Quantitative α-camera autoradiography. The intratumoral distribution of ²¹³Bi-DOTA-biotin after anti-CD45 PRIT was analyzed using a novel digital autoradiography bio-imaging system. This α-camera system is dedicated for the ex vivo detection of α-particles in tissue and uses a scintillation setup. The technique is quantitative and fully linear toward activity content in the imaged sections. At serial times after injection (10, 45, and 90 minutes), tumors were cryosectioned (thickness 12-16 μm). Three serial, immediately adjacent sections were obtained: (A) the first for α-imaging, (B) the second for H&E staining, and (C) the third for immunohistochemistry of blood vessels using CD34. This representative, digitally collected α-camera image was obtained 45 minutes after ²¹³Bi-DOTA-biotin injection and was color-coded to express the different levels of activity concentration of ²¹³Bi. Insets represent smaller sections of the image shown in the next panel (inset in panel A comprises entire picture in panel B; inset in panel B comprises entire picture in panel C).