Microwave spectroscopy of myocardial ischemia and infarction. 1. Experimental study

The purpose of this study was to assess whether physiologic changes in canine myocardium due to coronary blood flow reduction, ischemia, and infarction could be detected by changes in dielectrical properties. Measurements were made in the frequency range of 0.2-6.0 GHz. Percent coronary blood flow reduction was linearly related to the decrease in epsilon" at frequencies of 0.2 GHz(R =-0.997) and 1.1 GHz (R =- 0.9987). In 2 h occlusions, increased conduction time in the infarct area mirrored the temporal changes in dielectrical properties. In 2-week-old infarctions differences, in epsilon' between normal and central infarct zones were statistically significant (P<0.05) for all frequencies. For epsilon" the differences between normal and central infarct zones were also significant for all frequencies (P<0.01). In conclusion, coronary blood flow reduction, ischemia, and infarction can be detected by microwave spectroscopy and potentially can form the basis for a physiologic microwave tomographic imaging system.