add PulsatilityIndexCal

lib/process/calcuators/two_location.dart

@@ -0,0 +1,14 @@
+import 'package:fis_measure/process/primitives/combos/two_location.dart';
+
+import 'calculator.dart';
+
+class PulsatilityIndexCal extends Calculator<TwoLocation, double> {
+  PulsatilityIndexCal(super.ref);
+
+  @override
+  void calculate() {
+    if (ref.feature == null) return;
+
+    final feature = ref.feature!;
+  }
+}

lib/process/primitives/combos/two_location.dart

@@ -60,6 +60,13 @@ class TwoLocation extends TwoLengthAbstract<TwoLocationFeature> {
     twoLocation.calculator = MaxPgCal(twoLocation);
     return twoLocation;
   }
+
+  static TwoLocation createPulsatilityIndex(ItemMeta meta,
+      [IMeasureItem? parent]) {
+    TwoLocation twoLocation = TwoLocation(meta);
+    twoLocation.calculator = MaxPgCal(twoLocation);
+    return twoLocation;
+  }
 }
 
 class TwoLocationFeature extends TopMeasureItemFeature {