Impact of tissue-independent positron range correction on [<SUP>68</SUP>Ga]Ga-DOTATOC and [<SUP>68</SUP>Ga]Ga-PSMA PET image reconstructions: a patient data study

Purpose: The positron range effect can impair PET image quality of Gallium-68 ( ⁶⁸Ga). A positron range correction (PRC) can be applied to reduce this effect. In this study, the effect of a tissue-independent PRC for ⁶⁸Ga was investigated on patient data. Methods: PET/CT data (40 patients: [ ⁶⁸Ga]Ga-DOTATOC or [ ⁶⁸Ga]Ga-PSMA) were reconstructed using Q.Clear reconstruction algorithm. Two reconstructions were performed per patient, Q.Clear with and without PRC. SUV _max and contrast-to-noise ratio (CNR) values per lesion were compared between PRC and non-PRC images. Five experienced nuclear medicine physicians reviewed the images and chose the preferred reconstruction based on the image quality, lesion detectability, and diagnostic confidence. Results: A total of 155 lesions were identified. The PRC resulted in statistically significant increase of the SUV _max and CNR for soft tissue lesions (6.4%, p < 0.001; 8.6%, p < 0.001), bone lesions (14.6%, p < 0.001; 12.5%, p < 0.001), and lung lesions (3.6%, p = 0.010; 6.3%, p = 0.001). This effect was most prominent in small lesions (SUV _max: 12.0%, p < 0.001, and CNR: 13.0%, p < 0.001). Similar or better image quality, lesion detectability, and diagnostic confidence was achieved in PRC images compared to the non-PRC images as those assessed by the expert readers. Conclusions: A tissue-independent PRC increased the SUV _max and CNR in soft tissue, bone, and lung lesions with a larger effect for the small lesions. Visual assessment demonstrated similar or better image quality, lesion detectability, and diagnostic confidence in PRC images compared to the non-PRC images.