fix PulsatilityIndexCal

lib/process/calcuators/two_location.dart

@@ -1,4 +1,3 @@
-import 'package:fis_measure/interfaces/process/items/item_metas.dart';
 import 'package:fis_measure/interfaces/process/items/terms.dart';
 import 'package:fis_measure/process/primitives/combos/two_location.dart';
 import 'package:vid/us/vid_us_unit.dart';
@@ -19,10 +18,7 @@ class PulsatilityIndexCal extends Calculator<TwoLocation, double> {
 
     feature.values.clear();
 
-    feature.updateStringValue(
-      ItemOutputMeta(ref.displayName, ref.description, VidUsUnit.None),
-      '',
-    );
+    updateStringValue('');
 
     double pi = double.nan;
     double ps = double.nan;
@@ -42,6 +38,10 @@ class PulsatilityIndexCal extends Calculator<TwoLocation, double> {
       pi = GeneralFormulas.pi(ps, ed, vMean);
     }
 
+    if (!pi.isNaN) {
+      updateFloatValue(pi);
+    }
+
     for (var output in ref.meta.outputs) {
       if (output.name == pulsatilityIndexKey) {
         if (!pi.isNaN) {