Estimation of optimal number of gates in dual gated 18F-FDG cardiac PET

R Klén,E Hoppela,J Teuho,H T Sipila,T Noponen,E Lehtonen,K Thielemans,M Teräs,J Knuuti

doi:10.1038/s41598-020-75613-5

Abstract

Gating of positron emission tomography images has been shown to reduce the motion effects, especially when imaging small targets, such as coronary plaques. However, the selection of optimal number of gates for gating remains a challenge. Selecting too high number of gates results in a loss of signal-to-noise ratio, while too low number of gates does remove only part of the motion. Here, we introduce a respiratory-cardiac motion model to determine the optimal number of respiratory and cardiac gates. We evaluate the model using a realistic heart phantom and data from 12 cardiac patients (47–77 years, 64.5 on average). To demonstrate the benefits of our model, we compared it with an existing respiratory model. Based on our study, the optimal number of gates was determined to be five respiratory and four cardiac gates in the phantom and patient studies. In the phantom study, the diameter of the most active hot spot was reduced by 24% in the dual gated images compared to non-gated images. In the patient study, the thickness of myocardium wall was reduced on average by 21%. In conclusion, the motion model can be used for estimating the optimal number of respiratory and cardiac gates for dual gating.

Highlights

Image quality in cardiac positron emission tomography (PET) is reduced by respiratory and cardiac motions
In most 18F-FDG patient studies, the respiratory and cardiac motion amplitudes have been determined to be more than 5 mm, which is above the full-width half maximum (FWHM) of modern PET s canners[1]
We report the total motion amplitude as function respiratory and cardiac gates from model (2) and the optimal number of gates given by model (4)

Summary

Introduction

Image quality in cardiac positron emission tomography (PET) is reduced by respiratory and cardiac motions. The effect of both motions can be minimised For this purpose, dual gating has been introduced[5,12,13,14,15,16,17,18,19], where simultaneous respiratory and cardiac gating is applied. In principle, increasing the number of gates enables to capture motion in each gate with increased accuracy, as each gate contains only a small fraction of the total motion seen in non-gated images While this reduces motion effects as a function of the number of gates, the signal-to-noise ratio (SNR) will be reduced as well which might cause variation in quantitative measurements[25] and result to a loss of contrast in small targets, Scientific Reports | (2020) 10:19362. To compensate for the reduced SNR, the acquisition time needs to be extended or the number of gates needs to be reduced

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Discussion

Conclusion