利用動態假體研究冠狀動脈電腦斷層之移動性假影

Using Dynamic Phantom Study for Motion Artifact in Coronary CT Angiography

廖學鍵(Shueh-Chien Liao) ； 劉益瑞(Yi-Jui Liu) ； 陳詩華(Si-Wa Chan) ； 彭曉微(Xiao-Wei Peng) ； 吳新華(Xin-Hua Wu)

《中華放射線技術學雜誌》 34卷1期 (2010/03) Pp. 42-52

https://doi.org/10.30045/CJRT.201003.0007

摘要

冠狀動脈多列式電腦斷層對於冠狀動脈疾病的診斷具有高度靈敏度之優勢，但是影像品質常受到移動性假影的影響，因此本研究透過動態假體來瞭解移動性假影的特性與所造成之因素。將動態假體放置於六十四列電腦斷層中，並選用冠狀動脈攝影條件進行掃描，而在動態假體上固定五條模擬冠狀動脈血管，直徑分別為1.0mm、1.5mm、2.0mm、2.5mm、3.0mm作為主要影像分析之對象，而動態假體主要受呼吸器來控制其動作。首先將假體以靜止與固定250ml振幅分別進行掃描，而模擬心臟運動頻率以每分鐘55次到80次來收集資料。其次固定75次頻率，控制150ml到350ml振幅來收集資料。在假體頻率與振幅的影像分析中，觀察到移動性假影影響程度與運動振幅與頻率呈線性關係。當假體頻率低於70次時能有佳的影像品質表現，而在350ml振幅中可以觀察到電腦斷層值皆產生明顯變化。進一步發現直徑較小受到移動性假影的影響較為顯著。因此心跳頻率高低、血管管徑大小、心跳振幅大小之因素會直接關係移動性假影的影響程度。

關鍵字

冠狀動脈多列式電腦斷層 ； 移動性假影 ； 動態假體

並列摘要

Due to the recent advances in the computed tomography (CT), multidetector row computed tomography (MDCT) has now become a valuable diagnostic modality for cardiovascular diseases. However, it comes with a potential problem which is motion artifacts that degraded the image quality. The purpose of this study is to use a dedicated phantom to evaluate the impact of heart rate on coronary CT angiography image quality and motion artifacts. A phantom made by five artificial coronary arteries of different diameter (1.0 mm、1.5 mm、2.0 mm、2.5 mm、3.0 mm) was attached to a moving anthropomorphic phantom controlled by a ventilation machine. The scan protocol is used as a retrospectively ECG gating under a 64-slice CT scanner. At first, data was acquired by the phantom at rest and 250 ml amplitude respectively. The cardiac motion was simulated by moving velocities from 55 to 80 times per minute periodically. And then, data is the imaged at 150 and 350 ml amplitude simultaneously with a fixed velocity at 75 times per minute. An analysis of image quality, phantom amplitude and motion velocity reveals a linear relationship between motion artifact severity, phantom velocity and amplitude. The image quality has been shown better preserved when phantom velocities are lower than 70 times per minute. The displayed images are also changed in CT attenuation when the phantom amplitude larger than 350 ml. Furthermore, motion-related artifacts are also found to degrade image quality easier in a smaller lumen diameter than a larger lumen diameter. The study concludes that image quality is closely related to the velocity of heart rate, CT amplitude and size of vessels.

並列關鍵字

Coronary CT angiography ； Motion artifact ； phantom