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锥束CT具有高效率和高精度的显著特点, 在医学成像与工业无损检测等领域已得到广泛应用, 但余晖的存在降低了CT图像的质量. 本文借鉴余晖多指数衰减模型的思想, 结合平板探测器输出信号的实际衰减规律, 提出了一种新的基于多指数拟合的余晖衰减建模及校正方法. 首先进行了基于平板探测器的锥束CT成像实验, 结果表明平板探测器各像素的余晖衰减规律具有良好的一致性, 且余晖衰减规律与初始灰度的大小无关; 其后根据建立的余晖衰减模型实现了余晖的快速校正, 并分析比较了余晖校正前后投影图像和切片图像质量, 表明余晖校正后的零件轮廓清晰度得到了显著提升. 该方法无需获取探测器闪烁体成分及其衰减时间常数, 便于实际锥束CT成像系统的余晖检测与校正.Cone-beam computed tomography (CT) has the notable features, viz high efficiency and high precision, and is widely used in the areas such as medical imaging and industrial non-destructive testing, but the presence of image lag reduces the quality of CT images. By referencing the multi-exponential decay model for the image lag and combining with the actual decay rule of the flat panel detector output signal, a new decay modeling and correction method for the image lag based on multi-exponential fitting is proposed. Firstly, an imaging experiment using cone-beam CT based on flat panel detector is carried out; the results show that the image lag decay of the pixels in the flat panel detector has a good consistency, and is irrelevant to the initial gray value. Then, the rapid image lag correction is achieved according to the image lag decay model, and the comparison of image quality of the projected images and slice images before and after image lag correction indicates that the edge sharpness of the part has been significantly improved after the lag correction. This method does not need to obtain the scintillation compositions and the decay time constants of the detector, and is easily applied to the practical cone-beam CT imaging systems for image lag detection and correction.
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Keywords:
- image lag /
- flat panel detector /
- cone-beam CT /
- multi-exponential decay
[1] Luo Z Y, Yang X Q, Meng Y Z, Deng Y 2010 Acta Phys. Sin. 59 8237 (in Chinese) [罗召洋, 杨孝全, 孟远征, 邓勇 2010 59 8237]
[2] Wang X C, Yan B, Liu H K, Li L, Wei X, Hu G E 2013 Acta Phys. Sin. 62 098702 (in Chinese) [汪先超, 闫镔, 刘宏奎, 李磊, 魏星, 胡国恩 2013 62 098702]
[3] Kasap S, Frey J B, Belev G, Tousignant O, Mani H, Greenspan J, Laperriere L, Bubon O, Reznik A, DeCrescenzo G, Karim K S, Rowlands J A 2011 Sensors 11 5112
[4] Hsieh J, Gurmen O E, King K F 1999 Radiology 213 318
[5] Hsieh J, Gurmen O E, King K F 2000 IEEE Trans. Med. Img. 19 930
[6] Lei Y H, Liu X, Guo J C, Zhao Z G, Niu H B 2011 Chin. Phys. B 20 042901
[7] Benítez R B, Ning R, Conover D 2006 Proceedings of SPIE Medical Imaging 2006: Physics of Medical Imaging San Diego, USA, February 12–16, 2006 p61422K
[8] Hofmann T, Burtzlaff S, Voland V, Salamon M, Nachtrab F, Sukowski F, Uhlmann N 2009 Nuclear Instruments and Methods in Physics Research A 607 187
[9] Mainprize J G, Wang X Y, Yaffe M J 2009 Proceedings of SPIE Medical Imaging 2009: Physics of Medical Imaging Orlando, USA, February 7–12, 2009 p72580R
[10] Colbeth R E, Mollov I P, Roos P G, Shapiro E G 2005 Proceedings of SPIE Medical Imaging 2005: Physics of Medical Imaging San Diego, USA, February 15–17, 2005 p387
[11] Zhang Y, Ning R, Conover D 2006 Proceedings of SPIE Medical Imaging 2006: Physics of Medical Imaging San Diego, USA, February 12–16, 2006 p61420Z
[12] Tanaka R, Ichikawa K, Mori S, Dobashi S, Kumagaya M, Kawashima H, Morita S, Sanada S 2010 Proceedings of SPIE Medical Imaging 2010: Physics of Medical Imaging San Diego, USA, February 15–18, 2010 p76224S
[13] Carton A K, Puong S, Iordache R, Muller S 2011 Proceedings of SPIE Medical Imaging 2011: Physics of Medical Imaging Orlando, USA, February 13–17, 2011 p79611D
[14] Mail N, O’Brien P, Pang G 2007 J. Appl. Clin. Med. Phys. 8 2483
[15] Mail N, Moseley D J, Siewerdsen J H, Jaffray D A 2008 Med. Phys. 35 5187
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[1] Luo Z Y, Yang X Q, Meng Y Z, Deng Y 2010 Acta Phys. Sin. 59 8237 (in Chinese) [罗召洋, 杨孝全, 孟远征, 邓勇 2010 59 8237]
[2] Wang X C, Yan B, Liu H K, Li L, Wei X, Hu G E 2013 Acta Phys. Sin. 62 098702 (in Chinese) [汪先超, 闫镔, 刘宏奎, 李磊, 魏星, 胡国恩 2013 62 098702]
[3] Kasap S, Frey J B, Belev G, Tousignant O, Mani H, Greenspan J, Laperriere L, Bubon O, Reznik A, DeCrescenzo G, Karim K S, Rowlands J A 2011 Sensors 11 5112
[4] Hsieh J, Gurmen O E, King K F 1999 Radiology 213 318
[5] Hsieh J, Gurmen O E, King K F 2000 IEEE Trans. Med. Img. 19 930
[6] Lei Y H, Liu X, Guo J C, Zhao Z G, Niu H B 2011 Chin. Phys. B 20 042901
[7] Benítez R B, Ning R, Conover D 2006 Proceedings of SPIE Medical Imaging 2006: Physics of Medical Imaging San Diego, USA, February 12–16, 2006 p61422K
[8] Hofmann T, Burtzlaff S, Voland V, Salamon M, Nachtrab F, Sukowski F, Uhlmann N 2009 Nuclear Instruments and Methods in Physics Research A 607 187
[9] Mainprize J G, Wang X Y, Yaffe M J 2009 Proceedings of SPIE Medical Imaging 2009: Physics of Medical Imaging Orlando, USA, February 7–12, 2009 p72580R
[10] Colbeth R E, Mollov I P, Roos P G, Shapiro E G 2005 Proceedings of SPIE Medical Imaging 2005: Physics of Medical Imaging San Diego, USA, February 15–17, 2005 p387
[11] Zhang Y, Ning R, Conover D 2006 Proceedings of SPIE Medical Imaging 2006: Physics of Medical Imaging San Diego, USA, February 12–16, 2006 p61420Z
[12] Tanaka R, Ichikawa K, Mori S, Dobashi S, Kumagaya M, Kawashima H, Morita S, Sanada S 2010 Proceedings of SPIE Medical Imaging 2010: Physics of Medical Imaging San Diego, USA, February 15–18, 2010 p76224S
[13] Carton A K, Puong S, Iordache R, Muller S 2011 Proceedings of SPIE Medical Imaging 2011: Physics of Medical Imaging Orlando, USA, February 13–17, 2011 p79611D
[14] Mail N, O’Brien P, Pang G 2007 J. Appl. Clin. Med. Phys. 8 2483
[15] Mail N, Moseley D J, Siewerdsen J H, Jaffray D A 2008 Med. Phys. 35 5187
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