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研究生:于台珊
研究生(外文):YU, TAI-SHAN
論文名稱:生物氣膠與纖維性氣懸微粒採樣上遮蔽校應對計數效率的影響:電腦模擬研究
論文名稱(外文):Masking Effects on Bioaerosol Colony/Fibrous Aerosol Counting :A Computer Simulation Study
指導教授:陳志傑陳志傑引用關係
指導教授(外文):Chen Chih-Chieh
學位類別:碩士
校院名稱:國立臺灣大學
系所名稱:職業醫學與工業衛生研究所
學門:醫藥衛生學門
學類:公共衛生學類
論文出版年:1997
畢業學年度:85
語文別:中文
論文頁數:2
中文關鍵詞:遮蔽效應鑑別率計數效率覆蓋率胸腔區呼吸沈積曲線纖維
外文關鍵詞:Masking EffectResolution IndexCounting EfficiencyCoverageThoracic CurveFiber
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摘要I生物氣膠採樣分析上由於有計數的步驟,常會因採樣濃度過高而造
成計數誤差的問題。由理論及以往一些實驗得知:若是採樣密度過高,則
因菌落生長時互相重疊而造成計數結果的低估;若是採樣濃度過低,則又
有樣本代表性不足的問題。本研究嘗試以電腦模擬的方式,探討在不同參
數下遮蔽效應對菌落計數效率的影響,模擬參數包括:菌落大小(直徑
;1㎜、2㎜、5㎜、8㎜)、培養皿表面的菌落密度、GSD(對數常態分佈
的幾何標準偏差)、以及鑑別率等。結果發現計數的精確度會隨著培養皿
表面菌落密度的增加而降低。對直徑分別為2、5、8mm的菌落來說,若其
培養皿表面密度分別不超過1290、200及71 count/plate時,則其計數效
率可達95%(保守推估人眼及觀測系統鑑別率為0.8時)﹔如果想提高計數
效率到達97%,則前述各粒徑的上限值減為900﹑140﹑50 count/plate。
至於菌落密度對計數效率的影響則以大菌落為嚴重,其計數效率下降幅度
隨著菌落直徑的增加而增大。此外當GSD值等於1時,覆蓋率最低,也就是
說遮蔽效應的影響最小,所以其計數效率最高,而隨著GSD值繼續的增加
,覆蓋率也會隨之增加,計數效率也就逐關鍵詞:生物氣膠、遮蔽效應、
培養皿表面菌落密度、計數效率、覆蓋率、鑑別率 摘要II為了在石綿等
纖維在計數時能夠達到統計上的精確與準確,對於纖維性的氣懸微粒採樣
有其密度的限制,從以往的一些採樣經驗得知:計數結果在統計上變異性
的大小和薄膜濾紙上的纖維濃度有關。NIOSH METHOD 7400對計數上的濃
度限制為100~1300 fibers / mm2,而對纖維大小的限制則以纖維直徑需
大於0.25微米為限。本研究以電腦模擬產生雙變項對數常態分佈的纖維性
氣懸微粒,改變纖維的物理特性,如:纖維直徑、長度及其分佈幾何標準
偏差(Geometric Standard Deviation, GSD)、濾紙表面的纖維密度以
及背景非纖維性氣懸微粒分佈(Count Medium Diameter, CMD、結果發現
計數的精確度會隨著濾紙表面的纖維密度的增加而降低。而隨著纖維直徑
的增加,計數效率也隨之下降兩種計數方法皆然);A規則計數下計數效
率隨纖維長度增加而增加,但以B規則計數則纖維長度對計數效率沒有明
顯影響。纖維長寬分佈(GSD)的改變對B規則的計數效率並無明顯影響,
在A規則方面,GSD的增加會使計數效率更隨纖維粒徑的加大而降低,而鑑
別率的增加可增進計數效率。另外在非纖維性氣懸微粒的影響方面,當其
粒徑或GSD增加時,都會降低纖維的計數效率,而其與纖維的濃度比例增
加也會降低計數效率。在模擬加裝分徑器之後,不論是以A或B規則計在建
議上限值部分,若要求纖維計數效率達95%,以直徑中位數0.125~2mm、長
度中位數5~10mm,GSD為1.5、長寬關係係數為0.48的纖維為例,在背景
非纖維性氣懸微粒中位數粒徑為2mm、GSD為1.5、濃度為纖維的30倍時,
其採樣上限值建議為12 count/field (1530 fiber/mm2)。關鍵詞:纖維
、遮蔽效應、濾紙表面纖維密度、鑑別率、計數效率、胸腔區呼吸沈積曲

Abstract IThe study focusing on the error due to overcrowding of
the colonies has concluded that the bias did not become
significant until about 300 colonies/plate were present. The
resolution of 1000x 1000 was found accurate enough to represent
the actual size of the colony. The capability of distinguishing
overlapping colonies, defined as resolution index, the covering
fraction, the colony surface density, the colony size and
distribution were the primary parameters in this study.The
counting efficiency was found to consistently decrease with
increasing surface density, decreasing resolution index and
increasing colony size. To have a minimum counting efficiency of
95%, the colony count should not exceed 1290, 200, and 71 count/
plate, for the colony size of 2, 5 and 8 mm, respectively, given
the resolution index of 0.8. When GSD=1, the covering fraction
is found to be smallest, therefore, counting efficiency becomes
the highest. However, increasing GSD will result in higher
coveringKey Words: Bioaerosol, Masking Effect, Surface Density,
Counting Efficiency, Loading Coverage, Resolution Index Abstract
IIFibrous aerosols are of great importance to industrial
hygienists because of the severe health risks that can be
associated with inhaling such particles. The studies on the
error due to overcrowding of the fibers and non-fibrous
particles during counting by phase contrast microscopy have
concluded that 100-1300 fiber/mm2 filter area is the most
appropriate fiber density range to avoid or reduce bias in fiber
counts. No study has considered the effect of distributions of
both fibers and particles on the fibeIn present study, the
computer-generated points on a Cartesian coordinate system were
used to simulate the surface area of a standard diameter 100-mm
field of view. The resolution of 2000×2000 was found accurate
enough to distinguish the actual size of the fibers and the
particles. The width and length distribution of fibrous aerosols
were described by a bivariate lognormal distribution. The
capability of distinguishing overlapped fibers, the coverage of
the field, the surface densities and size distributiThe fiber
counting efficiency was greatly improved if a size-selective
pre-separator (thoracic sampler) was added to remove non-fibrous
particles larger than 10 mm in aerodynamic diameter. The
enhancement in counting efficiency is particularly notable when
the CMD and GSD of the non-fibrous particles, and the ratio of
particle to fiber increase. To have a minimum counting
efficiency of 95%, the fiber density should be less than 12
count/filed-of-view (equivalent to 1530 fiber/mm2), with the
following conditKey Words: Fiber, Masking Effect, Surface
Density, Resolution index, Counting Efficiency, Thoracic curve.
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