- 期刊
改變電腦斷層儀之掃描參數進行亨氏單位研究並討論機台變異性
Hounsfield Unit Variations Due to Different CT Imaging Parameters and the Assessment of Interscanner Variations
摘要
本研究主要目的為利用Catphan 504假體探討電腦斷層儀掃描參數，含管電壓、管電流、影像切面厚度與ROI 圈選面積對亨氏單位（Hounsfield unit, HU）量測的影響以及進行量化HU的機台變異性。Catphan504 假體內其中一模組由各種不同物質組成，包含air、PMP、LDPE、polystyrene、acrylic、Delrin 以及Teflon。因組成物質的電子密度相差甚大，故該模組適合提供作為量測一個廣泛區間的HU。再者，三台不同型號的電腦斷層儀：Philips Brilliance Big Bore、GE Discovery 590 RT 和GE Light Speed RT16 在相同的造影條件設定下，欲討論HU 是否存在機台變異性。改變四種電腦斷層儀掃描參數量測結果發現只有當管電壓改變時，HU 會隨著變化。除了air 此物質外，管電壓逐漸上升時，所有物質的HU 皆隨著增加，唯獨Teflon的趨勢相反。故由本研究之結果了解HU 具有能量依存性（energy dependent），而管電流、影像切面厚度和ROI 圈選面積都與HU 無任何顯著的相關性。此外，經由此研究實際量測後發現不同電腦斷層儀機台間存有機台變異性。
並列摘要
The aim of this study was to investigate the influence of varying tube voltage (kVp), tube current (mA), slice-thickness and selected ROI area on the measured Hounsfield unit (HU) and to quantity the interscanner variability in HU measurements made with one selected Catphan 504 phantom. One of the Catphan 504 modules, the sensitometry module, is suitable for measuring HU on a wide range which has inserts made from air, PMP, LDPE, polystyrene, acrylic, Delrin and Teflon. Three different CT scanners were tested for HU interscanner variability: Philips Brilliance Big Bore, GE Discovery 590 RT and GE Light Speed RT16. Measured HU for all materials except for air changed substantially only when kVp settings were modified. The measured HU increased with increasing kVp for all the materials where changes in HU were observed, except for Teflon. The measured HU values presented in this study for the sensitometric inserts in the Catphan 504 phantom are energy dependent only. Furthermore, there was no correlation between CT attenuation value and tube current, slice-thickness and selected ROI area. Substantial interscanner variability in measured HUs was found when a Catphan 504 phantom was scanned on the three different CT scanners.