Page 112 - Cellular Imaging in Regenerative Medicine, Cancer and Osteoarthritis

Chapter 5
SPECT/MRI
For SPECT/MRI, PC-3-xenografted mice were intravenously injected with 25 MBq/200 pmol [111In]SB3, co-injected with either 300 μg/100 μL PA in 0.5% ethanol or 100 μL saline solution. Subsequently, imaging was performed 1 h, 4 h and 24 h p.i. of the radiotracer, while animals were anesthetized using isoflurane/O2, body temperature was maintained using warm air flow and respiratory rate was monitored. Whole body SPECT images were acquired using the novel and state-of-the-art 4-head multipinhole system (NanoScan SPECT/MRI, Mediso Medical Imaging) in 30 min (28 projections, 29 s/projection and 7 cm axial field of view). Images were reconstructed using OSEM with 6 iterations and 4 subsets on a 120 × 120 matrix with 0.25 × 0.25 × 0.25 mm isotropic voxels. MR based attenuation correction was applied to all images. T2 MR images were acquired using a spin echo sequence (TR/TE=4500/52 ms) with a 35 mm diameter solenoid coil. Other scan parameters were: field of view: 70 mm, matrix: 256 × 128 and slice thickness: 1 mm with 0.1 mm spacing between slices. An ROI of the tumor was drawn by an experienced technician on the T2-weighted MR image to measure the intensity in the SPECT image.
Statistics
All statistical evaluations were performed with Graphpad Prism software (v 5.01). The IC50 value was calculated using a log (inhibitor) vs response model. To compare in vivo stability -/+ PA, radioactivity uptake in the tumor -/+ PA and radioactivity uptake in the tumor without and with an excess of unlabeled peptide an unpaired t-test was used. P values <0.05 were considered statistically significant. Tumor to organ uptake ratios were calculated per animal and expressed as mean and standard deviation per group.
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