title: Differential registration of two types of radionuclides on macroautoradiograms for studying coronary circulation: concise communication.
abstract: Double-radionuclide autoradiography proved to be feasible using combinations of Tc-99m and I-125, or Tc-99m and C-14. Because of the short half-life of Tc-99m (6 hr), we first registered Tc-99m on x-ray film. Given an adequate Tc-99m:I-125 activity ratio of 20:1, the exposure duration for Tc-99m was still too short for I-125 to blacken the x-ray film. The pure emission from C-14 is completely absorbed by a thin aluminum sheet--hence no problem there. After the decay of Tc-99m, therefore, it was entirely feasible to continue autoradiography with I-125 (T1/2 = 60.2 days) or C-14 (T1/2 = 5730 yr). Based on these conditions, we applied (a) tracer microspheres labeled with I-125 and Tc-99m to define the respective perfusion areas of the left anterior descending, septal, and left circumflex coronary arteries of the beating heart, and (b) Tc-99m pyrophosphate and C-14 antipyrine to demarcate respectively the localization of the infarct-avid substance and the regional blood flow. We verified the first procedure with postmortem angiography and the second with histochemistry.
mesh_terms: D000792:Angiography; D000818:Animals; D001345:Autoradiography; D002250:Carbon Radioisotopes; D003326:Coronary Circulation; D011756:Diphosphates; D004285:Dogs; D006651:Histocytochemistry; D007457:Iodine Radioisotopes; D009203:Myocardial Infarction / Q000503:physiopathology; D013667:Technetium; D016698:Technetium Tc 99m Pyrophosphate
chemical_list: D002250:Carbon Radioisotopes; D011756:Diphosphates; D007457:Iodine Radioisotopes; D016698:Technetium Tc 99m Pyrophosphate; D013667:Technetium