# Accurate Needle Localization in the Image Frames of Ultrasound Videos
## 4 Discussion and Conclusions  
The proposed method provides an effective approach for detecting the needle in the image frames of ultrasound videos acquired during ultrasound-guided needle insertion procedures. The proposed method introduces innovative contributions to enhance needle detection. These innovative contributions include the use of the speckle variations feature to detect ultrasound speckle variations associated with needle insertion and the customized RadT kernel that is specifically designed to detect the needle trajectory. Furthermore, a major advantage of the proposed method is the capability to localize the needle without the need for changing the workflow of the intervention or using external needle tracking devices. The needle angle, \(\Theta\), is essential for computing the local phase feature. Since \(\Theta\) is unknown in the first image frame of the ultrasound video, the operator is required to provide an initial estimation of \(\Theta\) for the first image frame. For the subsequent image frames, \begin{table}
\begin{tabular}{c c c c c c c} \hline _Ex Vivo_ & **Number of** & **Failure** & **Angular** & **Axis Error** & **Tip Error** & **Run Time per** \\
**Ultrasound Video** & **Image Frames** & **Rate (\%)** & **Error (\({}^{\circ}\))** & **(mm)** & **(mm)** & **Image Frame (s)** \\ \hline Ultrasound video 1 & 88 & 0 & 0.6 \(\pm\) 0.3 & 0.4 \(\pm\) 0.3 & 0.5 \(\pm\) 0.3 & 0.52 \(\pm\) 0.02 \\ Ultrasound video 2 & 111 & 0 & 0.4 \(\pm\) 0.4 & 0.3 \(\pm\) 0.2 & 0.5 \(\pm\) 0.2 & 0.53 \(\pm\) 0.02 \\ Ultrasound video 3 & 78 & 0 & 0.4 \(\pm\) 0.3 & 0.4 \(\pm\) 0.3 & 0.6 \(\pm\) 0.4 & 0.51 \(\pm\) 0.02 \\ Ultrasound video 4 & 83 & 0 & 0.3 \(\pm\) 0.2 & 0.3 \(\pm\) 0.2 & 0.5 \(\pm\) 0.4 & 0.52 \(\pm\) 0.02 \\ Ultrasound video 5 & 95 & 0 & 0.7 \(\pm\) 0.3 & 0.7 \(\pm\) 0.4 & 0.8 \(\pm\) 0.4 & 0.52 \(\pm\) 0.02 \\ Ultrasound video 6 & 110 & 0 & 0.3 \(\pm\) 0.3 & 0.2 \(\pm\) 0.1 & 0.4 \(\pm\) 0.3 & 0.51 \(\pm\) 0.02 \\ Ultrasound video 7 & 112 & 0 & 0.4 \(\pm\) 0.4 & 0.3 \(\pm\) 0.2 & 0.4 \(\pm\) 0.3 & 0.52 \(\pm\) 0.02 \\ \hline \end{tabular}
\end{table} 
Table 1: The performance results obtained by the proposed method for the _ex vivo_ ultrasound videos. \begin{table}
\begin{tabular}{c c c c c c c} \hline _In Vivo_ & **Number of** & **Failure** & **Angular** & **Axis Error** & **Tip Error** & **Run Time per** \\
**Ultrasound Video** & **Image Frames** & **Rate (\%)** & **Error (\({}^{\circ}\))** & **(mm)** & **(mm)** & **Image Frame (s)** \\ \hline Ultrasound video 1 & 96 & 0 & 0.2 \(\pm\) 0.2 & 0.3 \(\pm\) 0.2 & 0.3 \(\pm\) 0.2 & 0.44 \(\pm\) 0.02 \\ Ultrasound video 2 & 101 & 0 & 0.9 \(\pm\) 0.5 & 1.0 \(\pm\) 0.6 & 1.1 \(\pm\) 0.6 & 0.44 \(\pm\) 0.01 \\ Ultrasound video 3 & 142 & 0 & 0.7 \(\pm\) 0.5 & 0.9 \(\pm\) 0.5 & 1.0 \(\pm\) 0.6 & 0.44 \(\pm\) 0.03 \\ Ultrasound video 4 & 127 & 0 & 0.8 \(\pm\) 0.5 & 0.7 \(\pm\) 0.5 & 0.7 \(\pm\) 0.4 & 0.43 \(\pm\) 0.01 \\ Ultrasound video 5 & 137 & 0 & 0.5 \(\pm\) 0.4 & 1.0 \(\pm\) 0.5 & 0.9 \(\pm\) 0.5 & 0.44 \(\pm\) 0.02 \\ Ultrasound video 6 & 114 & 0 & 1.0 \(\pm\) 0.6 & 0.9 \(\pm\) 0.5 & 1.0 \(\pm\) 0.6 & 0.43 \(\pm\) 0.03 \\ Ultrasound video 7 & 108 & 0 & 0.8 \(\pm\) 0.5 & 1.0 \(\pm\) 0.6 & 1.1 \(\pm\) 0.6 & 0.42 \(\pm\) 0.02 \\ \hline \end{tabular}
\end{table} 
Table 2: The performance results obtained by the proposed method for the _in vivo_ ultrasound videos. the initial estimation of \(\Theta\) is set to match the needle angle that is computed for the previous image frame. The sensitivity analysis provided in Section 3.3 demonstrates that our method achieves a mean angular error of less than 0.5\({}^{\circ}\) for the initial image frame, provided the initial estimation of \(\Theta\) deviates from the gold standard needle angle by no more than 20\({}^{\circ}\). Furthermore, in needle insertion procedures, the needle is typically directed toward a target anatomical structure. With ultrasound imaging frame rates typically ranging from 15 to 30 frames per second, the variations in needle angle between subsequence image frames are usually small.