Optimise demo

[agrimwood]

Subject of the issue

Adapt/modify/improve the demos, so that they perform well when applied to specific applications.

Modifications could include:
-- hyperparameter tuning
-- dataset expansion
-- output validation/benchmarking

[mathpluscode]

The following demos are using num_channel_initial: 4

• paired_mrus_brain
• paired_ct_lung
• unpaired_ct_lung

So for these demos, we definitely need to update the pretrained models

[agrimwood]

Thanks for pointing this out @mathpluscode.
@YipengHu has also suggested looking at the abdominal demo. I'll take a serious look at this before next week's meeting.

[YipengHu]

i'm closing this as specific demo ones will be generated.