- 期刊
放射治療錐狀射束電腦斷層使用疊代重建算法（Iterative）之影像品質
Image Quality of Cone-beam Computed Tomography in Radiotherapy by Using Iterative Agorithm
摘要
本研究使用錐狀射束電腦斷層（cone-beam computed tomography, CBCT）的影像來探討有無使用疊代重建算法的CBCT影像（有使用疊代重建算法的CBCT影像稱為iCBCT）是否可以改善影像品質。分別使用Halcyon 2.0^(TM)的兩種Head（100 kV）與Pelvis（125 kV）CBCT Mode掃描CIRS 062QA-35假體，其假體內部包含有均勻度層（Uniformity Layer）、CT值線性層（CT number linearity layer）、低對比層（low contrast layer）、空間解析度層（spatial resolution layer）。利用假體的分層分析iCBCT影像的均勻度指標（Uniformity Index, UI）、訊號雜訊比（signal-to-noise ratio, SNR）、對比可見度（Low contrast visibility, LCV）與對比雜訊比（contrast-to-noise ratio, CNR）等參數，進行iCBCT的影像品質評估。研究結果顯示疊代重建算法能夠有效地將雜訊過濾，使整體的數值和離散程度降低，也將整體的SNR皆提高，並且在處理低密度材質的數據上是相當有效，但可能因過於抑低數值而稍微犧牲空間解析度。經此研究可證明使用疊代算法的iCBCT影像可改善整體影像品質，並且提高軟組織間的對比度，有助於臨床治療判別定位。
並列摘要
This study used cone-beam computed tomography with or without iterative algorithm (iCBCT or CBCT) to evaluate the efficacy of iCBCT in improving image quality. Both iCBCT and CBCT were used to scan the CIRS 062QA-35 phantom by Head (100 kV) and Pelvis (125 kV) mode by Halcyon 2.0^(TM) linear accelerator. The phantom contained uniformity layer, CT number linearity layer, low contrast layer, and spatial resolution layer. Data were acquired by scanning the different layers of phantom and were analyzed by using the uniformity index (UI), signal-to-noise ratio (SNR), low contrast visibility (LCV), contrast-to-noise ratio (CNR), and other parameters to evalution image quality of iCBCT. Most the measurements demonstrated that the Iterative algorithm can effectively filter the noise, reduce the overall values and statistical dispersion, and improve the overall SNR. It was also effective in processing data in low-density materials. However, it filtered noise too much to slightly affect spatial resolution. In conclusion, this study presents that iCBCT can improve the overall image quality and contrast between soft tissue, which can improve the precision of set-up and localization of radiotherapy in clinical practice.