Differences in edge artifacts between ⁶⁸Ga- And ¹⁸F-PET images reconstructed using point spread function correction

Objective Edge artifacts have been reported on in relation to ¹⁸F-PET using point spread function correction algorithms. The positron range of ⁶⁸Ga is longer than ¹⁸F, and this difference is thought to result in different edge artifacts. The purpose of this study is to clarify the difference in edge artifacts in PET images using point spread function correction in ⁶⁸Ga- and ¹⁸F-PET. Methods We used a National Electrical Manufacturers Association International Electrotechnical Commission body phantom. The phantom was filled severally with ⁶⁸Ga and ¹⁸F solution. The PET data were obtained over a 90 minutes period using a True Point Biograph 16 scanner. The images were then reconstructed with the ordered subset expectation maximization with point spread function correction. The phantom image analyses were performed by a visual assessment of the PET images and profiles, and an absolute recovery coefficient, which was the ratio of the maximum radioactivity of any given hot sphere to its true radioactivity. Results The ring-like edge artifacts of ⁶⁸Ga-PET were less prominent than those in ¹⁸F-PET. The relative radioactivity profiles of ⁶⁸Ga-PET showed low overshoots of the maximum radioactivity although high overshoots did appear in ¹⁸F-PET. The absolute recovery coefficients of ⁶⁸Ga-PET were smaller than those of ¹⁸F-PET. Conclusion The edge artifacts of ⁶⁸Ga-PET were less prominent than those of ¹⁸F-PET, and their overshoots were smaller. The difference in the positron range between ⁶⁸Ga and ¹⁸F may possibly result in the difference in edge artifacts of images reconstructed using the point spread function correction algorithm.