What are the MRI signal characteristics of intracerebral hemorrhage in the hyperacute phase with oxyhemoglobin present, and how do they relate to the integrity of red blood cells and T1/T2 signal changes?

In the hyperacute phase of intracerebral hemorrhage (less than 24 hours), oxyhemoglobin is present with intact red blood cells. On MRI, this results in T1 isointensity to hypointensity and T2 hyperintensity. Key diagnostic features include the bright T2 signal, which can help differentiate it from other phases of hemorrhage. Clinically, recognizing this phase is crucial for timely management. A common pitfall is confusing it with ischemic stroke, which typically shows restricted diffusion on DWI.