Zr-cetuximab-IR in tissues assessed by IR fluorescence and gamma ray quantifications. Tumors and organs were collected 24 h p.i. of the biodistribution probe. Each organ was halved: one half was processed for IR fluorescence quantification and the other half for gamma ray quantification. Six mice with two tumors each were employed; graph bars show mean values ± SEM. Statistical significance is as follows: double asterisks for p < 0.01 and triple asterisks for p < 0.001.