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題名 | 超高速電腦斷層掃描儀之維修保養 |
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作者姓名(中文) | 馬慶仁; | 書刊名 | 醫學工程 |
卷期 | 6:5 1994.10[民83.10] |
頁次 | 頁780-784 |
專輯 | 電腦斷層掃描--理論與應用 |
分類號 | 416.14 |
關鍵詞 | 超高速電腦斷層掃描儀; 預防保養; 電子光束; Ultrafast CT; Preventive maintenance; Electron beam; |
語文 | 中文(Chinese) |
中文摘要 | 超高速電腦斷層掃描儀是基於電子光速(ELECTRON-BEAM)之科技它排除機械式之運轉及機械在先天上的限制、所以能以0.05秒或0.1秒完成掃瞄。 高壓電子槍(HIGH-VOLTAGE ELECTRON GUN)置於電子光束管之尾端,電子槍本身具有獨立之槍室及真空系統並以閥門(VALVE)與偏向線圈、聚焦線圈階開、高壓電子光束大學在640毫安培(MA)、130仟伏特(KV)。當光速在真空管內進行時,其聚焦是電子控制電極(INTENSITY CONTROLLING ELECTRODE)及螺線型電導管修正焦距。以四極線圈之X、Y線圈來集中控制光束點;另以雙極線圈之X、Y線圈來引導光速點沿著鎢靶行進。在鎢靶環之前有Z和W感應線圈幫助調整及校與光束,上述幾個系統會影響光速的控制。連鎖系統(INTERLOCK SYSTE)可感應機器所設定之參數(PHYSICAL PARAMETERS) 然後決定當時情況(參數值)是否適合操作(運轉)。若有意外狀況發生光束可低於0.3秒內被停止。偏向系統調整光速真空管的磁場,這些磁場是由許多電磁組件所產生的。真空系統維持並控制槍室(CHAMBERS)內的真空度。 有四組鎢靶環,每組靶環弧度大約在210度(15° +180° +15°)、靶環以橫的水平面垂真排列且部分靶環圍繞著患者。當光束點(BEAM SPOT)打在鎢靶上則產生X光散射。銅製的準直儀環可以限制光束之寬度為二頭分,結果造成扇形狀的X光光束,光束頂端沿著鎢靶掃描(SWEPT)。 這些X光經過(穿過)不同的密度(DENSITY)產生不同之衰減、這些強度不同之訊號由偵測器吸收面,兩者對立(偵測器環在上、靶環在下)第一組貞測器與鎢靶環(靠近電子槍)包含423個偵測器,第二組偵測器環包含864個偵測器,兩組皆可吸收X光,偵測器將X光轉換成電流和放大。 X光經偵測器轉換成電流和放大後,將這些訊號送到資料擷取系統(DATA ACQUISTITION SYSTEM)、DAS架於偵測器上。DAS將資料數據化和以每秒八佰萬十六位元字之速度儲存資料。記憶容量超大之LSI 11/23電腦運轉偏向控制系統和診斷檯。軟體程式則運轉掃描機和從事影像分析及診斷。所有掃描操作和顯像是在電腦操作檯來完成。醫師診斷檯可作影像分析診斷用,而不影響掃描。 患者診斷檯可以向前、往後移動,上升或下降及傾斜(打角度)和左右旋轉各30度,所有診斷檯之移動皆可由掃描基座之面板及電腦操作檯來控制、除了診斷檯左右旋轉必需由工作人員以人工方式移動。 雷射定位系統可以準確定丑病患接受掃描之位置。 |
英文摘要 | 1. ULTRAFAST CT SCANNER DESIGN AND OPERATION The Ultrafast Ct developed by Dr. Douglas Boyd is available from 1983. this system is based upon electron beam technology that eliminates mechanical motion and its inherent limitation has no moving parts except for the patient table. During operation, an electron beam is focused to a 1 to 2 mm size focal spot that is deflected across a series of four semicircular tungsten target beneath the patient, each of which produced a fan beam of X-radiation. Several scanning options are currently available including multilevel 50 msec scan acquisition at frame rates of up to 34 images per second. Two detector rings are above the patient so that a pair of CT images is obtained each scan. One of the tungsten rings is “swept” by the electron beam, as many eight levels can therefore be scanned without table movement. Scans can be acquired at two, four, six or eight levels during a single acquisition. Slice thickness can also be varied from1.5 to 10 mm. The X-ray data once received at the detectors is converted to digital data. Then the images are reconstructed by a powerful computer and display at the operator’s console. 2. PREVENTIVE MAINTEANANCE PROCEUDRES a. Set field service b. Check the following: --ERRLOG for unusual errors *HVH for regulation (High Voltage Histogram) *BCH for excessive droop (Beam Current Histogram) --VEM LOG for unusual or repetitive errors --Nitrogen pressure --Helium pressure --Cryopump temperature --Chiller: water pressure and flow --Fans and filters --Tuning --Beam path obstructions --Calibration --Squeeze disks --Update HVH and BCH --Examine error logs --Logit and set filed service 3.CONCLUSION X-rays and Gamma-rays are dangerous to the engineer and others in the vicinity unless established safe exposure produres are strictly observed. Failure to observe these warnings (direct beam and scattered beam) may cause serious or fatal body injuries to the engineer or those in the area. When troubleshooting the high-voltage tank, always turn OFF the appropriate breakers and wait 5 minutes before removing a cover. Never enter a tank before discharging the internal circuitry with a properly grounded discharge rod in accordance with manufacturer’s instructions and posted safety labels. |
本系統之摘要資訊系依該期刊論文摘要之資訊為主。