.. _USImgFormation.EnvelopeDetection:

Envelope Detection
==================

The Envelope Detection Algorithm extracts the amplitude envelope from pre-scan ultrasound data and can optionally apply log compression, producing images suitable for B-mode visualization or further analysis.

Input
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The algorithm is invoked with pre-scan ultrasound data (typically RF or IQ data) as input, this can be either one or more images (for offline processing) or a stream (for online processing).
The input should be organized as a SharedImageSet, and may include acquisition metadata such as sampling frequency and demodulation frequency.

Output
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The output is an ultrasound image with the envelope detected.
If log compression is enabled, the output is a log-compressed B-mode image. Otherwise, the output is the envelope or IQ data, depending on the settings.

Algorithm Options
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The following options are available in the Controller for the Envelope Detection Algorithm:

- **Log Compression:** Whether to apply log compression to the envelope. If disabled, the output is the intermediate IQ data.
- **Dynamic Range:** Dynamic range of the log-compressed image (dB).
- **Reference Amplitude:** Reference amplitude for log compression (sets the 0 dB point).
- **Normalize Envelope:** Whether to normalize the envelope to the range [0, 255].
- **Sampling Frequency:** Sampling frequency of the input image in the y-direction (MHz). Only used if the input data is RF data.
- **Demodulation Frequency:** Frequency of the signal to demodulate, usually the center frequency of the ultrasound signal (MHz). Only used if the input data is RF data.
- **Decimation Factor:** Factor by which to downsample the data during demodulation. Only used if the input data is RF data.