Abstract Archives of the RSNA, 2009
A Novel Molecular Fluorescent Technique for Imaging the Somatostatin Receptor 2, Using a DOTATOC Lanthanide Conjugate
Presented on December 1, 2009
Presented as part of SSG11: Molecular Imaging (Applications II)
Molecular Imaging Travel Award
Rune Wiik Andersen MS, Presenter: Nothing to Disclose
Vineet Prakash MBChB, Abstract Co-Author: Nothing to Disclose
Allan Stensballe PhD, Abstract Co-Author: Nothing to Disclose
Jeppe Lund Nielsen PhD, Abstract Co-Author: Nothing to Disclose
Søren Nielsen MSC, Abstract Co-Author: Nothing to Disclose
Somatostatin receptors are overexpressed in neuroendocrine tumors (NET).
Despite nuclear imaging techniques, such as 68-Gallium Dotatate, for in vivo imaging of these receptors, there is a void in their histopathological receptor verification, since it is presently difficult to easily obtain commercial receptor antibodies. We propose an alternative with the novel use of lanthanide fluorescent DOTATOC imaging.Purpose is to prove that it is feasible to combine the fluorescent nuclear imaging of neuroendocrine tumors with histopathological correlates using the same bio-functional DOTATOC component.
The chelation of Europium and Samarium to DOTATOC was proven using MALDI-TOF Mass Spectrometry. The rise in quantum yield between unchelated lanthanides and those bound by DOTATOC was examined using fluorescence spectroscopy.
Sequential paraffin tissue segments of a neuroendocrine tumor, originating from a patient previously scanned positive with 111In-Octreoscan, were unparaffinated and incubated with either free Samarium, Samarium-DOTATOC or otherwise and stained using HE-staining and immunohistochemical staining for synaptophysin.
It is feasible to usefully chelate Samarium and Europium to DOTATOC. There is a distinct higher fluorescent signal arising from the chelation of the two ions than by the DOTA functional group alone. The unparaffinated pancreatic tumor tissues demonstrate a higher fluorescent signal compared to normal pancreatic tissues. These are concordant with histopathology staining using H&E and immunohistochemical for Synaptophysin. Thus, the higher signals appear to originate from Sm-DOTATOC bound to the somatostatin receptors in the NET tissues.
DOTATOC holds a potentially great role in standard histopathology examinations due to its novel chimerical traits as a fluorescent and a radioactive marker. This aids confidence in both macroscopic nuclear imaging and microscopic pathological examinations of neuroendocrine tumors.
We propose a method for the histopatholgical receptor verification using fluorescent DOTATOC imaging. This potentially permits ex-vivo developmental platforms for DOTA-conjugated molecules.
A Novel Molecular Fluorescent Technique for Imaging the Somatostatin Receptor 2, Using a DOTATOC Lanthanide Conjugate. Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8016059.html