fix: 🐛 IDC1346, convert fractional segs into binary

Author: Punzo

src/adapters/Cornerstone/Segmentation_4X.js

@@ -264,6 +264,8 @@ function _createSegFromImages(images, isMultiframe, options) {
  * @param  {*} metadataProvider.
  * @param  {bool} skipOverlapping - skip checks for overlapping segs, default value false.
  * @param  {number} tolerance - default value 1.e-3.
+ * @param  {bool} binarizeFractionalSegs - binarize fractional segmentation by thresholding - default value true.
+ * @param  {number} fractionalSegsThreshold - thresholding parameter for fractional segmentations - default value 0.8 (80% respect to the maximum value).
  *
  * @return {[]ArrayBuffer}a list of array buffer for each labelMap
  * @return {Object} an object from which the segment metadata can be derived
@@ -276,7 +278,9 @@ function generateToolState(
     arrayBuffer,
     metadataProvider,
     skipOverlapping = false,
-    tolerance = 1e-3
+    tolerance = 1e-3,
+    binarizeFractionalSegs = true,
+    fractionalSegsThreshold = 0.8
 ) {
     const dicomData = DicomMessage.readFile(arrayBuffer);
     const dataset = DicomMetaDictionary.naturalizeDataset(dicomData.dict);
@@ -337,7 +341,11 @@ function generateToolState(
             return;
         }
     } else {
-        pixelData = unpackPixelData(multiframe);
+        pixelData = unpackPixelData(
+            multiframe,
+            binarizeFractionalSegs,
+            fractionalSegsThreshold
+        );
 
         if (!pixelData) {
             throw new Error("Fractional segmentations are not yet supported");
@@ -1218,9 +1226,15 @@ function checkIfPerpendicular(iop1, iop2, tolerance) {
  * unpackPixelData - Unpacks bitpacked pixelData if the Segmentation is BINARY.
  *
  * @param  {Object} multiframe The multiframe dataset.
+ * @param  {bool} binarizeFractionalSegs - binarize fractional segmentation by thresholding.
+ * @param  {number} fractionalSegsThreshold - thresholding parameter for fractional segmentations.
  * @return {Uint8Array}      The unpacked pixelData.
  */
-function unpackPixelData(multiframe) {
+function unpackPixelData(
+    multiframe,
+    binarizeFractionalSegs,
+    fractionalSegsThreshold
+) {
     const segType = multiframe.SegmentationType;
 
     let data;
@@ -1240,21 +1254,56 @@ function unpackPixelData(multiframe) {
 
     const pixelData = new Uint8Array(data);
 
-    const max = multiframe.MaximumFractionalValue;
-    const onlyMaxAndZero =
-        pixelData.find(element => element !== 0 && element !== max) ===
-        undefined;
+    // IDC: we encountered segmentations defined as fractional with a constant value which is not the MaximumFractionalValue.
+    // Here we add the following check: if the labelmap has a constant value (independently by the value itself), it is considered a binary segmentation
+    const firstNonZeroIndex = pixelData.findIndex(element => element > 0);
+    const firstNonZeroValue = pixelData[firstNonZeroIndex];
+    const onlyOneValueAndZero =
+        pixelData.find(
+            element => element !== 0 && element !== firstNonZeroValue
+        ) === undefined;
+
+    if (onlyOneValueAndZero) {
+        log.warn(
+            "This segmentation object is actually binary... processing as such."
+        );
 
-    if (!onlyMaxAndZero) {
-        // This is a fractional segmentation, which is not currently supported.
-        return;
+        return pixelData;
     }
 
-    log.warn(
-        "This segmentation object is actually binary... processing as such."
-    );
+    // This is a fractional segmentation, which is not currently supported.
+    if (binarizeFractionalSegs) {
+        console.warn(
+            "This segmentation object is fractional. Fractional segmentations are not supported. Computing binary labelMap by thresholding (80% from the maximum value)."
+        );
+        // IDC: binarize fractional segmentation if requested
+
+        // we calculcate the maximum since unfortunatly it looks like
+        // (at least for IDC datasets) the maximum value is the array
+        // is not the DICOM attirbute MaximumFractionalValue
+        let max = -Number.MAX_VALUE;
+        pixelData.forEach(element => {
+            if (element > max) {
+                max = element;
+            }
+        });
+        max = Math.min(max, multiframe.MaximumFractionalValue);
+
+        // use as threshold: max * factor (default 80%)
+        const thershold = max * fractionalSegsThreshold;
+
+        for (let i = 0; i < pixelData.length; i++) {
+            if (pixelData[i] < thershold) {
+                pixelData[i] = 0;
+            } else {
+                pixelData[i] = 1;
+            }
+        }
+
+        return pixelData;
+    }
 
-    return pixelData;
+    return;
 }
 
 /**