166Holmium–99mTechnetium dual-isotope imaging: scatter compensation and automatic healthy-liver segmentation for 166Holmium radioembolization dosimetry

• Published in: EJNMMI physics Vol. 9; no. 1; p. 30
• Main Authors: Stella, Martina, Braat, Arthur J. A. T., Lam, Marnix G. E. H., de Jong, Hugo W. A. M., van Rooij, Rob
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 21.04.2022; Springer Nature B.V
• Subjects: Applied and Technical Physics; Computational Mathematics and Numerical Analysis; Computed tomography; Density; Dosimeters; Engineering; Evaluation; Holmium; Image contrast; Image quality; Image reconstruction; Image segmentation; Imaging; Liver; Medical imaging; Medicine; Medicine & Public Health; Nuclear Medicine; Original Research; Quality assessment; Radiology; Recovery; Technetium; Technetium isotopes; Tumors; Segmentation; Holmium; Healthy-liver; Technetium; Dosimetry; Radioembolization; Dual isotope
• ISSN: 2197-7364; 2197-7364
• DOI: 10.1186/s40658-022-00459-x

Background Partition modeling allows personalized activity calculation for holmium-166 ( 166 Ho) radioembolization. However, it requires the definition of tumor and non-tumorous liver, by segmentation and registration of a separately acquired CT, which is time-consuming and prone to error. A protocol including 166 Ho-scout, for treatment simulation, and technetium-99m ( 99m Tc) stannous phytate for healthy-liver delineation was proposed. This study assessed the accuracy of automatic healthy-liver segmentation using 99m Tc images derived from a phantom experiment. In addition, together with data from a patient study, the effect of different 99m Tc activities on the 166 Ho-scout images was investigated. To reproduce a typical scout procedure, the liver compartment, including two tumors, of an anthropomorphic phantom was filled with 250 MBq of 166 Ho-chloride, with a tumor to non-tumorous liver activity concentration ratio of 10. Eight SPECT/CT scans were acquired, with varying levels of 99m Tc added to the non-tumorous liver compartment (ranging from 25 to 126 MBq). For comparison, forty-two scans were performed in presence of only 99m Tc from 8 to 240 MBq. 99m Tc image quality was assessed by cold-sphere (tumor) contrast recovery coefficients. Automatic healthy-liver segmentation, obtained by thresholding 99m Tc images, was evaluated by recovered volume and Sørensen–Dice index. The impact of 99m Tc on 166 Ho images and the role of the downscatter correction were evaluated on phantom scans and twenty-six patients’ scans by considering the reconstructed 166 Ho count density in the healthy-liver. Results All 99m Tc image reconstructions were found to be independent of the 166 Ho activity present during the acquisition. In addition, cold-sphere contrast recovery coefficients were independent of 99m Tc activity. The segmented healthy-liver volume was recovered fully, independent of 99m Tc activity as well. The reconstructed 166 Ho count density was not influenced by 99m Tc activity, as long as an adequate downscatter correction was applied. Conclusion The 99m Tc image reconstructions of the phantom scans all performed equally well for the purpose of automatic healthy-liver segmentation, for activities down to 8 MBq. Furthermore, 99m Tc could be injected up to at least 126 MBq without compromising 166 Ho image quality. Clinical trials The clinical study mentioned is registered with Clinicaltrials.gov (NCT02067988) on February 20, 2014.