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頁籤選單縮合
| 題 名 | 超高速電腦斷層掃描儀之原理 |
|---|---|
| 作 者 | 林俊民; | 書刊名 | 醫學工程 |
| 卷 期 | 6:5 1994.10[民83.10] |
| 頁 次 | 頁772-775 |
| 專 輯 | 電腦斷層掃描--理論與應用 |
| 分類號 | 416.14 |
| 關鍵詞 | 超高速電腦斷層掃瞄儀; 空間解析度; 對此解析度; 顯影劑; 劑量; Ultrafast computed tomography; Spatial resolution; Constrast resolution; Contrast media; Dose; |
| 語 文 | 中文(Chinese) |
| 中文摘要 | Godfrey Hounsfield和Alen Cormack在1979年因為發明電腦斷層掃瞄儀而得諾貝爾生理醫學獎。電腦斷層掃瞄儀與一般X光機有兩點不同一、電腦段層掃瞄儀(CT)可提供剖面斷層的影像來避刷重疊部份,二、電腦斷層掃描儀X光衰減的靈敏度較X光機好。 應用在CT上,X光球管在病人四周移動有掃描時間的限制,因為要移動沉重的X光球管。且這種移動必須精密及均勻的機械式移。CT掃瞄時間低於5秒是很大的進步,這可作全身的掃瞄而得到影像。隨著掃瞄時間的減少,使用CT來應用身體掃瞄大幅持續增加。 雖然如此,在CT掃瞄時間仍有明顯的限制,單層切片環設計的CT因需移動大的X光球管關係掃瞄時間最少要1 秒。而且因為某些器官是非自主象動特別是心臟跳動與腸胃蠕動,其動作時間在1秒以內因此作心臟或腸胃掃瞄就會有假影存在。 假如掃瞄與掃瞄間歇時間更縮短,將可獲得傳統CT無法取得的臨柿資料例甘掃瞄時間智刀而足雨鎖定跳動的器官以及影像可快速順序的取得;那麼跳動器官的影像就可獲得;心臟影像就是一例。快速掃瞄的第二個好處是可看到顯影劑在掃瞄間歇時產生變化。同時快速掃瞄可用來追蹤顯影劑在全身桫勇的情形,幫助作更清楚的記錄。 |
| 英文摘要 | Godfrey Hounsfield and Allen Cormach, were awarded the Nobel Prize in Physiology and Medicine 1979 for their Contributions in the development of Computed Tomography, the CT is attributable to two characteristics that differ from x0Ray radiography. First, CT forms a cross-sectional topographic image, eliminating superimposition of structure. Second, the sensitivity of CT to subtle differences in x-Ray attenuation is considerably better than in plane films x-Ray. The requirement to move the X-Ray source around the patient has been a limitation in computer tomography (CT) imaging, because of the time it takes to physically mone a heavy X-Ray tube through such a distance. Additionally, this movement must be mechanically precise. The development of CT machines with scan time of less than 5 seconds was the critical advancement permitting scanners to produce images of the body trunk with acceptable image quality. Indeed, as scan time continues to decrease, the utilization of CT for body imaging continues to increase. Nevertheless, the scan time remains a significant limitation in CT. Difficulty in mechanically and precisely mouing a large X-Ray tube has limited scan times to approximately 1 second for even the frailest, slip-ring designed scanners. Because most involuntary organ movements specifically cardiac motion and peristalsis of the gastrointestinaltract, occur in times shorter than 1 second, motion blurring and motion induced-artifacts occur when the heart or gut are imaged. If scan and interscan delay times could be made still shorter, benefit would be the ability to acquire new clinical information, unobtainable from conventional CT images. For example, if the scan time were short enough to freeze organ motion and if a rapid sequence of these images could be taken, a movie of organ movement could be obtained. Cardiac imaging is the bect example of this application. A second use of raped scanning would be to image the passage of a bolus of iodinated contrast media though a vessel or organ. These images could be used for quantitative measurements of blood flow. Scan times must be short so that the concentration of contrast media does not change during the scan interval. Similarly, rapid scanning can be used to follow a protracted bolus of contrast media through multiple body levels, maximizing the contrast enhancement recorded at each level. |
本系統中英文摘要資訊取自各篇刊載內容。