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Resolution recovery with 3D PET extravascuclar density imaging

Interpretation of FDG PET images is complicated by partial volume (PV) averaging, a result of cardiac motion and limited scanner resolution. An extravascular (EV) density image, created from the subtraction of a blood pool scan from a transmission scan, can be used for correction of PV averaging. Computer simulations were performed to develop this method. The PSF of the scanner was measured and found to be gaussian with a FWHM of 9.7 mm. Images were subsequently created through convolution of a true activity distribution with the PSF. The simulations showed that the EV density image could perfectly correct for PV effects, and predicted a value of 0.67 g/cc for the EV image, later validated using a cardiac phantom (0.68 +/- 0.016 g/cc). Measurements on a plastic phantom with a constant myocardial thickness of 10 mm were performed to validate the proposed method. A 32% reduction in myocardial activity was found before correction, significantly less than the true value (p<0.001). Application of the EV density image yielded the true myocardial activity (p=ns) after an artifact inherent to phantom studies was accounted for. These results indicate that PV averaging within the myocardium can be accurately corrected using an EV density image.