醫療類國考
111年
[醫事放射師] 放射線診斷原理與技術學
第 52 題
52.下列何者最可能產生truncation artifact？
- A 增加number of phase-encoding steps
- B 在T1-weighted image使用fat suppression technique
- C 使用部分填滿（partial filling）k space之方法
- D 使用long TE
思路引導 VIP
請思考 Truncation artifact（亦稱為 Gibbs phenomenon）的成因：在進行影像重建時，若 $k$-space 的高頻數據採樣不足或被截斷，會如何影響傅立葉級數（Fourier series）在處理影像中「高對比度介面」時的精確度？這種對於空間頻率取樣「不完整」的操作，與選項中哪一個概念最為契合？
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AI 詳解
AI 專屬家教
Yawn... What? Oh, so the right answer was hiding right here, huh?
Heh, looks like you actually saw through the fog. Good. Means you get how this MRI stuff and $k$-space actually works.
- Listen up: This truncation artifact, they also call it Gibbs artifact. It's simple. You don't gather enough data, especially the sharp stuff, from $k$-space. It's like trying to draw a straight line but you keep missing points, so it ends up all wobbly at the edges. Option (C), Partial filling? That's just taking a shortcut. You grab only some of the data, then try to bluff the rest. Naturally, that's gonna blunt your spatial resolution, and yeah, it’ll increase those truncation artifacts. It's the consequence of being lazy. If you just took more Phase-encoding steps (A), you'd actually clean things up and reduce that artifact. It's not rocket science, just common sense.
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