A Rotational Phantom for Evaluation of MR-Compatible Biopsy Devices: Experiment and Preliminary Observations

以旋轉假體評估磁振造影機相容的器械：實驗及初步觀察

陳中和(Jeon-Hor Chen) ； 沈戊忠(Wu-Chung Shen)

《Mid-Taiwan Journal of Medicine》 4卷2期 (1999/06) Pp. 84-90

https://doi.org/10.6558/MTJM.1999.4(2).2

摘要

近年來介入性磁振造影檢查或治療已日漸受重視。因這種發展，與磁振造影機相容的各種器械也因應而生。儘管這些器械具極低或不具磁性，但假影仍然產生。假影的大小、形式，除與器械本身結構及材質有關外，並與其在磁場中的位置有很大的關係。另外，採用的脈衝波序及之中的參數改變亦影響假影的嚴重程度。在此，我們設計一種可旋轉的假體，此假體由一底座及一旋轉箱所構成。旋轉箱內並可置入一試驗版。底座上標示著不同角度的直線，試驗板上則刻劃有不同角度的溝槽。藉著改變旋轉箱的角度與器械在試驗板中溝槽的位置，我們遂能評估在磁振造影機中其三度空間的位置與假影大小的關係。另外，由於試驗板上均勻分佈著作為標記用的小孔，故假影的變寬、拉長、偏移及對周圍組織的扭曲程度，都可得到較正確之測量。我們以此假體，對不同口徑的穿刺針，用各種不同的快速掃描脈衝波序作試驗，並找出一些影嚮假影產生及嚴重程度的因素。

關鍵字

假影 ； 磁振造影 ； 與磁振造影機相容的器械 ； 假體

並列摘要

We designed a rotatable phantom which could evaluate artifacts of magnetic resonance (MR)-compatible devices. This phantom was made of polymethyl-metacrylate (PMMA). It had two major parts: a basic plate and a rotational box. There was a test plate in the box. Devices to be evaluated were fixed in different tunnels of the test plate. Small holes were evenly distributed on the plate which acted as markers for measurements. By changing the angle of the rotational box related to the main magnetic field (Z-axis) and the position of the needle in various tunnels, three-dimensional analysis of the artifacts of MR-compatible devices was possible. With this phantom, measurements of artifacts including width, elongation, shifting and geometric image distortion could be precisely obtained. We used various fast imaging techniques such as turbo spin echo, turbo field echo, and echo-planar imaging, to test the biopsy needles. The preliminary results showed that multiple factors affected the artifacts. They included the echo time, the direction of the frequency or phase encoding, the pulse sequences, the diameter of the device, and the position of the device in relation to the main magnetic field. Full exploration of the impact and to what extent on artifact formation, however, demand further evaluation.

並列關鍵字

artifact ； magnetic resonance (MR) ； MR-compatible device ； phantom