Low-cost absorption materials remove more than 90% of lutetium-177 (Lu-177) and iodine-131 (I-131) from wastewater, according to research presented May 31 at the Society of Nuclear Medicine and Molecular Imaging (SNMMI) meeting.
An increase in the use of radionuclide therapy has added burden to wastewater management systems, noted a team led by Hiroto Yoneyama, PhD, of Kanazawa University Hospital in Japan. The investigators explained that, in particular, Lu-177 radiopharmaceuticals have a long half-life of 160 days, which can accumulate and decay and storage tanks.
They sought to evaluate the effectiveness of low-cost, domestically available absorption materials to remove both Lu-177 and I-131 from nuclear medicine wastewater. For the study, the team used samples of Lu-177 DOTATATE and I-131 MIBG (metaiodobenzylguanidine) diluted to approximately 10 kBq/mL, with a total volume of 200 mL per sample, to test three absorption materials:
- Metal grid A, a domestic heavy-metal absorbent,
- Promembranes, an amyloid fibril-activated carbon hybrid membrane, and
- Commercial activated carbon.
The researchers added each absorbent to the solutions, stirring them for 60 minutes and then filtering them. They measured radioactivity concentrations (Bq/mL) before and after absorption using a "well-type" thallium-doped sodium iodide [NaI(Tl)] scintillation counter and calculated the removal efficiency of each type of absorbent.
The team reported that promembranes showed the highest removal efficiency for both isotopes.
Performance of three types of absorbents for removing Lu-177 and I-131 from waste water | ||
Type of absorbent | Lu-177 | I-131 |
Promembranes | 94.3% | 91.5% |
Metal Grid A | 76.7% | 90.7% |
Activated carbon | 78.2% | 85.1% |
The group also reported results related to dose amounts, noting that each absorbent's performance increased in performance for clearing Lu-177 as doses increased: Promembranes showed Lu-177 removal of 94.3% at 1 g and 99.4% at 15 g; Metal Grid A reached 76.7% at 1 g and climbed to 94.4% at 15 g; and activated carbon started at 78.2% at 1 g and increased 93.4% at 15 g.
Experimental results comparing removal efficiency of three filtration materials: Metal Grid A, Promembranes, and Activated Carbon, with CT and SPECT/CT imaging analysis.Hiroto Yoneyama, PhD, and SNMMI
The bottom line? "This absorption-based approach may substantially reduce long-term radionuclide accumulation, including Lu-177m, in wastewater storage systems and represents a practical and scalable solution for the future expansion of radionuclide therapy," the group concluded.
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