在不同溫度下之超音波性質組織模擬膠的光譜變化分析

Abstract

本論文從事的超音波模擬膠(Ultrasonic Tissue-mimicking gel)性質之觀測這項研究計畫，主要利用了此種具有超音波性質的組織模擬膠材料，進行一連串的實驗。根據實驗的結果，我們讓此模擬膠材料在不同溫度、厚薄程度下，利用紫外光可見光光譜分析法分析其吸收光譜，觀察其光譜之改變。而此種超音波組織模擬膠，是參考著名學者 Eugene L. Madsen 之研究，其各種參數，皆可比擬至人體的組織，至今仍被廣為應用並獲得國際之認可。我們觀測了這種模擬膠分別置入10 mm及2 mm石英管比色皿中，使其在常溫(約攝氏25度)至攝氏 80 度之區間內，使用CT-2800 spectrophotometer，使用觀測光的穿透度，來跑出其光譜。在 10 mm 的厚度下，因石英比色皿厚度太厚，模擬膠的透光度有限，因此跑出來的光譜 變化不明顯並且曲線雜亂，並不適合用於接下來的實驗當中。而在更換成2 mm的厚度之下，並觀察從190 nm至1000 nm在各溫度下的光譜表現，並且發現了在長波長的部分(700 nm至1000 nm區間)的光吸收度，有非常顯著的變化。為保其準確性，經過數次的測試，確認其變化並非偶然，於是將致力於長波長部分作數據的分析與探討。

Spectrophotometric results for a well-known agarose-based ultrasonic tissue-mimicking gel phantom material, as developed by Eugene L. Madsen and colleagues, are reported for the purpose of temperature change detection. The gel consists of a combination of agarose, distilled water, n-propanol, and evaporated milk. Gels were tried to cast into 2 mm and 10 mm thick cuvettes and allowed to cool to room temperature(About 25 degrees centigrade). Spectra obtained include those at room temperature and those following heating to temperatures between 30 and 80 degrees centigrade using CT-2800 spectrophotometer. But the 10 mm cuvettes were too thick for light to penetrate the tissue-mimicking gel. Temperature elevation causes substantial irreversible changes in gel absorption spectra, with increased absorption between wavelengths of 800 to 1000 nm at 80 degrees centigrade. Such spectral changes with heating may provide a means for estimating ultrasonically induced localized heating in this material, for instance with high-intensity focused ultrasound or other ultrasonic exposures.