Usually a phantom is a real physical object, with particular properties similar to a desired subject. The phantom is experimented with instead of the actual obj

Usually a phantom is a real physical object, with particular properties similar to a desired subject. The phantom is experimented with instead of the actual object. Because you made the phantom, you have "ground truth". Whereas, for example, there is no way to validate your reconstruction of a living person's brain. Because you can't measure it without xrays, which might be the thing you're trying to improve. But if you xray a phantom, you know what you should find.