Technically no. Currently, there are is only one upright MRI in Australia that does brain MRIs (there are other upright MRI places but as of 2019 they don't do upper spine/brain). It is also imaging with no medicare rebate so you would have to privately fund it yourself. currently. all members of our group have been diagnosed by conventional supine MRI's and only a small handful have gone on to get upright MRI's for other issues.
There is no medical evidence or research showing that this type of imaging is helpful or that it finds Chiari that is missed by a standard supine MRI. All the information about upright MRI and Chiari diagnosis is anecdotal so far and mostly mentioned by the patients without strong evidence. There is also no normative data used for upright MRI's that are agreed on.
So we aren't saying don't get one, but it is definitely not a required test to diagnose Chiari.