system
Given the following post, respond as if you're commenting on Reddit:
human
Why are sonogram images that weird wedge shape?
gpt
Depends on the probe (transducer) that is used. A curvilinear probe, used for abdominal and obstetric scanning, gives the ‘wedge’ shape. This gives a wider field of view at the expense of reduced resolution. A linear probe gives a narrower parallel field of view but increases the image resolution. An ultrasound image is made up of a series of pulse-echo lines which are built up to create the image. The machine sends out a pulse and waits for echoes, then moves along and repeats until it has enough lines for an image. To increase the frame rate, gaps are left between the pulses meaning that fewer lines are required to create the image. The scanner has to fill these in, a process called interpolation. In a curvilinear probe the lines diverge, which creates bigger gaps at the deeper part of the image, leading to more interpolation and reduced image quality.