Preclinical SPECT/CT and MR images. (a) SPECT/CT images of four NMRI nude mice with LNCaP xenografts on the right flank. Top left, 48 h post-injection; Top right, 72 h post-injection; Bottom left, blocked mouse pre-injected with 0.8 mg of cold antibody 48 h prior to injection of radiolabelled antibody. Bottom right, image of a mouse at 48 h co-injected with 1.5 mg of unlabelled 5A10, which did not block the tumour uptake of 111In-DTPA-11B6. It should be noted that for the calculation of the T/B ratio (1.6) in the biodistribution and for the ROI analysis of the SPECT images with a derived T/heart ratio of 1.7, the whole tumour is taken into account. Since the colour scale in the SPECT image is scaled partially based upon high uptake areas of the tumour, a direct comparison between these (which are strikingly visible) and the T/B or T/heart (ROI) is not totally fair. (b) SPECT/MR images of SCID mice with intra-tibial xenograft in the left hind limb. Left, SPECT/CT side view, 48 h post-injection; middle, transverse SPECT/CT image slices of the same mouse. The accumulation of 111In-DTPA-11B6 in intra-tibial tumours is clearly shown in both images. Right, MR image of the same animal, where the growth of the intra-tibial tumour is well visualized (arrow).