Disclosed are methods of radioisotope infusion comprising infusing saline comprising a diagnostic dose of a radioisotope, and delivering a pre-measured volume of push saline. The disclosed methods confer improved image quality with low background noise, higher signal to noise ratio (SNR) and higher contrast to noise ratio (CNR), leading to better diagnosis and thus eliminating the need of repeating the infusion and imaging which in turn reduces exposure of a patient to radiation.