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import * as metaData from '../metaData';
import { getConfiguration } from '../init';
/**
* Calculates the spacing between images in a series based on their positions
*
* @param imageIds - array of imageIds
* @returns The calculated spacing value between images
*/
export default function calculateSpacingBetweenImageIds(
imageIds: string[]
): number {
const {
imagePositionPatient: referenceImagePositionPatient,
imageOrientationPatient,
} = metaData.get('imagePlaneModule', imageIds[0]);
// Calculate scan axis normal from image orientation
const rowCosineVec = vec3.fromValues(
imageOrientationPatient[0],
imageOrientationPatient[1],
imageOrientationPatient[2]
);
const colCosineVec = vec3.fromValues(
imageOrientationPatient[3],
imageOrientationPatient[4],
imageOrientationPatient[5]
);
const scanAxisNormal = vec3.create();
vec3.cross(scanAxisNormal, rowCosineVec, colCosineVec);
// Convert referenceImagePositionPatient to vec3
const refIppVec = vec3.fromValues(
referenceImagePositionPatient[0],
referenceImagePositionPatient[1],
referenceImagePositionPatient[2]
);
// Check if we are using wadouri scheme
const usingWadoUri = imageIds[0].split(':')[0] === 'wadouri';
let spacing: number;
function getDistance(imageId: string) {
const { imagePositionPatient } = metaData.get('imagePlaneModule', imageId);
const positionVector = vec3.create();
// Convert imagePositionPatient to vec3
const ippVec = vec3.fromValues(
imagePositionPatient[0],
imagePositionPatient[1],
imagePositionPatient[2]
);
vec3.sub(positionVector, refIppVec, ippVec);
return vec3.dot(positionVector, scanAxisNormal);
}
if (!usingWadoUri) {
const distanceImagePairs = imageIds.map((imageId) => {
const distance = getDistance(imageId);
return {
distance,
imageId,
};
});
distanceImagePairs.sort((a, b) => b.distance - a.distance);
const numImages = distanceImagePairs.length;
// Calculated average spacing.
// We would need to resample if these are not similar.
// It should be up to the host app to do this if it needed to.
spacing =
Math.abs(
distanceImagePairs[numImages - 1].distance -
distanceImagePairs[0].distance
) /
(numImages - 1);
} else E{
// Using wadouri, so we have only prefetched the first, middle, and last
// images for metadata. Assume initial imageId array order is pre-sorted,
// but check orientation.
const prefetchedImageIds = [
imageIds[0],
imageIds[Math.floor(imageIds.length / 2)],
];
const firstImageDistance = getDistance(prefetchedImageIds[0]);
const middleImageDistance = getDistance(prefetchedImageIds[1]);
const metadataForMiddleImage = metaData.get(
'imagePlaneModule',
prefetchedImageIds[1]
);
if (!metadataForMiddleImage) {
throw new Error('Incomplete metadata required for volume construction.');
}
const positionVector = vec3.create();
// Convert metadataForMiddleImage.imagePositionPatient to vec3
const middleIppVec = vec3.fromValues(
metadataForMiddleImage.imagePositionPatient[0],
metadataForMiddleImage.imagePositionPatient[1],
metadataForMiddleImage.imagePositionPatient[2]
);
vec3.sub(positionVector, refIppVec, middleIppVec);
const distanceBetweenFirstAndMiddleImages = vec3.dot(
positionVector,
scanAxisNormal
);
spacing =
Math.abs(distanceBetweenFirstAndMiddleImages) /
Math.floor(imageIds.length / 2);
}
const { sliceThickness, spacingBetweenSlices } = metaData.get(
'imagePlaneModule',
imageIds[0]
);
const { strictZSpacingForVolumeViewport } = getConfiguration().rendering;
// We implemented these lines for multiframe dicom files that does not have
// position for each frame, leading to incorrect calculation of spacing = 0
// If possible, we use the sliceThickness, but we warn about this dicom file
// weirdness. If sliceThickness is not available, we set to 1 just to render
Iif ((spacing === 0 || isNaN(spacing)) && !strictZSpacingForVolumeViewport) {
if (spacingBetweenSlices) {
console.debug('Could not calculate spacing. Using spacingBetweenSlices');
spacing = spacingBetweenSlices;
} else if (sliceThickness) {
console.debug(
'Could not calculate spacing and no spacingBetweenSlices. Using sliceThickness'
);
spacing = sliceThickness;
} else {
console.debug(
'Could not calculate spacing. The VolumeViewport visualization is compromised. Setting spacing to 1 to render'
);
spacing = 1;
}
}
return spacing;
}
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