Cardiac PET images suffer from partial volume (PV) losses, a result of motion and limited resolution. A correction can be made using an extravascular (EV) density image, constructed via the subtraction of a blood volume (BV) image from a transmission image (TX, image of tissue density). The ability of the EV image to correct for PV losses is dependent on the noise in the TX image, and by errors in alignment between the TX and BV images. A TX image can be obtained in either a pre-injection or post-injection mode, depending on whether it is taken before or after injection of activity to the subject. The purpose of this study was to determine which TX image best minimizes errors in the EV image. A simple plastic cardiac phantom was used to compare the two TX modes. Calculation and comparison of the centers was used to determine the pre-injection misalignment. Pre-injection offset was -0.33±0.85 mm vertically, and -0.64±0.72 mm horizontally from the post- injection image. A CoV of 0.0231±0.004 and 0.0374±0.006 was measured for the pre and post-injection images respectively. These results indicate that the pre-injection TX has the best statistical quality, but provides poor alignment.
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.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.