Recent Insights in Barium-131 as a Diagnostic Match for Radium-223: Cyclotron Production, Separation, Radiolabeling, and Imaging

• Main Authors: Falco Reissig (Author), David Bauer (Author), Martin Ullrich (Author), Martin Kreller (Author), Jens Pietzsch (Author), Constantin Mamat (Author), Klaus Kopka (Author), Hans-Jürgen Pietzsch (Author), Martin Walther (Author)
• Format: Book
• Published: MDPI AG, 2020-09-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.

Summary

Barium-131 is a single photon emission computed tomography (SPECT)-compatible radionuclide for nuclear medicine and a promising diagnostic match for radium-223/-224. Herein, we report on the sufficient production route ¹³³Cs(<i>p</i>,<i>3n</i>)¹³¹Ba by using 27.5 MeV proton beams. An average of 190 MBq barium-131 per irradiation was obtained. The SR Resin-based purification process led to barium-131 in high radiochemical purity. An isotopic impurity of 0.01% barium-133 was detectable. For the first time, radiolabeling of the ligand macropa with barium-131 was performed. Radiolabeling methods under mild conditions and reaction controls based on TLC systems were successfully applied. Small animal SPECT/ computed tomography (CT) measurements and biodistribution studies were performed using [¹³¹Ba]Ba(NO₃)₂ as reference and ¹³¹Ba-labeled macropa in healthy mice for the first time. Biodistribution studies revealed the expected rapid bone uptake of [¹³¹Ba]Ba²⁺, whereas ¹³¹Ba-labeled macropa showed a fast clearance from the blood, thereby showing a significantly (<i>p</i> < 0.001) lower accumulation in the bone. We conclude that barium-131 is a promising SPECT radionuclide and delivers appropriate imaging qualities in small animals. Furthermore, the relative stability of the ¹³¹Ba-labeled macropa complex in vivo forms the basis for the development of sufficient new chelators, especially for radium isotopes. Thereby, barium-131 will attain its goal as a diagnostic match to the alpha emitters radium-223 and radium-224.

Item Description

10.3390/ph13100272
1424-8247