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import getValue from './getValue';
import getNumberValue from './getNumberValue';
import getSequenceItems from './getSequenceItems';
// DICOM tags for the Waveform module
const TAG = {
WaveformSequence: '54000100',
NumberOfWaveformChannels: '003A0005',
NumberOfWaveformSamples: '003A0010',
SamplingFrequency: '003A001A',
MultiplexGroupLabel: '003A0020',
ChannelDefinitionSequence: '003A0200',
ChannelSourceSequence: '003A0208',
CodeMeaning: '00080104',
WaveformBitsAllocated: '54001004',
WaveformSampleInterpretation: '54001006',
WaveformData: '54001010',
} as const;
export interface EcgModule {
numberOfWaveformChannels: number;
numberOfWaveformSamples: number;
samplingFrequency: number;
waveformBitsAllocated: number;
waveformSampleInterpretation: string;
multiplexGroupLabel: string;
channelDefinitionSequence: Array<{
channelSourceSequence?: { codeMeaning?: string };
}>;
waveformData: {
retrieveBulkData: () => Promise<Int16Array[]>;
};
}
/**
* Decodes a base64 string to a Uint8Array.
*/
function base64ToUint8Array(base64: string): Uint8Array {
const binaryString = atob(base64);
const bytes = new Uint8Array(binaryString.length);
for (let i = 0; i < binaryString.length; i++) {
bytes[i] = binaryString.charCodeAt(i);
}
return bytes;
}
/**
* Converts raw waveform buffer to per-channel Int16Array data.
* Handles interleaved 16-bit signed short format.
*/
function convertBuffer(
dataSrc: ArrayBuffer | Uint8Array,
numberOfChannels: number,
numberOfSamples: number,
bits: number,
type: string
): Int16Array[] {
const data = new Uint8Array(dataSrc);
if (bits === 16 && type === 'SS') {
const ret: Int16Array[] = [];
const bytesPerSample = 2;
const totalBytes = bytesPerSample * numberOfChannels * numberOfSamples;
const length = Math.min(data.length, totalBytes);
for (let channel = 0; channel < numberOfChannels; channel++) {
const buffer = new Int16Array(numberOfSamples);
ret.push(buffer);
let sampleI = 0;
for (
let sample = 2 * channel;
sample < length;
sample += 2 * numberOfChannels
) {
const highByte = data[sample + 1];
const lowByte = data[sample];
const sign = highByte & 0x80;
buffer[sampleI++] = sign
? 0xffff0000 | (highByte << 8) | lowByte
: (highByte << 8) | lowByte;
}
}
return ret;
}
console.warn(
`[ECGHelpers] Unsupported waveform format: ${bits}-bit ${type}. Only 16-bit SS is supported.`
);
return [];
}
/**
* Decodes multipart/related response to extract binary parts.
*/
function multipartDecode(response: ArrayBuffer): ArrayBuffer[] {
const message = new Uint8Array(response);
const separator = new TextEncoder().encode('\r\n\r\n');
// Find the header separator
const headerIndex = findToken(message, separator, 0, 1000);
if (headerIndex === -1) {
return [response];
}
const headerStr = new TextDecoder().decode(message.slice(0, headerIndex));
const boundaryString = identifyBoundary(headerStr);
if (!boundaryString) {
return [response];
}
const boundary = new TextEncoder().encode(boundaryString);
const components: ArrayBuffer[] = [];
let offset = headerIndex + separator.length;
let boundaryIndex = findToken(message, boundary, offset);
while (boundaryIndex !== -1) {
const contentStart = findToken(message, separator, boundaryIndex, 1000);
if (contentStart === -1) {
break;
}
const dataStart = contentStart + separator.length;
const nextBoundary = findToken(message, boundary, dataStart);
const dataEnd = nextBoundary === -1 ? message.length : nextBoundary - 2;
components.push(response.slice(dataStart, dataEnd));
if (nextBoundary === -1) {
break;
}
offset = nextBoundary;
boundaryIndex = findToken(message, boundary, offset + boundary.length);
if (boundaryIndex === -1) {
break;
}
}
return components.length > 0 ? components : [response];
}
function findToken(
message: Uint8Array,
token: Uint8Array,
startIndex: number,
maxLength?: number
): number {
const end = maxLength
? Math.min(message.length, startIndex + maxLength)
: message.length;
for (let i = startIndex; i < end - token.length + 1; i++) {
let found = true;
for (let j = 0; j < token.length; j++) {
if (message[i + j] !== token[j]) {
found = false;
break;
}
}
if (found) {
return i;
}
}
return -1;
}
function identifyBoundary(header: string): string | null {
const match = header.match(/boundary=([^\s;]+)/i);
if (match) {
return `--${match[1].replace(/"/g, '')}`;
}
return null;
}
/**
* Creates a closure that retrieves bulk waveform data from various sources
* (InlineBinary, BulkDataURI, or dicomweb-client retrieveBulkData).
*
* @returns A function that returns a Promise resolving to the decoded channel arrays.
* @throws If no data source is found.
*/
function makeRetrieveBulkData(
waveformData: Record<string, unknown>,
numberOfChannels: number,
numberOfSamples: number,
bitsAllocated: number,
sampleInterpretation: string,
wadoRsRoot?: string,
studyUID?: string
): () => Promise<Int16Array[]> {
return async () => {
// Method 1: Already decoded Value
if (waveformData.Value) {
return waveformData.Value as Int16Array[];
}
// Method 2: InlineBinary (base64)
if (waveformData.InlineBinary) {
const raw = base64ToUint8Array(waveformData.InlineBinary as string);
return convertBuffer(
raw,
numberOfChannels,
numberOfSamples,
bitsAllocated,
sampleInterpretation
);
}
// Method 3: retrieveBulkData function (from dicomweb-client)
if (typeof waveformData.retrieveBulkData === 'function') {
const bulkdata = await waveformData.retrieveBulkData();
return convertBuffer(
bulkdata,
numberOfChannels,
numberOfSamples,
bitsAllocated,
sampleInterpretation
);
}
// Method 4: BulkDataURI
if (waveformData.BulkDataURI) {
let url = waveformData.BulkDataURI as string;
if (url.indexOf(':') === -1 && wadoRsRoot) {
url = studyUID
? `${wadoRsRoot}/studies/${studyUID}/${url}`
: `${wadoRsRoot}/${url}`;
}
const response = await fetch(url);
const buffer = await response.arrayBuffer();
const contentType = response.headers.get('content-type') || '';
const decoded = contentType.includes('multipart')
? multipartDecode(buffer)[0]
: buffer;
return convertBuffer(
decoded,
numberOfChannels,
numberOfSamples,
bitsAllocated,
sampleInterpretation
);
}
throw new Error('[ECGHelpers] No data source found in WaveformData');
};
}
/**
* Parses the DICOM WaveformSequence and returns an EcgModule object.
*
* @param metadata - The DICOM metadata object
* @param wadoRsRoot - Optional WADO-RS root URL for BulkDataURI resolution
* @param studyUID - Optional Study Instance UID for BulkDataURI path construction
* @returns EcgModule object or null if no waveform data is found
*/
export function getECGModule(
metadata: Record<string, unknown>,
wadoRsRoot?: string,
studyUID?: string
): EcgModule | null {
const waveformSeqItems = getSequenceItems(metadata[TAG.WaveformSequence]);
Eif (!waveformSeqItems || waveformSeqItems.length === 0) {
return null;
}
const waveform = waveformSeqItems[0];
const numberOfChannels = getNumberValue(
waveform[TAG.NumberOfWaveformChannels]
) as number;
const numberOfSamples = getNumberValue(
waveform[TAG.NumberOfWaveformSamples]
) as number;
const samplingFrequency = getNumberValue(
waveform[TAG.SamplingFrequency]
) as number;
const waveformBitsAllocated =
getNumberValue(waveform[TAG.WaveformBitsAllocated]) ?? 16;
const waveformSampleInterpretation =
(getValue(waveform[TAG.WaveformSampleInterpretation]) as string) ?? 'SS';
const multiplexGroupLabel =
(getValue(waveform[TAG.MultiplexGroupLabel]) as string) ?? 'ECG';
// Parse channel definitions
const channelDefItems = getSequenceItems(
waveform[TAG.ChannelDefinitionSequence]
);
const channelDefinitionSequence = (channelDefItems || []).map(
(channelDef) => {
const channelDefRecord = channelDef as unknown as Record<string, unknown>;
const sourceSeqItems = getSequenceItems(
channelDefRecord[TAG.ChannelSourceSequence]
);
const sourceSeq =
(sourceSeqItems?.[0] as unknown as Record<string, unknown>) || {};
const codeMeaning = getValue(
sourceSeq[TAG.CodeMeaning] as WADORSMetaDataElement
) as string;
return {
channelSourceSequence: {
codeMeaning: codeMeaning || 'Unknown',
},
};
}
);
const waveformDataObj = waveform[TAG.WaveformData] || {};
return {
numberOfWaveformChannels: numberOfChannels,
numberOfWaveformSamples: numberOfSamples,
samplingFrequency,
waveformBitsAllocated,
waveformSampleInterpretation,
multiplexGroupLabel,
channelDefinitionSequence,
waveformData: {
retrieveBulkData: makeRetrieveBulkData(
waveformDataObj,
numberOfChannels,
numberOfSamples,
waveformBitsAllocated,
waveformSampleInterpretation,
wadoRsRoot,
studyUID
),
},
};
}
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