Bio-distribution based on SPECT/CT of 188Re-liposome in SD rat

Objectives SPECT has been widely accepted for quantification of radioisotope. Comparison of quantification from planar and SPECT were proposed and evaluated. This is the first study to evaluate bio-distribution of 188Re-labeled liposomes in Rat which is critical because 188Re-labeled liposomes clinical trial will be conducted early 2012. According to past studies the maximal tolerance dosage (MTD) of 188Re is limited due to its major energy of beta emission and imaging of 188Re is difficult since it has only 15% gamma emission rate therefore standard model for bio-distribution based on SPECT/CT is then important. Bio-distribution evaluation will be made to human only via the SPECT/CT imaging.

Methods Bio-distribution studies of Rat after intravenous (i.v.) administration was performed via sacrificing (n=3 per time frame) versus imaging of the animals (n=3). NanoSPECT/CT with 2mm multiple pinhole collimators and apertures were used to image the animals. Agreement of radioactivity and %ID/g measurements was assessed by Lin's concordance correlation coefficient (CCC).

Results Liver %ID/g varies from 0.224%-0.466% for imaging group and 0.387%-1.359% for sacrificing group at 24H post injection, and 0.826%-1.129% or imaging group and 0.325%-0.804% 48H post injection. Spleen %ID/g varies from 5.153%-9.059% for imaging group and 9.995%-20.232% for sacrificing group at 24H post injection, and 3.753%-13.5% or imaging group and 3.305%-21.623% 48H post injection. All studies were examined and confirmed significantly agreed (CCC=0.938).

Conclusions SPECT/CT bio-distribution based on SPECT/CT of 188Re-liposome confirmed high agreement compared to traditional way to calculate bio-distribution of sacrificing animals