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顯微斷層掃描（Micro CT）在昆蟲學研究的應用
Micro Computed Tomography in Entomological Research
摘要
顯微斷層掃描是一項針對小型動物研究的造影技術。利用X光的穿透性及三維影像的構築，相比過去的解剖切片，非侵入性的手法觀察生物體內部的構造可以減少目標的變形。過去的機型主要應用於針對小型活體動物的醫學研究，而近年來在影像技術的進步下，影像的解析度已提升至奈米（nanometer, nm）等級，更有利於將此技術使用在昆蟲學的研究上。台灣的研究單位所配置的機型，解析度為0.1至9 μm，使用者可以依照自身需求選擇。但初期的樣本製備，影像測試及修正，以及後期的影像處理上需要許多繁雜的技術。為了讓更多的使用者在使用顯微斷層掃描之前，能夠理解並活用此項技術於更多的研究上，本文章以現有的成果，以及目前該技術的過往研究整理以供參考。顯微斷層掃描藉由X光的非侵入性觀察可以讓我們更加了解生物或非生物內部的構造，但它在樣本的選擇及製備上卻有許多限制。樣本密度差異過大以及厚度不平均都會造成影像品質的下降，現今較長的造影時間也難以完成活體觀察。肌肉等軟組織還需要輔以碘液（iodine solution）或是磷鎢酸（phosphotungstic acid）作為顯影劑長時間浸染，並且依照樣本的不同，所需的顯影劑濃度及染色時間也需要個別調整。儘管如此，非破壞性多角度切片及三維結構提供了昆蟲學的研究上許多新的發展。透過觀察昆蟲外部形態的特徵和內部組織的變化，我們可以推斷棲地環境和食性，進一步深入研究物種的分類和特徵演化。其中肌骨組織運動的模擬，對於力學研究方面可以用來製作立體模型和仿生機器。那些難以使用光學儀器觀察的化石標本，也在維持樣本完整性的同時獲得內部結構的資訊。三維影像還有助於研究者之間的信息交流，以及在收藏和展示方面提供便利性。除了昆蟲本身，這項技術也適用於觀察非生物體，包括白蟻巢腔內部的挖掘情況和周圍棲息地的變化，進一步了解昆蟲的行為和防治研究。因此近年來，顯微斷層掃描已經成為防檢疫、法醫昆蟲學和考古學等領域不可或缺的技術。
並列摘要
Micro-computed tomography (Micro-CT) is an imaging technology used in small animal research. It employs noninvasive X-rays that do not harm a sample, thereby facilitating detailed observations of in vivo structures. Initially, micro-CT was used primarily in medical research involving small living animals. As the process of imaging techniques, nano-level resolution has been achieved, expanding its applications. This high-resolution imaging technique is particularly useful for observing minute samples. In Taiwan, several micro-CT machines with varying resolutions are currently available. However, the utilization involves various complex processes, such as sample preparation, image testing, and editing. This article introduces and provides a discussion of the principles of micro-CT, suitable samples for this technique, preparation methods, and relevant studies and applications. Micro-CT enables the noninvasive observation of X-rays to gain insights into the internal structures of biological samples. Nevertheless, there are limitations associated with the sample selection and preparation processes of micro-CT. Problems such as beam hardening and uneven thickness can result in low image quality and noise. Additionally, the lengthy imaging time required for performing micro-CT poses challenges for observing live samples. For soft tissues such as muscles, the use of iodine solution or phosphotungstic acid as a radiocontrast agent is necessary. The concentration and staining duration for an agent should be adjusted for each sample. Nevertheless, micro-CT enables researchers to visualize three-dimensional structures, which is highly valuable in entomological research. The external structures and internal tissues of insects can be observed to identify differences in habitat and food preferences, which, in turn, can clarify their taxonomy and evolution. The simulation of musculoskeletal tissue motion aids in mechanical research, facilitating the creation of three-dimensional models and bionic machines. To obtain useful information, micro-CT can be used to study fossil samples that are difficult to observe through optical instruments, without damaging them. Furthermore, exchanging, collecting, and displaying three-dimensional images are straightforward. Through micro-CT, researchers can observe nonbiological aspects, including the internal of nests and adjacent habitats, to further understand insect behavior and conduct pest control research. Micro-CT has also been applied to develop various types of equipment in fields such as quarantine research, forensic entomology, and archaeology, and it has become an indispensable technique in multiple scientific fields.