MRI is considered the gold standard for imaging children because it avoids the risks of ionizing radiation and produces clear, accurate images. The use of MRI is increasing, but scanning children can be challenging.
To get an accurate scan, current MR systems require a child to lie perfectly still for up to an hour. That's a challenge for adults and older children, which makes it almost impossible for children under the age of five!
The MRI experience can be distressing and even traumatic, for young children, due to the small bore and the loud noises.
Not optimized
Most MRI systems are not optimized for children. Adult resonators must be adapted, for example by using pieces of foam rubber to hold a child's head in place.
The costs of sedation
Because of the difficulties, children are increasingly being sedated or given a general anesthetic (GA) before an MRI exam. This requires the presence of a nurse or doctor and takes additional time. MR exams with sedation or GA are three to ten times more costly than those without.
Side effects
Sedation and general anesthesia expose children to the risk of unwanted side-effects.
All these factors contribute to slower throughput, which leads to longer wait times and waiting lists. 
Refusal to cooperate
Ultimately, the child or the parents may refuse the scan or not cooperate, making it difficult or impossible to get an accurate diagnosis.
Wasted time
A non-compliant child or a refused scan wastes the time of highly-trained medical professionals and technologists.