Evaluation of 209At as a theranostic isotope for 209At-radiopharmaceutical development using high-energy SPECT.

The development of alpha-emitting radiopharmaceuticals using 211At requires quantitative determination of the time-dependent nature of the 211At biodistribution. However, imaging-based methods for acquiring this information with 211At have not found wide-spread use because of its low abundance of decay emissions suitable for external detection. In this publication we demonstrate the theranostic abilities of the 211At/209At isotope pair and present the first-ever 209At SPECT images. The VECTor microSPECT/PET/CT scanner was used to image 209At with a collimator suitable for the 511 keV annihilation photons of PET isotopes. Data from distinct photopeaks of the 209At energy spectrum (195 keV (22.6%), 239 keV (12.4 %), 545 keV (91.0 %), a combined 782/790 keV peak (147 %), and 209Po x-rays (139.0 %)) were independently evaluated for use in image reconstructions using Monte Carlo (GATE) simulations and phantom studies. 209At-imaging in vivo was demonstrated in a healthy mouse injected with 10 MBq of free [209At]astatide. Image-based measurements of 209At uptake in organs of interest-acquired in 5 min intervals-were compared to ex vivo gamma counter measurements of the same organs. Simulated and measured data indicated that-due to the large amount of scatter from high energy (>750 keV) gammas-reconstructed images using the x-ray peak outperformed those obtained from other peaks in terms of image uniformity and spatial resolution, determined to be <0.85 mm. 209At imaging using the x-ray peak revealed a biodistribution that matched the known distribution of free astatide, and in vivo image-based measurements of 209At uptake in organs of interest matched ex vivo measurements within 10%. We have acquired the first 209At SPECT images and demonstrated the ability of quantitative SPECT imaging with 209At to accurately determine astatine biodistributions with high spatial and temporal resolution.

Pulmonary adiaspiromycosis in a patient with acquired immunodeficiency syndrome.

Adiaspiromycosis is a noninfectious, nonarthropod-transmitted fungal infection that occurs worldwide in lower vertebrates, especially rodents. However, humans may become accidental hosts. Reported here is a case of adiaspiromycosis of the lung in an HIV-positive, 40-year-old, bisexual man who first presented with cough and dyspnea. Cultures of a bronchoalveolar lavage and protected brush specimen revealed the presence of fungal elements that were identified as Emmonsia parva var. parva. The patient was successfully treated with amphotericin B and thereafter with fluconazole. This organism should be added to the list of pathogens that cause pulmonary infection in AIDS patients.