[Niagara] RenderTargetVolume Data Interface Write only, not read?

I use hlsl in UE5.1 iteration source particle to call sample and get functions and the return value is 0,0,0,0.
Is RenderTargetVolume Data Interface not readable in niagara?
I use the machine translation may have grammatical errors sorry if there are mistakes

The problem has been solved
I found that RenderTargetVolume cannot read and write at the same time in one stage
You can only read or write, choose one mode