適合幼兒腦部核磁共振影像之3T多通道射頻接收相列線圈研發

Abstract

本論文旨在研究開發一個應用在3T磁振造影系統上，適合接收幼兒腦部影像的多通道射頻接收相列線圈。相列線圈的外罩是設計成服帖於七歲幼兒頭部及頸部曲線以增加雜訊比。相列線圈包含32個圓形的平面線圈。所有的線圈設計為平均直徑8公分，並且均勻地分佈于整個外罩。利用調整線圈重疊區域在最佳面積以及低雜訊前端放大器，我們減少了線圈之間的耦合影響。在性能測試上，S12的平均值為-14dB (最小值 = -28dB)。這個相列線圈是用來接收大腦靜態以及動態的核磁共振訊號。影像分析是與32線圈的成人頭部線圈比較。我們發現幼兒相列線圈以及成人相列線圈的訊雜比的比例在邊緣為1.85，而在中間是差不多的。在動態的磁振造影掃描分析中，從幼兒相列線圈所得的時運上的訊雜比為從成人相列線圈所得的120%。以結論來說，我們設計的多通道射頻接收線圈能為幼兒腦部磁振造影影像提供在時域以及空間上較好的雜訊比。

The aim of this thesis is to develop a multi-channel radio-frequency (RF) receive coil array applicable to pediatric brains on a 3T magnetic resonance imaging (MRI) system. The helmet of the array was designed to fit 7-year-old children’s head and neck in order to improve the signal-to-noise ratio. The array consisted of 32 circular surface coils. All coils had 8 cm diameter and were evenly distributed. By optimally overlapping adjacent coils and using low input-impedance preamplifiers, we reduced the coupling between coils efficiently. The average of S12 from bench measurement was -14dB (minimum = -28dB). This array was used to acquire brain static and dynamic MRI. Images were compared with those from a 32-channel adult head coil array. We found that the ratio of SNR between the image from the pediatric array and that from the adult array at the periphery of the head was 1.85, and nearly the same in the center of the head. In dynamic MRI scans, the mean of temporal SNR (tSNR) of the data acquired from a pediatric array was 120% of that of the data acquired from an adult array. We conclude that our multi-channel RF receiving coil array can provide high SNR and tSNR pediatric brain magnetic resonance images.