ECG Parser Module

The ECG Parser Module is designed to extract and process ECG (Electrocardiogram) signal data from a DICOM dataset. It generates a normalized array of points representing the ECG signal, suitable for visualization or analysis in medical imaging workflows

Features

1. Signal Downsampling:

   • Reduces the number of points in the ECG signal for efficient processing and rendering.
   • Adjustable via the nSampling parameter.

2. Normalization:

   • Converts raw ECG signal values to a normalized scale for consistent visualization.

3. Integration with Series Metadata:

   • The processed ECG data is stored directly in the series metadata, making it accessible throughout the application.

API Reference

parseECG Generates an array of points representing the ECG signal from a DICOM dataset and stores the processed data in the series metadata.

Syntax

parseECG(
  seriesId: string,
  metadata: MetaData,
  nSampling?: number
): void

Parameters

Parameter	Type	Description
seriesId	string	The unique identifier of the series to which the ECG data belongs.
metadata	MetaData	Thes metadata object containing the ECG signal data
nSampling	number	The sampling rate to downsample the signal. Defaults to 2.

Returns

void – The function does not return a value. The processed ECG data is stored directly in the series metadata under ecgData.

How It Works

1. Data Extraction:

The function first looks for the raw ECG data within the metadata object using the private DICOM tag (5000,3000). It's designed to handle two common formats:

• A Base64 encoded string, which it decodes into a byte array (Uint8Array) -> singleFrame / frame by frame case.

• A pre-existing byte array (Uint8Array) -> default multiframe DICOM.

2. Downsampling:

   • The signal is downsampled to reduce the number of points based on the nSampling parameter. For example, if nSampling is 2, every second point is retained.

3. Normalization:

   • The signal values are normalized to a range of 0 to 100 for consistent scaling, calculated using the formula: Normalized Value = ((Value - Min) / (Max - Min)) × 100

4. Data Storage:

   • The processed ECG points are stored in the series metadata under the ecgData field.

Error Handling

1. Invalid Tag:

   • If the specified DICOM tag does not exist in the dataset, an error will occur.

2. Empty Data:

   • If the data element is empty or the byte array is invalid, the function will silently skip processing.

Limitations

1. Assumes Two-Byte Data:

   • The function assumes that the ECG data is stored as two-byte values (Uint16). Datasets with different formats may require modifications.

2. Single Signal Tag:

   • Currently processes a single ECG tag at a time. Multiple tags or multichannel ECG data would require additional handling.

3. Fixed Normalization:

   • Normalization scales values to 0-100, which may not be suitable for all visualization needs.