angular-chart.js圆环图:如何更改圆环弧的宽度？

<script src="https://cdn.jsdelivr.net/angular.chartjs/latest/angular-chart.min.js"></script>
<script src="https://cdn.jsdelivr.net/chart.js/latest/Chart.min.js"></script>

angular.module('myApp', ['chart.js']);

<canvas id="myChart" chart-type="doughnut" chart-data="data" chart-options="options"></canvas>

angular.module('myApp').controller('myController', function($scope) {
  $scope.data = [50, 50]; // 圆环图的数据，这里只有两个数据，表示两个圆环的比例
  $scope.options = {
    cutoutPercentage: 70 // 圆环弧的宽度，取值范围为0-100，值越小弧越宽
  };
});