Dual isotope SPECT imaging of I-123 and I-125

Peripheral amyloidosis is a debilitating and often fatal disease. SPECT imaging of amyloid in mice has been established using ¹²⁵I-SAP. Current efforts are aimed at using ¹²⁵I-labeled synthetic peptides such as p5, which are easier to translate into the clinic in the US since SAP is of human origin. It needs to be shown that the new peptide biomarkers correlate well with the gold standard, SAP. As both materials can be radioiodinated using facile chemistry, the challenge then becomes to develop a protocol that supports dual isotope SPECT imaging of ¹²³I-labeled SAP and the ¹²⁵I-labeled peptide. We address this challenge by first quantifying the amount of cross-talk between the two radio nuclides. We subsequently suggest a correction method.