Eleanor Lee Ormsby MD, Presenter: Nothing to Disclose

Jai Woong Seo PhD, Abstract Co-Author: Nothing to Disclose

Hua Zhang PhD, Abstract Co-Author: Nothing to Disclose

John P. McGahan MD, Abstract Co-Author: Nothing to Disclose

John Michael Boone PhD, Abstract Co-Author: Consultant, Varian Medical Systems, Inc Research funded, Varian Medical Systems, Inc Research funded, FUJIFILM Holdings Corporation Research funded, Hologic, Inc

Katherine W. Ferrara PhD, Abstract Co-Author: Equipment support, Siemens AG Research grant, Pfizer Inc Scientific Advisory Board, Endra, Inc

Kate Watson BS, Abstract Co-Author: Nothing to Disclose

00030490-DMT et al, Abstract Co-Author: Nothing to Disclose

With its 12.7-hour half-life, 64Cu enables imaging of long-circulating liposomes over 48 hrs or more, facilitating estimates of particle pharmacokinetics. Images of the radiolabeled particles can also be used to guide future interventions. To evaluate image quality with 64Cu-labeled liposomes and 18F-FDG, this study compares the tumor-to-background ratio and contrast.

Preformed liposomes were labeled with 64Cu using solid phase synthesis. In one study (n=4), mice bearing bilateral MET-1 tumors implanted within the mammary fat pad were intravenously injected with 18F-FDG at t=0 and imaged using microPET. At t=2.5 hrs, 64Cu-radiolabeled liposomes were injected and imaged at 6, 18, and 24 hrs post-injection. In a second study (n=4), 64Cu-radiolabeled liposomes were injected and imaged at 0, 6, 18, 24, and 48 hrs post-injection. 3D ROIs in the tumor, blood, liver and adjacent thigh were analyzed and %ID/g was calculated assuming a tissue density of 1 g/mL. The %ID/g contrast ratios were calculated as (tumor-background)/(tumor+background) and averaged across subjects. Image data were compared with a well count-based biodistribution at 24 or 48 hrs post-injection.

In each case, the tumors were visible within a few minutes post-injection. The image-based estimate of maximum %ID/g was similar for the two tracers: 17.2 ± 2.5 %ID/g following the injection of 18F-FDG and 17.9 ± 3.6 %ID/g at 24 hrs following the injection of 64Cu-liposomes. The contrast for 18F-FDG was 0.68 ± 0.04 and for 64Cu-liposomes was 0.63±0.1 at 24 hrs after injection. For our long-circulating particles, the tumor concentration peaks near 24 hrs and remains stable for 48 hrs, the liver concentration peaks near 6 hrs and blood concentration decreases from ~32% to ~14% of the initial value at 24 and 48 hrs, respectively. Therefore, depending on the location of the tumor, image contrast can increase with time, with a maximum contrast of 0.87±0.08 observed for 64Cu-liposomes at 48 hrs post-injection.

64Cu labeled liposomes facilitate visualization of tumors with a high tumor-to-background ratio over 48 hrs post-injection with an image contrast that is comparable to 18F-FDG.

The versatility of liposomes as activatable and molecularly-targeted vehicles with multi-imaging capabilities is well known. 64Cu-liposomes promises to be an important agent in facilitating agent.

Ormsby, E, Seo, J, Zhang, H, McGahan, J, Boone, J, Ferrara, K, Watson, K, et al, 0, Comparison of 64Cu-Liposomes and 18F-FDG Tumor-to-Background Ratio in Micro-Positron Emission Tomography  .  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8016607.html