Holmium-166 poly(L-lactic acid) microsphere radioembolisation of the liver: technical aspects studied in a large animal model

Abstract

ObjectiveTo assess the accuracy of a scout dose of holmium-166 poly(L-lactic acid) microspheres (166Ho-PLLA-MS) in predicting the distribution of a treatment dose of 166Ho-PLLA-MS, using single photon emission tomography (SPECT).MethodsA scout dose (60 mg) was injected into the hepatic artery of five pigs and SPECT acquired. Subsequently, a ‘treatment dose’ was administered (540 mg) and SPECT, computed tomography (CT) and magnetic resonance imaging (MRI) of the total dose performed. The two SPECT images of each animal were compared. To validate quantitative SPECT an ex vivo liver was instilled with 166Ho-PLLA-MS and SPECT acquired. The liver was cut into slices and planar images were acquired, which were registered to the SPECT image.ResultsQualitatively, the scout dose and total dose images were similar, except in one animal because of catheter displacement. Quantitative analysis, feasible in two animals, tended to confirm this similarity (r 2 = 0.34); in the other animal the relation was significantly better (r 2 = 0.66). The relation between the SPECT and planar images acquired from the ex vivo liver was strong (r 2 = 0.90).ConclusionIn the porcine model a scout dose of 166Ho-PLLA-MS can accurately predict the biodistribution of a treatment dose. Quantitative 166Ho SPECT was validated for clinical application.