.. _ConceptChannelData:

Channel Data
============

The concept of **Channel Data** in the Ultrasound Image Formation module refers to the raw data acquired directly from the ultrasound transducer before any envelope detection or image post-processing. Channel data is typically organized as a 3D image, a time sequence of 3D images, or a real-time 3D image stream. This data contains the signals received by each transducer element for every pulse emission, capturing the most detailed information about the ultrasound acquisition.

Channel data is fundamental for advanced ultrasound processing, such as custom beamforming, simulation, or research applications. It enables users to reconstruct images with different parameters or algorithms and to analyze the raw ultrasound signals in detail.

Required Metadata
-----------------

To be recognized as channel data, the dataset must include a **PulseEchoSequence**. This metadata describes all relevant acquisition parameters, such as the timing and geometry of each pulse and echo event. Without this information, it is not possible to correctly interpret or process the channel data.

Optional Metadata
-----------------

Additional metadata can further describe the structure and meaning of the channel data:

- **ChannelDataLayout**: Specifies how the three axes of the data correspond to physical or acquisition dimensions (e.g., channels/elements, fast time, slow time/pulse emissions). If not provided, a default layout of (Channels, FastTime, SlowTime for the data x, y and z dimension) is assumed.
- **UltrafastBeamformingRois**: Defines specific regions of interest for beamforming in ultrafast imaging. If not present, these regions are derived from the pulse-echo sequence.

By including these metadata components, the channel data can be flexibly processed and interpreted by different algorithms within the module.
The available input streams for channel data (such as the :doc:`SimulatedChannelDataStream`) already provide the necessary metadata.