From 28888e6af3e2b76b1b88242d641eeb86b800bb08 Mon Sep 17 00:00:00 2001
From: salim kanoun <salim.kanoun@gmail.com>
Date: Sun, 28 Jun 2026 22:58:34 +0200
Subject: [PATCH] fix middle slice circle 3d

---
 .../CircleROIStartEndThresholdTool.ts             | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/packages/tools/src/tools/segmentation/CircleROIStartEndThresholdTool.ts b/packages/tools/src/tools/segmentation/CircleROIStartEndThresholdTool.ts
index 5af7c47197..7474d39bcf 100644
--- a/packages/tools/src/tools/segmentation/CircleROIStartEndThresholdTool.ts
+++ b/packages/tools/src/tools/segmentation/CircleROIStartEndThresholdTool.ts
@@ -426,9 +426,14 @@ class CircleROIStartEndThresholdTool extends CircleROITool {
       // if it is inside the start/end slice, but not exactly the first or
       // last slice, we render the line in dash, but not the handles
 
-      let isMiddleSlice = false;
-      if (roundedCameraCoordinate === middleCoordinate) {
-        isMiddleSlice = true;
+      let isNearMiddleSlice = false;
+      const targetId = this.getTargetId(viewport);
+      const imageVolume = cache.getVolume(targetId.split(/volumeId:|\?/)[1]);
+      if (
+        Math.abs(roundedCameraCoordinate - middleCoordinate) <
+        csUtils.getSpacingInNormalDirection(imageVolume, viewplaneNormal)
+      ) {
+        isNearMiddleSlice = true;
       }
 
       data.handles.points[0][
@@ -467,7 +472,7 @@ class CircleROIStartEndThresholdTool extends CircleROITool {
         !isAnnotationLocked(annotationUID) &&
         !this.editData &&
         activeHandleIndex !== null &&
-        isMiddleSlice
+        isNearMiddleSlice
       ) {
         if (this.configuration.simplified) {
           activeHandleCanvasCoords = [canvasCoordinates[activeHandleIndex]];
@@ -493,7 +498,7 @@ class CircleROIStartEndThresholdTool extends CircleROITool {
       let lineWidthToUse = lineWidth;
       let lineDashToUse = lineDash;
 
-      if (isMiddleSlice) {
+      if (isNearMiddleSlice) {
         lineWidthToUse = lineWidth;
         lineDashToUse = []; // Use solid line for real line
       } else {