Quantitative bone SPECT/CT-derived tumor burden as a prognostic biomarker in metastatic castration-resistant prostate cancer treated with Ra-223. - Fukushima, Yoshimitsu; Kimura, Go; Akatsuka, Jun; Honda, Yoshimitsu; Nakaoka, Yujiro; Hayashi, Hiromitsu; Kumita, Shinichiro (EJNMMI Reports, 2026)