Leveraging small voxel with optimal acquisition time for [18F]mFBG total-body PET/CT imaging in pediatric patients with neuroblastoma: a preliminary study.

Purpose: The advent of total-body PET/CT presents an opportunity for significant advancements in imaging of neuroblastoma with [¹⁸F]meta-fluorobenzylguanidine ([¹⁸F]mFBG). Small voxel imaging has proven to have better lesion detectability but need enough radioactivity counts. This study aims to balance shortened acquisition times and small voxel reconstruction to keep sufficient image quality and diagnostic confidence on [¹⁸F]mFBG total-body PET for neuroblastoma.

Methods: We retrospectively enrolled 33 pediatric patients with neuroblastoma who underwent 37 [¹⁸F]mFBG total-body uEXPLORER PET/CT scans of 10-min duration. PET images were reconstructed with varying acquisition times (0.5-10 min) and three matrix sizes (192 × 192, 512 × 512 and 1024 × 1024). The subjective (scored on a 5-point scale) and objective image quality (signal-to-noise ratio, SNR) of all the sets of reconstructed images were analyzed by nuclear medicine physicians. For indeterminate lesions identified in the group of 192 × 192 matrix with the 10-min scan (G192-10), diagnostic confidence was further evaluated in images reconstructed with the 512 × 512 and 1024 × 1024 matrices (G512 and G1024).

Results: Of the 33 patients with 37 [¹⁸F]mFBG PET/CT scans, 17 patients with 20 scans had positive [¹⁸F]mFBG PET/CT findings. Sufficient subjective image quality was achieved with at least 2-min acquisition of 192 × 192 matrix and 4-min acquisition of 512 × 512 matrix (with all scores ≥ 3). SNR increased with longer acquisition times for the same voxel size, while decreased as voxel size shrunk. Although the Curie and SIOPEN scores remained consistent across G192, G512, and G1024-10 groups, the G512 groups with at least 2-min acquisition and G1024-10 showed significantly higher confidence scores for characterizing indeterminate lesions on the G192-10 images, with almost all indeterminate lesions being rated as very confident.

Conclusions: A matrix of 512 × 512 with a minimum of 4-min acquisition on [¹⁸F]mFBG total-body PET/CT is recommended for sufficient image quality and improved diagnostic confidence, particularly in detecting indeterminate lesions.