Abstract: The Katsevich algorithm of spiral cone-beam needs to compute the derivation of projection data in the process of reconstruction，but the projection data are discrete and cannot be derivatived.Therefore，interpolation polynomial derivation formula is used to compute the derivative of the projection data.In order to verify the validity of this method，the actual collected data of fish are used to reconstruction and the average gradient is used to measure the clarity of the image.The Experimental results show that this method can make the image clearer and can improve image quality.

Key words: image reconstruction, Katsevich algorithm, interpolation polynomial

摘要： 螺旋锥束Katsevich重建算法在重建过程中需要对投影数据求导，但投影数据本身是离散的，不能求导，因此考虑利用插值多项式函数的导数作为所求导数的近似值。为了验证此方法的有效性，采用实际采集的鱼的数据进行重建，并用平均梯度来衡量图像的清晰程度。实验结果表明，该方法能使图像更清晰，从而提高图像质量。

关键词: 图像重建, Katsevich算法, 插值多项式