Prototype catheter-based device for real time dual-isotope myocardial mapping

Background Molecular signals from radiotracers have potential utility for guiding localized interventions to the myocardium. To address potential technical challenges related to the coordination of these interventions with PET and SPECT imaging, we are developing an integrated catheter-based device for real time myocardial mapping and molecularly-guided intervention (1). In this context, a catheter-based device that performs dual-isotope evaluations may be especially useful. Purpose Develop a prototype gamma detection catheter for dual-isotope myocardial assessment. Methods Our prototype device (see image) consists of a flexible catheter with a gamma detection tip that contains a miniature plastic scintillator coupled to an Si photodiode. Signals from the catheter are transmitted wirelessly to the remote display unit. We utilized the catheter to measure gamma emission spectra from plastic vials containing variable concentrations of 99mTc (peak 140 keV) and 201Tl (68-80 keV). Peak counts for each radionuclide were normalized and compared to normalized data generated by gamma well counting. Results Normalized catheter-based measurements of gamma emissions from 99mTc/ 201Tl solutions correlate linearly with the relative amounts of the radionuclides in solution (solid bars in chart). These dual-isotope catheter-based measurements also show good agreement with corresponding well counting data (cross-hatched bars). Conclusion The miniature gamma detector in our prototype catheter device reliably performs dual-isotope measurements in vitro; further evaluation is needed to determine its effectiveness in detecting myocardial gamma emissions and guiding interventions.