μSPECT/CT studies with the 99mTc-labeled MJ9 derivatives at 1 h p.i. in PC-3 tumor-bearing mice (Figure 4) confirmed the biodistribution data, with [99mTc]Tc-N4-asp-[Bta8]MJ9 displaying the highest tumor-to-abdomen contrast at 1 h p.i. due to a rapid clearance from GRPR-positive pancreas and stomach. Here, GRPR is linked to neoplasm.