Quantitative ⁸⁹Zr Immuno-PET for In Vivo Scouting of ⁹⁰Y-Labeled Monoclonal Antibodies in Xenograft-Bearing Nude Mice

Biodistribution of coinjected cmAb U36-N-sucDf-⁸⁹Zr (0.37 MBq, white bars) and cmAb U36-p-BSCN-Bz-DOTA-⁸⁸Y (0.13 MBq, black bars) in HNX-OE xenograft-bearing mice at 3 h (A), 24 h (B), 48 h (C), 72 h (D), and 144 h (E) after injection. At the indicated time points, 4 mice were bled, sacrificed, and dissected, and radioactivity levels (%ID/g ± SE) of blood, tumor, organs, and gastrointestinal contents were assessed. BL = blood; TU = tumor; SM = sternum; HE = heart; LU = lung; LI = liver; SP = spleen; KI = kidney; MU = muscle; TB = thighbone; CO = colon; CC = colon content; IL = ileum; IC = ileum content; ST = stomach; SC = stomach content.

⁸⁹Zr-counting-rate linearity determination with HRRT PET camera. Plot is of PET-assessed radioactivity in cylinder phantom versus radioactivity based on dose calibrator measurements. Note presence of linearity, except for highest radioactivity measurement.

Spatial resolution determination for ⁸⁹Zr (dotted line) with HRRT PET camera. Line profile was drawn through image of line source containing ⁸⁹Zr. For comparison, line profile for ¹⁸F (solid line) is also shown.

HSRCs (A) and sphere size estimations (B) for ⁸⁹Zr (○) with HRRT PET camera. For comparison, ¹⁸F (▪) data are also shown. For this purpose, 50% isocontour ROIs were drawn around spheres of Jaszczak phantom.

HRRT PET images of HNX-OE xenograft-bearing mouse injected with cmAb U36-N-sucDf-⁸⁹Zr (3.7 MBq) at 72 h after injection. Coronal image plane (A) in which both tumors (left, 124 mg; right, 26 mg) were visible was chosen. Transaxial image planes in which right tumor was optimally visible (B, top) or left tumor was optimally visible (B, middle and bottom) were chosen. Bottom panel of B illustrates approach to arrive at ring-shaped area used for surroundings determination.