By far the most investigated metric is apparent diffusion coefficient (ADC), acquired using diffusion weighted imaging (DWI).
The current consensus reports that medulloblastoma has significantly reduced ADC compared to both astrocytomas \cite{Yamasaki2005,Rumboldt2006,Yamashita2009,Gimi2012,Bull2012,Pierce2014,Assis2015,Zitouni2017} and ependymomas \cite{Rumboldt2006,Yamashita2009,Jaremko2010,Gimi2012,Bull2012,Pierce2014,Assis2015,Zitouni2017}. This has been confirmed when using both average ADC \cite{Yamasaki2005,Rumboldt2006,Jaremko2010,Yamashita2009,Gimi2012,Bull2012,Assis2015,Zitouni2017} and minimum ADC \cite{Yamashita2009,Jaremko2010,Pierce2014} from within tumour volumes. Furthermore, the ADC reduction alone in medulloblastoma has allowed medulloblastoma to be identified from astrocytomas and ependymomas with classification rates greater than 88% \cite{Rumboldt2006,Jaremko2010,Gimi2012,Bull2012}. However, some contradicting reports have suggested that medulloblastoma cannot be reliably distinguished from ependymomas using the mean ADC from within the tumour volumes \cite{Pillai2011,Jaremko2010}.
[Explain how this links to cellularity of the tumour].
Despite the literature having good success identifying medulloblastoma from other posterior-fossa tumour types using single MR features, single measurements are not sufficient to further classify medulloblastoma into all subgroups. A single study has shown that the WNT subgroup can be isolated from the remaining subgroups, but the remaining three cannot distinguished \cite{Patay2015}.
Radiomics
Genetics
Genomics
Radiogenomics
Conclusion