Disclosed is a pixel element comprising a semiconductor substrate, a primary charge-collection node, a peripheral node, a modulating node, a circuitry and a backside conductive layer. The semiconductor substrate is configured to convert a flux of photons to first and second conductivity-type mobile charges. The peripheral node at least partially surrounds the primary charge-collection node, which at least partially surrounds the modulating node. The circuitry is used to connect and disconnect a reset voltage to/from the primary charge-collection node, provide a peripheral node voltage to the peripheral node, and measure an amount of the first conductivity-type mobile charges collected by the primary charge-collection node. The modulating node is electrically connected to a modulating voltage source, which is independent of the peripheral node voltage. The backside conductive layer is configured to collect and conduct the second conductivity-type mobile charges, and configured to be electrically connected to a bias voltage.