比較濾波反投影法與疊代演算法兩種技術用於偵測標幟紅血球斷層掃描肝臟血管瘤的差異—先期研究

Comparison of Filtered Back Projection and Iterative Reconstruction in Detecting 99mtc Labeled Red Blood Cell SPECT for Liver Hemangiomas — A Preliminary Report

蔡政謙(Cheng-Chien Tsai) ； 許靖涵(Ching-Han Hsu) ； 曾凱元(Kai-Yuan Tzen) ； 閻紫宸(Tzu-Chen Yen)

《核子醫學雜誌》 13卷2期 (2000/06) Pp. 93-97

摘要

背景：利用疊代法(iterative)重建核醫單光子射出電腦斷層影像，由於其能較精準地描述單光子的統計特性，因此能夠產生比濾波反投影法(filered back proiection)更佳的結果。這份先期研究旨在比較疊代法和濾波反投影法兩種方法運用於鎝-99m標幟紅血球偵測肝臟血管瘤的診斷準確性。材料與方法：我們評估了二十位超音波發现有肝臟腫瘤並且經證實為血管瘤的病人，全部以三偵測頭閃爍攝影機施行斷層造影，並分別將造影結果以濾波反投影法以及疊代法運算重建影像，交付三位核子醫學專科醫師判讀。本研究之濾波反投影法均利用Chang's方法衰減校正，而疊代法則未進行衰減校正。結果：整體而言，使用疊代法所重建影像品質比濾波反投影法為佳，總共36顆肝臟血管瘤裡面有27顆在疊代法中偵測到，只有23顆在濾波反投影法中偵測到。在偵測週邊位置的肝臟血管瘤方面，疊代法具有較高的敏感度。至於在偵測中心位置的肝臟血管瘤方面，未接受衰減校正之疊代法具有和衰減校正後之濾波反投影法相當的敏感度。結論：本研究顯示疊代法可以提供比濾波反投影法更佳的重建影像品質，並且在偵測肝臟血管瘤方面具有較高的靈敏度。至於將衰減校正加入疊代法運算這部份，尚待下一步的研究。

關鍵字

濾波反投影法 ； 疊代運算 ； 標幟紅血球斷層掃描 ； 肝臟血管瘤

並列摘要

Background: Iterative reconstruction methods for SPECT imaging can produce image results superior to filtered back projection(FBP),since they can explicitly model the underlying Poisson statistics of photon emissions as well as the physical properties of a SPECT scanner. The purpose of this study is to compare the diagnostic accuracy of(superscript 99m)Tc labeled red blood cell(RBC)liver SPECT images reconstructed by FBP and iterative method based on maximum likelihood expectation maximization(MLEM).The performance is evaluated in terms of liver hemangiomadetectability.Methods:20 patients(5 males,15 females, age range:30-82yrs;49±13yrs)with 36 hemangiomas found on ultrasound(US)are selected in this study. The final diagnosis of each patient is made after liver biopsy, aspiration with cytology and/or autopsy, or follow-up with both clinical and US findings. The corresponding SPECT studies of these patients are performed using Siemens Multi SPECT 3 scanner, and are reconstructed following the default clinical FBP protocol with attenuation correction(AC)using Chang's method. These SPECT data are also reconstructed by MLEM without AC. Early stopping rule with total 20 iterations are applied in MLEM to ensure proper image convergence. Three nuclear physicians compare the image results reconstructed by FBP with AC and MLEM without AC. Results: The overall image quality of MLEM is superior to FBP.MLEM detects 27 of 36 hemangiomas while FBP only detects 23 of 36 ones. MLEM has higher sensitivity than FBP in detecting peripheral lesions, and provides compatible sensitivity in detecting central lesions. There are also many cases that lesions are not detected in FBP, but can be easily located by using MLEM. Diagnostic results based on MLEM images also match with the original case reports. Conclusion: MLEM image reconstructions can produce image results with higher quality and significantly improve diagnostic accuracy for lesion detection in RBC liver SPECT compared to the conventional FBP methods. However, the influences of AC to MLEM image reconstructions still need further investigation.

並列關鍵字

filtered back projection ； iterative method ； RBC SPECT ； hemangioma