启动新线程后UI会阻塞

单击按钮时，我将启动一个新线程（在画布上绘制省略号），但在此之后，所有窗口和按钮都被锁定。我看过这个网站上的模拟线程，但它没有帮助（对不起我的英语）

using System;
using System.Threading;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Shapes;
using System.Windows.Threading;
using Xceed.Wpf.Toolkit;
namespace WpfПотоки
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            //PriorityCombo.Items.Add(1);
            //PriorityCombo.Items.Add(2);
            //PriorityCombo.Items.Add(3);
            //PriorityCombo.Items.Add(4);
            //PriorityCombo.SelectedIndex = 3;
            PriorityCombo.Items.Add(ThreadPriority.Highest);
            PriorityCombo.Items.Add(ThreadPriority.AboveNormal);
            PriorityCombo.Items.Add(ThreadPriority.Normal);
            PriorityCombo.Items.Add(ThreadPriority.BelowNormal);
            PriorityCombo.Items.Add(ThreadPriority.Lowest);
            PriorityCombo.SelectedIndex = 2;
        }
        public void Circle()
        {
            var rand = new Random();
            while (true)
            {
                this.Dispatcher.Invoke(() =>
                {
                    var e = new Ellipse();
                    e.Height = 25;
                    e.Width = 25;
                    var brush = new SolidColorBrush(ColorPicker.SelectedColor);
                    var y = rand.Next(25, (int)(Canvas1.ActualHeight - 28));
                    var x = rand.Next(25, (int)(Canvas1.ActualWidth - 28));
                    Canvas.SetTop(e, y);
                    Canvas.SetLeft(e, x);
                    e.Fill = brush;
                    Canvas1.Children.Add(e);
                });
            }            
        }

        private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
        {
            var thread=new Thread(Circle);
            thread.Priority = (ThreadPriority)PriorityCombo.SelectionBoxItem;
            thread.IsBackground = true;
            thread.Start();
        }
    }
}