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磁振造影血管攝影-磁振血流代償技術之開發及應用經驗

MR Angiography-Deduction of Flow Compensation Gradient and Preliminary Experience

摘要


流動的物體如血流等在磁振造影時,使用一般的脈衝波序常產生假影且不易得到足夠的訊號,因此呈現出無訊號(signal-void)的結構。磁振造影欲攝取清晰的血管影像,如血管攝影般的提供診斷時,則必須使用特殊的脈衝波序,才能得到足夠的訊號。欲達到此目的,有許多的方法可以使用,且各有優劣點。過去我們嚐試使用投射取得法(prolection acquisition),但此法只適用於週邊血管,且需使用較厚的切面厚度,以致影像效果不佳,同時對扭曲的血管亦無法-窺全貌,因此我們再使用磁振血流代償技術(MR flow compensation)作為取得血流訊號的工具。本篇即由血流引起的位移,相移(phase shift),及至代償技術的開發,作數學式的推導,並證之以水管實驗,再實際以二度空間飛躍時間(2D Time of Flight, 2D TOF)方法,應用於人體。最後加上最大強度投射(maximal intensity projection, MIP)及Summation等影像處理方法形成初步磁振血管造影(MRA)的經驗。

並列摘要


Flowing spins like blood flow usually experience rapid dephasing and cause signal void and artifact under magnetic field. Brightening up of blood flow signal and diminishment of its artifact require special design of gradient. This is called MR flow compensation. Flow compensation is an essential technique in time of flight method, either 2D or 3D, for MR angiography. Mathematical deduction of flow compensation from position change of flowing spins, its phase shift under magnetic field to gradient design for flow compensation and its preliminary use, in vitro and in vivo, were presented. Imaging processing including summation and maximal intensity projection (MIP) were added also.

並列關鍵字

MR, vascular studies MR, technology

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