應用田口方法以自製往復型動態水假體最佳化錐形射束電腦斷層解析

Optimizing the Spatial Resolution of the Cone-beam CT Image using Taguchi Analysis and Dynamic Water Phantom

劉慧蘭(HUI-LAN LIU)

指導教授 ： 潘榕光

中臺科技大學/健康科學院/醫學影像暨放射科學系暨研究所/碩士(2017年)

摘要

本研究設計一個動態假體，模擬人體動態情形，並使用田口方法求來調整這些參數及其相互作用影響，降低因呼吸而造成的殘影，找出錐形射束電腦斷層影像品質的最佳化條件。直線加速器外掛X光管和影像接收器，選定儀器參數：重組濾片、像素數目、切片厚度、掃瞄範圍。為模擬實際病人狀態，動態水假體條設為：假體長度與寬度為30公分、水深20cm、7mm壓克力球、每分鐘17轉、振幅10mm。機器旋轉360度，腹部拍攝條件，量測影像條件的灰階(W/L)調整為1400/500，為腹部條件。利用田口八標直交表之望小分析，其S/N值越大越好，找出最佳化模式。依據田口分析的平均值、標準差、S/N值、 因子反應圖、交互作用圖、變異分析及驗證實驗結果，顯示最佳參數組合為重組濾片_ 平滑型，像素數目_256*256，Slice切片厚度_2.5，掃瞄範圍_45*45。將研究數據進行ANOVA分析，通過顯著因子99﹪的驗證包含像素數目、掃瞄範圍，以像素數目的顯著因子為最高的100﹪，即主要因子為像素數目。比較廠商建議條件S/N值為25.80、常規使用條件S/N值為42.48、研究的最佳化組合條件S/N值為43.33，其研究的最佳化條件的S/N值最高，而主要因子的極值為256*256，可提高影像品質降低殘影。因動態條件在銳利濾片，精細的像數，較薄的切片厚度，更容易顯示出殘影 。

關鍵字

錐形射束電腦斷層 ； 田口方法 ； 影像品質

並列摘要

This work optimized the spatial resolution of cone-beam CT using Taguchi optimization analysis and a dynamic water phantom. The dynamic water phantom was designed to well simulate the metabolic mechanism of human body during CT examination. The 30x30x30 cm3 size of water tank equipped with an indigenous device on the top of water tank to imply the reciprocating motion such like respiratory or cardiac system in reality. Four factors of cone-beam CT, Reconstruction Filter, Reconstruction Volume, Slice Distance, and Diameter were assigned in this work to organize an eight combination according to Taguchi’s recommendation. The water phantom was preset as 20 cm depth of water, 7 mm in diameter of canter PMMA ball, 10 mm of amplitude and 17 rpm of the reciprocating motion. The CT was preset as abdomen protocol and the grey index (W/L) was preset as 1400/500. The optimal result was obtained as SMOOTH Reconstruction Filter, 256*256 Reconstruction Volume, 2.5 Slice Distance, and 45*45 Diameter. Three out of four factors, Reconstruction Volume, Slice Distance, and Diameter were passed the ANOVA test and defined as dominant factors. The derived S/N was 43.33, 42.48, and 25.80 dB for optimal, conventional and system default setting of the same CT, thus the optimal setting of cone-beam CT was verified.

並列關鍵字

CBCT ； Taguchi method ； Image quality

參考文獻

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