fix(seg): prevent segmentations from spreading to all viewports before hydration confirmation in 3D four-up (#5967)

extensions/cornerstone/src/commandsModule.ts

@@ -2096,6 +2096,15 @@ function commandsModule({
         displaySetInstanceUIDs,
       });
 
+      if (!updatedViewports?.length) {
+        return;
+      }
+
+      updatedViewports.forEach(({ viewportId: csViewportId }) => {
+        const csViewport = cornerstoneViewportService.getCornerstoneViewport(csViewportId);
+        csViewport?.setNeedsRender?.();
+      });
+
       actions.setDisplaySetsForViewports({
         viewportsToUpdate: updatedViewports.map(viewport => ({
           viewportId: viewport.viewportId,

extensions/cornerstone/src/services/ViewportService/CornerstoneViewportService.ts

@@ -49,6 +49,47 @@ const EVENTS = {
 const MIN_STACK_VIEWPORTS_TO_ENQUEUE_RESIZE = 12;
 const MIN_VOLUME_VIEWPORTS_TO_ENQUEUE_RESIZE = 6;
 
+function getVolumeActorReferencedIds(viewport: Types.IVolumeViewport): string[] {
+  const actors = viewport.getActors?.() ?? [];
+  return actors
+    .filter(ac => ac.actor?.getClassName?.() === 'vtkVolume')
+    .map(ac => ac.referencedId)
+    .filter(Boolean) as string[];
+}
+
+function volumeIdPrefixesMatch(
+  existingIds: string[],
+  prefixLen: number,
+  targetIds: string[]
+): boolean {
+  if (prefixLen > targetIds.length) {
+    return false;
+  }
+  for (let i = 0; i < prefixLen; i++) {
+    if (existingIds[i] !== targetIds[i]) {
+      return false;
+    }
+  }
+  return true;
+}
+
+/**
+ * Returns true when the viewport type matches a volume-based presentation (ORTHOGRAPHIC or VOLUME_3D).
+ */
+function viewportMatchesDesiredVolumePresentation(
+  viewport: Types.IViewport,
+  desiredViewportInfo: ViewportInfo
+): boolean {
+  const desiredType = desiredViewportInfo.getViewportType();
+  if (viewport.type !== desiredType) {
+    return false;
+  }
+  return (
+    desiredType === csEnums.ViewportType.ORTHOGRAPHIC ||
+    desiredType === csEnums.ViewportType.VOLUME_3D
+  );
+}
+
 export const WITH_NAVIGATION = { withNavigation: true, withOrientation: false };
 export const WITH_ORIENTATION = { withNavigation: true, withOrientation: true };
 
@@ -1112,7 +1153,44 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
       });
     }
 
-    await viewport.setVolumes(volumeInputArray);
+    const baseVolumeInputs = filteredVolumeInputArray.map(({ volumeInput }) => volumeInput);
+    const nextBaseVolumeIds = baseVolumeInputs.map(v => v.volumeId);
+    const existingVolumeIds = getVolumeActorReferencedIds(viewport);
+
+    let skippedIdenticalBaseVolumes = false;
+
+    if (baseVolumeInputs.length) {
+      const singleBaseViewport = nextBaseVolumeIds.length === 1;
+
+      // Only skip setVolumes() when the viewport type already matches the desired OHIF type
+      // (ORTHOGRAPHIC / VOLUME_3D); otherwise a stack → MPR switch with the same volumeId
+      // would incorrectly skip rebuilding the viewport.
+      if (
+        singleBaseViewport &&
+        existingVolumeIds.length >= nextBaseVolumeIds.length &&
+        volumeIdPrefixesMatch(existingVolumeIds, nextBaseVolumeIds.length, nextBaseVolumeIds) &&
+        viewportMatchesDesiredVolumePresentation(viewport, viewportInfo)
+      ) {
+        // Same primary volume already loaded (e.g. labelmap / extra actors after it) — avoid
+        // setVolumes(), which tears down all actors and blanks MPR during SEG hydrate.
+        skippedIdenticalBaseVolumes = true;
+      } else if (
+        existingVolumeIds.length &&
+        nextBaseVolumeIds.length > existingVolumeIds.length &&
+        volumeIdPrefixesMatch(existingVolumeIds, existingVolumeIds.length, nextBaseVolumeIds) &&
+        typeof viewport.addVolumes === 'function'
+      ) {
+        const toAdd = baseVolumeInputs.slice(existingVolumeIds.length);
+        if (toAdd.length) {
+          await viewport.addVolumes(toAdd);
+        }
+      } else {
+        await viewport.setVolumes(baseVolumeInputs);
+      }
+    } else if (volumeInputArray.length) {
+      await viewport.setVolumes(volumeInputArray);
+    }
+
     await this._addOverlayRepresentations(overlayProcessingResults);
     viewport.render();
 
@@ -1124,8 +1202,11 @@ class CornerstoneViewportService extends PubSubService implements IViewportServi
     });
 
     this.setPresentations(viewport.id, presentations);
+    // Presentations apply segmentation (hydrated labelmap etc.) after the render above — redraw so
+    // every orthographic/3D tile shows the updated scene (fixes MPR siblings blank after SEG hydrate).
+    viewport.render();
 
-    if (!presentations.positionPresentation) {
+    if (!presentations.positionPresentation && !skippedIdenticalBaseVolumes) {
       const imageIndex = this._getInitialImageIndexForViewport(viewportInfo);
 
       if (imageIndex !== undefined) {

extensions/cornerstone/src/stores/useSegmentationPresentationStore.ts

@@ -135,16 +135,27 @@ const _getSegmentationPresentationId = ({
     return;
   }
 
+  const { displaySetService } = servicesManager.services;
   const { displaySetInstanceUIDs, viewportOptions } = viewport;
 
+  // Match keys used by updateStoredSegmentationPresentation (referenced volume only).
+  // Including overlay UIDs (e.g. SEG) produced ids like "MR&SEG" while the store
+  // entry is under "MR", so hydrated segmentations never applied and viewports could mis-render.
+  const nonOverlayUIDs = displaySetInstanceUIDs.filter(uid => {
+    const ds = displaySetService.getDisplaySetByUID(uid);
+    return ds && !ds.isOverlayDisplaySet;
+  });
+
+  if (!nonOverlayUIDs.length) {
+    return;
+  }
+
   let orientation = viewportOptions.orientation;
 
   if (!orientation) {
     // Calculate orientation from the viewport sample image
-    const displaySet = servicesManager.services.displaySetService.getDisplaySetByUID(
-      displaySetInstanceUIDs[0]
-    );
-    const sampleImage = displaySet.images?.[0];
+    const displaySet = displaySetService.getDisplaySetByUID(nonOverlayUIDs[0]);
+    const sampleImage = displaySet?.images?.[0];
     const imageOrientationPatient = sampleImage?.ImageOrientationPatient;
 
     orientation = getViewportOrientationFromImageOrientationPatient(imageOrientationPatient);
@@ -152,7 +163,7 @@ const _getSegmentationPresentationId = ({
 
   const segmentationPresentationArr = [];
 
-  segmentationPresentationArr.push(...displaySetInstanceUIDs);
+  segmentationPresentationArr.push(...nonOverlayUIDs);
 
   // Uncomment if unique indexing is needed
   // addUniqueIndex(

extensions/cornerstone/src/utils/hydrationUtils.test.ts

@@ -262,6 +262,57 @@ describe('getUpdatedViewportsForSegmentation', () => {
     expect(result).toEqual(mockUpdatedViewports);
   });
 
+  it('should merge all grid viewports that reference the volume after hydration (e.g. 3D four-up)', () => {
+    const volumeUid = 'volume-1';
+    const viewports = new Map([
+      [
+        'vp-axial',
+        {
+          viewportId: 'vp-axial',
+          viewportOptions: { viewportId: 'vp-axial' },
+          displaySetInstanceUIDs: [volumeUid],
+        },
+      ],
+      [
+        'vp-sagittal',
+        {
+          viewportId: 'vp-sagittal',
+          viewportOptions: { viewportId: 'vp-sagittal' },
+          displaySetInstanceUIDs: [volumeUid],
+        },
+      ],
+      [
+        'vp-other-study',
+        {
+          viewportId: 'vp-other-study',
+          viewportOptions: { viewportId: 'vp-other-study' },
+          displaySetInstanceUIDs: ['other-volume'],
+        },
+      ],
+    ]);
+
+    mockViewportGridService.getState.mockReturnValue({
+      isHangingProtocolLayout: true,
+      viewports,
+      activeViewportId: 'vp-axial',
+    });
+
+    mockHangingProtocolService.getViewportsRequireUpdate.mockReturnValue([
+      { viewportId: 'vp-axial', displaySetInstanceUIDs: [volumeUid] },
+    ]);
+
+    const result = getUpdatedViewportsForSegmentation({
+      viewportId: 'vp-axial',
+      servicesManager: mockServicesManager as unknown as AppTypes.ServicesManager,
+      displaySetInstanceUIDs: [volumeUid],
+    });
+
+    expect(result).toEqual([
+      { viewportId: 'vp-axial', displaySetInstanceUIDs: [volumeUid] },
+      { viewportId: 'vp-sagittal', displaySetInstanceUIDs: [volumeUid] },
+    ]);
+  });
+
   it('should handle complex viewport structure', () => {
     const complexViewport = {
       viewportOptions: {

extensions/cornerstone/src/utils/hydrationUtils.ts

@@ -1,3 +1,63 @@
+import type { Types } from '@ohif/core';
+
+/**
+ * After SEG hydration we must refresh every viewport that shows the referenced volume so
+ * presentations (including segmentation) apply to all MPR/3D tiles. Hanging-protocol matching
+ * can return only the active viewport when protocol definitions omit viewportId (e.g. 3D four-up)
+ * or when layout state diverges from the protocol; this merges in all grid panes that already
+ * list that volume in `displaySetInstanceUIDs`.
+ *
+ * Only exact displaySetInstanceUID matches are used (no Frame-of-Reference inference): sibling
+ * MPR planes must already share the same referenced volume UID in grid state, or HP matching
+ * must list them; otherwise forcing a different UID onto a volume viewport can leave it blank.
+ */
+function mergeVolumeSharingViewports(
+  hangingProtocolUpdates: Types.HangingProtocol.ViewportUpdate[] | null | undefined,
+  volumeUid: string | undefined,
+  viewports: AppTypes.ViewportGrid.GridViewports
+): Types.HangingProtocol.ViewportUpdate[] {
+  if (!volumeUid) {
+    return (hangingProtocolUpdates ?? []) as Types.HangingProtocol.ViewportUpdate[];
+  }
+
+  const byId = new Map<string, Types.HangingProtocol.ViewportUpdate>();
+
+  const add = (viewportId: string, uids: string[]) => {
+    if (!viewportId) {
+      return;
+    }
+    byId.set(viewportId, { viewportId, displaySetInstanceUIDs: uids });
+  };
+
+  if (Array.isArray(hangingProtocolUpdates)) {
+    for (const entry of hangingProtocolUpdates) {
+      const vid = entry.viewportId ?? entry.viewportOptions?.viewportId;
+      if (vid) {
+        add(vid, entry.displaySetInstanceUIDs?.length ? entry.displaySetInstanceUIDs : [volumeUid]);
+      }
+    }
+  }
+
+  viewports.forEach(vp => {
+    const uids = vp.displaySetInstanceUIDs || [];
+    if (uids.includes(volumeUid)) {
+      add(vp.viewportId, [volumeUid]);
+    }
+  });
+
+  const merged = Array.from(byId.values());
+
+  if (
+    merged.length === 0 &&
+    Array.isArray(hangingProtocolUpdates) &&
+    hangingProtocolUpdates.length > 0
+  ) {
+    return hangingProtocolUpdates;
+  }
+
+  return merged;
+}
+
 function getUpdatedViewportsForSegmentation({
   viewportId,
   servicesManager,
@@ -5,7 +65,7 @@ function getUpdatedViewportsForSegmentation({
 }: withAppTypes) {
   const { hangingProtocolService, viewportGridService } = servicesManager.services;
 
-  const { isHangingProtocolLayout } = viewportGridService.getState();
+  const { isHangingProtocolLayout, viewports } = viewportGridService.getState();
 
   const viewport = getTargetViewport({ viewportId, viewportGridService });
   const targetViewportId = viewport.viewportOptions.viewportId;
@@ -16,7 +76,11 @@ function getUpdatedViewportsForSegmentation({
     isHangingProtocolLayout
   );
 
-  return updatedViewports;
+  if (updatedViewports == null) {
+    return updatedViewports;
+  }
+
+  return mergeVolumeSharingViewports(updatedViewports, displaySetInstanceUIDs[0], viewports);
 }
 
 const getTargetViewport = ({ viewportId, viewportGridService }) => {

extensions/default/src/utils/layerConfigurationUtils.ts

@@ -67,8 +67,14 @@ export function configureViewportForLayerAddition(params: {
 
   // If a viewport type was already set do not reset it.
   if (!viewport.viewportOptions.viewportType) {
-    // Special handling for overlay display sets
-    if (requestedLayerDisplaySet.isOverlayDisplaySet) {
+    // If the live Cornerstone viewport is already orthographic (volume), keep it as
+    // 'volume'. Prevents accidentally downgrading a volume viewport to 'stack' when
+    // viewportOptions arrives without a viewportType (e.g. from the HP overlay path).
+    const csViewport = cornerstoneViewportService.getCornerstoneViewport(viewportId);
+    if (csViewport?.type === 'orthographic') {
+      viewport.viewportOptions.viewportType = 'volume';
+      // Special handling for overlay display sets
+    } else if (requestedLayerDisplaySet.isOverlayDisplaySet) {
       // Do not force volume for SEG and RTSTRUCT if it and all the current display sets are for the same display set
       const isSameDisplaySet = currentDisplaySetUIDs.every(uid => {
         const currentDisplaySet = displaySetService.getDisplaySetByUID(uid);
@@ -131,7 +137,9 @@ export function configureViewportForLayerRemoval(params: {
     viewport.viewportOptions = {};
   }
 
-  viewport.viewportOptions.viewportType = 'volume';
+  const csViewportOrthographic =
+    cornerstoneViewportService.getCornerstoneViewport(viewportId)?.type === 'orthographic';
+  viewport.viewportOptions.viewportType = csViewportOrthographic ? 'volume' : 'stack';
 
   // orientation
   if (!viewport.viewportOptions.orientation) {