Deriving Hounsfield units using grey levels in cone beam CT: a clinical application
Deriving Hounsfield units using grey levels in cone beam CT: a clinical application
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DOI：
10.1259/dmfr/31640433
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发表时间：
2012-09-01
影响因子：
3.3
通讯作者：
McDavid, W. D.
中科院分区：
文献类型：
--
作者：
Reeves, T. E.;Mah, P.;McDavid, W. D.
目的：介绍一种从锥形束CT （CBCT）灰度中提取霍斯菲尔德单位的临床研究方法。方法：采用铝、外骨等效材料（皮质骨）、内骨等效材料（小梁骨）、聚甲基丙烯酸甲酯和水等效材料组成的丙烯酸酯口内对照物。患者被问及他们是否愿意在常规CBCT扫描期间将参考物体放置在口腔中的丙烯酸咬板。在Asahi Alphard 3030 （Belmont Takara，京都，日本）和Planmeca ProMax 3D （Planmeca，赫尔辛基，芬兰）CBCT上分别进行了31次扫描和30次扫描。对不同光子能量的参考物质进行了灰度与线性衰减系数的线性回归。选取回归系数最高的能量作为有效能量。使用标准Hounsfield单位方程，将五种材料在有效能量下的衰减系数换算为Hounsfield单位，并使用回归方程将衰减系数与从材料的测量灰度得到的衰减系数进行比较。结果：总体而言，灰度值与衰减系数之间存在满意的线性关系。这样就可以根据测量的灰度值计算出霍斯菲尔德单位。有效能量确定的不确定性导致有效能量不现实，计算出的CT数也有很大的可变性。在特定能量下，从灰度直接到霍斯菲尔德单位的线性回归导致了更大的一致性。结论：证明了一种从CBCT灰度中提取霍斯菲尔德单位的方法的临床应用。牙颌面放射学（2012）41,500-508。doi: 10.1259 / dmfr / 31640433
Objective: To present a clinical study demonstrating a method to derive Hounsfield units from grey levels in cone beam CT (CBCT).Methods: An acrylic intraoral reference object with aluminium, outer bone equivalent material (cortical bone), inner bone equivalent material (trabecular bone), polymethlymethacrylate and water equivalent material was used. Patients were asked if they would be willing to have an acrylic bite plate with the reference object placed in their mouth during a routine CBCT scan. There were 31 scans taken on the Asahi Alphard 3030 (Belmont Takara, Kyoto, Japan) and 30 scans taken on the Planmeca ProMax 3D (Planmeca, Helsinki, Finland) CBCT. Linear regression between the grey levels of the reference materials and their linear attenuation coefficients was performed for various photon energies. The energy with the highest regression coefficient was chosen as the effective energy. The attenuation coefficients for the five materials at the effective energy were scaled as Hounsfield units using the standard Hounsfield units equation and compared to those derived from the measured grey levels of the materials using the regression equation.Results: In general, there was a satisfactory linear relation between the grey levels and the attenuation coefficients. This made it possible to calculate Hounsfield units from the measured grey levels. Uncertainty in determining effective energies resulted in unrealistic effective energies and significant variability of calculated CT numbers. Linear regression from grey levels directly to Hounsfield units at specified energies resulted in greater consistency.Conclusions: The clinical application of a method for deriving Hounsfield units from grey levels in CBCT was demonstrated. Dentomaxillofacial Radiology (2012) 41, 500-508. doi: 10.1259/dmfr/31640433