I am new to the design of this transimpedance amplifier PCB layout. I have seen the waveguide-like layout for Inum and Iden input currents. And also Vsm is passing parallel to these tracks in the Evaluation board for ADL5304. I can also observe the bare PCB (without masking) in this Inum, Vsm, and Iden region. Also, there are many through-holes are poured all over the PCB. This observation of mine leads me to ask the rules for this specific layout design rules. I also want to learn how this helps to measure the very small current and the noise immunity. Please someone guide me. I want to get a thorough understanding. The reference image is shown below.