正子/單光子雙用途分子影像儀之平面式成像探頭研發

Development of a Flat-Panel Positron/Single-photon Camera for Molecular Imaging Devices

梁鑫京(Hsin-Chin Liang)

指導教授 ： 蘇振隆

中原大學/工學院/生物醫學工程研究所/博士(2012年)

https://doi.org/10.6840/cycu201200246

摘要

由於分子影像利用追蹤核醫藥物來進行功能性造影的特性，使其成像提供了生物體內組織功能與生理作用機制的資訊，較之其它提供結構性資訊的影像方法，能更早期且正確的偵測病灶所在。將高解析探頭應用於人體特定部位之臨床診斷的趨勢，越發受到重視。本研究的目的是開發一個平面式加馬成像探頭，探討相關技術之可行性；此探頭不但要適用於正子與單光子雙用途的成像，亦同時擁有具臨床實用價值的成像性能(小於3mm的解析度)與有效成像面積(80×80 mm2以上)，且有效成像區域為連續不間斷。
本研究選定性能較具競爭力的細針光學隔離晶陣耦合位敏光電管之組態設計，作為其發展基礎。主要分五階段進行，首先比較六種不同材料的成像偵檢性能、操作性以及取得性，並經實測，選取矽酸鎦釔(LYSO)作為閃爍材料。其次是單光電管成像單元實作與測試，結果顯示，此單元不論在高(正子—511 keV)、低(單光子—140 keV)能加馬射線下皆展現了極佳的成像性能(Pixel width < 0.8 mm，energy resolution < 15%)。第三階段則是研究連續導光介質對成像偵檢性能劣化的影響，結果顯示了導光材料厚度越大，雖然會使事件位置判斷更加線性，但其分布卻變得更加寬闊，造成解析能力的劣化。因此使用厚度2 mm的連續導光材來進行成像面積的擴展。第四階段是進行成像面積連續不間斷擴展的可行性研究，並實做出本文標的之成像探頭。實測結果顯示此一成像探頭有效成像面積達89×89 mm2，並在正子與單光子成像應用上皆展現了極佳的成像性能；此探頭預期於正子影像系統上可提供約2 mm的空間解析度，於針孔準直單光子影像系統上，預期可提供小於1 mm (sub-millimeter)的解析度極限。最後是研究此探頭的自發背景輻射對單光子成像應用的影響，實驗結果顯示即使在自發性背景的干擾下，此一探頭仍能輸出正確且高品質的影像，驗證其雙用途成像的可行性。
本研究依據成像原理，嘗試以光學處理技術，克服感光區域不連續的物理限制，成功由基礎材料完成製作一正子/單光子成像探頭原型，此一探頭原型不但具有完整且連續的成像區域，更具有實用化的有效成像面積；以均勻加馬射源量測此探頭於正子與單光子成像應用時所能展現之性能，結果顯示此一成像探頭不但可應用於正子與單光子雙成像用途，並展現符合預期的優良成像性能。

關鍵字

正子成像 ； 成像偵檢器 ； 點陣式加馬成像探頭 ； 雙用途成像 ； 單光子成像

並列摘要

By using the feature of radio-pharmaceutical tracking, molecular imaging modalities offer bio-functional information of living tissues. Compare to those modalities offering anatomical images, molecular imaging offers more specific diagnosis and earlier detections to the lesions. Applying small cameras with high-resolution capability to image specific target on human body at a close position to gain high quality images for diagnosis, has been showing its potential on clinical use. The purpose of this study is to develop a flat panel gamma camera and to study the required technology. The proposed camera is requested to satisfy the following three specifications to show its practicality of in-vivo imaging. First, the proposed camera should be capable of processing dual-modality imaging applications, i.e. positron and single-photon imaging. Second, a good resolution performance (better than 3 mm) should be shown. Third, a successive imaging area larger than 80×80 mm2 is required.
In this study, the architecture of crystal array composed of needle like elements coupling onto PSPMTs was chosen to be the development basis. Five terms of work were processed to achieve the objectives. The first term is to evaluate the imaging performances, manipulation, and availability of six scintillators. According to the test results, LYSO was chosen for processing the following terms of work. The second term is to build a base imaging unit (an imaging detector based on a single PSPMT) for technology validating and evaluate its performance. The results showed that the proposed imaging unit is capable of offering promising performances (pixel width < 0.8 mm and energy resolution < 15%) for the dual-modality imaging. The third term is to study the influences of the continuous light guide on degradations of imaging performances, and to evaluate the effectiveness of light guide thickness to make the imaging area successive. According to the experimental results, 2mm-thick light guide was chosen to develop the proposed dual-modality camera. In the fourth term of work, a camera meeting the purpose of this study and with the specifications obtained from the previous terms of work applied was built. The effective imaging area was extended successively to 89×89 mm3. The results showed that the proposed camera offers outstanding performances for positron (about 2 mm resolution) and single-photon imaging (sub-millimeter achievable with pin-hole collimation). The last term is to evaluate the influence of the camera’s intrinsic radiations on single-photon imaging. The results showed that the proposed camera is capable of offering correct and quality images in single-photon imaging applications.
In this study, by basic studies on scintillation materials and continuous light-guide influences, a dual-modality camera for positron and single-photon imaging was completed. It is shown that outstanding performances and a practical size of imaging area were achieved, therefore, the objectives and technical requests of this study are satisfied.

並列關鍵字

pixellated gamma camera ； positron imaging ； Imaging detectors ； single-photon imaging ； dual-modality imaging

參考文獻

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