Solved by KFrank in post #2 
              
              
                Hi phdproblems! 

Let me add some hypothetical context to your question to make it 
more concrete: 
As you say, you have a batch size of one.  Each batch tensor is 
of torch.Size([1, 1, 60, 40, 40]), so each sample is of 
torch.Size([1, 60, 40, 40]). 
Let me imagine that each sample represents, say,…