Quantification of myocardial blood flow and myocardial flow reserve by 13N-NH3 PET/CT is not significantly affected by pixel size.

Abstract

Myocardial blood flow (MBF) and myocardial flow reserve (MFR) are measurable by 13N-NH3 positron emission tomography (PET). MFR, which is the ratio of MBF under adenosine stress to MBF at rest, is prognostically valuable. The ASNC imaging guidelines/SNMMI procedure standards recommend using 2-3mm pixels, and pixel size does differ between institutions. We sought to evaluate the effects of pixel sizes on the quantitative values calculated from 13N-NH3 PET images. Thirty consecutive patients with ischemic heart disease who underwent 13N-NH3 PET were retrospectively enrolled. Dynamic images were quantified using PMOD's cardiac PET analysis tool (pixel sizes: 3.18, 2.03, and 1.59mm). MBF under adenosine stress, MBF at rest, and MFR for the right coronary artery (RCA) region, left anterior descending artery region, and left circumflex coronary artery branch region innervation regions were calculated at each pixel size and compared. Quantitative values did not significantly differ according to pixel size in any of the regions. However, MFR values for the RCA fluctuated the most. Ischemic and non-ischemic regions remained visually discernible in qualitative images, with no variation in quantitative values, regardless of pixel size. Quantitative values were not significantly affected by pixel sizes within the recommended range of 2-3mm. Values for the RCA region may have been overestimated, but this was true for all pixel sizes.