The ultrasound (US) imaging technique has been applied to scoliosis assessment, and the proxy Cobb angle can be acquired on the US coronal images. The spinous process angle (SPA) is a valuable parameter to indicate 3-D deformity of spine. However, the SPA cannot be measured on US images since the spinous process (SP) is merged in the soft tissue layer and impossible to be identified on the coronal view directly. A new method based on the gradient vector flow (GVF) snake model was proposed to automatically locate SP position on the US transverse images, and the density-based spatial clustering of application with noise (DBSCAN) was used to remove the outliers out of the detected location results. With marking the SP points on the US coronal image, the SP curve was interpolated and the SPA was measured. The algorithm was evaluated on 50 subjects with various severity of scoliosis, and two raters measured the SPA on both US images and radiographs manually. The mean absolute differences (MADs) of SPAs obtained from the two modalities were 3.4° ± 2.4° and 3.6° ± 2.8° for the two raters, respectively, which were less than the clinical acceptance error (5°), and the results reported a good linear correlation ( ${r} > 0.85$ ) between the US method and radiography. It indicates that the proposed method can be a promising approach for SPA measurement using the US imaging technique.

中文翻译：

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临床超声脊柱图像上棘突曲线的自动检测与测量

超声（US）成像技术已应用于脊柱侧弯评估，并且可以在US冠状动脉图像上获取代理Cobb角。棘突角度（SPA）是指示脊柱3-D变形的有价值的参数。但是，由于棘突（SP）合并在软组织层中，因此无法在US图像上测量SPA，并且不可能直接在冠状视图上识别出SPA。提出了一种基于梯度矢量流（GVF）蛇模型的新方法，可以自动在美国横断面图像上定位SP位置，并利用基于密度的空间聚类结合噪声（DBSCAN）来去除异常点。检测到的位置结果。通过在美国冠状动脉图像上标记SP点，对SP曲线进行插值并测量SPA。该算法在50例脊柱侧凸严重程度不同的受试者上进行了评估，并且有两个评估人员手动在US图像和X射线照片上测量了SPA。两种评估者从两种方式获得的SPA的平均绝对差（MAD）分别为3.4°±2.4°和3.6°±2.8°，小于临床接受误差（5°），并且报告了结果良好的线性相关性（ $ {r}> 0.85 $ ）在美国方法和射线照相之间。这表明所提出的方法可能是使用美国成像技术进行SPA测量的有前途的方法。