My toaster is a single slot toster, i.e. takes 2 slices of normal bread side by side.
It will take my machine made bread, but only 1 slice on it's side.
My machine is not panasonic, but I have used one, and I know a slice cut in half fits in a normal 2 slot tosater, so I don't see why it should not fit in a 1 slot toster, maybe to need to measure a slice so we know what size we are looking at.
My bread slices are 135mm x 170mm