Automatic healthy liver segmentation for holmium-166 radioembolization dosimetry.

Background: For safe and effective holmium-166 (Ho) liver radioembolization, dosimetry is crucial and requires accurate healthy liver definition. The current clinical standard relies on manual segmentation and registration of a separately acquired contrast enhanced CT (CECT), a prone-to-error and time-consuming task. An alternative is offered by simultaneous imaging of Ho and technetium-99m stannous-phytate accumulating in healthy liver cells (Ho-Tc dual-isotope protocol). This study compares healthy liver segmentation performed with an automatic method using Tc images derived from a Ho-Tc dual-isotope acquisition to the manual segmentation, focusing on healthy liver dosimetry and corresponding hepatotoxicity. Data from the prospective HEPAR PLuS study were used. Automatic healthy liver segmentation was obtained by thresholding the Tc image (no registration step required). Manual segmentation was performed on CECT and then manually registered to the SPECT/CT and subsequently to the corresponding Ho SPECT to compute absorbed dose in healthy liver.

Results: Thirty-one patients (66 procedures) were assessed. Manual segmentation and registration took a median of 30 min per patient, while automatic segmentation was instantaneous. Mean ± standard deviation of healthy liver absorbed dose was 18 ± 7 Gy and 20 ± 8 Gy for manual and automatic segmentations, respectively. Mean difference ± coefficient of reproducibility between healthy liver absorbed doses using the automatic versus manual segmentation was 2 ± 6 Gy. No correlation was found between mean absorbed dose in the healthy liver and hepatotoxicity.

Conclusions: Ho-Tc dual-isotope protocol can automatically segment the healthy liver without hampering the Ho dosimetry assessment.

Trial Registration: ClinicalTrials.gov, NCT02067988. Registered 20 February 2014. https://clinicaltrials.gov/ct2/show/NCT02067988.