Bidirectional dynamic frame prediction network for total-body [⁶⁸Ga]Ga-PSMA-11 and [⁶⁸Ga]Ga-FAPI-04 PET images

Total-body dynamic positron emission tomography (PET) imaging with total-body coverage and ultrahigh sensitivity has played an important role in accurate tracer kinetic analyses in physiology, biochemistry, and pharmacology. However, dynamic PET scans typically entail prolonged durations ( \(\:\ge\:\) 60 minutes), potentially causing patient discomfort and resulting in artifacts in the final images. Therefore, we propose a dynamic frame prediction method for total-body PET imaging via deep learning technology to reduce the required scanning time.

On the basis of total-body dynamic PET data acquired from 13 subjects who received [⁶⁸Ga]Ga-FAPI-04 (⁶⁸Ga-FAPI) and 24 subjects who received [⁶⁸Ga]Ga-PSMA-11 (⁶⁸Ga-PSMA), we propose a bidirectional dynamic frame prediction network that uses the initial and final 10 min of PET imaging data (frames 1–6 and frames 25–30, respectively) as inputs. The peak signal-to-noise ratio (PSNR) and structural similarity index measure (SSIM) were employed as evaluation metrics for an image quality assessment. Moreover, we calculated parametric images (⁶⁸Ga-FAPI: \(\:{K}_{1}\) , ⁶⁸Ga-PSMA: \(\:{K}_{i}\) ) based on the supplemented sequence data to observe the quantitative accuracy of our approach. Regions of interest (ROIs) and statistical analyses were utilized to evaluate the performance of the model.

Both the visual and quantitative results illustrate the effectiveness of our approach. The generated dynamic PET images yielded PSNRs of 36.056 ± 0.709 dB for the ⁶⁸Ga-PSMA group and 33.779 ± 0.760 dB for the ⁶⁸Ga-FAPI group. Additionally, the SSIM reached 0.935 ± 0.006 for the ⁶⁸Ga-FAPI group and 0.922 ± 0.009 for the ⁶⁸Ga-PSMA group. By conducting a quantitative analysis on the parametric images, we obtained PSNRs of 36.155 ± 4.813 dB (⁶⁸Ga-PSMA, \(\:{K}_{1}\) ) and 43.150 ± 4.102 dB (⁶⁸Ga-FAPI, \(\:{K}_{i}\) ). The obtained SSIM values were 0.932 ± 0.041 (⁶⁸Ga-PSMA) and 0.980 ± 0.011 (⁶⁸Ga-FAPI). The ROI analysis conducted on our generated dynamic PET sequences also revealed that our method can accurately predict temporal voxel intensity changes, maintaining overall visual consistency with the ground truth.

In this work, we propose a bidirectional dynamic frame prediction network for total-body ⁶⁸Ga-PSMA and ⁶⁸Ga-FAPI PET imaging with a reduced scan duration. Visual and quantitative analyses demonstrated that our approach performed well when it was used to predict one-hour dynamic PET images. https://github.com/OPMZZZ/BDF-NET.