Lung-shunt fraction measured in the intervention room directly after Tc-99m-MAA injection in hepatic radioembolization

Hepatic radioembolization treatments consist of two sessions: a pre-treatment procedure for safety and planning, and, if a suitable particle distribution is achieved, the subsequent treatment. Merging these into a single-session procedure could reduce costs and increase patient comfort. Such a workflow requires the lung-shunt fraction (LSF) to be measured in the intervention room shortly after technetium-99 m macro-aggregated albumin (Tc-99m-MAA) injection. This study investigates whether such a measurement is logistically feasible and sufficiently accurate for clinical practice. A dedicated mobile dual-layer scanner with simultaneous fluoroscopy and nuclear imaging (SPECT/CBCT) for the intervention room (IXSI) was used. Planar LSF measurements were performed directly after Tc-99m-MAA injection in six patients. Patients were also imaged on a conventional SPECT/CT scanner (Siemens Symbia) for comparison. Digital simulations investigated the theoretical accuracy of both scanners. Clinical LSF measurements were compared between modalities, with and without correction for the time interval between injection and imaging, using a logarithmic correction factor derived from published data. Digital simulations showed a difference in LSF values between IXSI and the conventional SPECT scanner of -0.3 ± 1.9% points (pp). In clinical measurements, the uncorrected LSF difference was 4.5 ± 2.3 pp, which reduced to 0.0 ± 1.1 pp after correcting for the time interval between Tc-99m-MAA injection and imaging. Direct evaluation of LSF following Tc-99m-MAA injection using IXSI in the intervention room was logistically feasible. Digital simulations indicated similar performance for IXSI and the conventional SPECT scanner, and clinically observed LSF values aligned with simulations after correcting for the time difference between injection and imaging.