# Clinical evaluation of tissue-dependent and spatially-variant positron range correction for Gallium-68 PET imaging

## TL;DR

This study evaluates a new method to improve Gallium-68 PET image quality by adjusting for positron range effects based on tissue type and location.

## Contribution

The study introduces a tissue-dependent and spatially-variant positron range correction technique for 68Ga PET imaging in clinical settings.

## Key findings

- TDSV PRC improved SUVmax and CNR for soft tissue and lung lesions compared to non-PRC.
- TDSV PRC showed greater improvement in lung lesions than tissue-independent PRC.
- The technique was feasible in clinical data and most beneficial for lung lesions.

## Abstract

Positron range correction (PRC) can mitigate the effect of the larger positron range on the image quality of Gallium-68 (68Ga) PET-imaging. The aim of this study is to evaluate the improvement in 68Ga-PET image quality by applying a tissue-dependent and spatially-variant PRC (TDSV PRC) for 68Ga in a clinical setting.

A TDSV PRC technique was developed employing CT-driven segmentation masks of different tissue types (soft tissue, bone, lung) and the corresponding tissue-specific positron range kernels. OSEM reconstructions were performed using the proposed TDSV PRC, a tissue-independent PRC, and without any PRC (non-PRC). For lesions identified in [68Ga]Ga-DOTATOC or [68Ga]Ga-PSMA PET/CT data from 20 patients, the maximum standardized uptake value (SUVmax) and contrast-to-noise ratio (CNR) of this technique was compared to tissue-independent PRC and non-PRC images.

A total of 93 lesions were analyzed (48 soft tissue, 35 bone, 10 lung lesions). For soft tissue lesions, TDSV and tissue-independent PRC showed similar increases in SUVmax (13.7%, p < 0.001 vs. 13.6%, p < 0.001) and CNR (11.0%, p < 0.001 vs. 11.1%, p < 0.001) compared to non-PRC. For bone lesions, tissue-independent PRC showed slightly higher not statistically significant increases than TDSV PRC in SUVmax (18.6%, p < 0.001 vs. 17.4%, p < 0.001) and CNR (14.6%, p < 0.001 vs. 13.8%, p < 0.001). In lung lesions, TDSV PRC increased SUVmax and CNR compared to non-PRC (SUVmax: 57.9%, p = 0.012; CNR: 43.9%, p = 0.012) and tissue-independent PRC (SUVmax: 46.0%, p = 0.012; CNR: 32.5%, p = 0.012).

TDSV PRC for 68Ga PET/CT demonstrated to be feasible in clinical patient data, showing the greatest benefits for lung lesions.

The online version contains supplementary material available at 10.1007/s00259-025-07456-z.