new Thread(new ThreadStart(() => {
var bitmap = new BitmapImage();
bitmap.BeginInit();

using (var stream = new MemoryStream(File.ReadAllBytes(...))) {
bitmap.StreamSource = stream;
bitmap.CacheOption = BitmapCacheOption.OnLoad;
bitmap.EndInit();
bitmap.Freeze();

}
this.Dispatcher.Invoke((Action)delegate {
Image1.Source = bitmap;

});

})).Start();

using (var stream = new FileStream(path, FileMode.Open)) {
image.BeginInit();
image.StreamSource = stream;

image.DecodePixelWidth = 100;

image.CacheOption = BitmapCacheOption.OnLoad;
image.EndInit();
image.Freeze();
}