實施組織切片術時，降低針頭的初始切削力能有效的提升檢體品質，以提升診斷精度。因此在針頭的設計上，如何降低初始切削力一直是主要目標。然而，活體篩檢後的主要併發症:血腫，卻鮮少被探討，組織的破壞會導致出血嚴重，而過多的出血則與血腫有著正相關。
本研究利用徑向應力探討後斜面針與柳葉針這兩種穿刺針在進行組織穿刺時，其針頭對周圍組織的損傷程度。徑向應力已被用來評估針管壁和組織間的緊密程度，越高的徑向應力代表著越低的組織破壞。
我們利用設計針頭上常用的特徵角:斜角(rake angle)，來做為評估切削能力的指標。製作以斜面針(bias bevel)以為基礎的柳葉針(lancet)及後斜面針(back bevel)時，會因為α及β角的不同而有不同角度的切削面。在柳葉針中，發現斜角主要與β角變化有關，且和徑向應力呈現正相關，在後續的田口實驗中發現β角對提升徑向應力的貢獻高達45.56%。而在後斜面針中，發現徑向應力主要和轉換角的位置有關係，轉換角越早發生徑向應力越大，α及β角皆會顯著的影響轉換角的位置，透過田口實驗發現α及β角的貢獻分別為49.49%、47.92%。
後續以影像輔佐驗證組織損傷的面積，雖然未明確的顯示φ角對破壞的影響，但β角其影響的程度與徑向應力的評估結果顯示一致。
我們發現這個較少被人討論的斜角確實可以用來衡量徑向應力的大小，而徑向應力確實與組織破壞有關，進一步利用田口品質設計方法預測了最佳的參數組合以獲得最大的徑向應力。

One of the most common complications in the needle biopsy is the hematoma, which is believed to be related to tissue fragmentation. Previous studies suggested that different designs of needle tip geometry used in the biopsy procedure can cause different levels of tissue damage (fragmentation), which is believed to be highly related to tissue bleeding. The purpose of this study is to understand the effect of biopsy needle geometry on tissue damage.
In this study, two major needle tip designs, the lancet and back bevel, are evaluated. The parameter configurations of the lancet tip needle are φ of 15°, 20°, 25° and β of 15°, 30°, 45°. As for back bevel tip, the φ are 15°, 20°, 25°and the β are 105°, 120°, 135°. The rake angles of these needles are calculated to assess the cutting ability. The tissue damage is quantified by measuring the radial stress during the needle insertion. Furthermore, the optimal parameter configurations for minimal radial stresses are investigated, and the relationship between the rake angle and the radial stress is discussed.
We found that the lancet tip needle of φ=25°and β=15°and the back bevel tip needle of φ=25°and β=135°would produce the highest radial stress. For lancet tip needles, a design with a higher rake angle would cause a greater radial stress during the needle insertion. As for back bevel tip needles, a higher transition angle results in a larger rake angle near the needle tip, which would cause greater radial stresses.
In conclusion, the rake angle of a needle can be used to determine the radial stress that would occur in the needle insertion. For the lancet tip needle, the design strategy is to choose a larger rake angle around the needle. As for the back bevel tip needle, it is suggested to choose a higher transition angle.

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