In Hamilton v State of New South Wales [2013] NSWSC 1437, the Court was required to consider a request by a defendant that a plaintiff undergo MR imaging, 

The claim arose from an alleged assault and detention by police officers, with the asserted injuries including a head injury.

The plaintiff having declined to undergo MR imaging, the application, the Court considered the medical issues in dispute and formed the view that the plaintiff should submit to the test, commenting at [56]:

…n particular, the defendant wishes to be in a position to compare the results of the MRI scan which is sought to be performed with the results of that performed in 2009, to then determine the extent of any further cerebral shrinkage, and to then consider whether that shrinkage may be attributable to some other form of cerebral pathology which is unrelated to the accident but which might account for the cognitive symptoms of which the plaintiff complains. Given that there is an evidentiary onus placed upon a defendant to disentangle alternative causes for a plaintiff’s condition (as to which see Watts v Rake (1960) 108 CLR 158 and Purkess v Crittenden (1965) 114 CLR 164) that, in my view, is a perfectly legitimate line of investigation.