![]() ![]() ![]() įor tumor dosimetry calculations, quantitative imaging is essential, which would also allow assessment of the radiation dose delivered to the non-tumorous liver tissue. This has been reported to frequently lead to retrograde flow and/or failure to deliver the intended dose. A disadvantage of SIR-Spheres® is the relatively low specific activity, which necessitates the administration of relatively high amounts of these microspheres. SIR-Spheres® are resin-based microspheres of near-plasma density. This may increase the risk of proximal intravascular settling. These two devices differ considerably in physical characteristics, particularly with regard to density and specific activity (Table 1) TheraSphere® microspheres are glass microspheres, consequently not biodegradable, and more importantly, of a high density compared to plasma. Two 90Y microsphere products are currently commercially available and in clinical use: TheraSphere® (MDS Nordion Inc., Kanata, Ontario, Canada) and SIR-Spheres® (SIRTeX Medical Ltd., Sydney, New South Wales, Australia). Internal radiation therapy with yttrium-90 ( 90Y)-loaded microspheres injected into the hepatic artery has demonstrated to be an effective treatment option in the management of patients with unresectable intrahepatic malignancies. This result offers a good perspective for upcoming patient trials. In pigs, hepatic arterial embolization with 166HoMS in amounts corresponding with liver-absorbed doses of over 100 Gy, if correctly administered, is not associated with clinically relevant side effects. It can be concluded that the toxicity profile of HoMS is low. The actual radioactivity distribution was assessed through ex vivo 166mHo measurements. In pigs from the 166HoMS group, atrophy of one or more liver lobes was frequently observed. Nuclear scans were acquired from all animals from the 166HoMS group, and MRI scans were performed if available. In the other blood parameters, no abnormalities were observed. AST levels were transitorily elevated post- 166HoMS administration. Four lethal adverse events occurred in the 166HoMS group due either to incorrect administration or comorbidity: inadvertent delivery of microspheres into the gastric wall ( n = 2), preexisting gastric ulceration ( n = 1), and endocarditis ( n = 1). ![]() ResultsĪfter microsphere administration, some animals exhibited a slightly diminished level of consciousness and a dip in appetite, both of which were transient. Finally, a pathological examination was undertaken. The animals were monitored clinically, biochemically, and ( 166HoMS group only) hematologically over a period of 1 month ( 165HoMS group) or over 1 or 2 months ( 166HoMS group). The microspheres’ biodistribution was assessed by single-photon emission computed tomography and/or MRI. ![]() Healthy pigs (20–30 kg) were injected into the hepatic artery with holmium-165-loaded microspheres ( 165HoMS n = 5) or with holmium-166-loaded microspheres ( 166HoMS n = 13). The aim of this study is to evaluate the toxicity of holmium-166 poly( l-lactic acid) microspheres administered into the hepatic artery in pigs. ![]()
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