Some ANers would like to also measure their tumor size themselves. If you get your MRI on CD, the process is easy. The CD images come with a scale and, at least in my case, the CD comes with measurement tools. This way you have an independent check of the dimensions and when measuring a series of MRIs can reduce interoperator and intraoperator variance.
The picture below is from https://www.researchgate.net/publication/268986458_Gamma_Knife_radiosurgery_for_vestibular_schwannoma_clinical_results_at_long-term_follow-up_in_a_series_of_379_patients
Picture A is an axial view (horizontal slices if you are standing up) of the slice with the largest tumor size.
Picture B is the coronal view (front to back vertical slices if you are standing up) of the slice with the largest tumor size.
Dimension 1 is the maximum anteroposterior (AP) extrameatal (outside the internal ear canal) diameter. That is, the length from (sort of) front to back.
Dimension 2 is the medial-lateral (ML ) is calculated perpendicular to the AP dimension and stops at the imaginary line shown above. That is, the tumor length from the middle of your body going outwards.
Dimension 4 is the cranio-caudal (CC) height. That is, the height from top to bottom.
When reporting tumor sizes there is the AAO-HNS 1995 and the Tokyo Consensus 2003 method. Both only consider the extrameatal/CPA/cisternal dimensions. That is, the inner auditory canal portion is reported separately. In the AAO-HNS method the square-root of APxML is reported and in the Tokyo Consensus method the maximum dimension is reported. They each give different answers, but if comparing growth rate either can be used (as long as you don't switch between the two, or worse still, include the intrameatal/internal auditory canal portion).
If you report tumor size as APxMLxCC, you can always convert to either method.
Another factor to consider is slice thickness. If you get 0.5 mm slice thicknesses, you're going to end up with a good measurement. If you get 3 mm slice thicknesses, you're likely to miss the maximum dimension and under-report the size. Or worse still measure growth when there isn't! There are way to correct this. Rather than explain it, just send me the dimensions at the maximum image size and the dimension on the images either side and I'll sent you back the maximum dimension.
If you would like to know more or would like clarification, don't hesitate to add to this post. I'm looking forward to some interesting discussion.