The most common material used for interventional embolization of intracranial aneurysms is a spring coil. Simply put, a spring coil is a platinum wire, made in various sizes of different diameters, lengths and shapes, with a soft texture, that is connected to a metal push rod. During embolization surgery, a microcatheter is inserted into the aneurysm lumen, and then the spring coil is pushed into the aneurysm lumen through the microcatheter with a push rod. When the spring coil is stabilized in the aneurysm lumen, the connection between the push rod and the spring coil is released by physical methods such as electricity or water pressure or mechanical pulling, a process called spring coil uncoupling, and different companies may use different methods of uncoupling the spring coil. After the spring coil is uncoupled and stays in the aneurysm lumen, the pusher is withdrawn from the microcatheter and the next spring coil is prepared for feeding and uncoupling. If the shape and size of the coil is found to be a mismatch with the aneurysm before the coil is released, it can always be pulled out with the pusher and replaced with another coil that is more suitable. However, if the coil has already been released, it can no longer be pulled out with the push rod. Below is an enlarged photo of the different types of spring coils, and if you look at their shape, isn’t it a good image to call them “spring coils”? Are spring coils that are permanently placed in the skull harmful to humans? The answer is yes, there is no problem, it does not affect your normal life, there is no problem in the security check of airplane, and it does not affect the normal MRI of the skull. Long-term placement in the cranium does not have any effect, safe and reliable.