Assessment of atherosclerotic plaque inflammation can be improved by delayed time point FDG PET CT imaging

Objectives Blood pool FDG activity can cloud the atherosclerotic plaque FDG signal. Over time, blood pool FDG activity declines. Therefore, delayed time point FDG PET CT imaging can potentially enhance the assessment of atherosclerotic plaque inflammation.

Methods Twelve healthy volunteers without traditional cardiovascular risk factors and three subjects with angina pectoris were prospectively assessed by dual time point 18-FDG PET CT imaging at 90 and 180 minutes after tracer injection. The ratio between aortic SUVmax and the blood pool SUVmean (TBR) was calculated to show the change in contrast between plaque activity and blood pool activity over time. Global aortic uptake of 18-FDG was quantified by subtracting the blood pool SUVmean from aortic SUVmax (cSUV). The change in aortic TBR and cSUV over time was determined by a Student’s paired t-test. Regression coefficients summarized the data.

Results At 90 minutes, the aortic TBR was 2.072 ± 0.599. At 180 minutes, the aortic TBR significantly increased to 3.488 ± 1.138 (P = <0.0001). At 90 minutes, the aortic cSUV was 1.122 ± 0.505. A significant relationship was observed between aortic cSUV, aging (β = 0.019; t = 2.79; df = 12; P = 0.016) and gender (β = 0.502; t = 2.30; df = 12; P = 0.040). At 180 minutes, the aortic cSUV significantly increased to 1.524 ± 0.577 (P = <0.0001). This resulted in a more significant relationship between aortic cSUV, aging (β = 0.025; t = 3.44; df = 12; P = 0.005) and gender (β = 0.542; t = 2,35; df = 12; P = 0.037).

Conclusions Based on these preliminary data, we can make three conclusions: 1) aging and male gender are significantly correlated to atherosclerotic plaque FDG avidity, 2) over time, a significant increase is observed in TBR, and 3) the increase in cSUV over time results in a more significant relationship between plaque FDG avidity, aging and gender.