System evaluation of automated production and inhalation of 15 O-labeled gaseous radiopharmaceuticals for the rapid 15 O-oxygen PET examinations

摘要

Abstract Background15O-oxygen inhalation PET is unique in its ability to provide fundamental information regarding cerebral hemodynamics and energy metabolism in man. However, the use of 15O-oxygen has been limited in a clinical environment largely attributed to logistical complexity, in relation to a long study period, and the need to produce and inhale three sets of radiopharmaceuticals. Despite the recent works that enabled shortening of the PET examination period, radiopharmaceutical production has still been a limiting factor. This study was aimed to evaluate a recently developed radiosynthesis/inhalation system that automatically supplies a series of 15O-labeled gaseous radiopharmaceuticals of C15O, 15O2, and C15O2 at short intervals.MethodsThe system consists of a radiosynthesizer which produces C15O, 15O2, and C15O2; an inhalation controller; and an inhalation/scavenging unit. All three parts are controlled by a common sequencer, enabling automated production and inhalation at intervals less than 4.5?min. The gas inhalation/scavenging unit controls to sequentially supply of qualified radiopharmaceuticals at given radioactivity for given periods at given intervals. The unit also scavenges effectively the non-inhaled radioactive gases. Performance and reproducibility are evaluated.ResultsUsing an 15O-dedicated cyclotron with deuteron of 3.5?MeV at 40?μA, C15O, 15O2, and C15O2 were sequentially produced at a constant rate of 1400, 2400, and 2000?MBq/min, respectively. Each of radiopharmaceuticals were stably inhaled at ?4.5?min intervals with negligible contamination from the previous supply. The two-hole two-layered face mask with scavenging device minimized the gaseous radioactivity surrounding subject’s face, while maintaining the normocapnia during examination periods. Quantitative assessment of net administration doses could be assessed using a pair of radio-detectors at inlet and scavenging tubes, as 541?±?149, 320?±?103, 523?±?137?MBq corresponding to 2-min supply of 2574?±?255?MBq for C15O, and 1-min supply of 2220?±?766 and 1763?±?174 for 15O2 and C15O2, respectively.ConclusionsThe present system allowed for automated production and inhalation of series of 15O-labeled radiopharmaceuticals as required in the rapid 15O-Oxygen PET protocol. The production and inhalation were reproducible and improved logistical complexity, and thus the use of 15O-oxygen might have become practically applicable in clinical environments.