The present invention is directed to a method of forming a positive image in a photothermographic element comprising a potentially negative-working emulsion wherein fog density development is imagewise inhibited in exposed areas of the image upon thermal development, the element further comprising a developer or precursor thereof and an oxidized developer scavenging agent to accelerate development by removing oxidized developer as it is formed during the thermal development step. In one embodiment of the invention, in which a density-inhibiting agent is released during thermal development that inhibits the thermal development of unexposed silver salts in the exposed areas relative to the unexposed areas, the method comprises imagewise exposing the film with a non-solarizing amount of radiation/energy to form a latent image and thermally developing the latent image in a single development step to produce a positive image in the element. The present invention is also directed to a photothermographic element that can be used in the present process in which a positive image characterized by high speed and discrimination is formed when exposed and thermally heated above 150° C.