Distance measurement for tumor treatment

Hello ,
I am working to 3D modeling of distance between a tumor and its largely treated zone.
I have already registered modalities of patients which are segmented using medical software.
« Substract » Boolean operators are used to separate the volumes.
I am using the ModeltoModel model and Hausdroff distance to calculate the distance to the normal liver.
However, I tried to use the Thermoablation margin extension,
I got several questions : for the ModelToModel distance, the signed distance between tumor ( as reference) and normal liver shall be acceptable? Does this correspond to the Average surface distance ?
As for Hausdroff distance, I don’t get a minimum from the available module (which I read because of its use for evaluating overlapping volumes). The maximum are usually greater than the ModelToModel distance (because it takes the maximum of the minimum).
Are there other metrics for distance evaluation?
Thanks a lot!