fig2
![Advancements in needle visualization enhancement and localization methods in ultrasound: a literature review](https://image.oaes.cc/79a69f4a-333a-43e6-b302-f191c95e0ebf/ais4020.fig.2.jpg)
Figure 2. Existing literature on improving needle visibility in ultrasound can be categorized into two: (top row) those improving needle alignment with the ultrasound beam (bottom row), and those improving needle visualization and localization. Each of these two categories can be further classified into hardware-based methods (left column) and software-based methods (right column). It can be noted that there are currently no software-based approaches for improving needle alignment.