RT Journal Article
SR Electronic
T1 Improving Contrast and Detectability: Imaging with [<sup>55</sup>Co]Co-DOTATATE in Comparison with [<sup>64</sup>Cu]Cu-DOTATATE and [<sup>68</sup>Ga]Ga-DOTATATE
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 228
OP 233
DO 10.2967/jnumed.119.233015
VO 61
IS 2
A1 Andersen, Thomas L.
A1 Baun, Christina
A1 Olsen, Birgitte B.
A1 Dam, Johan H.
A1 Thisgaard, Helge
YR 2020
UL http://jnm.snmjournals.org/content/61/2/228.abstract
AB PET imaging at late time points after injection may allow tracer clearance from normal tissue and hence improve image contrast and detectability. 55Co is a promising isotope with high positron yield and a long half-life suitable for imaging at delayed time points. Here, we compared the 3 radioconjugates [68Ga]Ga-DOTATATE, [64Cu]Cu-DOTATATE, and [55Co]Co-DOTATATE by PET/CT imaging in NOD-SCID mice bearing subcutaneous somatostatin receptor–expressing AR42J tumors. Methods: 55Co and 64Cu were produced by the 54Fe(d,n)55Co and 64Ni(p,n)64Cu nuclear reactions, whereas 68Ga was obtained from a 68Ge/68Ga generator. 55Co and 64Cu were labeled with DOTATATE by heating in a sodium acetate buffer and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer, respectively. AR42J tumor–bearing mice were dynamically scanned 0–1 h after injection. For 64Cu and 55Co, additional imaging was also performed at late time points after 4 and 24 h. Dose calculations were based on a known biodistribution. The cumulated disintegrations in each organ were calculated by integration of a fitted exponential function to the biodistribution of each respective organ. Equivalent doses were calculated by OLINDA/EXM using the MIRD formalism. Results: Tumor uptake was rapid from 0 to 1 h after injection for all 3 radioconjugates. Normal-tissue ratios as represented by tumor-to-liver, tumor-to-kidney, and tumor-to-muscle ratios increased significantly over time, with [55Co]Co-DOTATATE reaching the highest ratio of all radioconjugates. For [55Co]Co-DOTATATE, the tumor-to-liver ratio increased to 65 ± 16 at 4 h and 50 ± 6 at 24 h, which were 15 (P &lt; 0.001) and 30 (P &lt; 0.001) times higher, respectively, than the corresponding ratios for [64Cu]Cu-DOTATATE and 5 (P &lt; 0.001) times higher than that of [68Ga]Ga-DOTATATE at 1 h. Correspondingly, tumor-to-kidney and tumor-to-muscle ratios for [55Co]Co-DOTATATE were 4 (P &lt; 0.001) and 11 (P &lt; 0.001) times higher than that of [64Cu]Cu-DOTATATE at 24 h. An equivalent dose was calculated as 9.6E−02 mSv/MBq for [55Co]Co-DOTATATE. Conclusion: [55Co]Co-DOTATATE demonstrated superior image contrast compared with [64Cu]Cu-DOTATATE and [68Ga]Ga-DOTATATE for PET imaging of somatostatin receptor–expressing tumors, warranting translation into clinical trials. Dosimetry calculations found that effective doses for [55Co]Co-DOTATATE were comparable to those for both [64Cu]Cu-DOTATATE and [68Ga]Ga-DOTATATE.