an unfocused ultrasound transducer based optical resolution photoacoustic micro-imaging system (OR-PAM) for in vivo micro-vasculature imaging of small animals. Photoacoustic imaging is a novel bioimaging modality based on the photoacoustic effect. For micro-vasculature imaging, it owns the advantages of label free high optical absorption contrast and can be performed non-invasively. It also can provide blood-related functional imaging capability for the measure of total hemoglobin concentration and hemoglobin oxygen saturation. Conventional OR-PAM employs a focused ultrasound transducer to improve the signal-to-noise ratio (SNR) and performs mechanical scanning for imaging. However, mechanical scanning is time-consuming. Such a problem can be solved by optical scanning while the optical objective lens and focused ultrasound transducer limit the field of view (FOV) instead. In our design, the FOV is improved by using an unfocused ultrasound transducer. In addition, based on the spatial impulse response of the unfocused transducer, the center frequency, size, and imaging distance of the unfocused ultrasound transducer are optimized to improve the SNR. The experimental results showed that the spatial resolution of the developed OR-PAM was 13.5  m in the en-face imaging plane. In vivo micro-vascular imaging capability was also demonstrated. Future work will focus on the improvement of the imaging frame rate and spatial resolution and the development of multi-wavelength functional micro-vascular imaging.